THE BORN - EINSTEIN LETTERS
The correspondence between
MAX& HEDWIG BORN and
ALBERT EINSTEIN
1916/1955
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Commentaries MAX BORN
Translation IRENE BORN
Introduction WERNER HEISENBERG
Foreword BERTRAND RUSSELL
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' "You believe in the God who plays dice,
and I in complete law and order in a world
which I, in a wildly speculative way, am
trying to capture.' Thus Einstein, writing
to Max Born in 1944, summed up two
utterly contrasted attitudes to science
which were never reconciled throughout
this long series of letters. Born, in holding
that the basis of the material world was
the purely random behaviour of the
constituent particles of atoms, shared the
majority viewpoint among quantum
scientists; yet Einstein persisted in
thinking that every event must have its
cause, and searched constantly for a
deeper explanation which might bring
order into the seemingly chaotic sub-
atomic world. Their conflicting views
provide the intellectual stimulus of
much of this correspondence.
But at a time when politicians were
realizing the terrifying power of atomic
physics to provide weapons of unforeseen
destructiveness neither Born nor Einstein
could turn their backs on the social
implications of the new science. At first
their letters share atone of concern; in
the end, when the atomic bomb has been
used and the innocence of science has
been left far behind, they can only regret
'the evil which our once-so-beautiful
science has brought upon the world'.
The wider effects of war dominate many
of the letters, for both Born and Einstein
werefd'rced to flee from Germany during
the Hitler regime, and the scars of the
experience lasted so long with Einstein
that he never felt able to return.
In spite of their scientific differences
Born and Einstein sustained a rare and
close friendship for more than forty years,
until Einstein's death in 1955 (Max Born
was to live until 1970). For long periods
these letters were the only link between
them. Whether they are commiserating
over the plight of German Jews in exile,
or delighting in the plays and poems of
Bern's wife Hedwig, or exchanging sharp
and often witty comments about their
scientific colleagues, the two men reveal
throughout the essential warmth and
generosity of their personalities. As
Bertrand Russell writes in his foreword:
'In an age of mediocrity and moral pygmies,
their lives shine with an intense beauty.
Something of this is reflected in their
correspondence, and the world is richer
for its publication'.
/L ^
Drawing of Albert Einstein by Wolgang Born, 1924
The
BORN-EINSTEIN
Letters
Correspondence between Albert Einstein
and Max and Hedwig Born
from 1916 to 1955
with commentaries by
MAX BORN
Translated by Irene Bom
MACMILLAN
The Born Letters © igyi G. V. R. Born, I. Newton- John, M. Pryce
The Einstein Letters © ig^i Estate of Albert Einstein
Commentaries © igyi G. V. R. Bom
Translation © 197 J I. Neviton-John
All rights reserved. No part of this publication may be
reproduced or transmitted, in any form or by any means,
without permission.
First published igyi
Published by
THE MACMILLAN PRESS LTD
London and Basingstoke
Associated companies in New York Melbourne
Toronto Dublin Johannesburg and Madras
Printed in Great Britain by
ROBERT MACLEHOSE AND GO LTD
The University Press, Glasgow
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Foreword
hy Bertrand Russell
The correspondence of Albert Einstein and Max Born will
provoke the greatest interest, both among men of science and a far
wider pubUc. Not only are they among the most eminent scientists of
our century, but they had wide interests and an uncommon aware-
ness of the social responsibility of the scientist.
These letters, which clearly were not written for publication,
record their hopes and anxieties in war and peace, their private
thoughts about the progress of their work and that of colleagues, and
much that will prove invaluable source material in the history of
science.
Something of the nobility of their lives is also revealed. I have
deeply valued their friendship over many years. Both men were
brilliant, humble and completely without fear in their pubhc
utterances. In an age of mediocrity and moral pygmies, their lives
shine with an intense beauty. Something of this is reflected in their
correspondence, and the world is the richer for its publication.
/ December ig68
Introduction
by Werner Heisenberg
The relativity and quantum theories, the theoretical foundation of
modern physics, are generally held to be abstract systems of ideas,
inaccessible to the layman, which no longer show much evidence of
their human origin. It is, however, the human aspect of the develop-
ing science, more than anything else, which this correspondence
between Albert Einstein and Max Born renders intelligible.
Einstein and Born were both in the front rank of those who contri-
buted towards the formation of modern physics. In the year 191 6, at
the beginning of the correspondence, Einstein had just completed
his papers about the general theory of relativity, and was con-
centrating his efforts on the then still very puzzling quantum
phenomena. During the years which followed Born, together with
his pupils in Gottingen, took a number of decisive steps which led
to an understanding of these very phenomena. Nothing demonstrates
more clearly the exceptional difficulties which stood in the way of a
clearer understanding of atomic phenomena - in spite of the con-
siderable amount of experimental data already obtained - than the
fact that these two scientists, who on the human level were on such
intimate terms, failed to agree about the final interpretation of the
quantum theory.
But their correspondence does not merely bear witness to the
dramatic argument about the correct interpretation of atomic
phenomena. It also shows the way in which human, political and
ideological problems are intermingled in this discussion, and for this
reason the contemporary history of the years 191 6 to 1954 plays an
important part in these letters. Einstein and Born, both interested in
the social structures around them, actively participated in the history
of their time, suffering and hoping, and many people who have
vu
INTRODUCTION
suffered in different ways and hoped for other things during this
epoch will find it instructive to have a look at the world of those days
through the eyes of these two eminent scientists.
In the year 1916 Einstein and Born were both in Berlin. Einstein
had a research appointment at the Prussian Academy of Sciences;
Born was Professor Extraordinarius for theoretical physics at the
University of Berlin, but was then on wartime service as scientific
collaborator of the Artillery-Testing Commission in BerUn. Soon
after the end of the war Bom became Professor Ordinarius for
theoretical physics at the University of Berlin; Einstein undertook
extended lecture tours to many universities in America, Asia and
Europe.
The working methods of these two scientists were rather different.
Einstein basically worked alone. However, he liked to talk to other
physicists about his problems; now and again he called upon
individual young collaborators, predominantly mathematicians, to
help with difficult mathematical investigations. But Einstein did
not teach according to the usual custom at universities; rather, one
gained the impression that, even in most of the papers he published
in collaboration with other people, the inspiration and direction
were his.
Born, on the other hand, founded a school of theoretical physics
in Gottingen. He held the normal courses of lectures, organised
seminars, and soon succeeded in collecting a fairly large band of
excellent younger physicists about him, with whom he tried to
penetrate the unknown territory of the quantum theory. Gottingen
was then one of the world's most important centres of modern
physics. In the small university town the mathematical tradition
had been carried on for more than a century by some of the most
illustrious of names: Gauss, Riemann, Felix KJein and Hilbert
all taught in Gottingen. Gottingen thus offered most of the prere-
quisites for the search for the mathematical laws describing the
atomic phenomena. James Franck, the experimental physicist,
awakened the interest of young physicists in the curious behaviour of
atoms exposed to radiation by his experiments there into electronic
coUisions. Born and his pupils were striving for insight into the
fundamental laws of nature underlying these experiments. In this
way a lively intellectual atmosphere was generated, where
conversation revolved more frequently around the behaviour of
electrons within the atom than the events of the day or political
vui
INTRODUCTION
questions. Born and his wife Hedwig, whose letters to Einstein
constitute a considerable portion of this correspondence, looked
after this group of young physicists, in both the scientific and the
human sense. Bern's house was always open for social gatherings
with young people, and anyone who happened to meet this group
of youngsters, in the university, or on the ski-slopes of the Harz
Mountains, may well have wondered how the academic staff
succeeded in focusing interest so exclusively on such a difficult and
abstract science. It was part of Germany's great tragedy that the
revolution of 1933 put a sudden and violent end to this scientific life.
Born and Franck had to leave Germany. Born found a new sphere of
activity in England, Franck in America.
In 1923 Einstein returned to Berhn from his great round-the-world
trip. He participated regularly in the colloquia where the 6lite of
Berlin physicists, among them Planck, v. Laue and Nernst, gathered
to discuss topical research problems. Einstein's contributions to these
discussions in the colloquia, and his private conversations with
individual scientists which often took place in his private apartment,
may well have been the most important part of his educational
activity at that time. But what limited effectiveness he was still able
to achieve within a small circle was soon curtailed by political
developments and their consequences, which were less easily evaded
in a large city like Berlin than in the friendly little university town of
Gottingen. Einstein predicted the political catastrophe very early on.
He therefore assumed new responsibilities in California, and after
1933 found his ultimate sphere of activity in Princeton, which
developed into one of the most important American research centres
during the following decades.
Relativity theory and quantum theory were the central scientific
themes of the time. As there were no differences of opinion between
Einstein and Born about the theory of relativity and the corresponding
formulation of space and time, the most interesting discussions are
concerned with the interpretation of the quantum theory. Einstein
agreed with Born that the mathematical formulation of quantum
mechanics, developed in Gottingen and consolidated further in
Cambridge and Copenhagen, correctly described the phenomena
within the atom. He may also have been willing to admit, for the
time being at least, that the statistical interpretation of Schroedinger's
wave function, as formulated by Born, would have to be accepted as a
working hypothesis. But Einstein did not want to acknowledge that
IX
INTRODUCTION
quantum mechanics represented a final, and even less a complete
description of these phenomena. The conviction that the world
could be completely divided into an objective and a subjective
sphere, and the hypothesis that one should be able to "^ake Pr^^JJ
statements about the objective side of it, formed a Part of his W
philosophical attitude. But quantum mechanics could not satisfy
diese claims, and it does not seem likely that science will ever find
ts way back to Einstein's postulates. The whole tnckiness of this
central problem is shown clearly in Born's commentaries on the
individual letters, which also give us much information about the
socill and political circumstances connected with the development of
physics at that time. All scientific work is, of course, based consciou^
or subconsciously on some philosophical attitude ; on a Particular
thought structure which serves as a solid foundation for further
development. Without a definite attitude of this kind, the concepts
and associations of ideas produced would be unlikeb^ to attain the
degree of clarity and lucidity essential for scientific work. Most
sclLists are willing to accept new empirical data and to recognise
new results, provided they fit into their philosophical frame-
work. But in the course of scientific progress it can happen that
a new range of empirical data can be completely understood on^
wheTthe enormous effort is made to enlarge this framework and to
change the very structure of the thought processes. In the case of
quantum mechanics, Einstein was apparently no longer willing to
Tke this step, or perhaps no longer able to do so. The letters between
Einstdn and Born, and Born's subsequently added commentaries
movingly demonstrate the degree to which the work of the scientist,
XcSts subject matter seems to be so far removed from all things
human, is fundamentally determined by philosophical and human
^"fiut'^this correspondence should not only be rated an extremely
valuable document in relation to the history of modern science ; it also
bears witness to a human attitude which, in a world full of political
disaster, tries with the best of intentions to help wherever possible,
anTwhich considers love for one's fellow men to be fundamentally
of far greater importance than any political ideology.
W. Heisenberg
Acknowledgments
I am greatly obliged to Einstein's executor Dr Otto Nathan in New
York for permission to use Einstein's letters. I also thank Miss Helen
Dukas, Einstein's former secretary, for preparing and sending copies
of these letters to Europe. Mrs Franca Pauli very kindly allowed me
to use letters of her late husband Professor Wolfgang Pauli, for which
I am very grateful. I would further like to thank Professor Armin
Hermann in Stuttgart for his valuable help in reading the proofs.
I am very grateful to Earl Russell for his warm-hearted preface and
Professor Werner Heisenberg for his perceptive, sympathetic fore-
word, I thank my daughter Mrs Irene Newton-John for her excellent
translation of the original letters. I would like to thank Mrs Hedwig
Geib for her careful typing of this manuscript, which was often
illegible. Finally I would like to thank my son Professor Gustav V. R
Born in London for the efforts he made in dealing with the problems
which arose in the course of publication.
Max Born.
The publishers thank Paul Atkins for his careful work in editing the
letters and commentaries.
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{Photograph by Karsch)
Plate J. Albert Einstein, late 1940's
Plate 4. Max AND Hedwig Born, iq^sfS
{Photograph by Alananne Foche)
The Born-Einstein Letters
Einstein's famous paper^ containing the fundamentals of his theory
of relativity appeared in 1905. The same volume of Annalen der
Physik contained two more epoch-making papers by him on the
hypothesis of the light quantum* and the statistical theory of Brow-
nian movement.^ At that time I was a student in Gottingen and
attended a seminar conducted by the mathematicians David Hilbert
and Hermann Minkowsky. They dealt with the electrodynamics and
optics of moving bodies - the subject that was Einstein's point of
departure for the theory of relativity. We studied papers by H. A.
Lorentz, Henri Poincare, G. F. Fitzgerald, Larmor and others, but
Einstein was not mentioned. I found these problems so fascinating
that I decided to concentrate on theoretical physics. However, I had
to postpone any deeper investigation into electrodynamics for other
reasons.*-^-* After graduating in 1906 I took up the threads again
and attended lectures by Larmor in Cambridge, England, on more
recent developments in the Maxwellian theory of electromagnetism,
and by J. J. Thomson on the experimental progress of the theory of
electrons. Again Einstein's name was not mentioned.
When I later (i 907-1 908) tried to develop my experimental skills
at the Institute presided over by Lummer and Pringsheim in my
home town of Breslau, I joined an active group of young physicists,
including Rudolf Ladenburg, Fritz Reiche and Stanislaus Loria.
We studied the more recent physics Uterature and reported on what
we had read. When I mentioned Minkowsky's contributions to the
seminars in Gottingen, which already contained the germ of his
four-dimensionzd representation of the electromagnetic field, published
in 1907-8, Reiche and Loria told me about Einstein's paper and
suggested that I should study it. This I did, and was immediately
deeply impressed. We were all aware that a genius of the first order
had emerged. But nobody knew anything about his personality or
his life, except that he was a civil servant at the Swiss Patent Office in
Berne. Then Ladenburg decided to look him up during a hoUday
trip, and his account was the first I heard of Einstein the man. Even
then he was as he appeared later: completely unpretentious, simple
and modest in his habits, kind and friendly, yet witty and humorous.
Ladenburg was enthusiastic and made us curious about the great
unknown.
But some time passed before I met him. This was in 1909 at the con-
BORN-EINSTEIN LETTERS
ference of natural scientists in Salzburg. As I have described this
incident and the years following, during which our friendship
developed, on various occasions,'-'-* I shaU not repeat it here. I
shall recount only the events which brought us together. In 19 13
Einstein was appointed as successor to J. H. van't HofFin a research
post at the BerUn Academy of Sciences, and he was made an ordinary
member of the mathematical physics division. one year later,
shortly after the outbreak of the first world war, I became Extra-
ordinarius for theoretical physics at the University of BerUn, a position
which was created in order to reUeve Planck of teaching duties.
Nothing much came of this, as I was called up for military service
shortiy afterwards (summer 1915). After a short training course as an
aircraft wireless operator at the Doberitz Camp, I was sent to the
artillery inspectorate in BerUn as a scientific assistant. The otface
building in Spichernstrasse was quite close to Einstein's flat at Haber-
landstrasse 5. Thus it happened tiiat I was able to visit him and talk
with him frequently, .^ „ , , ,-.• n
We understood each otiier not only scienufically, but also pohtically
and in our attitude towards human relationships. I cannot say with
certainty whether any'correspondence existed between Einstein and
myself during the preceding years, for nothing has been preserved.
But I find it hard to beUeve that, when I was working witii Theodor
von Karman on the furtiier development of Einstein's tiieory of
speciHc heat of soUd bodies (1912). I did not write to Einstein about
it Presumably I did not keep any letters at tiiat time. The first letter
from Einstein to my wife and myself dates from the year 1916, and
no letters from us to Einstein exist before 1920. The commentary I
wrote in 1965 therefore depends entirely on my memory for this
period The firstitem which has been preserved is apostcard addressed
to me which deals with scientific matters. It was obviously sent from
Einstein's flat in Wilmersdorf to mine in TepUtzerstrasse,
Grunewald.
J Sunday
sy February, igi6
Dear Born
This morning I received the corrected proofs of your paper for
Physikalische Z<Atschrift, which I read with a certain embarrass-
ment but at the same time with a feeUng of happiness at being
BORN-EINSTEIN LETTERS
completely understood and acknowledged by one of the best of
my colleagues. But, quite apart from the material contents, it
was the spirit of positive benevolence radiating from the paper
which delighted me - it is a sentiment which all too rarely
flourishes in its pure form under the cold light of the scholar's
lamp.
I thank you with all my heart for this happiness which you
have allowed me to share.
With kind regards
Yours
A. Einstein
The article which Einstein was so pleased with was on his theory of
gravitation and general relativity;* I would not write very differently
about this subject to-day. Since then it has become fashionable to regard
the relativity aspect of Einstein's general theory as of secondary importance
and to consider the new law of gravitation as the essential part. I cannot
share this point of view, which is represented particularly by my Russian
friend and former collaborator, V. Fock. Einstein's starting point was the
empirical fact of the equality of inertial and gravitational mass. It follows
that an observer enclosed inside a box is unable to distinguish whether
the acceleration of a body inside the box is caused by an external gravi-
tational field or by the acceleration of the box itself in the opposite
direction. The existence and the size of a gravitational field inside a small
space can thus be assumed only in relation to a certain (accelerated)
system of reference. This was the historical basis of the theory, and it is
still today, in my opinion, the rational approach. I used it in my book
Die Relativitatstheorie Einsteinsj'-'^ which was first published in 1920, and
also retained it in the recendy published new edition. I believe that this is
justified, both in regard to Einstein's own intention and objectively.
The following letter to my wife can be understood only if the friendly
intercourse between Einstein's house and ours is appreciated. My wife
described this in an article which appeared in the journal Weltwoche a
few years ago.' It explains the references to the poem and the TIemish
sow'. The book he mentions is probably one by Max Brod.
BORN-EINSTEIN LETTERS
BORN-EINSTEIN LETTERS
8 September, igi6
Dear Mrs Born
Your poem gave me much pleasure, mainly because it is an
indication of your happy state of mind, but also because it
shows that you are on the best of terms with both the Muse of
Parnassus and the 'Flemish sow'. The latter, though, is not really
needed to make a few cosy evening hours spent in your and
Max's den appear to me in the most alluring colours !
I read the book with great interest. It is certainly enter-
tainingly written by a man who knows the depths of the human
soul. Incidentally, I believe that I met him in Prague. I think
he belongs to a small circle there of philosophical and Zionist
enthusiasts, which was loosely grouped around the university
philosophers, a medieval-like band of unwordly people whom
you got to know by reading the book.
Best regards to you both
Yours
Einstein
The two papers you wanted are enclosed. The book I will
return personally.
Einstein's next letter is again addressed to my wife, but its subject matter
concerns mc just as much. Presumably I was absent on a lengthy official
trip.
8 February, igi8
Dear Mrs Born
Your detailed letter with its comforting ｅxpression of sympathy
and confidence gave me much pleasure. My answer will take
the form of a monologue, thereby completely eliminating the
ugly chasm between 'you' and 'I'.
.
Laue wants to come here. Some time ago he had the chance
of obtaining a sort of research post here, free from teaching
duties, through a private award. His effort to get to Berlin then
was, according to him, based on his dislike of teaching activities.
Now that this plan will apparently not come off, he is thinking
of an exchange of posts with your husband. Primary motive,
therefore: 'BerUn'. Motivation: ambition (of the v«fe?).
Planck knows about this, the Ministry probably not. I have not
yet talked about it with Planck. I suppose his efforts are directed
towards becoming Planck's successor. The poor fish. Nervous
subtlety. To strive for an aim which is in direct contradiction
with his natural desire for a quiet life, free from complicated
human relationships. In this connection please read Andersen's
pretty little fairytale about the snails. Seen objectively, the
chance of Laue's plan being successful depends on two
conditions :
1 . Sufficient income for Laue from your post,
2. Your husband's inclination to exchange jobs.
Just assuming that i. is fulfilled, there remains the question
of whether you should agree; this is, of course, the question
which worries you already. My opinion is :
Accept unconditionally.
I have no need to assure you how fond I am of you both and how
glad I am to have you as friends and kindred spirits in this . . .
desert. But one should not refuse such an ideal post, where one is
completely independent. There is a wider and freer sphere of
activity than here, and it gives your husband a better chance to
display his powers. And most important of all: to be near to
Planck is a joy. But when Planck eventually retires, you cannot
be certain, even if you remain there, that your husband will
succeed to his position. If, on the other hand, it were to be
someone else, it would be rather less pleasant. one has to be
prepared for every eventuality. You should not expose yourselves
to this unless it is necessary.
Look after yourself, and let my example be a warning to you.
For me the 'sudden jerk upwards' is no longer possible.
Sincerest greetings to you, to your children, and to your, I
hope, soon-to-return lord and master.
Yours
Eirutein
BORN-EINSTEIN LETTERS
I do not believe that Einstein would later have persisted in attributing
the motive of ambition to Laue. He probably did not yet know Laue
well at that time. Later, he acknowledged him not only as a physicist but
also as an upright and thoroughly honourable human being, as is shown
in a later letter (No. 8i). To me Laue maintained that his efforts to get to
Berlin were due less to his dislike of teaching than to his wish to be near
his admired and much loved teacher, Planck.
The next letter is without an address, but was presumably sent between
our two flats in Berlin.
24 June, igi8
Dear Born
Tomorrow we must be off to our summer holiday resort at
Ahrenshoop (at a Mrs Nieman's, nee Ronow). These lines come
as a solemn farewell. A Danaean present too. With Haber's
help I have managed to obtain a travel permit to Finland for
Nordstrom (from the General Staff). Now he wants to return to
Holland, but unfortunately I am no longer in a position to attend
to it. I would ask you to settle the matter, please. It is urgent, as
Mrs Nordstrom is soon to give birth to her child, in Holland if
possible.
With best wishes for a happy time to you and your little band.
Yours
Einstein
I hope the 40 M have arrived — I sent it off in an ordinary letter.
The Finnish physicist Nordstrom had developed, almost simultaneously
with Einstein's first publications about the general theory of relativity,
a rival relativistic theory of gravitation, which contained only one scalar
potential, as with Newton. According to Einstein, however, the ten
components of a symmetrical tensor determine the gravitational field.
Nordstrom' s ideas were shrewd and ingenious. I found out later that he
had been my strongest competitor for the Berlin Extraordinary
Professorship.
BORN-EINSTEIN LETTERS
Einstein's next letter, clearly from Ahrenshoop, and undated, shows that I
did attempt to do something for Nordstrom. Whether I was successful I
cannot remember; I also know nothing of Nordstrom's subsequent fate.
In Einstein's letter the words 'must' and 'Frische' (holiday resort) were
underlined. Presimaably he was in some doubt as to whether he would
'refresh himself' in Ahrenshoop. He was clearly following the wishes of
his second wife, his cousin Elsa, for she had nursed him during a serious
illness and had probably saved him from death.
5
[undated^
Dear Bom
It is very kind of you to look after the Nordstroms. Just write
to the General Staff that Nordstrom has already been granted
a permit for the outward journey, at Haber's request. Then the
return journey will be readily allowed. As I wrote to you before,
he has to be back at the beginning of August.
It is wonderful here, no telephone, no duties, absolute peace.
I simply can't imagine now how you can bear life in the big city.
And the weather is wonderful too. I lie on the beach like a
crocodile and let myself be roasted by the sun, I never see a
newspaper and don't give a damn for what is called the world.
What you tell me about the inertia in a crystal lattice is very
satisfactory. It can only be a matter of electrical energy, since
the potential energy of the other assumed forces does not enter
into the inertia, according to the fundamental laws of mechanics.
I look forward very much to your explanation of this.
I am reading Kant's Prolegomena here, among other things,
and am beginning to comprehend the enormous suggestive
power that emanated from the fellow, and still does. once you
concede to him merely the existence of synthetic a priori
judgements, you are trapped. I have to water down the 'a
priori' to 'conventional', so as not to have to contradict him,
but even then the details do not fit. Anyway it is very nice to
read, even if it is not as good as his predecessor Hume's work.
Hume also had a far sounder instinct.
When I am back again, we will all sit down cosily together
so that you can gently reintroduce me to the bustle of human
BORN-EINSTEIN LETTERS
activity, of which I take no notice at the moment. In the
meantime, I hope that you and your wife are again in good
health. We are well, and the small harem eat well and are
thriving.
Best wishes
Yours
Einstein
So he liked Ahrenshoop after all, and it did him good. The remark about
inertia in crystal lattices refers to the result of my investigations into
electromagnetic fields in crystals, which I have published in several books
and papers. These investigations were a further development of P. P.
Ewald's fundamental work on dispersion in crystal lattices, but made use
of a different method which Hilbert had suggested in one of his lectures.
My result was new: it automatically followed that the electromagnetic
reciprocal action of the lattice particle's charges contributed to the inertia
(electromagnetic mass). Einstein's remark that only electrical energy
would be involved was, however, absolutely correct.
The letter then contains Einstein's attitude towards the philosophy of
Kant: it amounts to a rejection. In those days he was a complete empiricist
and a follower of David Hume. Later on this changed. Speculation and
guesswork without much empirical foundation played an increasingly
important role in his thinking.
I have no idea what his closing remark about the 'small harem' (I cannot
make it out as anything else) means. Probably it refers to his wife and
stepdaughters.
A picture postcard from Ahrenshoop follows.
^ Ahrenshoop
2 August, igi8
Dear Bom
The closer our journey home approaches, the more I am
plagued by conscience and the fear of a scolding for being
BORN-EINSTEIN LETTERS
lazy about writing. But what can a fellow write who lazes about
all day, who sees no-one and who at the very most wanders about
for half an hour in bare feet? If only we could introduce this
last deUghtful habit (voluntarily) in Berlin! The clover leaf
amused me very much. one can see that it represents three
incorrigible hobby-horse riders in brotherly unity; two are
introspective, one stares unconcernedly into space. The other day
I read that the population of Europe has grown from 1 13 million
to almost 400 million during the last century ... a terrible thought,
which could almost make one reconciled to war!
To a happy reunion !
Yours
Einstein
I can't remember what the clover leaves represented.
The observation about population increase and war is remarkable.
He added the following to a postcard from Arosa in Switzerland with a
picture of the Silser Lake that Mrs Elsa Einstein sent.
7
ig January, igig
BrilUant landscape and satisfied citizens, who have nothing to
fear. This is how it looks. But God knows, I prefer people with
anxieties, whose tomorrow is threatened by uncertainty. How
will it all end ? one cannot tear one's thoughts away firom Berlin ;
so changed and still changing. I believe some good will come
of it in another sense, once it is calm again. The young who have
lived through it all will not quickly become philistines.
Hearty best wishes
Yours
Einstein
That trip abroad was probably Einstein's first after the war. His thoughts
were still of a Berlin shaken by revolution. The card's brief message shows
BORN-EINSTEIN LETTERS
what hopes he had of the new regime, the Republic under Ebert. He
deeply detested Prussianism with its arrogant militarism, and he believed
it now to be finally defeated and that everything could improve. I
believed the same at that time, and this was one bond in our friendship.
We were completely wrong - it got very much worse. Subsequent letters
contain reminders of this time of hope.
After a certain amount of to-ing and fro-ing, the exchange of chairs be-
tween myself and Laue was finally agreed.We succeeded in acquiring an
attractive house with a garden in Frankfurt, in Cronstettenstrasse. Ein-
stein's first letter addressed to us there follows.
8
Berlin
4 June, igig
Dear Bom
I already have a bad enough conscience because I have not
answered your wife's extremely kind letter, and now your
delightful letter arrives instead of a scolding. I am glad that
you have made such a splendid nest for yourselves there, in your
little house and garden. It is wicked of you, though, to take on
such a burden of responsibility. Do you want to become a
torment to your students and a reproach to your colleagues?
Will you even keep your literary promises, e.g. to Sommerfeld ?
That is going too far. If Shakespeare had lived under present-
day conditions he may well have altered his lines: 'At lovers'
perjuries, They say, Jove laughs', which is a little hard, to:
'At the forgotten promise of a report'.
And then you tell me that, according to friend Oppenheim, I
am supposed to have made heaven only knows what wonderful
discovery. But there is no truth in it. The modest suggestion I
made to him about this affair, which I told you about at Lake
Grunewald, has become dangerously swollen in his exuberant
imagination ! The quantum theory gives me a feeling very much
like yours. one really ought to be ashamed of its success,
because it has been obtained in accordance with the Jesuit
maxim: 'Let not thy left hand know what thy right hand doeth'.
I do not see the political situation as pessimistically as you.
ID
BORN-EINSTEIN LETTERS
Conditions are hard, but they will never be enforced. They are
more to satisfy the enemy's eye than his stomach. Ludendorf
was undoubtedly much worse than the Parisians. The French
are motivated by fear. Ludendorf, however, had the desires of a
Napoleon. The hardships resulting from the errors of the French
are alleviated by a slovenliness which never fails, as in my one-
time fatherland, Austria.* Eventually, Germany's dangerousness
will go up in smoke, together with the unity of her opponents,
accompanied no doubt by a certain hysteresis. May a hard-
bitten x-brother and determinist be allowed to say, with tears
in his eyes, that he has lost his faith in humanity ? The impulsive
behaviour of contemporary man in political matters is enough to
keep one's faith in determinism alive.
I am convinced that in the next few years things will be less
hard than in those we have recently lived through.
With sincere regards to you and your wife, also from my wife.
Yours
Einstein
Haber's adaptation of your theory to monovalent metals is
puzzling.
The Uterary promise concerned my promise to Sommerfeld (Professor of
Theoretical Physics in Munich) to write an article about atomic theory of
the soUd state for the volume 'Physics' in the Enzyklopddie der Mathemattk.
This lengthy treatise later appeared as a book.
Friend Oppenheim was the son of an important Frankfurt businessman
(a jeweller), who had founded and endowed the Chair of Theoretical
Physics occupied first by Laue and later by myself. Oppenheim junior
was interested in philosophy, particularly the philosophical ideas contained
in Einstein's theory of relativity. He was probably alludmg to the begin-
nings of 'a unified field theory', which was intended to combme gravitation
and electromagnetism and which occupied Einstein throughout his hfe.
The poUtical remarks show that at that time I took a more pessimistic
view of the situation than Einstein. The ｅxpression 'hard-bitten x-brother
and determinist' (we used to say 'to x' when calculating with unknown
values oix, as is normal in mathematics) was probably correct then, lor
my non-determinist views only arose some years later.
* Einstein probably meant his time in Prague as Professor at the German
University; Bohemia was a part of Austria at that time.
II
BORN-EINSTEIN LETTERS
I cannot remember now what Haber's application of my theory to mono-
valent metals meant.
y Sunday
I September, igig
Dear Mrs Bom
I have a terribly bad conscience about both of you, but par-
ticularly you, because I so infrequently settle down to write to
you. Let me say straight away, so that I won't forget, that I will
do my best to squeeze some funds out of the K. W. Institute
[Kaiser- Wilhelm Institute] for your husband, if possible, and
if we ever have some to give away. I will visit you soon enough
in your comfortable nest - provided you have no-one billeted on
you -just you wait !
That business with Oppenheim has gone wrong. My aca-
demic remuneration does not depend on his purse but on that
of Mr Koppel. I had no idea that your husband's chair was
founded by Oppenheim - I only know of the observatory there.
The relationship between Oppenheim (junior) (I have only
seen old man O. on one single occasion) and us is of a strictly
private nature and is due to Mr O. junior's philosophical
hobby-horse. There is just one problem - 1 promised to come and
stay both with you and with Mr O. junior, if I came to Frankfurt ;
the solution is beyond my powers, but no doubt it will turn out
all right in the end. It is nothing like as bad as the answer
AlthofF gave to someone who had just been passed over for
someone else for a professorship he had been promised. He said,
cheerfully and rudely, 'Well, did you believe you were the only
one to whom I have promised the professorship?'! Yesterday
Stem came to see me. He is delighted with Frankfurt and with
the Institute. I quite liked Rausch, though Strindberg's Traum-
spiel is incomparably better.
Mr Bieberach's love and veneration for himself and his
Muse is quite delicious. May God preserve him, for it is the best
way to be. Years ago, when people lived their lives in greater
isolation, eccentrics like him were quite the rule amongst
university professors, because they did not come into personal
12
BORN-EINSTEIN LETTERS
contact with anyone of their own stature in their subject, and
apart from their subject nothing existed for them.
Politically, I am more on your husband's side than on yours.
I believe in the growth potential of the League of Nations, and I
believe further that the hardships connected with its formation
will disappear after a while. Even now the conflict of interests of
the Allies is so considerable that much is being modified (the
constitutional incident concerning Austria; the intervention
of the Allies in Silesia). In my opinion, the greatest danger to
future development would be a withdrawal by the Americans;
one can only hope that Wilson will be able to prevent it.
I don't believe that human beings as such can really change
but I am convinced that it is possible, and indeed necessary, to
put an end to anarchy in international relations, even if it were
to mean sacrificing the independence of various countries.
Now to philosophy. What you call 'Max's materialism' is
simply the causal way of looking at things. This way of looking
at things always answers only the question 'Why?', but never
the question 'To what end ?'. No utility principle and no natural
selection will make us get over that. However, if someone asks
'To what purpose should we help one another, make life easier
for each other, make beautiful music or have inspired thoughts ?',
he would have to be told: 'If you don't feel it, no-one can
explain it to you.' Without this primary feeling we are nothing
and had better not live at all. If someone wanted to make a
basic investigation to prove that these things help to preserve
and further human existence, then the question 'To what end?'
would loom even larger, and an answer on a 'scientific' basis
would be an even more hopeless task. So if we want to proceed
in a scientific manner at any cost, we can try to reduce our
aims to as few as possible and derive the others from them. But
this will leave you cold.
I do not agree with the pessimistic assessment of cognition.
To have a clear view of relationships is one of the most beautiful
things in life; you could only deny that in a very gloomy,
nihilistic mood. But you should not quote the Bible to prove
your point. In Luther's translation it says in many places : 'And
he knew her; and she bore him a son; his name was. . . .' one
can assume that the Tree of Knowledge refers to this. Therefore,
it probably has very little in common with epistemology in our
13
BORN-EINSTEIN LETTERS
sense; or maybe the old fathers fancied themselves in tiiis
ambiguity? But that is not really like these lovers of speculation
and argument.
Thank you very much for the lovely photographs. The one
of your husband is wonderful: its subject is not so bad, either.
He has not been here yet; I look forward greatly to seeing him.
I have spent these last few days very pleasantly sailing, but
unfortunately have contracted another ailment (stomach) on
naval service, and I have to spend a few days in bed once more.
Thus the indistinct writing.
With kindest regards to you both.
Yours
Einstein
Althoff was for many years an official concerned with university admini-
stration at the Ministry of Education, where he earned great merit in
building up the universities. He was well known and feared for his lack of
consideration and rudeness.
Otto Stern was a young physicist from Silesia who became my assistant.
Our Institute possessed a workshop and an able technician called Schmidt.
Stem made very good use of this to carry out his experiments, later to
become famous, into a peculiar effect of the quantum, the so-called
quantisation of direction. Up to that time, this effect had been only
indirectly deduced from spectroscopic observations; Stern undertook to
prove it directly by using atomic radiation in a high vacuum. He was
supported in this by Walter Gerlach, assistant at the Institute of Experi-
mental Physics (whose head was Prof Wachsmuth). Stem later received
the Nobel Prize for these investigations. At his suggestion I also experi-
mented successfully at that time; with my assistant, Elisabeth Bormann,
I made a direct measurement of the length of the free paths of atoms with
the aid of atomic radiation.
I cannot remember what kind of play Rausch vfas.
The Bieberbach affair was as follows: The Faculty of Natural Sciences
had a beautifully bound book, in which each new professor was required to
write a short autobiographical note. When it was given to me by the Dean,
the mathematician Schoenflies, I naturally read some of the cameo-
biographies, and also showed them to my wife. She discovered a rather
comic one - the young mathematician Bieberbach's, which was full of
vanity. She copied some of the finest passages for Einstein.
Einstein's explanation to my wife of the nature of scientific research
reveals the basis of his philosophy in a concise and clear way that is hard
14
BORN-EINSTEIN LETTERS
to find elsewhere. It led to a discussion of the Biblical concept 'cognition'
which continued for some time between my wife and Einstein. In contrast
to Einstein, who interpreted the tasting of the forbidden fruit from the
tree of knowledge as sexual experience, she insisted that it meant spiritual
enlightenment. For the first chapter of Genesis says : 'And God blessed
them [man and wife], and God sjiid unto them, Be fruitful, and multiply'.
And later it says: 'And out of the ground made the Lord God to grow every
tree . . . the Tree of Life also in the midst of the garden, and the Tree of
Knowledge of good and evil . . . But of the fruit of the tree which is in the
midst of the garden, God hath said Ye shall not eat of it.' In the third
chapter the serpent says to Eve : 'For Gk)d doth know that in the day ye
eat thereof, then your eyes shall be opened, and ye shall be as gods,
knowing good and evil.'
The next letter shows that Einstein ceded this point to her, but not its
consequences.
10
t6 October, igig
Dear Bom
You are a splendid fellow! Have forwarded your pamphlet
with ｅxpressions of agreement plus a few quibbles to the lucky
recipient.
Your wife was right about the Tree of Knowledge. I clearly
rated my ancestors more primitive than they were. But we
won't allow her to reduce - 'cognition' like that. What better
concept is there? Also, she should not grumble about loneliness
in company when she has such a splendid fellow with her. It
all comes from feeling cold. Perhaps the cold will also make you
lose your temper about that business with the Ministry - that
would be a good thing. The letters from your wife, incidentally,
are masterpieces - and that is no flattery.
Best wishes to you both.
Yours
Einstein
In the original of the letter, the formal German 'Sie' (you) was
crossed out and the more familiar 'Du' substituted. Several more similar
15
BORN-EINSTEIN LETTERS
alterations occur later, in each instance the more intimate form of 'you'
being substituted.
I have forgotten which pamphlet earned me the epithet of a 'splendid
fellow'. I only remember that I often supported him and his work.
on the 'cognition' question Einstein freely admits that my wife was right -
but only in relation to the Tree of Knowledge in the Garden of Eden.
He remained adamant about the value of 'cognition' in the sense of
knowledge : 'What better concept is there ?'
Although I knew that Einstein had a good opinion of me, the offer in the
first few lines of the next letter, which acknowledged the 'Du' used
previously, gave me great pleasure.
II
g November, igig
Dear Bom
From now on we shall use 'Du', if you agree. I have received
your manuscript. But I cannot help thinking that it is too long
for the Transactions according to the new rules. I will talk
to Planck about it. Your application for the K. W. Institute
will soon be dealt with; just have a little patience.
In regard to the Toeplitz affair, I can't make a noise again
just yet, or my bark may prove ineffective in worse cases.
Antisemitism must be seen as a real thing, based on true
hereditary qualities, even if for us Jews it is often unpleasant. I
could well imagine that / myself would choose a Jew as
my companion, given the choice. on the other hand I
would consider it reasonable for the Jews themselves to
collect the money to support Jewish research workers outside
the universities and to provide them with teaching
opportunities.
We look forward very much to seeing your wife. Meanwhile
I want to apologise to her because, as she has shown, I have not
yet eaten enough of the fruit of the Tree of Knowledge,
though in my profession I am obliged to feed regularly on it.
Many thanks for the pears - your productiveness really extends
to every imaginable delight.
i6
BORN-EINSTEIN LETTERS
I hope you are not too cold; we are amazingly well organised
in this respect.
More soon. For the present, kind regards
Yours
Einstein
Although I was very conscious of Einstein's superiority to myself, it was
quite easy to address him with the informal 'Du'. He was so simple and
natural, so entirely without conceit, that the brotherly form of address
seemed almost inevitable. Of course I was aware of the honour of being on
such a familiar footing with him. Our friendship was never shaken, even
though we had some sharp scientific arguments later on (some of which
are in subsequent letters).
I cannot remember which manuscript was referred to.
The Toeplitz affair was probably a snub sustained by my old friend and
fellow student. Otto Toeplitz, in connection with some appointment or
other, which he put down to antisemitism.
Toeplitz was a brilliant mathematician; he made a considerable contri-
bution to the theory of the square forms of an infinite number of variables
(in the so-called Hilbert Space), which is currently used in quantum
mechanics. An important contribution was a long article in Enzjklopddie
der Mathematik, written in collaboration with another friend and fellow-
student, Ernst Hellinger.
Einstein's remarks about antisemitism show that he was very conscious
of the contrast between Jews and Northern Europeans, and that he took
the existence of mutual antipathy very much for granted. He often argued
the case in favour of the suggestion that Jews ought not to press their
claims in an attempt to obtain the more desirable positions, particularly
academic ones, but should create jobs for themselves, to be filled from their
own ranks. I was, as far as I can remember, not altogether of the same
opinion; my family was amongst those who strove for complete assimi-
lation and who regarded antisemitic ｅxpressions and measures as unjusti-
fied humiliations. History has shown that Einstein was the more profound,
although he was then still a long way from recognising the magnitude
of the threat of antisemitism, and of the shocking crimes resulting
from it.
17
BORN-EINSTEIN LETTERS
12
Monday
g December, igig
Dear Bom
Your excellent article in Frankfurter Z^itung gave me much
pleasure. But now you, as well as I, will be persecuted by the
press and other rabble, although you to a lesser extent. It is so
bad for me that I can hardly come up for air, let alone work
properly.
That article by Drill is comic, because he introduces into
philosophy the democratic method of appeaUng to and
haranguing the masses. Let the man continue to beat his drum;
it would be a pity to waste time on a reply. Save your temper,
and let the fellow run around and chatter. His proof of a priori
causality is truly amazing.
During the few days I spent with Schlick in Rostock for the
University's jubilee celebrations, I heard some vile political
mischief-making and saw some really delightful examples of
small-state poUtics. What made it so ludicrous was the fact
that they all knew each other so thoroughly as human beings
that, when one struck a lofty tone, it was jdways accompanied
by ridiculous dissonances. The only hall available for the
celebration was the theatre, which gave it an air of comedy. It
was charming to see the representatives of the old and the new
Government sitting together in the two proscenium boxes.
The new government was, of course, treated to every conceivable
jibe by the academic dignitaries, while the ex-Grand Duke was
given a seemingly endless ovation. No revolution can help
against such inbred servility. Schlick has a good head on him;
we must try to get him a professorship. He is in desperate need
of it because of the devaluation of property. However, it will be
difficult, as he does not belong to the philosophical established
church of the Kantians.
Planck's misfortune moves me very deeply. I could not hold
back the tears when I visited him after my return from Rostock.
He behaves remarkably bravely and properly, but one can see
that he is eaten up by grief.
Your wife's letters are charming, so original and to the point.
I hope that our friend Oppenheim will soon find the midwife
i8
BORN-EINSTEIN LETTERS
he is looking for; if not, the happy event will have to be post-
poned for a while. My friend Haber, who turned to me in his
misery after you moved away, suffers from a similar kind of
malignant pregnancy. He has such forceful methods for trying
to wrest truth from nature. For material doubts, he falls back
on his intuition. He is a kind of raving barbarian, but very
interesting all the same.
Your confused Lorenz has ordered me categorically to
attend an extremely superfluous lecture in Frankfurt; he is one
of the quaintest birds occupying a professorial chair. Unfortun-
ately I have other worries. My mother, who is mortally ill, is
coming to stay with us - sooner or later I must try to accommo-
date my children with my divorced wife in Germany. Difficulties
and anxieties at every turn.
The behaviour of the AlUes is beginning to appear disgusting
even by my standards. It seems that my hopes for the League of
Nations will not be realised. Nevertheless, France seems to be
suffering severely in spite of the coal imports, as can be seen from
its recent restrictions on railway passenger traffic. Here all fixed
and movable property is being bought up by foreigners, to the
point of our becoming an Anglo-American colony. Just as well
that we do not have to sell our brains, or make an emergency
sacrifice of them to the state. I hope you are all well and not
suffering too much from the cold.
Best wishes
Yours
Einstein
I saw the article in the Frankfurter recently but now I am unable to find it
again. I remember that after so many years I was still greatly amused by
my peppery criticism of those hide-bound philosophers. I can only vaguely
remember Drill, whose article Einstein found comic, as a typically rabid
opponent of Einstein. Schlick, on the other hand, was an important
philosopher. Later on he went to Vienna and was the founder of a school
of philosophy known today as logical positivism.
Einstein's description of the celebrations at Rostock University is typical
ofhim.
I assume that by Planck's misfortune he meant the death of his daughter
shortly after the birth of her first child. She had a twin sister who was very
like her, who took on the care of the child and later married her sister's
19
BORN-EINSTEIN LETTERS
husband. Then a terrible thing happened, for she too died under identical
circumstances after the birth of her first child.
Einstein's characterisation of Fritz Haber is quite accurate. During the
war he and I broke off our relationship. He wanted me to join his war
gas team, which I bluntly refused to do. Later on we became reconciled
and I made more frequent visits to his institute in Dahlem to get experi-
mental data from my friend Franck for my work on the calculation of
chemical heat variations from lattice energies. Haber was keenly interested
in this, and developed a way of representing my method of calculation
graphically. This theory later entered the literature of physical chemistry
as the Born-Haber cyclic process. Thus I had the opportunity to get to
know the 'raving barbarian', as Einstein called him. on one occasion,
for example, we were having a lively discussion in his room, but were
constantly interrupted by assistants, post-graduate students or technicians
who wanted something from the head of the institute. In the end, someone
opened the door without having knocked first and the furious Haber
seized a glass inkpot and flung it in the direction of the door, where it
broke into pieces, spattering ink over the wall and the door. At the door,
however, stood Haber's wife. She vanished, terrified, and we continued
with our work as if nothing had happened.
The 'confused Lorenz' was Professor of Physical Chemistry at Frankfurt.
He was indeed a little vague, but all the same very able in his field. I
received much encouragement from him, in my attempt to explain the
anomalies of ionic mobility of small ions with the help of dipolar experi-
ments, for example, and in the experiments concerning the mechanical
effects of dipoles carried out by my pupil Lertes.*
The final paragraph of this letter shows that Einstein was no longer able
to maintain his political hopes, which he had so often set against my
pessimism. But he tried hard to be fair about the difficulties of France. I
believe that none of us at that time recognised the real danger resulting
from the Allies' harsh treatment of Germany, namely, the injury to her
national pride. This led to the development of the myth of 'the stab in the
back', to secret rearmament, and ultimately to the rise of National
Socialism.
13
Monday
sy January, igso
Dear Bom
First of all, the matter of our young colleague Dehlinger, whom
you have written about to Berliner. We are now getting a lot of
money for astronomical research which I have entirely under
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BORN-EINSTEIN LETTERS
my own control. Would he like to work in astrophysics? I
could appoint him for the time being at a salary of approximately
6,000 M a year, possibly more if the present adverse conditions
require it. He would then work with Freundlich. Photometric
investigations on star spectra. If, however, he prefers a post in
technology, I have other connections who could try to find
something for him. It is difficult nowadays to make a living by
scientific work alone. Let me have further details as soon as
possible.
We are also having a sad time just now, because my mother is
at home in a hopeless condition and suffering unspeakably. It
could be many months before she is released. Else is doing a great
deal; it is not easy for her. All this has diminished still further
my already faltering desire to achieve great things. Now you are
quite different. Your little clan has its own difficulties to deal with,
and you, dear Mrs Born, make yourself interesting in a most
reprehensible way. (Whimsical poems and witty letters only
are permitted.) And you. Max, are giving lectures on relativity
to save the institute from penury, and writing papers as if you
were a single young man living in splendid isolation in his own
specially heated apartment, with none of the worries of a pater-
familias nagging you. How do you do it ?
Haber is complaining bitterly about Fajans. You have des-
cribed the latter very well. He is quite unaware of the number
of arbitrary assumptions he makes, and vastly overestimates the
value of consistent results. You are right in sticking uncompro-
misingly to your sound method. I myself do not believe that the
solution to the quanta has to be found by giving up the con-
tinuum. Similarly, it could be assumed that one could arrive at
general relativity by giving up the coordinate system. In
principle, the continuum could possibly be dispensed with.
But how could the relative movement of n points be described
without the continuum ?
PauU's objection is directed not only against Weyl's, but also
against anyone else's continuum theory. Even against one which
treated the electron as a singularity. I believe now, as before,
that one has to look for redundancy in determination by using
differential equations so that the solutions themselves no longer
have the character of a continuum. But how ?
The political situation is developing consistently in favour of
21
BORN-EINSTEIN LETTERS
the Bolsheviks. It seems that the Russians' considerable external
achievements are gathering an irresistible momentum in
relation to the increasingly untenable position of the West;
particularly our position. But before this can happen, streams
of blood will have to flow; the forces of reaction are also
growing more violent all the time. Nicolai is being attacked
and insulted so much that he is no longer able to lecture, not
even in the Charite. once again I have had to intercede
for him in public (one could write a new comedie called: 'The
friend against his will'). France is really playing a rather sorry
role in all this (all the same it is to their credit that they have
rid themselves of the Tiger [Georges Clemenceau]). Victory is
very hard to bear. Erzberger's trial is comic; those with clean
hands (and pockets) may stone him, if they exist! By the way, I
must confess to you that the Bolsheviks do not seem so bad to me,
however laughable their theories. It would be really interesting
just to have a look at the thing at close quarters. At any rate,
their message seems to be very effective, for the weapons the
Allies used to destroy the German Army melt away in Russia
like snow in the spring sun. Those fellows have gifted poli-
ticians at the top. I recently read a brochure by Radek - one
has to hand it to him, the man knows his business.
You think I should let my voice be heard in England? I
would do, if I really had something worthwhile to say. But I
can see that the people there are deeply involved in their own
problems. What could they possibly do to banish want? They,
and the Americans, are sending emergency supplies. But little
can be done in the face of this mass suffering.
The peace treaty certainly goes too far. But since its fulfilment
is quite impossible, it is better that its demands are objectively
impossible to fulfil, rather than just intolerable. one has to
acknowledge that the citizens on the other side had to have
something in black and white as a reward for the courage of the
French. To rise against the treaty would only make sense if one
believed in its real significance, which I do not. By the way, I
am going to England in the spring, to have a medal pressed into
my hand and to have a closer look at the other side of this
tomfoolery. Spengler has not spared me either. Sometimes one
agrees to his suggestions in the evening, and then smiles about
them next morning. one can see that the whole of his mono-
22
BORN-EINSTEIN LETTERS
mania had its origin in schoolteacher mathematics. Euclid
versus Descartes is brought into everything, although, one must
admit, ingeniously. These things are amusing; if someone
should say the exact opposite tomorrow with sufficient spirit, it
is amusing once more, but the devil only knows what the truth is.
That business about causality causes me a lot of trouble, too.
Can the quantum absorption and emission of light ever be
understood in the sense of the complete causality requirement,
or would a statistical residue remain ? I must admit that there I
lack the courage of my convictions. But I would be very unhappy
to renounce complete causality. I do not understand Stern's
interpretation because I cannot make real sense of his statement
that nature is 'intelligible'. (The question whether strict
causality exists or not has a definite meaning, even though
there can probably never be a definite answer to it.) Sommer-
feld's book is good, although I must say frankly that, for heaven
only knows what subconscious reason, this person does not ring
true to me.
I am pleased that your letters to the Ministry have served
their purpose. That speaks well for those people; after all you
did not mince your words. It has really got much better. Just
imagine what would have happened before, had you written
like that. Now the dictatorial omnipotence of you Ordinarii
will be brought to a horrible end, or so I heard the other day.
Just you wait !
For you, Mrs Born, I have an interesting suggestion. As soon
as your children are up and about again, start learning how to
experiment in the laboratory. This is such wonderful work if
one has the time to devote oneself to it. I mean it quite seriously.
Even assuming that a year or more would have to be spent in
studying, it would be very much worth while. And once you
are involved in it, it is a splendid way of working together. You
do need something to stretch your mind. What do you think of it ?
Best wishes to you all
Yours
Einstein
Dehlinger was a gifted young physicist from Vienna, who had developed
a formula for the dispersion of light in the infrared for simple diatomic
23
BORN-EINSTEIN LETTERS
lattices, using my papers on the lattice theory of crystals as his point of
departure. I know nothing of his subsequent fate. Arnold Berliner was
then known to every natural scientist as the founder and editor of the
journal Die Naturwissenschaften (The Natural Sciences) . He was an electrical
engineer by profession and occupied an important position at the A. E. G.
(General Electric Co.). Through his journal he exerted considerable
influence in scientific research circles. Extended correspondence with his
authors gave him a deep insight into their psychology, which he summar-
ised as 'Mimosa-like porcupines'. He lived to see the rise of Hitler, was
unable to go abroad because of his age, and took his own life.
After his brief reference to the great suffering of his mother and to the
small troubles in our house (my wife and children had gone down with
measles), Einstein mentions my lectures on relativity in Frankfurt. In
those days the inflation of the German currency had already gone so far
that the Institute's budget was not sufficient. We needed money for the
experiments into the quantisation of direction that Otto Stern, assisted by
Walter Gerlach from the Institute for Experimental Physics under
Wachsmuth, had just begun at the Institute. I myself weis also doing
some experimental work with beams of silver atoms. It occurred to me to
exploit the popular interest in Einstein's theory of relativity for this
purpose by organising lectures on the subject and charging an entrance
fee for the benefit of the Institute. There was a wave of enthusiasm for
Einstein's theory at the time, following Sir Arthur Eddington's announce-
ment to the Royal Society that Einstein's prediction about the deflection
by the sun of light beams from the stars had been confirmed by a British
expedition under his leadership. The lectures were well patronised and I
later wrote a book based on them.
The remarks concerning the physical chemists Fajans and Haber refer
to problems which are no longer of interest.
Einstein's statements about the quanta are more important. They
contain the early basis for his subsequent position on quantum mechanics.
He insists unconditionally on retaining a continuum theory, that is,
differential equations, and on obtaining quantum phenomena (discon-
tinuities) by redundancy in determination (more equations than unknowns) .
In this letter Einstein's political views are particularly informative. He
believed at that time, like many others, that the Bolshevik revolution
would mean deliverance from the principal evils of our time : militarism,
bureaucratic oppression, and plutocracy; and he hoped for an improve-
ment in conditions from the Communists, 'however comic their theories'.
I do not know if he had read much of Marx, Engels and Lenin's works.
Similarly he was not very familiar with political and economic writers
of a bourgeois leaning. At any rate, his hope for the Russian revolution
was based on his dislike, one could almost say hatred, of the ruling powers
24
BORN-EINSTEIN LETTERS
in the West, than on a rational conviction of the correctness of Communist
ideology. I emphasise this point because Communist writers often repre-
sent him as a supporter, or at least a precursor, of their doctrines.*
The theme of the Russian revolution frequently recurs in later letters. In
any C£ise, Einstein did not go to Russia but to America when he had to
leave Germany. He also, as far as I know, never visited Russia.
My wife never took seriously his suggestion to learn to experiment. That
kind of activity does not appeal to her.
The next letter must have been written in answer to the news from us that
I had obtained a chair in Gottingen. Peter Debye had been there during
the war as successor to my former teacher, Woldemar Voigt. During my
time as a private lecturer there were two professors ordinarius in the
department of physics, E. Riecke in experimental physics and W. Voigt
in theoretical physics. To attract Debye to Gottingen, an additional
extraordinariat was founded in 1914. Voigt took this so that Debye
could become Professor Ordinarius. After Riecke's death a professorship
extraordinarius was arranged for Robert Pohl. After the end of the war,
Debye decided to accept an appointment in Zurich. I was offered his
position in 1920. Einstein's reply to my question as to what we should
do was as follows.
14
5 March, igso
Dear Bom
It is difficult to know what advice to give. Theoretical physics
will flourish wherever j)iom happen to be; there is no other Born
to be found in Germany today. Therefore the question is really:
where do you find it more pleasant? Now when I put myself
in your position, I think I would rather remain in Frankfurt.
For I would find it intolerable to be assigned to a small circle
of self-important and, for the most part, unfeeling (and narrow-
minded) academics (no other social intercourse available).
Just remember what Hilbert had to endure with these people.
Something else must be taken into consideration. If Max should
be faced with the necessity of earning something on the side, a
possibility one cannot altogether rule out under the present
• For example, in his book Albert Einstein (Berlin, 1953), Friedrich Herneck
begins with the words: 'Albert Einstein, one of the greatest Germans after Karl
Marx . . . '. Einstein would have found that laughable.
25
BORN-EINSTEIN LETTERS
unstable economic conditions, it would be incomparably
better to live in Frankfurt than Gottingen. on the other hand,
life in Gottingen may well be more pleasant for the housewife
than in Frankfurt, and better for the children; but this I cannot
judge, as I do not know enough about conditions in Frankfurt.
And after all, it is not so important where one settles. The
best thing is to follow your instinct without too much reflection.
And besides, as a person without roots anywhere, I do not feel
qualified to give advice. My father's ashes lie in Milan. I
buried my mother here only a few days ago. I myself have
journeyed to and fro continuously - a stranger everywhere. My
children are in Switzerland under conditions which make it
a troublesome undertaking for me when I want to see them. A
person like me has as his ideal to be at home anywhere with his
near and dear ones ; he has no right to advise you in this matter.
I was very interested in your observations about ion mobility;
I believe the concept is right. In my spare time I always brood
about the problem of the quanta from the point of view of
relativity. I do not think the theory can work without the
continuum. But I do not seem to be able to give tangible form
to my pet idea, which is to understand the structure of the quanta
by redundancy in determination, using differential equations.
Hoping that this letter will find all four of you in good health
and spirits, I remain, with best wishes
Yours
Einstein
We finally decided in favour of Gottingen. I went to Berlin to negotiate
with the Ministry of Education, and explained to Ministerial Councillor
Wende that I felt unable to take on both the theoretical and the experi-
mental physics departments, but that I would be prepared to go to
Gottingen if a second chair were to be given to an experimental physicist
closely connected with me. Wende said that there was no position avail-
able, that the budget for the current year had already been allocated, and
that it was extremely unlikely that a new professorship would be approved
for the next financial year. To prove this, he gave me a great thick book
which contained the budget estimates of the Ministry, and left the room.
I studied the pages dealing with physics in Gottingen very carefully, and
discovered the following: There were two professorships extraordinarius
for experimental physics, one for Voigt, and the other for Pohl. one bore
26
i ;
BORN-EINSTEIN LETTERS
the remark: 'To be abolished on the death of the occupant'. Now Voigt
had just died; but this remark was not placed, as it should have been,
underneath the column dealing with his position, but below that of Pohl's
- who was very much alive. This meant that Voigt's position was available.
When Wende returned I gleefully pointed out the facts to him. But he
shrugged his shoulders and said that it was obviously a clerical error:
Voigt's position had only been provided for during his lifetime. However, I
insisted so forcefully on the letter of the text, that Wende eventually said
that he could not take the responsibility and would have to consult his
superiors. The Minister, Professor Becker, and the Ministerial Director,
Professor Richter, entered the room. When I had explained the position
to them, they laughed, and Becker said: 'Well, as the revolution is still
with us one can get away with that sort of thing. We will stand by the
wording. Please give us some suggestions for the second professor.' So I
accepted the chair; however, I did not become a full professor, but a
professor extraordinarius, like the soon-to-be-appointed experimentalist.
In the following year all three of us, Pohl, the new man and I, were pro-
moted to full professorships.
The choice of the 'new one' caused me a few headaches. I followed my
instinct for the essential requirements of the position, and proposed my
old friend James Franck. I very much admired his experiments into the
excitation of atomic line spectra by electronic collision carried out in
collaboration with Gustav Hertz; they confirmed the fundamental and
revolutionary assumptions of Bohr's atomic theory, and were therefore one
of the foundations of quantum physics. That I had made the right choice
was shown not only by the award of the Nobel Prize for 1925 to Franck and
Hertz, but also by the flowering of experimental physics in Gottingen
during the next twelve years (i 921- 1933). This was all therefore basically
due to a clerical error.
The letter ends with two remarks about physics. The first of these refers to
a paper of mine; the second, and more important, contains Einstein's
ideas about the nature of the quanta. My work on ion mobility had been
encouraged by the Frankfurt physical chemist R. Lorentz. This work was on
the fact that ions in aqueous solution, particularly monovalent ones,
exhibit a strange abnormality of movement : one would think that the
small ions must be the fastest, the large ones the slowest, but the opposite is
the case. The chemists explained this by the somewhat vague notion of
hydration. I was able to define this idea more closely using Debye's
theory, according to which the water molecules are dipoles. An ion
moving about amongst them causes them to rotate, the more forcefully
the smaller its radius. I developed this into a general theory which
can be termed hydrodynamics, by analogy with the modern magneto-
hydrodynamics. Also, one of my pupils, Lertes, was able to demonstrate
27
BORN-EINSTEIN LETTERS
experimentally one of the simple effects (the rotation of a sphere, filled
with water, in a rotating electric field) .
Einstein was occupied for many years with the idea of explaining quanta
within the normal framework of differential equations supplemented
in such a way as to contain a redundancy in determination. We frequently
talked about it. Although nothing ever came of it, he believed so strongly
in the value of the idea that he clung to it even after the discovery of
quantum mechanics. His rejection of the latter was probably connected
with this.
What makes this letter of special value to me is the light it throws upon
Einstein's life and personality.
A postcard from Berlin follows.
15
[Undated]
Dear Bom
By the same post I am sending you my last copy of the paper
you asked for. It got smudged in Teubner's printing works. I
am very pleased about your little book on relativity. Forgive
me for not having written in spite of all your kind messages.
That rogue of a postman is to blame. What is happening about
Gottingen ? Debye's paper is very good.
Best wishes
Yours
Einstein
Best wishes to your wife. I will not be able to return to
Frankfurt for some time. I hope we can meet here before
that.
My book on relativity arose out of the lectures I mentioned before which
I had delivered in Frankfurt. Einstein himself read the proofs and was
satisfied with my method of presentation. Three editions were published,
one after another. Now in 1962, after 44 years, it has been re-issued in a
modernised English language paperback edition, and a similar German
one appeared in 1964.
s8
BORN-EINSTEIN LETTERS
The following postcard from Kristiania is addressed to my wife, and
contains condolences on the death of her mother. She died at our house
in Frankfurt from the so-called 'Asian flu' which was raging all over
Europe at the time. Underneath Einstein's message there are a few lines
from his step-daughter Use.
16
Kristiania
18 April, igso
Dear Mrs Bom
The news of the bitter experience you had to go through has
touched me deeply. I know what it means to see one's mother
suffer the agony of death and be unable to help. There is no
consolation. All of us have this heavy burden to bear, for it is
inseparably bound up with life. However, there is one thing:
to unite in friendship, and to help one another to carry the
burden. We do, after all, share so many happy experiences that
we have no need to give way to pointless brooding. The old,
who have died, live on in the young ones. Don't you feel this
now in your bereavement when you look at your children? I
am here with Use, giving a few lectures to the students - a lively,
congenial crowd. Also the wonderful scenery and a truly
formidable heatwave, which one would not have suspected up
here.
Kindest regards to you and Max
Yours
Einstein
Dear Mrs Born, I want to tell you that I also feel with you in
your grief, and think of you with warmest sympathy.
Yours
Ilse Einstein
The first of my letters to have been preserved is addressed not to Einstein
himself but to his wife; it requires no commentary, nor does the letter
from me to Einstein himself which follows it.
29
BORN-EINSTEIN LETTERS
17
Frankfurt a.M.
21 June, igso
Dear Mrs Einstein • • cu •
I have sent your kind letter on to my wife in Leipzig, bhe is
staying there with her father. The last few weeks have been
very sad; I cannot describe it all to you in detail. Hedi collapsed
in the end, as a result of all the excitement, pain and over-
exertion. In spite of this she went to Leipzig, but had to stay in
bed and recuperate there. Apparently she is getting better now.
Just now a card arrived from Albert in Kristiania with the sort
of kind words only he can find; Miss Use also added a few
words.
I want to ask a favour of you. You know that I have written a
largish popular book about the theory of relativity. This will
also contain a short description of Albert's life and personality.
Could you possibly get the proofs from Dr Berliner, and read
through the biographical summary? It was written with great
sincerity, but I am not sure if the tone is right. There could also
be some factual errors. I would be most grateful for your un-
sparing criticism, and for any suggestions for alterations, I want,
above all, to avoid any suggestion of burning incense before the
idol. Albert does not need it anyway. Please let me have your
opinion as soon as possible.
Yet another favour. The galley proofs, corrected for the
second time, will be sent off to Albert within the next few days.
I am or course very much concerned that he should read or at
least look through the book before it is printed, and that he
should make suggestions for alterations. He is probably hard to
get at right now, and I will have to have the proofs back from
him very soon, because the printing must not be delayed.
Please make sure that he receives the proofs by the fastest
possible means, that he reads them as quickly as possible and
returns them to me by express post. I am most grateful to you
for selecting and giving us a picture of Albert for the book.
My little ones are sweet, darling little things, and surround me
with sunshine.
The question 'Gottingen, yes or no?' worries us a great deal.
30
BORN-EINSTEIN LETTERS
We are still undecided. If you know what we should do, please
let us into the secret.
With kind regards, also to your daughter
Yours
M. Born
18
Institute for Theoretical Physics
University of Frankfurt a.M.
Robert Mayer Str. 2
16 July, ig20
Dear Einstein
We will in all probability go to Gottingen, that is, if Franck is
offered the chair and accepts; the faculty has put him forward.
Now the question of my successor becomes urgent. Schonflies
wanted to write to you and to ask for your expert opinion. I
would, of course, like to have Stern. But Wachsmuth does not;
he said to me, 'I think very highly of Stern, but he has such an
analytical Jewish intellect,' At least it is open antisemitism. But
Schonflies and Lorenz want to help me. Wachsmuth has
proposed Kossel, which is very crafty of him; for nothing can
be said against him, except perhaps that he knows no mathe-
matics, but that is hardly a fault. Stern has raised the standard
of our little Institute and really deserves recognition. I do not
need to explain his value to you, of course. Then Lenz and
Reiche are under consideration, and perhaps outsiders as well.
Embarras de richesse! I have asked Laue to give his opinion;
perhaps it would be best if you were to talk to him about it, so
that your verdicts do not clash.
I am being very lazy at the moment and hardly do any work;
the only experiments I pursue with any eagerness are those on
the free path lengths of silver atoms. My assistant is very good at
her job. We have now constructed the apparatus, but the
measurements will unfortunately not be started before the holi-
days. We depart for Sulden in the Southern Tyrol (Italy) on
August 6th; I am looking forward impatiently to getting away
from it all completely again, and seeing beautiful things. My
wife has recovered a little from the hard time after the death of
her mother. We often take trips out, which does her good. To-
morrow we are going to the Rhine, where she has never been
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BORN-EINSTEIN LETTERS
before. The children are well. Unfortunately the decision about
Gottingen drags on endlessly; we have not yet found a flat there.
My wife will go there next week and try to find accommodation.
Are you coming to Southern Germany at all? We would so
much like to see you and talk to you.
With best wishes to your dear wife and to the young ladies
Yours
Max Born
The following letter, the first of my wife's to Einstein to be preserved, is
particularly warm and profound and was perhaps the stimulus for his
keeping our letters from that time onwards.
19
Frankfurt
31 July, igso
Dear Mr Einstein
Max has asked me to thank you very much for your letter;
your judgment is especially important to him, because
Wachsmuth is agitating against Stern on antisemitic grounds.
Epstein, as a Jew and a Pole, will therefore be even more
strongly rejected. Max is working very hard; his experiment
(atomic diameter of. . . . ?) is under way at last, and he stays at
the Institute until eight o'clock at night making measurements.
We are very happy that you will be coming to Nauheim, and I
hope that you will stay with us for a few days. I am now - after
my mother's death - so much in need of those true relationships
of the spirit which are left to me. The further the hour of her
death Hes behind us, the stronger is my longing for the departed;
the darker and more incomprehensible seems the enigma of
death. The ending of such a strong personality and the sudden
extinction of life is such a tormenting problem that one wonders
how one is able to live without being constantly troubled by it.
But it teaches one to live more consciously, to feel more deeply
and strongly and to hold on to what one possesses. If one did not
do this, one could sink without hope into the bitter and pessi-
mistic attitude of mind of Widman's Maikdfer-Komodie; do you
32
BORN-EINSTEIN LETTERS
know it ? Its images constantly haunted my imagination in the
first bitterness of my grief. one lives under the illusion that it is
forever May, and that the whole world is constantly filled with
young, juicy and delicious greenery, put there just for one's own
use, and then all of a sudden and incredibly fast it happens, and
one finds oneself lame and weary of life in the mud of a rain-
soaked road. So I thought, well, I am now in the mud, but I
can see that it is still May, after all, and I must not allow myself
to be pulled down.
We have now decided for Gottingen, but we have as yet no
prospect of accommodation there and may possibly remain here
for the winter as the Ministry is still dawdling.
Something else: Max wants to stay in Nauheim for two days
so that he will be able to spend the evenings with his colleagues.
Would you like to do that as well ? Or would you rather travel
there from here each day (one hour's journey) ? Shall we book a
room for you in any case and, if so, for how many days ? But
you must stay with us before and afterwards, whatever happens.
If you do not, God help you ! We are going to Sulden, Sulden-
hotel, Tyrol (Italy), on August 6th, via Munich, Merano and
Bolzano, complete with passports and lire. Your wife was going
to write to me when your are due to go to Southern Germany;
how is she, and how are your daughters ?
With best wishes to you all
Yours sincerely
Max and Hedi Bom
The next letter from my wife initiated a discussion between her and Einstein
about 'publicity', his attitude to attack or glorification. The first of these
letters shows that we, and Hedi particularly, were not in agreement with
him about his reaction to that kind of irritation. We still believed in the
'secluded temple of science', as Hedi said. From this beginning a real
conflict developed, as the following letters show.
33
BORN-EINSTEIN LETTERS
20
Cronstettenstr. g
8 September, igso
Dear Mr Einstein
When are you coming to Nauheim, and on which days are we
going to have you to ourselves? We will tell no-one of your
presence and, if you prefer, you can remain incognito. Paulchen
Oppenheimer seems to be away still. Please send us a postcard
about your plans.
We are extremely sorry to hear about the unpleasant rows
that are worrying you. You must have suffered very much
from them, for otherwise you would not have allowed yourself
to be goaded into that rather unfortunate reply in the news-
papers. Those who know you are sad and suffer with you,
because they can see that you have taken this infamous mischief-
making very much to heart. Those who do not know you get a
false picture of you. That hurts too. In the meanwhile I hope
you are like old Diogenes again and smile about the beasts
thrashing about in your barrel. That people can still
disappoint and irritate you to the point where it affects your
peace of mind just does not fit my image of you, which I
keep on the private altar of my heart. You could not have
withdrawn from the rough and tumble of ordinary life to the
'secluded temple of science' (see your talk to Planck) had
you been able to find the same illusions, the same happiness and
peace in your fellow-man as in your temple. So if the filthy
waters of the world are now lapping at the steps of your temple,
shut the door and laugh. Just say, 'After all, I have not entered
the temple in vain.' Don't get angry. Go on being the holy
one in the temple - and stay in Germany! There is filth every-
where - but not another female preacher as enthusiastic and
self-opinionated as your affectionate friend
Hedi Bom
P.S, Now look here! If you or Elsa, to whom best wishes by the
way, don't get in touch with us soon, I'll join the anti-relativity
league, or set up in competition with you.
You simply must read The Home and the World by Rabindranath
Tagore - the finest novel I've read for a long time.
34
BORN-EINSTEIN LETTERS
21
g September, igzo
Dear Boms
Don't be too hard on me. Everyone has to sacrifice at the altar
of stupidity from time to time, to please the Deity and the human
race. And this I have done thoroughly with my article. This is
shown by the exceedingly appreciative letters from all my dear
friends. A witty acquaintance said the other day : 'With Einstein
all is for the sake of publicity; the Weyland G.m.b.H. is his
latest and most cunning trick'. This is true, or at least partly so.
Like the man in the fairytale who turned everything he touched
into gold - so with me everything turns into a fuss in the news-
papers : suum cuique.
In the first moment of attack I probably thought of flight.
But soon my insight and the phlegm returned. Today I think
only of buying a sailing boat and a country cottage close to
water. Somewhere near Berlin.
I'll arrive at your place around the i8th, if you can put up
with me. However, if I am expected to live in Nauheim for the
duration of the scientific meeting, would you please see to it, dear
Born, that we are staying close together. I shall not book any-
thing from here, as you can judge better what is the best thing
to do. But I would also like to stay with you for a little while, if
possible, so that I can have a chat with my charming correspon-
dent. Writing does not seem to be as effective, because of the
annoying blotchiness of my ink. Else is also coming, but will
stay with the Oppenheims.
We will have to be in Stuttgart on the 28th, where I am going
to lecture in aid of a public observatory. Afterwards, we are going
to Swabia, where my boys have been asked to meet me.
With kindest regards
Yours
Einstein
The important meeting of the Association of German doctors and natural
scientists took place in Nauheim in September 1920. Einstein lived with
us in our house on Cronstetterstrassc; we travelled to Nauheim each
35
BORN-EINSTEIN LETTERS
morning and returned in the evening. Nauheim was the scene of an angry
encounter between Einstein and his opponents, whose motives were by
no means purely scientific but strongly mixed with antisemitism." In the
physics section, Philipp Lenard directed some sharp, malicious attacks
against Einstein, which were undisguisedly antisemitic. Einstein was
provoked into making a caustic reply and I seem to remember that I sup-
ported him. Einstein returns to this incident in a later letter (26), where
he regrets that he allowed himself to lose his temper and reply in anger.
From then on Lenard carried out a systematic persecution of Einstein.
He invented the difference between 'German' and 'Jewish' physics. He
and another important physicist, Johannes Stark, who both later received
the Nobel Prize, became leading scientific administrators under the Nazis
and were responsible for the removal of all Jewish scholars. It was in
Nauheim on this occasion that the outlines of the great danger of anti-
semitism to German science first appeared.
22
Frankfurt a.M.
2 October, igso
Dear Einstein
To judge by your card, Hechingen must be a charming, sleepy
little place; just right to calm down the agitation which, to our
regret, you were forced to endure here and in Nauheim. We
do not want to disturb your slumbering consciousness with
effusive letters; sometimes it is a good thing if one's friends are
removed from one's consciousness, and I have the feeling that
now is the time for us to disappear. After all, there is really
nothing more obtrusive than 'suffering with someone' ; it is an
encroachment on a friend's life, a baring of the soul, of which one
is ashamed afterwards.
But before we disappear from sight, like Punch, we have two
other requests, and I would like to charge you, dear Mrs Elsa,
to remind your husband of them from time to time. i. That your
husband should write to Mrs HofF, Giintersburg AUee 57. This
would not really be a waste of time, as there are few people like
her. 2. My husband feels an inclination to slay the golden calf
in America and to earn enough through lecturing to build a
small house in Gottingen to his own requirements. Should you,
by any chance, have the opportunity to recommend someone to
36
BORN-EINSTEIN LETTERS
lecture over there, please suggest Max. He would be able to go
there in February, March and April, and appease his longing
for Broadway at the same time (I can't understand this love of
his, but forgive him for it.)
And now without further ado your Punch and Judy bow
out,
Max and Hedi Bom,
until you happen to remember them in their toy chest once again.
Why I am supposed to have 'longed for Broadway' is incomprehensible
to me. Anyway, the journey to America did not materialise then.
The following letter concerns the problem of publicity that I have already
referred to. In Nauheim, Einstein's enemies had reproached him with
self-advertising, and with allowing his fame to be broadcast. We had
already discussed this with Einstein during our talks every evening, after
returning from Nauheim. We found that he was far too accommodating
towards journalists, possibly because his wife was understandably pleased
about his popularity.
Soon a new incident required urgent attention. An author and journalist,
who had called on Einstein and had won his and especially Elsa's sympathy
as a poor Jew, wanted to write and publish a book called Conversations with
Einstein. We advised Einstein not to allow it, but without success. Following
is my wife's spirited reaction to this piece of news ; the letter was written
in Leipzig, where she was visiting her parents, and thus without my
knowledge. The letter is very long and detailed; I have abbreviated it
considerably.
23 Leipzig
7 October, IQ20
Dear Mr Einstein
Today, a friendly but serious word with you. I would much
prefer not to have to disturb you during your week's holiday,
but it is a matter of great consequence which has troubled your
friends ever since Nauheim :
You must withdraw your permission to X for the publication of
the book Conversations with Einstein, and what's more at once,
and by registered letter. And, whatever happens, it must under
37
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no circumstances be published abroad. I wish I had the eloquence
of an angel, so that I could make the consequences clear to you.
Quite by chance ... [a book by X] fell into my hands here;
the level of this book disgusts me so much that I wrote the enclo-
sed somewhat malicious comments, which I swear I am going
to publish unless you withdraw your permission immediately.
And I have a lot more to spill out, if it is a question of saving
the honour and respect of a friend. I am not painting too black
a picture.
[There follows a list of titles of the books by Mr X.]
That is good enough in itself. . . .
Now the contents. The man has no idea of the seriousness of
your personality, of what is important and valuable to you and to
us; otherwise he would neither have written the book nor
exploited your kindheartedness to wrest your permission from
you. Your 'conversations' will therefore be conducted at a very
low level. The gutter press will get hold of it and paint a very
unpleasant picture of you. And afterwards you will be quoted
all over the place, and your own jokes will be smilingly thrown
back at you, to show that people have read the book. Verses will
be composed in your honour; a completely new and far worse
wave of persecution will be unleashed, not only in Germany but
everywhere, until the whole thing will make you sick with disgust.
And how could we, your good friends, then defend you ? 'But
look here -Mr Einstein, your "modest friend", surely gave
permission himself.' Then it would be useless for us to protest
that you gave permission out of weakness and good nature
Nobody would believe it. (This is confirmed by my father, who
studied with X and has told me a great deal about him.) The
fact is simply that a man in his early forties, a comparatively early age,
gave permission to an author to record his conversations. If I did not
know joM well, I certainly would not concede innocent motives
to any other human being given these circumstances. I would
put it down to vanity. This book will constitute your moral
death sentence for all but four or five of your friends. It could
subsequently be the best confirmation of the accusation of self-
advertisement.
We, your friends, are deeply shocked at this prospect. This
book, if published anywhere at all, would be the end of your
peace, everywhere and for all time. . . .
38
BORN-EINSTEIN LETTERS
Please reassure us soon about this worry which pursues us
day and night. Max has just written to me today: 'I have just
had an express letter from Freundlich with X's answer, which
is, of course, in the negative. I do not know what to do. I would
so much like to discuss it with you; every day I have worries of
this kind.'
Please, dear friend, quickly relieve our worries, and do not
refuse our advice and request. I shall never talk to anyone about
this business, for I have heard enough how much you dislike
it when women meddle in your affairs. 'Women are there to
cook and nothing else'; but it sometimes happens that they
boil over [a play on words in German, where 'cooking' is
'Kochen', and 'boiling over', 'Ueber-kochen'] .
Yours
Hedi Born
24
Frankfurt a.M.
I J October, igso
Dear Einstein
The enclosed pages from the bookseller's financial paper have
come to me from various people. Comment is superfluous.
It seems that you are less excited about it than your friends. My
wife has already written to you saying what I think about this
affair. (She is already regretting that she, too, has tried to turn
your name into gold by sending me to America; women, poor
creatures, carry the whole burden of existence, and grasp at
any relief.) You will have to shake off X, otherwise Weyland
will win all along the line, and Lenard and Gehrcke will
triumph.
According to the advice of experts, the following is best: write
strongly to X, saying that you can not, after all, agree to the
publication of the conversations, because you have been accused
of publicity seeking, and in view of the fact that the advertise-
ment in the bookseller's financial paper has offered a useful new
lever to your enemies. If X refuses, as is to be expected, you
will obtain a provisional order from the Public Prosecutor's
Office against the appearance of the book, and make sure that
39
BORN-EINSTEIN LETTERS
this is reported in the newspapers (or we could do this). I
shall send you the details of where to apply soon. The experts
have established that, just as one can no more print another
person's photograph without his permission, thoughts expressed
during conversation may not be published. This is a better
method than having the proofs sent to you and reading them,
for you would then have no responsibility for the book whatever.
If, on the other hand, there were a statement in the introduction
that you had read the proofs and approved of them, all the
muck thrown up by the book would fall on you. I implore you,
do as I say. If not: Farewell to Einstein! Your Jewish 'friends'
will have achieved what that pack of antisemites have failed to
do.
Forgive the officiousness of my letter, but it concerns every-
thing dear to me (and Planck and Laue, etc.) You do not
understand this, in these matters you are a little child. We all
love you, and you must obey judicious people (not your wife) .
Should you prefer to have nothing further to do with the
whole business, give me written authority. If necessary, I will
go to Berlin, or even to the North Pole.
Yours
Born
25
// October, igso
Dear Bom
Your wife has sent me an urgent letter about Mr X's book. She
is objectively right, though not in her harsh verdict of X. /
have informed him by registered letter that his splendid work must not
appear in print.
With kindest regards to you both
Yours
Einstein
1 would like to thank your wife most sincerely.
40
BORN-EINSTEIN LETTERS
Apparently my wife had succeeded after all in making clear to Einstein
the danger threatening him if the book were to be published. A postcard
which followed from Holland on 26 October confirms this.
26
[undated]
Dear Bom
Have categorically forbidden publication of X's book. Ehrenfest
and Lorentz advise against legal proceedings, as they would
only serve to increase the scandal. The whole affair is a matter
of indifference to me, as is all the commotion, and the opinion
of each and every human being. Therefore nothing can happen
to me. In any case, I have used the strongest means at my
disposal, apart from legal ones, particularly the threat that
I would break off our relationship. However, I still prefer X
to Lenard and Wien. The latter two squabble because of a
passion for squabbling, while the former does it only to earn
money (which is, after all, better and more reasonable). I will
live through all that is in store for me like an unconcerned
spectator and will not allow myself to get excited again, as in
Nauheim. It is quite inconceivable to me how I could have lost
my sense of humour to such an extent through being in bad
company. Lorentz yesterday mentioned your lattice equili-
brium in his lecture; I was also mentioned! He is a man one can
admire 1
Kindest regards to you and your wife.
I am having a very pleasant time here in Leiden. Weiss and
Langevin are also here.
H. A. Lorentz was Professor of Theoretical Physics in Leiden, and in those
days was held to be the foremost man in his field. He had given the classical
theory of electrons the form considered final at that time. Ehrenfest, who
was born in Vienna and educated there in the school of theoretical physics
(with Boltzmann and Hasenohrl, inter alia) went to Russia and married
an extremely gifted Russian woman physicist. He became widely known
for his outstanding works of criticism, particularly in the field of statis-
tical mechanics (partly in collaboration with his wife, Tatyana), his
41
'
BORN-EINSTEIN LETTERS
unusual talent for teaching and his sparkling wit. When Lorentz retired
from his chair, he pushed through Ehrenfest's appointment as his successor.
The two people mentioned at the end of the letter, Weiss and Langevin,
were French physicists, the first one from Strasbourg, the second from
Paris. Both carried out fundamental research into magnetism; Langevin
had important achievements in other fields as well.
Einstein's clearly expressed indifference to the opinion of everyone else is
as characteristic of him as the judgment that he thought more of the
motives of the journalist than of those of two outstanding physicists.
With this card, the X affair is substantially at an end, though it is still
mentioned from time to time in the letters which follow. It may well be
asked whether there is any justification for giving so much space to it in
this correspondence. In fact my wife's inflammatory letter (No. 23) was
originally considerably longer. I have left out the second half, which
contains some legsil advice from my wife's father, as well as grotesque
descriptions of the possible consequences of Einstein's compliance. What
remains is sufficient to show why we, with all respect for Einstein's superior
intellect, could presume to criticise his behaviour in every-day life.
The contemporary reader may well think 'much ado about nothing'.
Nowadays the kind of pubhcity we fought against is commonplace, and
spares no-one. Every one of us is interviewed and paraded before the
general public in the papers, on radio and television, or written about in
pamphlets and books. Nobody thinks anything of it.
In those days it was different. only when great discoveries were made did
brief, factual reports appear in the newspapers. I can remember the way in
which Roentgen's discovery in 1896 was reported by the press; he himself
was hardly mentioned. As far as I am concerned, I myself committed a
minor offence against the rules in my book Einstein's Theory of Relativity.
The first edition of 1920 contains a photo facing the title page, and at the
end a short biography of Einstein in which I described not only his
scientific achievements but also his personality. Immediately after publi-
cation I received a letter from Max v. Laue, in which he wrote that he
and many other of my colleagues objected to the photo and biography.
Such things did not belong in a scientific book, even when addressed to a
wider audience. Impressed by this, I left out both these personal details
from the new editions published soon afterwards. I was possibly particularly
sensitive about Mr X's plan to compile a book from interviews with Einstein
about all kinds of topics, not only scientific ones, because my own much
more harmless attempt to describe the person of the author in my book
on relativity had been rejected by my colleagues.
But what chiefly caused me and my wife to object to this business was
its connection with antisemitism. Einstein's theories had been stamped as
'Jewish physics' by colleagues who did not understand them. And now a
42
BORN-EINSTEIN LETTERS
Jewish author, who had already published several books with frivolous
titles, came along and wanted to write a similar book about Einstein. It is
understandable that this upset us greatly. Einstein probably did not
consider any of this to begin with. He wanted to show his gratitude
towards X, who had helped him while he was ill in Berlin during the period
of wartime deprivation. But he saw our point of view and did everything to
prevent publication of the book. He did not succeed. A copy of it Ues in
front of me. I have browsed through it a little, and find it not quite as bad
as I had expected. The scientific part is primitive and contains frequent
misunderstandings. Otherwise, however, it contains many rather amusing
stories and anecdotes which are characteristic of Einstein. It is quoted in
more recent books about Einstein.
Our agitated correspondence about this affair was thus pointless in the end.
Large-scale movements such as antisemitism and the prevalence of
pubUcity, etc., necessarily run down in accordance with the law of
determinism so often quoted by Einstein in this connection.
27
Frankfurt a.M.
28 October, igzo
Dear Einstein
I am very glad that you have taken energetic steps against the
book by X. only the future will show whether they are enough
to prevent any trouble. The main thing is that you are deter-
mined not to have your peace disturbed in future. Hov^rever,
when all is said and done, you are not the only person involved,
as we, who venture to call ourselves your friends, would also be
affected by the stench and, I fear, would be unable just to hold
our noses as you have done before. You can simply flee to
Holland, but we are settled in the territory of Weyland, Wien
and company.
I am writing to you quickly in Holland, as I want Mr Fokker's
address. He has sent me a fine paper in which he expiates one
of the sins of my youth. The address was actually on the envelope
but, as I was ill in bed with asthma and unable to be on my
guard, my children destroyed the envelope. I would very much
like to thank Fokker ; Ehrenfest will know where he lives.
Get Ehrenfest to show you a copy of Boguslavski's letter
which I sent to him, and think how the poor fellow can be
43
BORN-EINSTEIN LETTERS
saved. Planck said that he was willing to help, but thought that
nothing could be done officially in Berlin. Now I am negotiating
with Hilbert for him to invite Boguslavski through the Wolf-
skehl Foundation.
I am glad that things are going so well for you in Holland.
But you must not be angry with me if as a result of recent events
I doubt you as a judge of human nature to the extent that I do
not share your admiration for Lorentz. In Lenard and Wien
you see devils, in Lorentz an angel. Neither is quite right. The
first two are suffering from a political illness, very common in
our starving country, which is not altogether based on inborn
wickedness. When I was in Gottingen just recently I saw
Runge, reduced to a skeleton and correspondingly changed
and embittered. It became clear to me then what is going on
around here. on the other hand, Lorentz: he even refused to
write anything for Planck's sixtieth birthday. I take that very
much amiss. You can tell him so quietly. one can disagree with
Planck, but one could only doubt the honesty and nobility of
his character if one had none oneself. Lorentz is apparently
more afraid of losing his well-fed friends amongst the Allies than
he cares about justice. I am not taken in by his using my lattice
calculations in his lectures. This is not the only thing I hold
against him, but then I am not writing just to slander someone.
However, I must confess that I find your association with
Lorentz, Ehrenfest, Weiss and Langevin far happier than the
intercourse with the author of '.
You will also have met Chulanovski from Russia there;
please ask him for information about G. Krutkov, who has sent
me a paper of his about adiabatic invariants, which I thought
excellent. He must be an outstanding theoretician; I had never
heard of him before.
My wife sends her best regards. She is driving herself very
hard, as our cook had to be dismissed a few weeks ago for
thieving and deceit (countless times). Also, miserable creature
that I am, I was confined to bed with asthma until yesterday,
and had to be nursed. The children are well.
With kindest regards
Yours
Max Bom
44
BORN-EINSTEIN LETTERS
Boguslavski was a Russian pupil of mine, extremely talented and an
attractive and worthwhile person. He suffered from tuberculosis of the
lungs, and as he came from a tided feimily he suffered great hardships
during the revolution. Eventually he turned to me for assistance, and I
tried to do something for him with the help of Planck, Einstein and others.
28
Institute for Theoretical Physics
of the University of Frankfurt a.M.
Robert Mayer St. s
8 December, igso
Dear Einstein
Enclosed is the circular of the Mathematische Annalen. As I have
never received any paper intended for this publication, and
know nothing about it, I have not added any remarks.
I also enclose a copy of a letter from Russia, from my pupil
and friend Boguslavski. The letter arrived some time ago. The
contents may interest you. It can be seen that an attempt should
be made to invite the poor man (who has TB as well) to Germany,
to prevent him from starving to death. I have already tried
everything possible, first Planck, then Klein and Hilbert in
Gottingen, whom I asked to get the Academy to send an
invitation of some sort to B. But they all refused; to use Hilbert's
ｅxpression, they want nothing to do with 'foreign polities'.
Perhaps you can think of a way. Some of what Boguslavski
writes about his work is clearly nonsense, but this is probably
due to his piteous condition; he is a fine intelligent man. By the
way, a mutual friend, Dr Bolza from Wurzburg, has tried to
send a few things to Boguslavski through the Red Cross; with
what success I do not know.
While on this subject: some time ago I sent you a letter from
Epstein, who was asking for help. In the meantime I have
received an answer from G. N. Lewis in America, to whom I
had written about this matter. He has created a position for
Epstein at the University of California, Berkeley, and offered it
to him. But I have not heard from Epstein whether he intends to
accept or not; perhaps the Swiss are keeping him. An attempt
to bring him here as my successor has been wrecked by the
opposition of the faculty. I did not succeed in having Stern
45
BORN-EINSTEIN LETTERS
made first choice either, because Wachsmuth wanted Madelung.
Stern is now second choice, Kossel third.
As regards science, I have tried a number of things without
getting enthusiastic about anything. What attracts me most is a
proper theory for the irreversible processes in crystals, once
suggested by Debye. But I cannot find reasonable general
formulations. The measurements in the Institute on free path
lengths are going quite well ; the main thing was to keep the gas
pressure constant for the thirty-minute vaporisation of the
silver; we are now doing it to 5 per cent. However, we have not
yet completed an exact measurement of the thickness of the
silver deposit, as we had to get together the optical equipment
bit by bit. Lande, who was recently at the conference in
Heidelberg, told me yesterday that Ramsauer {alias Lenard)
had severely criticised my book on relativity because I had
given the impression that Maxwell's proposal (for determining
the absolute movement of the solar system from the eclipse of
Jupiter's satellites) had in fact been carried out with a negative
result. I can see that the criticism is not unjustified, and there-
fore expect vociferous attack by Lenard or one of his associates.
Healthwise I have been bad for several weeks, as may have
been apparent from the bilious tone of my last letter to Holland.
But I am now fairly well again, although the political situation
depresses me more than I like to admit to myself.
With kindest regards
Yours
Bom
Saratov
18 August, igso
Dear Bom
At last I have the opportunity to send letters out of the country,
and I am using it to write to you. For almost two years now I
have been professor in Saratov at the local University. Although
I accepted a chair in Moscow as much as a year and a half ago,
I dare not return there for fear of starving to death. But this
year even we, here in the South-East, are going to have a bad
46
BORN-EINSTEIN LETTERS
time, as the harvest has been extremely poor. Now I dream of
being able to go abroad once again; my scientific interests, as
well as my state of health, demand it. Life in the socialist Eden
does not seem to be meant for me. I have been feeling ill for
almost six months now, and am staying in a kind of sanatorium.
Scientific life has almost ceased to exist here. No journals are
being published, neither are there opportunities to have
anything printed. A mimimum of scientific work is being done;
anyone wanting to do it would soon starve. Furthermore, for
the last three years we have not received any foreign journals.
Therefore I now have very little idea of what is currently being
thought about in scientific circles. I myself have, of course, done
much during these last few years, and would like to be able to
talk about it. As recently as last spring I was still working,
and had just started to write a small book. However, now I feel
so ill that for the time being I am obliged to give it all up. In my
book I intended to give a fairly comprehensive description of
the movement of electrons in different kinds of electromagnetic
fields. The second part of the book was to contain an outline of
the theory of atoms. I have investigated several types of move-
ment presumably for the first time.
Some time ago I had the following idea which I have not yet
been able to verify. The nucleus of heavy atoms need not be
a charged point. By developing the potential of the nucleus as
powers of ijr and retaining only the term with ijr one can treat
the nucleus as a positive point charge and a dipole. The problem
of the movement of the electron in the field of this nucleus can
be rigorously solved. The projection of the electron path on the
unit sphere is then the orbit of a spherical pendulum, where
gravity acts parallel to the dipole axis. The elliptical integral
representing the action (quantum integral) can be developed
as a series of powers of the dipole moment, and one can thus
determine the position of the spectral lines in the presence of this
dipole. The solution can be most easily written with the help of
the partial differential equation of Jacobi; the variables can be
separated for polar coordinates.
Lately I have been much interested by the following train of
thought; I still regard it as important, although I have not yet
obtained positive results. Thermodynamics and electrodynamics
alone are insufficient for developing a radiation formula.
47
BORN-EINSTEIN LETTERS
because radiation pressure ought to be used only integrally
(for all frequencies) to obtain the work done. Now we have
substances which absorb (and reflect) selectively, and one can
probably use as an ideal limiting conception a piston which
completely reflects the radiation of a certain spectral range but
allows all others to pass through. Such a piston would separate
the radiation of difierent frequencies in the same way as a
semi-permeable membrane separates molecules of different
kinds. This concept certainly contains nothing to contradict
the fundamental laws of electrodynamics and thermodynamics.
But with the help of such a piston and a Planck coal dust
particle it is easy to construct a perpetuum mobile of the second
order. And this can be done for any radiation law. Now a
radiation law can be regarded as a definition of the temperature
concept, since the temperature can be derived from it as a
function of the mechanical quantities 'energy' and 'frequency'.
How is temperature to be defined so that the contradiction of
the second law of thermodynjunics can be avoided? The
answer is: the temperature is a monotonically increasing
function of frequency only (independent of the energy). For
instance, T= ay. All this is absurd but very attractive.
I cannot write much. I only wish I could talk to you in
person. Do try to get me an official invitation to Berlin to give
a few lectures there. The invitation will have to look as official
as possible, so that I can attempt to obtain a passport for leaving
the country with it. You would be rendering me a great service,
as I am in urgent need of a few months recuperation. Einstein
can help you forward the invitation to Russia. It should be sent
either to my Moscow address, Pokrova, Litde Uspanki 8, or here
(University of Saratov) .
It is difficult to describe our living conditions. As a Professor I
earn approximately 1.5 x lo* roubles per month. With this one
can buy approximately one pound of bread per day. Everyone
is allowed to buy only 1 50 g of bread at the controlled price.
This is, moreover, practically the only thing one does get.
Everything else has to be bought at 'speculative' prices. Trading
in the normal sense, as is well known, does not exist here. There
are only secret 'deafings' whereby one must procure all the
necessities. one pound of butter costs approximately 2 x 10'
roubles, sugar somewhat more. A pair of boots costs 3-6 x 10*
48
BORN-EINSTEIN LETTERS
roubles, etc. one frequently meets people who spend their entire
month's salary in a single day. How this squares with the
continuity equation of money is extremely puzzling. one must
assume, however, that the money in circulation is confined to the
official issue, as the forging of paper currency would hardly
be a paying proposition. Firewood costs about 100 roubles per
kilogram! But very few people are able to pay that much.
Therefore everybody has to cut their own wood. Generally
speaking, life for the majority of people is quite unbearable.
Winter will soon be here again, and we can look forward to
enjoying room temperatures of 4-5°.
A congress of physicists is due to begin in Moscow in ten
days' time. Unfortunately I will be unable to make the journey
because of the state of my health.
If you see any of my Gottingen friends, please give them my
regards. I would particularly like to see Bolza and Karman
again. Please write to Debye and tell him that I am still alive,
and ask him please to continue to look after my cases of books
at the Physics Institute. I am not writing to him myself, as I
cannot at present send more than two letters out of the country.
Give my regards to your wife. You are all fortunate people.
You cannot imagine the amount of misery which surrounds one
here. Look after yourself.
Yours
S. Boguslavski
(Reply through Prof. Dr M. Vasmer, Dorpat, Estland, Teichstr.
19)
Gilbert N. Lewis was a distinguished physical chemist in Los Angeles,
whom I got to know through Fritz Haber. When I later visited California
(1926), both Lewis and Epstein gave me a very friendly reception.
The following letter from Einstein begins with a return to the formal
('Sie') mode of address. This may be connected with the morally presump-
tuous tone of my previous letter (which I later attributed to my illness).
Einstein's reference to 'burying the hatchet' had nothing to do with this,
but with an exchange of letters between my wife and his, of which I
knew virtually nothing. Einstein chivalrously defended his wife. More of
this in my next letter.
49
BORN-EINSTEIN LETTERS
29
30 January, igsi
Dear Born
Today I write principally because I want solemnly to bury
the hatchet. I have had a tiff with your wife for the sake of
mine, mainly because of a rather exaggerated letter which she
wrote to her. But a lot has happened since and it is wrong for
men like us to lose contact over such a trifle. X's unfortunate
opus has appeared without any earth tremors (so far) and
without my having read any of it.
I do not know of anything I could do for Boguslavski, much
as I pity him; what he says about the theory of radiation is
curious. It seems to be based on a misunderstanding of what
can be done with partially reflecting screens.
I have only thought up some trivialities lately. The best of
these is an experimental query regarding the radiation field.
The statistical laws of radiation make one doubt whether
Maxwell's field really exists in radiation. The mean field strength
in high temperature radiation is of the order of 100 volts/cm;
where such a field exists, it must produce a perceptible Stark
effect on emitting and absorbing atoms. But if the other distri-
bution of the field's effect according to the statistical laws of
radiation holds, then the effect should occur only on a few
molecules, but very strongly so that one would observe a quite
weak difiuse effect next to a sharp line. I shall investigate this
with Pringsheim; it is not easy. Have a look at the short paper
by Byk on the law of corresponding states and quanta in the
Phys. Z^itschrift - it is a nice piece of work. Your little book on
relativity has enabled many people to understand the subject.
E.g. half the Foreign Office are said to have pored over it (now
nothing can go wrong with it).
You need not be so depressed by the political situation. The
huge reparation payments and the threats are only a kind of moral
nutrition for the dear public in France, to make the situation
appear rosier to them. The more impossible the conditions, the
more certain it is that they are not going to be put into practice. I
hope you are in good health. With kindregardstoyouandyourwife
Yours Einstein
50
BORN-EINSTEIN LETTERS
This letter contains several scientific observations. Above all, there are
doubts about Maxwell's radiation field, which cannot be reconciled with
the statistical laws of radiation. In one of his earliest papers, Einstein had
shown that, according to one of Lorentz's calculations, the wave theory
of radiation implies that the mean square fluctuation of radiation energy
is proportional to the square of the mean energy density. Einstein's
quantum theory of light, which represents radiation as a kind of gas
consisting of photons, shows that in an ideal gas the mean square fluc-
tuation is proportional to the mean energy density itself. According to
Planck's empirically obtained radiation law, however, the mean square
fluctuation is exactly the sum of these two terms. This means that radiation
consists of neither waves alone nor pardcles alone but of both at the same
time. This was the famous and notorious 'duality' which always worried
Einstein from then on, and of which much will be said in these letters.
He was never willing to allow that this, his own result, was final. Here he
wants to remove Maxwell's field with the consideration that the Stark
effect of the temperature radiation field is large enough to enable one to
decide between the particle theory and the wave theory. Whether he ever
really carried out the experiments planned with Pringsheim, I do not know.
The remark suggesting that half the Foreign Office had pored over my
relativity book must have caused me a great deal of amusement at the
time.
30
Frankfurt a.M.
12 February, igzi
Dear Einstein
I should have liked to reply to your kind letter at once, but I had
to go to Gottingen suddenly, as there was some hope of accommo-
dation there (a hope which may, by the way, be fulfilled). I know
about only part of the unpleasant correspondence between our
wives, as my wife decided one day not to take me into her
confidence any longer. All the same, I feel guilty, as I did not
prevent her from writing sharp and hard words. I have taken
the matter very much to heart, more so than anything else I
can remember. For everything connected with you affects me
deeply. Believe me, if it were not so, I would not have been so
agitated about the X affair. The earth, as it happened, was not
exactly shaken ; but it is not very pleasant to see the advertise-
ments on every hoarding. Well, no more of this. I will probably
51
BORN-EINSTEIN LETTERS
get upset again over these relationships with the world, as my
own time scales do not seem to apply (they are too short) ; but
you will notice in[future.
If even you, in BerUn, are unable to do anything for Bogus-
lavski, I know of no way of helping him. one could at most send
him an invitation privately, containing our signatures; he
might get a passport on the strength of it. If he once got here,
I could soon provide the means to enable him to exist for a few
months. His theoretical speculations are not worth much; in
his observations about radiation he clearly forgets that com-
pression by reflecting pistons alters the frequency. I have given
quite a lot of thought to this in the past, and know that semi-
permeable screens do not offer a solution. Your bold idea of
using the Stark effect of the fields in thermal radiation in order
to determine their statistical character is very good; I hope
you will have some success with it. I have read Byk's paper, and
discussed it with Stern. We were not, however, particularly
enthusiastic about it; after all, it is only the beginning of the
beginning of a theory.
We are all very busy, for we have to complete all research in
the Institute before the end of the present term. Then comes the
new master, Madelung. Unfortunately I did not succeed in
arranging Stern's chair. He is very unhappy about it, for his
prospects are poor under the current antisemitic conditions.
He is thinking of going into industry, which I consider a crazy
idea. He intends to take a few weeks' leave this summer, and to
come to Gottingen - Bohr will be there from the beginning of
June. Can you come as well ?
My path-length measurements are still unsatisfactory.
Although I now have the knack of keeping the pressure constant
to within a few per cent with the silver radiation, and can also
measure the layer thickness of the deposits to within a few
per cent, the technique is not yet perfect. I make the thickness
measurement using an interference method developed by
Wiener for the optics of telescopes; but I do it in the micro-
scope, and that works much better. The thickness of a layer (of
about ifi) can be measured almost point by point (in visual
fields of 0.0 1 mm^). I want to use this method to measure the
bending constants of very small pieces of crystals - perhaps I
shall succeed in doing this with diamond, Paul Oppenheim has
(Photograph by Karsch)
Plate J. Albert Einstein, late 1940's
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BORN-EINSTEIN LETTERS
managed to get me a piece f cm long. As Voigt's successor I am
bound to try something like this.
I have done little theoretical work. I have recently written an
account of Caratheodory's thermodynamics, which will appear
shortly in the Physikalische Zeitung. I am very curious to know
what you will say about it. Caratheodory himself, to whom I
sent the proofs in Smyrna, thought that I had interpreted him
correctly. I have also proved the following proposition, which
had me considerably puzzled: if the positive and negative ions
in an NaCl type lattice are somehow interchanged, the electro-
static lattice energy always increases. The NaCl lattice therefore
has a minimum energy with respect to such exchanges and this
may also (partly) explain its frequent occurrence. I need this
proposition for a theory for the melting of salts I have in mind,
in which I visualise the ions as tumbUng about through one
another during melting. But that is difficult! As you can see, it is
not a very profound piece of research.
I am also working on my article for the Encyclopaedia, with
Dr Brody as my private assistant. He is a very clever man.
(Unfortunately he knows very Uttle German, and is rather hard
of hearing.) He found a new general quantisation method using
Poincare's integral invariants; he says that he has told you
about it. Maybe there is some truth in it. We now have Gerlach
with us, who really is splendid: energetic, well-informed,
ingenious and helpful. He has just received an offer from the
Chilean Government to take over physics and electrotechnology
there (in Santiago); I wonder if it is the sensible thing to do?
I think that he has good prospects here, too, but he is an
enterprising fellow and well suited to an overseas appointment
of this kind. Franck has now setded in Gottingen (although
for the time being he is with Bohr in Copenhagen) ; he must
have enough freedom there, and so I am busily collecting money
for him. So far I've got 68,000 M. It is not at all easy to inspire
laymen with some interest in our work. I must have more money.
Wien got a whole million for re-equipping his Institute in
Munich. I believe that what Wien has, Franck should also get.
I must revise my book on relativity, as Springer intends to
issue a second edition; but I will not get round to it this term.
If you have spotted any mistakes or omissions, I should be
grateful for the information. PauU's article for the Encyclo-
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BORN-EINSTEIN LETTERS
paedia is apparently finished, and the weight of the paper is
said to be 2| kilos. This should give some indication of its
intellectual weight. The little chap is not only clever but in-
dustrious as well.
I have had some fun here recently, in the form of a substantial
burglary. The rogues broke in at night through a cellar window
after breaking the bars, and got away with a lot of silver, linen,
both bicycles, and even my suit and shoes from the first floor.
Since then I have slept badly and feel insecure in my own house.
The police have failed completely.
I cannot share your optimism in political matters, although
I do not believe that things are quite as black as they are painted.
We are not going to pay as much as is asked for. But I can see
the effect of this power politics on the minds of the people ; it is
a wholly irreversible accumulation of ugly feelings of anger,
revenge, and hatred. In small towns such as Gottingen, this is
very noticeable. I can, of course, understand it. My reason tells
me that it is stupid to react in this way; but my emotional
reaction is still the same. It seems to me that new catastrophes
will inevitably result from all this. The world is not ruled by
reason ; even less by love. But I hope that the harmony between
us will not be disrupted again.
With sincere regards, also from my wife
Yours
Max Bom
Madelung was an old friend of mine, and a physicist of outstanding merit.
Quite recently, during a congress in Copenhagen in 1963, 1 suggested that
one of his papers should be acknowledged as the origin of the dynamic
theory of crystal lattices.* Stern has become a great physicist, as I had pre-
dicted. The method of molecular radiation which he introduced into atomic
physics has become one of the main instruments of present-day research ;
his teaching has spread all over the world, and has produced numerous
discoveries of the first rank as well as a significant number of Nobel
prizewinners.
The micro-interferometer, which Mrs Bormann and I used to measure
thin layers of silver deposit, was built by Carl Zeiss of Jena and was
listed in their catalogue for a number of years. I did not manage to measure
the elasticity constants of the diamond. About thirty years later the Indian
physicist Bhagavantam was the first to succeed in doing this, using a
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BORN-EINSTEIN LETTERS
completely different method (ultrasonics). Thus, a generation later, one of
my old formulae was finally proved correct.
My interpretation of Carath6odory's thermodynamics did not have the
effect I had hoped for of displacing the classical method which, in my
opinion, is both clumsy and mathematically opaque. only in recent years
have textbooks appeared which make use of it.
As for the financial assistance for Franck, the greater part of the sum of
68,000 M came from the Recklinghausen industrialist Carl Still. Gourant
had got to know him first and had introduced us to him. Still was the son
of a Westphalian peasant. He had started off as a lowly mechanic, and
built up a large firm through his own industry and ideas. The firm built
coke ovens and installations recovering all kinds of coal by-products. He
was profoundly interested in science and may even have hoped for help
from us with his distillation processes. He frequently invited all of us,
together with the mathematicians Hilbert and Runge and all our wives,
to hunt hares on his large country estate, Rogatz, on the Elbe, near Magde-
burg. Although we did no shooting I can still see Hilbert, dressed in rubber
boots, standing in front of me on the edge of a field. But all the same we
were all presented with a hare or a fat goose when we left. We introduced
Max Planck to Still; this was a good thing, for when Planck was bombed
out of his house in Grunewald (Berlin) during the war, he and his wife
found refuge in Rogatz. They stayed there until the Russians got close,
and then the Americans evacuated them to Gottingen. We saw Carl
Still once more, on our first visit to Germany after the end of the war.
He was already seriously ill and died shortly afterwards. Our friendship
with his wife, who is approximately the same age as I, still continues, and
is now being carried on by our children. Today the firm is fiourishing
again under his son Karl Friedrich Still. Both father and son have been
awarded honorary doctorates by the Aachen Technische Hochschule.
Still's gift was one of the few instances when I received financial assistance
from a private source. It was, of course, meant for Franck's research and
not for mine, but I was quite in favour of this. Like Einstein, I have
always held that a theoretician needs only pen and paper and a few books.
Though I had initially been offered the post of chief of the whole Gottingen
Institute, I actually occupied only a very small room there. Later on in
Edinburgh it was much the same, but that was as it should be.
The letter ends with some political reflections. When I read through them
again, I was amazed how accurately I evaluated the situation even then.
I experienced the growing bitterness of the German people and felt
that renewed warmongering would result, leading to catastrophe. The
catastrophe was not avoided.
55
BORN-EINSTEIN LETTERS
31
Gottingen
4 August, igzi
Dear Einstein
A small boy, Gustav Born, came into the world on July 29th.
My wife is quite well and sends her regards. I shall remain here
for another few weeks and then go somewhere to recuperate.
Unfortunately I have to attend the Physics Congress at Jena
because of the journals, etc. And I have sworn never to attend
another congress. Auerbach has invited me to stay with him and
wrote to tell me that you ought to be there as well. That would
be nice. Franck is going to visit Bohr in Copenhagen in Septem-
ber. I am now working with Brody on the equation of state of
solid bodies for which we are now developing a rigorous theory
for crystals - a difficult business. It is, however, coming on nicely.
Warm regards to you and your family,
Max Bom
32
22 August, ig2i
Dear Born
Many thanks for the detailed report you sent me. The K. W. I.
[Kaiser Wilhelm Institute] is rather slow, because I have to
summon all my dear colleagues for grants. What you want would
devour the greater part of all our worldy goods, but a good case
can be made out for it, and I hope to be able to arrange it.
Just a little patience.
I have thought of a very interesting and fairly simple experi-
ment on the nature of the emission of light. I hope to be able
to carry it out soon. Meanwhile I am again the slave of the
damned postman, who inundates me mercilessly. I have spent
a happy month at the lake with my boys. Congratulations to
you and your wife, and best regards,
Yours
Einstein
56
BORN-EINSTEIN LETTERS
33
Gottingen
21 October, igsi
Dear Einstein
In writing to you today I address the mighty Director of the
Institute of Physics of the Kaiser Wilhelm Society about the
X-ray equipment we applied for. Franck has already told
you how things are. In the meantime, however, something has
happened. About ten days ago a representative of the Veifa-
Werke was here and he made the following offer: if we order at
once, the firm will supply the equipment we want at the current
price. We could, however, cancel the order before October 31st
(3 weeks' grace) should no decision have arrived from the Kaiser
Wilhelm Society by then. If the order were placed later, we
would be subject to the full price increase caused by the currency
devaluation, which would amount to about 50 per cent (!!!).
We have accepted this proposal and placed our order in the
hope that confirmation of the grant will arrive from the Kaiser
Wilhelm Society within three weeks. The deadline, October 31st
is approaching and we are still waiting. Pohl and Franck have
asked me to write to you and ask what the position really is
and whether we should cancel the order on October 31st or
whether the grant is certain enough for us to let the order
stand. It would be a great pity if we received 100,000 M, but
so late that the cost of the equipment had increased to 1 50,000 M.
Maybe the decision could be speeded up a little. In the mean-
time, we have, by a complicated transfer of equipment, collec-
tions, toilets etc. cleared out two adjoining rooms and we will
use them for X-ray research, one room for each department.
Meanwhile, Dr Kuestner is working under very difficult con-
ditions at the medical clinic, where there is some Veifa equip-
ment, so that he can familiarise himself with it. We have lots
of problems and would be glad to receive the equipment.
After this official business, some private matters. My health
was not too good during the holidays; towards the end of
July I got catarrh and stiU have not got rid of it completely,
even though I spent three weeks in Ehrwald in the Tyrol.
Catarrh is not serious in itself, but I always get asthma with it
and that affects me a great deal. For months I have had dis-
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BORN-EINSTEIN LETTERS
turbed nights because of asthma. But it is getting very much
better now, and I hope to be quite free from it in a few weeks'
time. It is high time too, for the university term begins shortly,
and there is always a good deal going on here. W. Pauli is now
my assistant; he is amazingly intelligent, and very able. At the
same time, he is very human for a 2 1 year old - normal, gay
and childhke. Unfortunately he wants to go away again in the
summer, to Lenz in Hamburg, as he had already promised.
Brody is still with me as well; he is a very clever and stimulating
man. An attempt will have to be made to find a post for him
with a living wage; I can only pay him a pittance (from a fund
collected by Franck, Courant and myself). Polanyi intends to
discuss this with you.
Scientifically there is nothing special to report. A large paper
of mine about thermodynamics is at the printers, but already I
wish it could be unprinted because the basic arguments seem
shaky to me. The result (which incidentally I consider to be
correct in spite of its shaky basis) is curious: Gruneisen's idea of
the proportionality of energy and thermal expansion is not true
at low temperatures; the latter is satisfied by a T^-law instead of
a r*-law. This should be tested experimentally (Nemst?).
Then another paper of mine about lattice potentials, which is
quite nice mathematically, is at the printers, Pauli and I are
tackhng some quantum calculations of atoms, using the approxi-
mation method which Brody and I recently developed in the
Zeitschrift fur Physik with the example of the oscillator system.
Perhaps something will come of it. Apart from this I am thinking
about a number of things, but mostly without success. The
quanta really are a hopeless mess.
My wife and children are well; Gottingen agrees with them
splendidly. Our little son is flourishing.
The political situation is once more worrying me a great deal.
In spite of my good intentions to be objective, my aversion
towards the Allies grows because they are so disgustingly
hypocritical. The Germans, it is true, have also robbed and
stolen when they could, but they have not talked any nonsense
about 'saving civilisation', etc. But I can't even write about it
without getting excited so I had better stop.
Is it true that the Mount Wilson people have now confirmed
the red shift? Has this already been published, and if so, where?
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BORN-EINSTEIN LETTERS
I received (as editor of the Physikalische Zeitschrift) a letter from
Glaser asking me to accept the enclosed manuscript. Debye
also recommended its acceptance. I read it and found that it
contains a crude attack on Grebe and Bachmann and some
mudslinging at you. I have returned it with a request for changes
and for permission to bring it to Grebe's notice. It would be
rather nice if the announcement from Mt Wilson about the con-
firmation could appear in the same issue, for Glaser bases
his argument mainly on the negative result obtained at St
Johns. Could you write to them for a brief report for publication ?
But I must stop now.
With kindest regards to your family; also from my wife
(with all due respect, and modesty).
Yours
Born
The last letter touches on a matter of supreme importance -the announce-
ment of a confirmation of the general theory of relativity by the spectral
red-shift in the gravitational field.
The financial matters mentioned are practically incomprehensible today.
one has to remember that the inflation of the German currency was
beginning. A drop of one half in the value of money may have taken about
two to three months at that time. Later on it took only as many days.
Hence our troubles with the purchase of the X-ray equipment. Officialdom
and public corporations did not understand the situation. The courts
supported the currency catastrophe by rigid judgments. I myself lost the
greater part of my inheritance. A man who owed me money on a mortgage
sent me the entire nominal value of the mortgage (50,000 M, I believe)
in one single note of the inflated currency which was actually worth i M at
the time. This was held to be legal. The High Court had decided that a
mark is a mark. After such experiences as these, my faith in the wisdom of
financial and legal experts, instilled into me during my upbringing as the
son of middle-class parents, was very much weakened. However, at the
time when Franck and I moved to Gottingen, things were not quite as bad
as that - yet. Even so, we had to expend a considerable amount of time
and energy in order to keep the institute going. It was even worse for our
wives ; they were forced to convert our salaries into food, clothing and other
necessities immediately. But I am digressing.
Of the scientific comments, my remarks about calculations of atomic
structures done in collaboration with my young assistant Pauli are most
interesting. The aim was to see whether the Bohr-Sommerfeld rules for
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BORN-EINSTEIN LETTERS
the application of the quantum hypothesis to mechanical systems would
lead to correct results. We used appropriate approximation methods based
on Poincare's astronomical perturbation calculation. The results were
negative, and so it seemed that the quanta were a 'hopeless mess'.
Soon afterwards, however, I saw it differently. Was it possible that the
success of Bohr's theory in the case of the hydrogen atom and other
similar simple systems was a sort of accident? Could there perhaps be
another, better, theory? This became our programme, especially when
Heisenberg succeeded Pauli. We began to look systematically for cases
where Bohr's theory failed, and soon found one with the helium atom.
(Other cases had already turned up in the dynamics of crystal lattices ;
atomic lattices built of Bohr's atoms with plane electron orbits led to
completely wrong compressibilities.)
The red-shift remained a dubious phenomenon for a long time. only
very recently has anyone succeeded in verifying Einstein's result. It
became possible after a thorough study of the sun's atmosphere, whose
ascending and descending streams veil the gravitational effect by the
normal Doppler effect; clouds of sodium vapour were found which hovered
comparatively quietly over the atmosphere of the sun, and showed the
gravitational effect in purity. Finally, the red shift has also been verified
directly on the earth, by y-rays, by means of the Mossbauer effect.
This, however, is too far from the subject.
A postcard from Hedi follows with a photograph of her holding our little
son in her arms ; the few words are meant as an apology for her previous
abruptness.
34
/ November, igsi
With this card, Gustav Born begs to introduce himself to you,
and begs you (i) for your goodwill and affection and (2) not to
bear a grudge to his mother for whom he is, after all, not
responsible,
XXX Signed : Gustav
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BORN-EINSTEIN LETTERS
35
Gottingen
sg November, igzi
Dear Einstein
The authorities cannot decide whether you are still tarrying in
the warm countryside of Italy or are already in Berlin. However,
in the former case, it is probably correct to assume that you will
soon return. Therefore I am writing and I hope you will get my
letter soon.
First of all, I must thank you most sincerely for the magni-
ficent gift of the X-ray equipment. Franck, Pohl and I are
delighted with it, for it should be part of any decent institute
nowadays, and problems frequently arise which can only be
solved with the help of X-rays. Pohl will write you an official
letter of thanks, but I must add a few words of my own. This
valuable gift shows that you people in Berlin have confidence in
our ability to produce something worth while, and this is very
gratifying. Pohl is chiefly responsible for purchasing the equip-
ment, and a great many difficulties have been encountered, such
as lack of space and unrefiability on the part of the firms. The
Veifa works in particular have dealt with us in such a manner as
to make it unlikely that we shall buy from them. Pohl is shortly
going to Berlin to negotiate with Siemens. We do not want to
buy any of the sets that are ready-made for medical use; we
would rather, if possible, assemble a carefully planned unit of
our own, using the best available components.
Apart from this, there is not much pleasant news to report,
for I am almost constantly ill. My summer trip to the Tyrol did
not help much, for after my return I had asthma almost every
night and became very run down. About three weeks ago I had
a very severe attack, accompanied by bronchitis, and had to
keep to my bed for a long time. I had some treatment from
our medical specialists (especially E. Meyer) which succeeded
in curing the asthma. But I still have severe catarrh and am
unable to lecture. Pauli is deputising for me, and seems to be
doing quite well in spite of his mere twenty-one years. It is a
pity that I am so shaky, for in every other way things are good
here. To be working with Franck is a joy. I'm on good terms
with Pohl, too. Young PauU is very stimulating - I shall never
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BORN-EINSTEIN LETTERS
get another assistant as good. Unfortunately, he wants to go to
Lcnz in Hamburg in the summer. I have been unable to do any
serious work lately, but I now understand perturbation theory
rather better and have some inkling of what Bohr is really
doing. I am also systematically continuing with my work on
crystals; several papers written during the summer have
recently appeared in Z^tschriftfiir Physik.
I would like to know what you think of Polanyi's papers on
rates of reactions; he maintains that these could not be explained
without an as yet unknown kind of energy-transmission (the
transmission of quanta of energy from one molecule to another
without mechanical reciprocation, simply hopping through
space). Franck and I do not beUeve it. Langmuir was here
recently; he thinks on similar lines, but we stiU do not believe
any of it. Incidentally, we liked Langmuir very much; he knows
lots of physics. Polanyi's paper about tensile strength is also
quite crazy and yet it contains a grain of truth. We would so
much like to talk to you about it !
A pupil of mine (a nephew of Minkowski with the same
first name) is working out an exact theory for streams of slow
electrons (speed below the smallest hv) in gases. This is based on
the following idea of Franck's. In an extreme vacuum, the
Child-Langmuir equation gives the current as a function of the
voltage (Joe F^'S I think). If one now adds the gas, the electrons
are thrown about so that the space charge density is increased
and the JjV law altered. The free path length of the electron
in the gas should follow from this change, according to the
existing theory. This is of interest, however, in view of Ram-
sauer's quite crazy assertion (in Jena) that in argon the path
length of the electrons tends to infinity with decreasing velocity
(slow electrons pass freely through atoms!). This we would like
to refute. My theoretical ideas are: I start with the Maxwell-
Boltzmann collision equation
dF
dF
dt "^^ dx
m di
-l\
^. ..+__+... =11 collision integral.
This equation is usually integrated so that the left hand side is
equated to zero and in the first approximation the integral
vanishes because of MaxweU's distribution function. In
the second approximation this distribution is then inserted
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BORN-EINSTEIN LETTERS
into the left hand side. I then proceed the other way round. In
the first approximation, ignoring all collisions and with normal
space charge distribution, it is necessary to put
Z= -e
dX
and to use the second equation Atjs= -e/Fd^dryd^. In the
second approximation, one collision is taken into account, and
so on. This project seems to be going well. Minkowski intends
to carry out some experiments, together with Miss Sponer, but
these are sure to be very difficult.
We were greatly amused by Lenard's Soldner article. I
do not know if you saw the report on it which appeared in
Frankfurter JZeitung, as well as Lane's reply on the one hand, and
Hubert's and mine on the other?
I am reading Laue's second volume; I must say I like it very
much after all. All the same, Pauli's article for the Encyclopaedia
was an even greater achievement.
My wife is very well; she is breast-feeding the little boy, and
this agrees with both of them. At the moment, though, she is
confined to bed with a large and painful boil. The two little
girls are also well.
Please give my regards to your wife and the young ladies,
and to all our friends and acquaintances in Berlin.
With best wishes
Yours
M.Born
My report about 'young Pauli' is not quite complete. I seem to remember
that he liked to sleep in, and more than once missed his 1 1 a.m. lecture. We
used to send our maid over to him at half past ten, to make sure that he
had got up. He was undoubtedly a genius of the highest order, but my
fear that I would never get an assistant as good proved unjustified. His
successor, Heisenberg, was just as gifted, and also more conscientious:
there was never any need to have him woken up, or to remind him of his
duties in any other way.
The comments about the physical chemist Polanyi are too dated to be of
any interest today. I should just add that later, during the Hitler regime,
Polanyi went to England and obtained a chair at Manchester - not for chem-
istry, but for philosophy and sociology ; he was a versatile, imaginative man.
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BORN-EINSTEIN LETTERS
Ramsauer's assertion that the free path length of the electron in argon
increases with decreasing velocity was bound to seem crazy at the time.
But it was nevertheless right. It was first explained by means of dc
Broglie's wave mechanics: the matter waves of the electrons have a wave-
length proportional to the velocity. If their collisions with atoms arc
regarded as diffraction phenomena, it becomes clear immediately that
slow electrons, that is, those with long wavelengths, are less influenced by
atomic obstacles. At the time I had no inkling of all this, and thus called
these important experiments 'crazy'. Did Einstein already have a deeper
insight then? I do not know.
Soldner, a German mathematician and geodesist, had predicted the
deflection of light by the sun as early as 1 80 1. He had actually dealt with
the beam of light as if it were a comet, moving according to Newton's law.
(This makes sense, because the path of a small object attracted by a central
body does not depend on its mass.) He ended up with the same formula as
Einstein did in his first paper deaUng with this problem; but this differed
by a factor of two from Einstein's final formula, which took into account
the change in the gravitational field near the sun as required by the general
theory of relativity. Naturally, Soldner's work was exploited to the full
by Einstein's enemies.
36
30 December, igsi
Dear Boms
Today I wish you a happy new year. We were all delighted with
the photo of the youngest Born. The fight of the Amazons is
now forgotten. I am very sorry to hear that you, dear Born,
have had so much trouble with your health. I hope that you
are all fit and well again.
Pauli is a splendid fellow for his 21 years; he can be proud of
his article for the Encyclopaedia. Polyani's ideas make me
shudder. But he has discovered difficulties for which I know no
remedies as yet. In particular I am racking my brains over a
numerical analysis in connection with radiation-molecular
balance. There is probaWy a lot of truth in Polanyi's ideas about
the strength of crystals, but their extension to gases seems wide
of the mark to me. Your investigation of electron currents
sounds interesting. I liked your reply about Soldner in Frank-
furter Z^tung very much.
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The experiment on light emission has now been completed,
thanks to Geiger and Bothe's splendid cooperation. The result:
the light emitted by moving particles of canal rays is strictly
monochromatic while, according to the wave theory, the colour
of the elementary emission should be different in the different
directions. It is thus clearly proved that the wave field does not
really exist, and that the Bohr emission is an instantaneous
process in the true sense. This has been my most impressive
scientific experience in years. Ehrenfest writes enthusiastically
about Bohr's theory of atoms ; he is visiting him. If Ehrenfest
is convinced, there must be something in it, for he is a sceptical
fellow.
Regards to the little ones, and all good wishes to you both
for the New Year.
Yours
Einstein
Pauli's article for the Encyclopaedia dealt with the theory of relativity.
Sommerfeld was originally supposed to write it. He got Pauli to help him
with it, but Pauli made such a good job of it that Sommerfeld handed the
whole thing over to him. It is truly remarkable that a young student of
2 1 was capable of writing so fundamental an article, which in profundity
and thoroughness surpassed all other presentations of the theory written
during the next thirty years - even, in my opinion, the famous work by
Sir Arthur Eddington.
The investigation into the emission of light by positive rays, which Einstein
carried out in conjunction with Bothe and Geiger, is mentioned again in
subsequent letters. It was a great disappointment in the end.
37
Gdttingen
I January, igss
Dear Einstein
We have been very much shaken by the contents of your letter,
though in our stupidity we are unable to reconstruct the set-up
of the positive-ray experiment for ourselves. We have a thousand
questions in our minds and all sorts of reflections for which we
need you as a sedative. As this letter cannot run to 50 pages, and
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BORN-EINSTEIN LETTERS
as we can hardly expect a loo-page reply, we conceived the
brilliant idea of having you officially invited to visit us in
Gottingen, at the expense of the Wolfskehl Foundation, to give
an informal lecture. This means you would also be here for
Hubert's 6oth birthday, an idea which has delighted the old
man. His birthday is on January 23rd; the lecture could be held
on Tuesday, 24th, and we hope that you will devote at least
Sunday, the 22nd, to us. Maybe your wife would like to accom-
pany you. It would be wonderful if you could manage that, and
we look forward to it so much that you must not refuse under
any circumstances. Sincere regards and best wishes for the
New Year.
BomandFranck
38
Jan. '22
Dear Bom
I shall gladly come and visit you, partly in order to congratulate
Hilbert in person, and partly to tell you about the experiment,
and how simple it is. The joke is this: the positive ray particle,
according to the wave theory, continuously emits variable
colours in different directions. Such a wave travels in dis-
persive media with a velocity which is a function of position.
Thus the wave surfaces should be bent as in terrestrial re-
fraction. But the experimental result is reUably negative.
Kindest regards, also to Franck and to your family.
Yours
Einstein
39
7 January, ig22
Dear Mr Einstein
First of all I want to thank you and your wife most sincerely for
your new year greeting, which showed the warmth of your
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friendship. May all your own dearest wishes come true many
times over. I hurried over to Hilbert with your card. He could
hardly beUeve at first that you are really coming, and was then
tremendously pleased. He wants me to ask you to make sure to
be there on his birthday, Monday, 23rd, and to put in an
appearance at the large gathering in the evening. The lecture
can be held on Tuesday, at any time you like. I hope you will
not just streak past us like a meteorite, but will be able to
stay for a few days as our guest. You will see how well we live
here, and we shall feed you on easily digestible dishes. If
your wife would like to come with you, she is cordially invited
and will be very welcome. Max is with Blaschke today and
tomorrow. He is unfortunately in a very bad state. Perhaps you
could give him pleasure by visiting him once more? It must
not look too deUberate. With kindest regards to you and your
family.
Yours
Hedi Bom
40
18 January, ig22
Dear Bom and dear Franck
I must, with a heavy heart, decline after all. But it really cannot
be helped. I am so much behind with my writing and other
obligations that I just cannot afford an escapade into the
Eldorado of erudition. So I will have to pay homage to Hilbert
by letter. Please let Courant know as well; he wanted to engage
me as a musician.
Laue is violently opposing my experiment, or rather my
interpretation of it. He maintains that the wave theory does
not involve any deflection of rays whatever. He suggested a
nice experiment to investigate the supposed wave bending of
the rays by means of capillary waves which exhibit con-
siderable dispersion, as a substitute for a theory which it is so
hard to develop with the required rigour.
Today there was a great dispute at the coUoqium, to be
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continued next time. Do not be angry - to postpone is not to
abandon.
With warmest regards, also to your wives
Yours
A. Einstein
Many thanks to Mrs Born for the charming picture. The
other evening I read to Laue and Vegard all the poems she
dedicated to us. They found them delightful and all saw in her a
serious competitor to Master Busch. In view of the tussle we had
with one another, I want to send her my special greetings.
This letter contains, for the first time, some doubts about the ideas on
which the positive-ray experiments were based, raised by Max von Laue,
then unquestionably an expert in all optical matters. Franck and I were
delighted at Einstein's news of the experiment, not because of our own
reflections on it but because of our pleasure in Einstein's success in taking
another important step forward.
41
Gottingen,
30 April, igss
Dear Einstein
Laue was here recentiy - we very much enjoyed his stay. He
told us that you are going to Holland. I hope this letter will
reach you in time.
First of all I have to ask for your help again, this time for
Brody. When I talked to you last Christmas in Berlin, you said
it might be possible to secure a post for him in Kowno. I have
recently discussed this with I. Schur in Berlin (you were in
Paris at the time), who has all kinds of contacts with Kowno.
He was going to attend to it. It is now a matter of urgency that
something should be done. My wife, who is looking after Brody's
family (his wife and small child have been here for some time),
reports that they live under miserable conditions. I give him
something from our private fund (about 2000 M per month),
but that is very little for a family. Apart from that we give what
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help we can. But the man must get out of this humiliating
situation. I value him very highly as a physicist; if he had more
energy and was in better circumstances, I am sure he would
achieve a great deal. A pretty piece of work he did is about to
appear in Physikalische JZeitschrift, and he is also working with
me on thermal expansion. Hilbert thinks very highly of him,
particularly because he speaks extremely well in seminars. I
could, if I wished, secure a lectureship for him here without much
difficulty; but I consider it senseless because, as a Hungarian Jew
and with his decidedly Eastern ways, he would never be offered
a chair. I already have enough worries and responsibiUties with
Paul Hertz, who is also on the point of starving.
Could you perhaps find some modest post for Brody in
Holland? Or in some other part of the world? I have applied
to the Academic Assistance Council for a grant for him, but
they have not yet replied. Could you put in a good word for
him there ? Or is there some other way ?
Now to other things. I am spending a good deal of time
writing the article about lattice theory for the Encyclopaedia.
I hope to have it finished by May. It is a rather laborious task.
Unfortunately it now turns out that there is a mistake in my
recently published theory of the equation of state of crystals.
I had claimed that Gruneisen's law of the proportionality of
energy and expansion does not hold throughout but that, at
low temperatures, the former is proportional to T* and the latter
to T". This was nonsense, though. It was based on a bad
blunder. That this could happen to someone of my ripe old age
is somewhat depressing. But as long as one discovers the mistake
oneself it is not quite so bad, and I console myself with the know-
ledge of what a tricky business it is. Moreover, both Pauli and
Brody read the paper thoroughly without spotting the mistake.
Pauli has unfortunately gone to Lenz in Hamburg. We
recently started work on a joint paper, a continuation of the
one published in collaboration with Brody about the quantis-
ation of non-harmonic oscillators. The approximation method
developed there can be applied to all systems where the un-
perturbed system is quasi-periodic and the flow function can be
developed in powers of a parameter. The case when the un-
perturbed system is degenerate can also be included and leads
precisely to Bohr's method of secular perturbations. As a
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matter of fact we now really understand Bohr's ideas, at least
in part. We have also started to do calculations for ortho-helium
(two coplanar electrons) and were able to confirm Bohr's old
claim that the inner electron moves around fast on an elUptical
orbit whose major axis always points towards the slowly moving
outer electron. Pauli took the paper to Hamburg with him and
wants to finish it there. I cannot find the time because of the En-
cyclopaedia article. Then, too, the damned term is just starting
again, an unwelcome interruption of my serene contemplation.
Franck's Institute is full of doctoral students who do nice
work under his guidance. Hilbert is in Switzerland and will not
be back for another 8 days.
My family are well in spite of the continually frightful
weather. My wife sends warmest greetings. Please give my
regards to my coUeages in Holland and Berlin.
Yours
Bom
The plight of younger people like Brody who had to depend on small,
fixed, constantly devalued salaries was indeed miserable.
The report of the blunder I made in my article on solids was by way of a
prelude to the major blunder which Einstein reports in his next letter.
42
Berlin
Dear Bom
It is extremely difficult at the moment to find posts for theo-
reticians. Holland suffers from overproduction. Should there be
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BORN-EINSTEIN LETTERS
any chance of doing something for Brody here, it would be
because of the extraordinary significance of his achievements.
There are some excellent theoreticians there (such as Fokker)
in modest teaching posts in Gymnasia. A few months ago I
wrote about Brody to Millikan and Epstein in Pasadena, but
have not yet received a reply. I will talk to Laue who, unless
I'm very much mistaken, has some influence with the Not-
gemeinschaft. I got to know your perturbation method through
Becker's thesis [for a lecturer's qualification] and enjoyed it.
I too committed a monumental blunder some time ago
(my experiment on the emission of light with positive rays),
but one must not take it too seriously. Death alone can save
one from making blunders. I greatly admire the sure instinct
which guides all of Bohr's work. It is good that you should be
working on helium. The most interesting thing at the moment
is Gerlach's and Stern's experiment. The orientation of atoms
without colhsions cannot be explained by means of radiation,
according to current reasoning; an orientation should, by
rights, last more than a hundred years. I made a little calcu-
lation about it with Ehrenfest. Rubens considers the experi-
mental result to be absolutely reliable.
Make sure you use the money for the purchase of the X-ray
apparatus quite soon. Why is it taking so long?
Kindest regards to you all
Yours
Einstein
Here Einstein admits that the considerations which led him to the
positive-ray experiments were wrong; 'a monumental blunder'. I should
add that now (1965), when I read through the old letters again, I could not
understand Einstein's observation at all and found it untenable before I
had finished reading. This is, of course, quite simply because we have
learned a good many things about the propagation of light during the
intervening forty-odd years. The same is true of the idea that the laws of
the propagation of light in transparent media have nothing to do with
quanta but are correctly described by the wave theory (Maxwell's
equations and their relativistic generalisations for moving bodies). It is
quite possible that Laue had already realised this at that time, and used it
in argument against Einstein's ideas.
Now I can hear all Einstein's opponents, the anti-relativists, cry: 'What
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did we tell you? Einstein, too, makes mistakes - why should we believe in
his crazy theory of relativity?' The answer to this is that we all make
mistakes. 'Death alone can save us from making blunders.' At first there
were quite a number of serious scientists who did not want to know
anything about the theory of relativity; conservative individuals, who were
unable to free their minds from the prevaihng philosophical principles.
As long as such people conduct their polemics decently, there is no reason
why one should object to them.
Einstein himself belonged to this group in later years; he could no longer
take in certain new ideas in physics which contradicted his own firmly-
held philosophical convictions. But Einstein never engaged in polemics,
subjectively or maliciously. There are always real, disinterested scientists
who are so ruled by prejudices outside science and philosophy that they
reject any new ideas suggested by people of whose background, ancestry,
rehgion, etc., they disapprove. These included the antisemitic physicists
at whose hands Einstein, and later many other people including myself,
suffered.
Finally, there are the pure cranks, outsiders who can point to no
positive scientific achievements themselves but who believe that they have
found defects in some new doctrine such as Einstein's theory of relativity.
one would think that there would be fewer of these as time goes on. But
this is not so. Over the years a large number of first-class physicists and
mathematicians have thoroughly investigated the theory of relativity and
none has found fault with it. It is hard, therefore, today to take seriously
anyone who believes he has discovered a mistake. I have frequently
taken the trouble to uncover the errors in papers written by cranks of this
type, but never in all my experience has any of them admitted that he
had made a mistake, as Einstein did.
H. Rubens, professor of experimental physics at the University of Berlin,
was particularly known for his investigations of infra-red radiation and its
appUcation to Planck's radiation formula.
It is strange that Einstein referred me to Stern's and Gerlach's experiment
as the most interesting. He had forgotten that it had been carried out in
my Institute in Frankfurt under my very eyes, as a result of discussions
with me, and that it had been financed with money I myself had raised
with the aid of my relativity lectures.
If my memory does not deceive me, Stern also made the little calculation
which Einstein had made with Ehrenfest, namely that the orientation of
atoms in the magnetic field, predicted by Sommerfeld and experimen-
tally demonstrated by the Stern-Gerlach experiment, cannot be interpre-
ted classically.
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'•^ Gdttingen
6 August, igs2
Dear Einstein
We recently had a visit from a woman physicist who now lives
in Holland; she mentioned that Michelson's experiment had
been repeated in America, with positive success. H. A. Lorentz
is supposed to have brought the news with him. Do you know
anything about it? The Michelson experiment is one of those
which seem definitely a priori. I do not believe a word of the
rumour. But all of us here would be most grateful if you could
find time to write a postcard.
Franck and Courant have spoken to me about you. We have
a lot of worries about professional appointments. Pohl has
decided to stay on in Gottingcn. This relieves us of the worry
of selection. But now I fear that Franck may go to Berlin.
I sincerely want him to be offered the chair, but he would be
foolish to accept. Courant says that you are of the same opinion.
Scientifically there is nothing of any importance. My assistant
Hiickel and I are having a lot of trouble with the quantisation
of polyatomic molecules in calculations of the infra-red bands
(in H2O, for example) . We have the right approximation method,
but the calculations are very complicated. I expect to finish my
Encyclopaedia article this month ; I am completely fed up with
it. I have given a good deal of thought to the quantum theory
of molecule formation. A short notice in Die JVaturwissenschaften
about the Hj molecule contains some results of interest to
connoisseurs. But the more unequivocal these turn out to be,
the crazier the whole system seems. I am not yet on the right
track as far as questions of principle go.
My wife and children are well. The girls are staying in the
country with a former maid of ours; they are due to return
soon. We shall stay here until the middle of September, when
we are going to Leipzig and from there to Italy. We received
;(^22 sterling for the translation of my book, and have turned
it into lire. This will not take us very far, but we greatly look
forward to our little journey to the South. With warmest
greetings, also from my wife, to you and your family.
Yours
M.Bom
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The Michelson experiments were made by the American physicist Miller,
first in flat country and later on top of Mount Wilson, a high mountain.
To begin with, he claimed to have discovered, using his Michelson inter-
ferometer, the so-called aether wind. Some time later he withdrew the
claim; the shift of the interference fringes, on which he had based his
claim, had been too small. I believe he then attributed it to the movement
of the solar system. When I was in the United States in 1925/26, Miller's
measurements were still frequently being discussed. I therefore went to
Pasadena to see a demonstration of the apparatxis on top of Mt. Wilson.
Miller was a modest little man who very readily allowed me to operate
the enormous interferometer. I found it very shaky and unreliable; a
tiny movement of one's hand or a slight cough made the interference
fringes so unstable that no readings were possible. From then on I com-
pletely lost faith in Miller's results. I knew from my visit to Chicago in
191 2 that Michelson's own apparatus was very reliable and his measure-
ments accurate. My scepticism has been substantiated by later develop-
ments. Michelson's result that the aether wind does not in fact exist is
universally accepted today.
Then follows a brief report about my work on special problems of the
quantum theory, which is no longer of any interest today.
44
23 December, igss
Dear Boms
Splendid sunshine at Christmas. A happy, beautiful country,
with a delicate, sensitive people. We start for home again on the
29th, over the great waters, via Java, Palestine and Spain; it
will probably be April before we get there.
In the meantime, warmest greetings
Yours
Einstein
This postcard from Japan was the only message we received from Einstein
during his world trip, which took him and his wife to China, Japan,
Palestine and many other countries. on his way out there he received the
news that he had been awarded the Nobel Prize; not for his theory of
relativity, but for his explanation of the photoelectric effect by means of
his photon theory. Further details of this can be found in any of the
numerous biographies of Einstein, such as the one by Carl Seelig.^'
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BORN-EINSTEIN LETTERS
45
Gottingen
7 April, 1923
Dear Einstein
They say you are back. I had intended to write you a welcome-
home letter, but now it is too late. The most important thing is
for us to congratulate you heartily, if somewhat belatedly,
on the Nobel Prize. Two more deserving recipients than you
and Bohr could not be found, and we were as pleased as Punch.
We also want to thank you sincerely for the beautiful card from
Japan, We did not know your address, and so were unable to
reply. But now I would like to re-establish the exchange of
views between us, if I may lay claim to your time. I would like
to hear about your experiences during your great trip. I may
possibly come to Berlin for a few days towards the end of the
month, in order to visit an American friend and benefactor of
mine, who helps me to support my students. I hope to see you
then. We have been living very peacefully and quietly here.
The only external event of any importance has been a visit by
Lord Haldane. He seems to be rather confused; all the same,
the breadth of his education and his qualities as a European
made a deep impression on us (i.e. Hilbert, Franck, Courant
and myself).
If you happen to glance through the last six months' issues
of scientific journals, you will see that I have been fairly
industrious, and have kept quite a large number of students
going. But they are only minor problems that I am struggling
with. I don't seem to get any closer to the great mystery of the
quanta, in spite of all my efforts. We have been looking at
perturbation theory (Poincare's) to determine whether it is
possible to obtain the observed term values from Bohr's models
by exact calculation. But it is quite certainly vx)t the case, as was
demonstrated with helium, where we found any number of
multiple periodic orbits (to a sufficient approximation). I had
Heisenberg here during the winter (as Sommerfeld was in
America) ; he is easily as gifted as Pauli, but has a more pleasing
personality. He also plays the piano very well. Apart from the
work on helium, we examined together some questions of
principle in connection with Bohr's atomic theory - particularly
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with regard to the phase relations in atomic models {^eitschrift
furPhysik). I have at long last finished my great Encyclopaedia
article on the lattice theory ; it has grown to about 250 pages,
and will be published as the second edition of my old book.
I hope it will come out in May. Then I am going to put this
subject into cold storage until the question of homeopolar
binding forces between atoms has been solved from Bohr's
point of view. Unfortunately every attempt to clarify the con-
cept fails. I am fairly sure though that in reahty it must all be
very different from what we think now. But one can draw plenty
of qualitative conclusions from Bohr's ideas; Franck does that
magnificently, and is doing some nice experiments again. I live
in dread of Franck getting the position in Berhn. It would be
better for him, for physics, and also for Berlin if he were to
remain here. To say nothing of myself At the moment he has
gone to Hertz in Holland.
I hear that you have a new theory about the connection
between gravitational and electromagnetic fields, which
allegedly points to a relationship between gravitation and the
earth's magnetic field. I am very curious. Most of what is
published about relativistic problems leaves me cold. I find
Mie's pulpy effusions horrible. Hilbert follows all this half-
heartedly, as he is completely preoccupied with his new basic
theory of logic and mathematics. What I know of it seems to me
the greatest step forward imaginable in this field. But for the
time being most mathematicians refuse to recognise it.
The papers report that you have turned your back on the
League of Nations. I would like to know if this is true. It is,
indeed, almost impossible to arrive at any rational opinion
about poHtical matters, as the truth is systematically being
distorted just as in wartime. The folhes of the French sadden me,
because they strengthen our nationahsm, and weaken the
Republic. I give a lot of thought to what I could do to spare my
own son the fate of participating in a war of revenge. But I am
too old for America and, moreover, the war hysteria seems to
have been even worse there than here. The other day I read a
little essay by Coudenhove-Kalergi : 'Apology for the Technical
Age', which contained some enlightening arguments. If you do
not know it, you should certainly try to get hold of it.
We were in Berhn last March. I talked to Planck, and his
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company gave me much pleasure. on the other hand, the
German Physical Society, where I gave a lecture, was like a
waste-land - no trace of participation or discussion. Rubens is
much missed there; for all his coolness and caution, he was full
of interest and life as far as science went. My family are well
and send warmest regards to you all.
Yours
Max Bom
My American friend and benefactor was Henry Goldman, who was
senior partner of the great banking house Goldman, Sachs & Co. in New
York. I got to know him when an old friend went to New York after the
war to marry his American fiancee. Partly as a joke I said that he ought to
try to find me a rich G«rman-American, who would be prepared to give
some financial support to my Institute, which had been severely handi-
capped by the inflation. A few weeks later, I received a postcard from New
York : I have your man, his name is Henry Goldman, and he lives at. . . .
With my wife's help I drafted a nice letter to Mr Goldman, and a few
weeks later received a very charming reply, together with a cheque for a
few hundred dollars, quite a considerable sum by German standards. I
went to Berlin to get to know my benefactor. I should like to recount
briefly how things went with Goldman after that.
Goldman was a portly, Jewish-looking gentleman; his grandfather had
emigrated to the U.S.A. from Hessen without a penny, because the Jews
were treated particularly badly there. In America, he started off as a
door-to-door salesman, and ended up as the owner of a small bank.
His sons and grandsons developed this into a giant concern, which
amongst other things had financed the Woolworth Co. The family's
German memories meant much to my Henry Goldman and, when the
war broke out in 1 914, he did not believe that the Germans alone were to
blame. He even fell out with his family over this issue. Later, he did
everything he could to help Germans in those difficult times. I introduced
Goldman to Einstein, and both of them later visited us in Gottingen, and
stayed in our house. During our American journey in 1926, my wife and I
visited the Goldmans and spent Christmas Eve with them in their elegant
flat on Fifth Avenue in New York. Hitler's seizure of power was, of course,
a terrible blow to Henry Goldman. All his life he had defended the Germans
against American accusations, and helped them. Now he lived to see
antisemitism made into one of the main points in the programme of a
criminal government. I saw Henry Goldman once more (in 1934 or 1935),
in his London hotel. He was a broken man and died soon afterwards.
The story of Lord Haldane's visit is as follows : Years ago he had studied in
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Gottingen, and he liked the German culture and language. This must
have been why he resigned from his post as British War Minister in
1 9 14, when his country aligned itself with France and Russia. Soon eifter
the end of the 1914-18 war he visited CJottingen to look up a certain old
lady, Miss Schlote, in whose house he had lived during his student days.
My wife knew her, and in this way Haldane found out that we lived
in Gottingen. He had great admiration for Einstein and had read my
relativity book. He himself had written a large book. The Reign of Relativity, ^^
which, however, had virtually nothing to do with Einstein's theory
but merely enlarged upon the trivial proposition that 'everything is
relative'. His visit helped to enliven our usually very quiet existence in
Grottingen.
Later I met Haldane again. I had been invited to the opening of a new
physics laboratory at the University of Bristol, donated by the cigarette-
manufacturing firm of H. O. Wills. There I was to receive an honorary
doctorate, my first, together with a number of famous physicists, Lord
Rutherford, Sir William Bragg, Sir Arthur Eddington, Langevin (from
Paris) and others. To my surprise the Vice Chancellor, who conducted
the ceremony in the festive, but cold hall, was none other than Lord
Haldane. He welcomed me like an old friend. As it happened he, like
myself, was suffering from a bad cold. This prevented us from attending
the banquet that evening in that same cold hall, and we had our dinner
served to us in a small room, where a coal fire gave at least the illusion of
warmth. I remember that he talked almost the whole time, mainly about
the negotiations he had conducted in Berhn (known as the Haldane
Mission) to end the naval arms race between Grermany and Great
Britian. This foundered because of the stubborn attitude of von Tirpitz
and the Kaiser, which Haldane described vividly. Many historians believe
that the first world war might well have been prevented by such a pact, and
European history would have taken an entirely different course.
As regards perturbation theory: astronomers normally use simple, well
proven techniques, and they do not take much notice of the considerable
developments, systematically made by Henri Poincare. But the perturba-
tion problems involved in the theory of electron orbits in the atom make
the general rigorous theory indispensable. We therefore made ourselves
familiar with it, as did Niels Bohr in Copenhagen, who used it as the basis
for an interpretation of the periodic system of the elements. Heisenberg
and I, however, pursued a different objective. We had reason to doubt
that Bohr's ingenious but basically incomprehensible combination of
quantum rules with classical mechanics was correct. We therefore intended
to carry out a thorough calculation of the two-body problem of the helium
atom (nucleus with two electrons), and thus needed to use Poincar6's
rigorous approximation technique. The result was quite negative, and that
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led us finally to turn our backs on classical mechanics and establish a new
quantum mechanics.
The rumour about Einstein's new investigation, in which he attempted
the unification of his theory of gravity with Maxwell's theory of the
electromagnetic field, proved to be correct. At that time he began his
often repeated, although unavailing, attempts to develop a unified field
theory along these Unes.
Hubert's efforts to find a new basis for mathematics enthralled and
fascinated me to begin with. Later, I was no longer able to follow. I had
some correspondence with Einstein about these problems, when they became
the cause of a dispute between Hilbert and the Dutch mathematician
Brouwer (letter No. 58).
Einstein repudiated the League of Nations when he resigned his member-
ship of the Commission for Intellectual Collaboration under the chair-
manship of the philosopher Henri Bergson. The reason for this step was
probably hardly political at all, but mainly the lack of time and his dislike
of travelling. If I am not mistaken, it was Madame Curie who replaced
Einstein on the committee.
46
22 July, 1923
DearBorns
Neither my bad conscience, nor even my wife's, was strong
enough to stir my lazy flesh at last to answer your extremely
kind letters. But your card, dear Mrs Born, has really stung me
into action. However, the abortive twinges of a bad conscience
are the only unpleasant emotions I have when I think of you.
For not only have you always been so good and kind, but your
contributions in physics, music, poetry and prose, as well as in
cosy conviviality, have done much to enrich this curious existence
of ours. All is well with us.
Scientifically, I have at present a most interesting question,
connected with the affine field theory. There are prospects
now of understanding the earth's magnetic field and the
electrostatic economy of the earth, and examining the concept
experimentally. But we will have to wait for the experiment.
Both my wife and I thank you most sincerely for your kind
invitation. But I must stay here for a while in this overcrowded
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place, where one is driven almost to distraction by visitors,
correspondence and telephone calls. Langevin is making his
way here for a pacifist demonstration; a splendid fellow.
However ineffective the good and the just may be, they alone
make life worth living. With warmest wishes for a happy
holiday to you both, and the dear children.
Yours
A. Einstein
Kindest regards from my wife, who is very busy and intends to
write to you herself another time. Franck, who has just been
here, told me that according to the results of measurements of
ionised gases already made, the effect I am looking for cannot
exist. There is to be no understanding the earth's magnetic
field. I am sending this letter to you, to make sure that it
arrives safely. But please write and tell your wife that we both
think of her with affection, and not to be angry about our
laziness.
Institute for Theoretical Physics
4/ of the University
Gottingen
Bunsenstrasse g
25 August, 1923
Dear Einstein
Your kind letter gave us much pleasure. Thank you very much.
Today I should like to askyou something (and would appreciate a
prompt reply) : one is constantly bombarded with official communi-
cations from the Helmholtz Society, the German Physical
Society, etc., asking one to attend the congress of physicists
in Bonn. If this were to be somewhere else, I would not even
consider going. But in Bonn, because of the French occupation,
great importance seems to be attached to receiving large num-
bers of visitors, and Franck is of the opinion that we should go
for the sake of good form. In my opinion it would have been
more sensible not to hold the congress in occupied territory; for
it is a mistake to mix up scientific meetings with politics in any
way whatever. But now the folly has already been committed,
and the question is only whether it is necessary to take part.
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There could easily be considerable difficulties from an
embargo on travel and so on. I myself have no desire at all
for a high concentration of physicists, but would much rather
live and work quietly by myself, particularly as I have only
just returned from the North Sea. I would like you to tell me
what you Berlin physicists are doing (particularly Planck,
Laue, Haber, Meitner, etc.) and whether you think thisjourney
would be desirable. Please reply straight away, as one would
have to try and get a passport quite soon.
My wife was in Langeoog with the children for more than five
weeks, and I was there as well for the last three. We have all
recovered well; the children in particular have gained strength
and are looking very well. We bathed a lot but otherwise did
nothing except lie on the beach and laze about. Although I was
acclimatised, I came down with bad catarrh almost straight
away. I had imagined that the vacations in Gottingen would be
quiet and peaceful; but in the first three days after our return
we have already had two foreign visitors, an Englishman from
Oxford and Mr Grimm from Munich. But as from tomorrow I
am going to feign death and refuse to see anyone. It is not really
that I have anything special on. As always, I am thinking
hopelessly about the quantum theory, trying to find a recipe for
calculating helium and the other atoms; but I am not succeed-
ing in this either. My Encyclopaedia article has been published
and I will send you a copy soon. Otherwise I spend my time
reading, going for walks, playing music and occupying myself
with the children. I am practising systematically and have, I
think, made some progress. Unfortunately it is very difficult
here to get a trio or quartet together.
In the latest issue of the Annalen, containing the nice paper by
Gruneisen and Goens which verifies your theory of dissociation
velocity, there is a paper by Gerold v. Gleich about the peri-
helion of Mercury. I do not like its tone at all. Are you going to
reply to it ? It is odd that so many people have no feeling for the
intrinsic probability of a theory. Have you made any progress
with your affine world ?
Kindest regards to your wife from both of us.
Yours
Bom
8i
BORN-EINSTEIN LETTERS
48
29 April, 1924
Dear Boms
Your letter, dear Mrs Born, was really excellent. Indeed, what
causes the sense of well-being inspired by Japanese society and
art is that the individual is so harmoniously integrated into his
wider environment that he derives his experiences, not from the
self, but mainly from the community. Each of us longed for this
when we were young, but we had to resign ourselves to its im-
possibility. For of all the communities available to us there is
not one I would want to devote myself to, except for the society
of the true searchers, which has very few living members at any
time.
I called off my visit to Naples; I was pleased that a minor
indisposition gave me the opportunity. I am going to Kiel for a
while instead. Bohr's opinion about radiation is of great interest.
But I should not want to be forced into abandoning strict
causality without defending it more strongly than I have so
far. I find the idea quite intolerable that an electron exposed to
radiation should choose of its own free will, not only its moment
to jump off, but also its direction. In that case, I would rather
be a cobbler, or even an employee in a gaming-house, than a
physicist. Certainly my attempts to give tangible form to the
quanta have foundered again and again, but I am far from
giving up hope. And even if it never works there is always that
consolation that this lack of success is entirely mine.
Enjoy the beauty of the sunny land, with best wishes.
Yours
Einstein
The remark about the advertising agencies was quite un-
conscious, the result of a good mood, and I had no idea that
you were wedded to it in some way. Your pretty remark makes
me want to stroke your head, if that is at all permissible in the
case of a married lady.
The letter from my wife to which Einstein replied is missing.
The basic reason for the dispute between us on the validity of statistical
BORN-EINSTEIN LETTERS
laws was as follows. Einstein was firmly convinced that physics can supply
us with knowledge of the objectively existing world. Together with many
other physicists I have been gradually converted, as a result of experiences
in the field of atomic quantum phenomena, to the point of view that this
is not so. At any given moment, our knowledge of the objective world is
only a crude approximation from which, by applying certain rules such
as the probability laws of quantum mechanics, we can predict unknown
(e.g. future) conditions.
49 Gottingen
'5 J^b>> "925
Dear Einstein
Your kind letter gave us much pleasure. My wife left with the
children for Silvaplana in the Engadine the day before yesterday,
and I expect she will write to you from there. In the meantime,
I want to give you some of our news.
As regards physics, first of all, your kind remarks about my
activities spring from the kindness of your heart. I am fully
aware, however, that what I am doing is very ordinary stuff
compared with your ideas and Bohr's. My thinking box is very
shaky - there is not much in it, and what there is rattles to
and fro, has no definite form, and gets more and more compli-
cated. Your brain, heaven knows, looks much neater; its
products are clear, simple, and to the point. With luck, we may
come to understand them in a few years' time. This is what
happened in the case of your and Bose's gas degeneracy
statistics. Fortunately, Ehrenfest turned up here and cast some
light on it. Then I read Louis de BrogUe's paper, and gradually
saw what they were up to. I now believe that the wave theory
of matter could be of very great importance. Our Mr Elsasser's
reflections are not yet in proper order. To begin with, it trans-
pired that he had made a considerable error in his calculations,
but I still believe that the essence of his remarks, particularly on
the reflection of electrons, can be salvaged. I am also speculating
a little about de Broglie's waves. It seems to me that a connection
of a completely formal kind exists between these and that other
mystical explanation of reflection, diffraction and interference
using 'spatial' quantisation which Compton and Duane proposed
82
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BORN-EINSTEIN LETTERS
and which has been more closely Studied by Epstein and Ehrenfest.
But my principal interest is the rather mysterious differential
calculus on which the quantum theory of atomic structure
seems to be based. Jordan and I are systematically (though with
the minimum of mental effort) examining every imaginable
correspondence relationship between classical, multiple-peri-
odic systems and quantum atoms. A paper on this subject in
which we examine the effect of non-periodic fields on atoms
will appear soon. This is a preliminary study for an investigation
of the processes occurring in atomic collisions (quenching of
fluorescence, sensitised fluorescence a la Franck, etc.); one
can understand, I think, the essential characteristics of what
goes on. The different behaviour of atoms depends mainly on
whether they have an (average) dipole moment, a quadrupole
moment, or even higher electric symmetry still. As regards
your objections to Jordan's paper, I still feel very unsure of
myself; but as I am now coming to grips with these things
from my own somewhat complicated point of view, I will
understand them one of these days. on the whole, you are
certainly right; though Jordan's opinion is based on a somewhat
different consideration, as he allows coherent bundles of rays,
whereas you only mention incoherent ones.
Even if Jordan is mistaken in this, as I now think is highly
probable, he is still exceptionally intelligent and astute and
can think far more swiftly and confidently than I, on the whole
my young people, Heisenberg, Jordan and Hund, are brilliant.
I find that merely to keep up with their thoughts demands at
times a considerable effort on my part. Their mastery of the so-
called 'term zoology' is marvellous. Heisenberg's latest paper,
soon to be published, appears rather mystifying but is certainly
true and profound; it enabled Hund to bring into order the
whole of the periodic system with all its complicated multiplets.
This paper, too, is soon to be published. In addition, I am busy
calculating the lattice theory over and over again with some of
my other, less independent, pupils. We have just finished a paper
by BoUnow which calculates the relationship between the crys-
taUographic axes of two crystals of the tetragonal system, rutile
and anatase, two forms of TiOj, based on the requirement that
the lattice should be in electrostatic equilibrium. The result is
quite good.
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BORN-EINSTEIN LETTERS
I am tremendously pleased with your view that the unifi-
cation of gravitation with electrodynamics has at long last
been successful; the action principle you give looks so simple.
As we have time, Jordan and I are going to try some variations
of it. But we would be most grateful if you could send us your
paper on this subject as soon as possible. This kind of thing
is much deeper than our petty efforts. I would never dare
tackle it.
We have had many visitors again this term. Kramers was
here for eight days, as I mentioned before, and Ehrenfest, with
whom both of us, particularly my wife, are now on very firiendly
terms. Last week Kapitza from Cambridge was here, and Joffe
from Leningrad. He made a tremendous impression on us : he does
such beautiful work, and yet has published hardly anything at
all. Philipp Frank is now here with his wife, and many other
people as well. For us this is very stimulating, but it is often too
much for our wives. So they simply run away; my wife and Mrs
Courant have already left, and Mrs Frank is due to leave in
two days' time. But do not conclude from that that your visit
is going to be unwelcome! We are greatly looking forward to
it ! But it ought to be at a quieter time. In July, most of the
foreigners are already on holiday, and they descend on us in
droves. But you know all this business. There is going to be
another rumpus tomorrow; it is the inauguration of Prandtl's
new hydrodynamics institute, with guided tour, official dinner
and gala concert. It will cost me almost an entire working day.
But I, too, am about to escape. on July 30th I am giving a
lecture in Tiibingen for Gerlach and Lande, and then I am
going to join my family in the Engadine. In October I am sup-
posed to go to Cambridge, at Kapitza's invitation; we are
also all supposed to be going to the Russian Physicists' Congress
in Moscow next winter; Joffe is going to pay our travelling
expenses. As you see, we too get around, though not as far as
Japan and the Argentine. one more thing: in today's astronomy
colloquium, Kienle reported a beautiful new piece of work
(from Mt Wilson, I think) ; the satellite of Sirius is one of those
minute, mysterious dwarfs of enormous mass - a density of
28,000 - and, according to Eddington, is a conglomeration of
naked nuclei and electrons. The red shift (of approximately
20 km/s) has now been determined, and is exactly proportional
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BORN-EINSTEIN LETTERS
BORN-EINSTEIN LETTERS
to the enormous density (and small radius). But I must stop
now.
Kindest regards to your wife and daughters,
Yours Bom
This letter is the most significant so far, and (to me) the most important.
The theory of gas degeneracy, proposed by the Indian physicist Bose, had
immediately been taken up by Einstein and developed further in a
momentous treatise of his. He transferred the statistical behaviour of
radiation from a 'photon gas', whose statistical characteristics differ from
the normal (Boltzmann distribution), to ordinary gases, which should
then exhibit variations from normal behaviour (degeneracy) at low
temperatures. But the most important thing about it was its connection
with de Broglie's wave theory of matter. At Einstein's instigation I studied
de Broglie's theory, which had been published a few years earher. By a
strange coincidence, a letter arrived just then from the American physicist
Davisson, who had obtained puzzUng results with the reflection of elec-
trons from metal surfaces. The results were supported by graphs and tables.
While I was discussing this letter with Franck, it occurred to us that the
curious maxima of Davisson's curves could perhaps be explained by the
diffraction of the electronic matter waves in the crystal lattice. A rough
calculation with de BrogHe's formulae resulted in a wavelength of the
correct order of magnitude. We handed over the development of this idea
to our pupil Elsasser, who had done experimental work with Franck to
begin with but who now wanted to change over to theory. In spite of the
difficulties mentioned in this letter, Elsasser did eventually succeed. His
paper must be acknowledged as the first confirmation of de Broglie's
wave mechanics.
The connection I suggested with Duane's and Compton's 'spatial quan-
tisation' does indeed exist: de Broglie's spin quantum condition is exactiy
the same thing, but differentiy and more intuitively expressed. While Duane
speaks of conceptual decomposition of a radiation process into harmonic
components, de Broglie regards these as real, material waves, which are sup-
posed to replace the particles. Later on I showed the relationship between
particle and waves in another way, which today is fairly generally accepted :
the waves represent the spread of probability for the presence of particles.
But this is not the place to pursue these matters in detail. Nor will I go
into the 'mysterious' differential calculus here, which is the basis of the
quantum theory of atoms." I would like to draw attention to the book by
van der Waerden, which contains all the more important treatises on the
origins of quantum mechanics as well as a thorough introduction to the
relationship between them.**
86
I.
I
My praise of my young collaborators, Heisenberg, Jordan and Hund, was
well deserved. They all rank among today's leading physicists. We used
the ｅxpression 'term zoology' to describe the compilation of experimental
data about spectral lines and their dissection into 'terms' which, according
to Bohr, indicate steps of energy in the excitation of the atom. No satis-
factory theory existed for the regularities found in this way, and they had
to be accepted as empirical facts, rather like the distinguishing charac-
teristics of zoological species.
Then comes the most important matter: a few fines about Heisenberg's
new paper, which seems to have appeared 'mystifying' but nevertheless true.
This must have been the treatise in which he formulates the basic concepts
of quantum mechanics and explains them by using simple examples. As
my recollection of this time, which marked the beginning of a revolution
in physical thinking, is a litUe hazy, I wrote to Prof van der Waerden, who
confirmed my assumption. His book will enable the reader to look up the
sequence of events in complete detail. I shall just mention those matters
which have a direct bearing on Einstein's letter.
Heisenberg gave me his manuscript on the i ith or 12th of July, asking me
to decide whether it should be published and whether I had some use for
it, as he was unable to get any further. Although I did not read it straight
away, because I was tired, I had certainly read it before I wrote to Einstein
on July 15th. The certainty with which I maintained that it was correct,
in spite of its mystifying appearance, seems to show that I had already
discovered that Heisenberg's extraordinary calculus was really nothing
other than the well-known matrix calculation; moreover, I already knew
that Heisenberg's reformulation of the conventional quantum condition
represents the diagonal elements of the matrix equation
pq-gp= — :
■^^ ^-^ 2771
and that therefore the remaining elements of the quantity pq - qp must be
zero. If this is the case I was cautious enough not to mention any of this to
Einstein, since the disappearance of the non-diagonal elements had first to
be proved. Van der Waerden's book describes how he succeeded in this
with Jordan's help, and how the paper by Heisenberg, Jordan and myself
came into being. The paper by Hund which I mention follows another,
slightly earlier, investigation of Heisenberg's. I have gone into these
matters in so much detail, even though they are not directly connected
with Einstein, because I am rather proud of the fact that I was the first to
write a quantum mechanical formula in 'non-commuting' symbols. Two
further scientific matters of importance are mentioned in this letter: Ein-
stein's field theory, which was intended to unify electrodynamics and
gravitation, and the satellite of Sirius. I think that my enthusiasm about
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BORN-EINSTEIN LETTERS
BORN-EINSTEIN LETTERS
the success of Einstein's idea was quite genuine. In those days we all
thought that his objective, which he pursued right to the end of his life, was
attainable and also very important. Many of us became more doubtful
when other types of fields emerged in physics, in addition to these; the
first was Yukawa's meson field, which is a direct generalisation of the
electromagnetic field and describes nuclear forces, and then there were
the fields which belong to the other elementary particles. After that we
were incKned to regard Einstein's ceaseless efforts as a tragic error.
A few remarks on the list of the visitors to Gottingen. Kramers was a
Dutchman, a pupil of Bohr's, extremely gifted, and a likeable person.
Kapitza was a Russian physicist, who had escaped to England from the
Bolshevik revolution when he was young and had studied in Cambridge.
He had a very successful career, working at the Cavendish Laboratory and
becoming a Fellow of Trinity College. His visits to Gottingen took place
during this period. Later he returned to Russia, made his peace with the
Communists, and achieved great distinction. Joffe, older by a generation,
had remained in Russia and was held to be the leading physicist in the
Soviet Union. Philipp Frank was a theoretical physicist at the German
University of Prague, and afterwards went to America. While in Prague he
made friends with Einstein and later wrote a captivating biography of him.
Kienle was professor of astronomy at Gottingen. The lecture I men-
tioned concerns an astronomical observation which can be regarded as a
confirmation of Bose and Einstein's theory of gas degeneracy. But as the
letter does not mention this relationship, I rather think that it had not
been clear to Kienle or to us.
50
7 March, igs6
Dear Mrs Bom
Your short letter was truly delightful. Stomach aching but head
held high; only the strong are able to manage that. Even so, it
must have been a splendid experience to accompany your hus-
band on his travels, for he had a great deal to give; and to receive
is also very pleasant, when it is balanced with the giving. The
Heisenberg-Bom concepts leave us all breathless, and have
made a deep impression on all theoretically oriented people.
Instead of dull resignation, there is now a singular tension in
us sluggish people. You experience only the psychological
aspect of all this, but no doubt in a purer form than someone
with a more materialistic outlook. The most important thing
88
at the moment is for you to make a complete recovery, so that
you will be able to run about in the sun again and live your life
freely. I know from experience how to get well: to exist like
a plant for a while, and to vegetate quietly and contentedly.
Unlike most of your sex you have not got the knack of this; I
imagine that lively little head of yours does not want to be put out
of action. Remember the past of Asia; then you will experience
the comforting haziness of all living things, and get well.
Meanwhile best wishes
Yours
A. Einstein
Apart from Einstein's amiable words about my wife's illness in America
and how to get well, this letter is remarkable for his attitude to quantum
mechanics. Heisenberg and I felt pleased, but it was not long before the
cooling offset in (letter No. 53).
The following letter is from my wife again.
During the winter of 1925-26 we were at the Massachusetts Institute of
Technology (MIT) in Cambridge, near Boston. I gave lectures there on
two subjects: crystal-lattice dynamics and quantum mechanics. These
have appeared as a booklet, published by MIT in English and by Springer
in GJerman; it is probably the first book on quantum mechanics. In this
book I gave so much prominence to Heisenberg that my own contri-
bution to quantum mechanics has received very little attention until
quite recently. When my course ended at the beginning of 1 926, we wanted
to set out on a journey across the continent, taking in the Grand Canyon in
Arizona and ending up in California. But my wife fell ill and was sent
back to Europe. So I had to travel by myself, and proclaimed the new
quantum doctrine at many universities. The result was that hordes of
Americans, and soon many other foreigners as well, visited Gkittingen
during the next few years. My wife went back to Germany and entered
Prof. V. Noorden's well-known sanatorium in Frankfurt to take the 'cure'.
51
II April, igs6
I
Dear Einstein
My thanks for your kind letters are rather late, but the last
three weeks in Frankfurt were anything but enjoyable (whole-
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sale dentistry with 5 gold crowns, three extractions, two jawbone
operations, etc.), so that I was really unable to think of anything
but teeth. This led to an amusing incident, for one day when I
was on my way to an extraction, quite absorbed, a gentleman
whispered in my ear: 'dreaming of spring'. Whereupon I
repUed drily: 'no, dentist'. And we both grinned and went our
separate ways.
I have just asked my friend Elli Rosenberg {nee Husserl, of
philosophical descent) to send you copies of my American
reports. You may be able to spare the odd hour or so one day to
glance through them. Max, too, has now returned to this
country; his letters from Boston and San Francisco contained
a lot of physics. I am hoping that we may be able to make a
short trip to Berlin about the beginning of May, and will be
able to tell you more then. For example. Max saw Miller's
experiments on Mt Wilson, and was aghast at the slipshod way
they were carried out.
My head is too tired tonight to produce even the slightest of
thoughts. I find it rather annoying to realise that the output of
one's brain is proportional to the increase or decrease of the
amount of fat on one's body. As I have not yet regained any of
the twenty or so pounds I lost, you can well imagine how short
of ideas I am. I have never been so sure of Heaven as I am at
present (see the Sermon on the Mount; and blessed are the
poor inspirit . . .).
Look after yourselves. With warm wishes
Yours
Hedi Born
52
4 December, igzG
Dear Bom
You will have to be a little patient. My son-in-law is certain
to read the play, and will write to you. But the poor man has
to economise with his strength, as his heart is in poor condition.
I have reminded him again to give an opinion on the play as
soon as possible. I hked the beginning of the play very much,
and I think its impact will not be lost on him.
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BORN-EINSTEIN LETTERS
Quantum mechanics is certainly imposing. But an inner
voice tells me that it is not yet the real thing. The theory says
a lot, but does not really bring us any closer to the secret of
the 'old one'. I, at any rate, am convinced that He is not
playing at dice. Waves in 3-dimensional space, whose velocity
is regulated by potential energy (for example, rubber bands) . . .
I am working very hard at deducing the equations of motion
of material points regarded as singularities, given the differen-
tial equation of general relativity.
With best wishes
Yours
A. Einstein
Hedi had sent her play ^ Child of America to Einstein, asking for his opinion.
Einstein's son-in-law, who had married the eldest of his step-daughters.
Use, was the then well-known and respected author and critic, Rudolf
Kayser.
Einstein's verdict on quantum mechanics came as a hard blow to me : he
rejected it not for any definite reason, but rather by referring to an 'inner
voice'. This rejection plays an important part in later letters. It was based
on a basic difference of philosophical attitude, which separated Einstein
from the younger generation to which I felt that I belonged, although I
was only a few years younger than Einstein.
53
14 December, 1926
Dear Mr Einstein
Today my 'Bill' arrives with his 'new nose', as you so aptly
called it. I hope you will laugh at the three further acts as
much as you did at the first one. I am tremendously pleased
and encouraged to know that you enjoyed it so much. For
one cannot gain sufficient distance from one's own creation
oneself; one lived with it so intensely and only parts from it with
great trepidation.
At the moment, when I am not planning any work, I feel
dull and without aim and purpose, and anaesthetise myself
by attending some fine lectures on the history of art. When one
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BORN-EINSTEIN LETTERS
has begun even so modest a work of art, one looks at the creations
of the masters with very different eyes.
It would be nice if you could drop me a few lines when you
have read Bill. Why don't you take him on to the sofa with you
after lunch ?
Margot wrote to tell me that your wife is ill. I wish her a
speedy recovery, and all of you a restful Christmas.
With kindest regards to you all from Max and myself
Yours
HediBom
54
6 January, igzy
Dear Mrs Bom
I have very much enjoyed reading your play, and I think it
could be quite successful as a satire on the contemporary scene.
It is witty and amusing throughout, though it seems to me that
as a work of art it does not do much to confirm the well-
documented truth that the centre of gravity for creative
activity is located in different parts of the body in men and
women. You make your characters dance like marionettes;
they are nothing but puppets in your hands, whose purpose is
to demonstrate your opinion to the child of our times; that is all.
They are not permitted to have any lives of their own. They are
rather transparent, like ghosts, more or less abstract. But your
wit saves the day. Bernard Shaw has often done something
similar, and his fireworks are enjoyed by everyone. I do not
know whether Rudi has read it yet; the poor man lives con-
stantly under a deluge of paper, while conditions have improved
quite considerably in this respect where I am concerned.
I am going to give the play to Mr Jessner, and tell him that
I consider it witty, amusing and up-to-date, and will give
him some idea of the contents. I hope it will make its mark.
Kind regards to you and your husband
Yours
A. Einstein
Jessner was then manager at the State Theatre in Berlin.
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BORN-EINSTEIN LETTERS
55
Gbttingen, Plankst. 2
[undated]
Dear Mr Einstein
Thank you very much for your criticism, which has occupied
my mind a great deal. I have by now had all sorts of criticisms,
frequently diametrically opposed, e.g., as to the relative value
of the various acts, but I am, of course, particularly interested
in a fundamental criticism such as yours. There, too, I have
already heard quite different opinions, for example from
Hilbert, who approved of Bill as a character. But I am by now
sufficiently detached from this child of mine to know myself what
is wrong with him. I expect you are right in saying that my
characters are too cerebral. (I am not sure that this is not
inevitable in any satire, unless one allows Mephistopheles
himself to appear in person.) For me, the idea, when I have one,
is the most important thing, not the human being and its fate.
At best, an idea is closely bound up with a certain person. It is
not that the idea has to be extracted from my brain with pincers
and forceps; it arrives of its own accord after a particularly
powerful emotional experience. I once wrote to Margot: If I
had not felt such a tremendous disgust with our times (i.e. with
what I want to attack), I would never have foimd the strength
for creative ｅxpression. Why I experience this so overpoweringly
I cannot say. The serious purpose which provoked the play
may now be difficult to detect. It is one of the crazy contra-
dictions of my nature, though probably lucky for me, that all
tension and suffering is resolved in a smile.
I am fully aware that satire on the contemporary scene is, by
definition, condemned to be of temporary interest only. I still
hope that if one day I can give shape to more timeless problems
(which directly influence and control fate) I will find the proper
note to sound. I hope, but I certainly have no illusions about
myself. As you were kind enough to call me 'witty', you would
hardly expect me to be blind to my own nature.
There is no need to tell you that I myself am able to see, and
really get to know, my characters in my mind's eye. I was
'possessed' by them, for otherwise I would not have been able
to make them speak as they should. But what interests me most
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BORN-EINSTEIN LETTERS
in people is their spiritual attitude to life, rather than just their
fate; most of the so-called tragic destinies are nothing more
than the brutal vicissitudes of life, which are linked by pure
chance to one particular individual. When I think of you, for
example, I do not think of individual talents and achievements,
but I marvel at your supreme mastery of life itself. I remember
something you once said, which for me is the key to your per-
sonality and way of thinking: when you lay gravely ill you
said: 'I have such a feeling of solidarity with every living
being, that it does not matter to me where the individual begins
and ends'. You probably put it much more beautifully, but
this is what you meant. Individual acts mean nothing to me:
they are just a momentary flash of light.
Now to your droll pronouncement about creativity : 'the centre
of gravity for creative activity is situated in different parts of
the body in men and women.' Here the usual interpretation of
'head' and 'heart' does not apply, as, of all things, you have
conceded me 'wit'. And as to the still cruder, purely geometrical
interpretation? I would not put it past you. But even in this
case the contradiction above still applies, for wit is in the head.
And is the effort of imagination needed for a play that grows
from nothing, and for its dramatic composition, not really a
creative activity? Please do not misunderstand me: I am not
just trying to defend myself, but I cannot quite understand
what you mean. You could not really mean that women are
incapable of creating rounded characters. Do you know
•Kristin Lavranstochter' by Sigrid Undset? (particularly the
first volume). I beUeve that every creative person shows
in his characters what is most important to him personally;
where his own struggles lie. The passionate person over-
emphasises passion, the ecstatic ectasy, the split personality
the split, etc. A Shakespeare, who combines everything, is surely
unique.
I am most grateful to you for offering to pass the play on.
I do hope you do not find it embarrassing. At the special request
of the children, I enclose the result of a writing game we
played yesterday. They are sketches which are made up as
follows: one person draws the head, a second the trunk, a third
the lower part of the body, and none of them knows what has
been done by the others before him. Finally, a name is written
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underneath at random. You are going to be very pleased with
your portrait.
Kind regards to you all from Max and myself,
Yours
HediBom
56
I J January, igz^
Dear Mrs Bom
A few days ago I gave your manuscript to Jessner, who has
already promised to examine it. You should not take my
little joke too literally, nor as an 'either-or'. It is not meant too
seriously, nor does it claim that the following assertion is
unambiguous: one smiles, and goes on to the business of the day.
What applies to jokes, I suppose, also applies to pictures and to
plays. I think they should not smell of a logical scheme, but of
a delicious fragment of life, scintillating with various colours
according to the position of the beholder. If one wants to get
away from this vagueness one must take up mathematics. And
even then one reaches one's aim only by becoming completely
insubstantial under the dissecting knife of clarity. Living
matter and clarity are opposites - they run away from one
another. We are now experiencing this rather tragically in
physics.
By the way, there is no need for you to defend your work to
me, for I have every respect for it and enjoy it. It is rarely that
one finds someone like you who has such a wealth of ideas
allied with charm.
The best of luck for your endeavour, for yourself and for
your family.
Yours sincerely
A. Einstein
Many thanks for the lovely combined photo.
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BORN-EINSTEIN LETTERS
57
[undated]
Dear Born
I have just noticed that in my slovenliness I forgot to send you
the enclosed paper. You v/ere therefore unable to understand
the rest. Please forgive me.
Last week I handed in a short paper to the Academy, in
which I show that one can attribute quite definite movements to
Schrodinger's wave mechanics, without any statistical inter-
pretation. This will shortly be published in the minutes of the
meetings.
Kindest regards
Yours
A. Einstein
These lines had been added to a letter of Ehrenfest's to Einstein. They
concern some professional appointment, no longer of interest today.
The note shows that Einstein rejected the statistical interpretation of
quantum mechanics not just because of his 'inner voice'. He had tried a
different, non-statistical interpretation of Schroedinger's wave mechamcs
and was submitting a paper about it to the Academy. I cannot remember
it now; Uke so many similar attempts by other authors, it has disappeared
without trace.
At this point there is an interval of a year and a half in the correspondence.
Whether letters have been lost, or whether silence really reigned, I do not
know.
58
Institute for Theoretical Physics
of the University
Gottingen
Bunsenstr. g
so February, igzS
Dear Einstein
After consultation with Harald Bohr, who is in Gottmgen
this term, I want to write to you about a matter which is,
strictly speaking, none of my business, but which nevertheless
has caused me alarm and uneasiness on many occasions. I am
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BORN— EINSTEIN LETTERS
referring to the Hilbert and Brouwer affair. Up to now I have
merely followed it from a distance, and have only recently been
initiated into all the details by Bohr and Courant. In this way I
learnt that you remained neutral with regard to Hilbert's letter
to Brouwer, on the grounds that one should permit people to be
as foolish as they wish. I find this quite reasonable, of course, but
you seem not to be quite in the picture on some points, and so I
want to write briefly and tell you about it. There will probably
be a conference soon at Springer's about this matter, and Bohr
told me that he considered it very important for the inner
editorial staff to present a united front. I would therefore ask
you please to maintain your present neutrality, and not to take
any action against Hilbert and his friends. It would help to
restore my peace of mind, as well as Bohr's and that of many
other people, if you could write a few words to me about this.
I would like to tell you briefly why this business interests me.
It only matters to me because I am worried and concerned
about Hilbert. Hilbert is very seriously ill, and has probably
not very long to live. Any excitement is dangerous for him, and
means losing some of the few hours left to him in which to live
and to work. He still has, however, a powerful will to live, and
considers it his duty to complete his new basis for mathematics
with whatever strength is left to him. His mind is clearer than
ever, and it is an act of extreme callousness on Brouwer's part
to spread the rumour that Hilbert is no longer responsible.
Courant and other friends of Hilbert's have frequently said
that the sick man should be protected against any excitement,
and Brouwer has misrepresented this to mean that one should
no longer take Hilbert's actions and opinions seriously. Hilbert
is quite in earnest about his proposed action against Brouwer.
He talked to me about it a few weeks ago, but only in quite
general terms and without going into any detail. In his opinion
Brouwer is an eccentric and maladjusted person to whom he
did not wish to entrust the management of Mathematische
Annalen. I think Hilbert's evaluation of Brouwer has been shown
to be correct in view of Brouwer's most recent actions. In my
experience, Hilbert's judgment is almost always clear and to
the point in human affairs.
I have followed the previous history of the whole business,
including the quarrel about the visit to the Congress in Bologna,
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BORN-EINSTEIN LETTERS
from a distance only. But I do know that the visit to this
Congress was a heavy burden for Hilbert; anything of this kind
meant a tremendous exertion for him because of his illness.
Hilbert is not politically very left-wing; on the contrary, for my
taste and even more for yours, he is rather reactionaiy. But
when it comes to the question of the intercourse between
scientists of different countries, he has a very sharp eye for
detecting what is best for the whole. Hilbert considered, as wc
all did, that Brouwer's behaviour in this affair, where he was
even more nationalistic than the Germans themselves, was
utterly foolish.
But the worst of it all was that the Berlin mathematicians
were completely taken in by Brouwer's nonsense. I would like
to add that the Bologna business was not the decisive factor -
only the occasion for Hilbert's decision to remove Brouwer. I
can understand this in Erhard Schmidt's case, for he always
did lean to the right in politics, as a result of his basic emotions.
For Mises and Bieberbach, however, it is a rather deplorable
symptom. I talked to Mises about it in August, during our
journey to Russia, and he said right at the beginning of our
discussion that the people in Gottingen were blindly following
Hilbert, and that he was probably no longer responsible.
Thus the allegation about Hilbert's weakened mental powers
was made even then. I then immediately broke off my discussion
with Mises, for I do not consider him significant enough to
allow himself the liberty of passing judgment on Hilbert. I
also enclose a paper which Ferdinand Springer sent to Bohr
and Courant. This shows that Brouwer and Bieberbach have
threatened to denounce Springer as lacking in national feeling,
and that they would do him harm if he remained loyal to
Hilbert. I need not tell you what I think of such behaviour.
Forgive me for bothering you with so long a letter. My only
desire is to see that Hilbert's earnest intentions are put into
effect without causing him any unnecessary excitement. I
would have no objection to your showing this letter, or part of it,
to Schmidt, if you consider it correct. As an old friend of
Schmidt's I believe that it is possible to negotiate successfully
with him even if he is of a different opinion. I hope that you
yourself are feeling much better now. I get news of you from
time to time in Margot's letters to my wife. Those two are very
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BORN-EINSTEIN LETTERS
close friends indeed, and suit each other. I myself am busy
completing a book on quantum mechanics, which I have been
writing for the last year. Unfortunately I have overtaxed my
strength a little in doing this, and will probably have to go on
leave for a time during January. It is really not at all easy to
find the time and strength for that kind of work, on top of all
the lectures and other professional duties.
With kindest regards, also from my wife to yours
Yours
Max Bom
Harald Bohr, a brother of the physicist Niels Bohr, was a notable mathe-
matician who frequently visited us in Gottingen.
David Hilbert, my revered teacher and friend, was then (and still is)
considered to be the foremost mathematician of his time. At that time he
was busy trying to find sounder logical foundations for mathematics, in
order to eliminate the intrinsic contradictions found by Bertrand Russell
and others in the theory of infinite sets, without sacrificing any previous
mathematical knowledge. This led him to consider true mathematics as
a kind of logical game with symbols, for which arbitrary axioms are found.
The latter, however, should be applied by a 'metamathematics' based on
evident, real conclusions. Brouwer rejected this concept of mathematics,
and suggested another, termed intuitionism. The two ways of thinking
differed in one essential result. Hilbert's concept justified the so-called
existence proofs, whereby the existence of a certain number or a mathe-
matical truth is deduced from the fact that to assume the contrary would
lead to a contradiction. Brouwer, however, postulated that the existence of
a mathematical structure could only be taken for granted if a method
could be found that would actually construct it. As it happened, many of
Hilbert's greatest mathematical achievements were precisely such abstract
proofs of existence, which for some time had not only been accepted by
the mathematical world, but had been celebrated as great feats.
It is therefore no wonder that Brouwer's behaviour greatly upset Hilbert,
and that he expressed his opposition in no uncertain terms; whereupon
Brouwer replied with even greater rudeness. To make matters worse, a
political quarrel broke out on top of the scientific one. After the 1914-18
war, 'International Unions' had been founded for all the principal
branches of science; the Germans, however, had been excluded from
them. The hatred directed against Germany gradually diminished, and
at the time this letter was written (1928) the German mathematicians
were about to be admitted to the 'International Union for Mathematics',
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BORN-EINSTEIN LETTERS
on the occasion of a large mathematical congress in Bologna. But a group
of 'national' German mathematicians protested against this; they felt
that it would not be right to join the Union without further ado after
having been excluded for such a long time, and that one should protest
against it in Bologna. Three important BerUn mathematicians were
amongst the leaders of this movement: Bieberbach, who was a good
analyst; von Mises, a research worker of some significance, who was also
concerned with theoretical physics; and Erhard Schmidt, the most
outstanding of the three. Schmidt and I had been friends ever since my
student days and, although poUtically we were poles apart, we always
remained on the best of terms. But the Dutchman Brouwer was more
nationalistic than aU these proved to be. Hilbert went to Bologna, despite
his grave illness, and faced his adversaries. As far as I can remember, he
got his way and the Germans joined the Union. But the whole business
had annoyed him so much that he expelled Brouwer from the management
of the Mathematische Annalen.This started a new storm amongst German
mathematicians. But Hilbert finally got the upper hand.
The whole affair was, strictly speaking, no concern of mine. But, as I said
in the letter, I was moved to intervene by my anxiety about the state of
Hilbert's health. Hilbert suffered from pernicious anaemia, and would
no doubt have died within a short time had not Minot in the United
States discovered the specific remedy, a Uver extract, just in time. This
was not yet commercially available, but the wife of the Gottingen
mathematician Edmund Landau was a daughter of Paul Ehrlich, the
founder of chemotherapy and discoverer of Salvarsan. It was due to his
good offices that Hilbert was able to receive regular supplies of the
extract and so to live for many more years.
I doubt whether my letter to Einstein had any influence on the course
of the great mathematical quarrel.
As for the further development of the fundamental problems of mathe-
matics, Brouwer had many supporters to begin with, including some
important ones such as Hermann Weyl. But gradually Hilbert's abstract
interpretation was, after aU, reaUsed to be by far the more profound.
Things took a new turn when Godel discovered the existence of mathe-
matical theorems which can be proved to be incapable of proof. Today,
mathematics is more abstract than ever, and exacdy the same is true of
theoretical physics. , . . ,
The journey to Russia I mention was a kind of wandering physicists
congress, organised in Leningrad by Joffe, who has been mentioned
before. It began in Leningrad, and was continued first in Moscow and
then in Nizhni-Novgorod; there the participants boarded a Volga steamer
and travelled down river, stopping at all the large towns en route to con-
tinue the congress. The whole thing was very fascinating and stimulating.
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BORN-EINSTEIN LETTERS
but extremely fatiguing. I went as far as Saratov, and from there returned
to Germany by train.
The book about quantum mechanics I mentioned at the end of the letter
was written in collaboration with Jordan over a period of several years.
59
Gottingen
12 August, igsg
Dear Einstein
A young Russian turned up here some time ago with a six-
dimensional theory of relativity. Since I was already uneasy
about the various five-dimensional theories, and as I was
not at all convinced that it could lead to anything worthwhile,
I was very sceptical. But he talked very intelligently and soon
convinced me that there is something to his ideas.
Although I understand less than e of this matter, I have sub-
mitted his paper to the Academy of Gottingen, and enclose a
copy of it and urgently request you to read it and evaluate it.
The man, whose name is Rumer, left Russia because relati-
vists are badly treated there (truly!). The theory of relativity is
thought to contradict the official 'materialist' philosophy and,
as I have already been told by Joffe, its adherents are persecuted.
Rumer came to Germany, and has somehow managed to study
at the technical school in Oldenburg, where he is now going
to sit for the technical exam. Afterwards he intends to try and
make a living here as best he can, and if he fails, to emigrate to
South America.
If the paper makes a good impression on you, I would ask
you please to do something for this man. He is familiar with the
literature of mathematics, from Riemann's geometry right up
to the very latest publications, and may well be the ideal assistant
for you. He has a pleasant personality, and gives the impression
of being extremely intelligent. I do not know whether he is
really Russian, or Jewish; but I think the latter the more
likely. His address is: Georg Rumer, Oldenburg, Am Festungs-
graben 8.
I am still not feeling particularly well. I spent eight days in
Waldeck with my children, but it was noisy and restless. My
lOI
BORN-EINSTEIN LETTERS
nerves are in a bad state. Next week I travel alone to the
Vierwaldstatter See, where an acquaintance (a Swiss solicitor)
has a cottage and a motorboat in Kehrsiten-Burgenstock
(my address there is : Hotel Schiller) . I saw your picture in the
last issue of the Illustrierte in a sailing boat, looking sunburnt.
Hedi is suflfering from colitis, and is undergoing a strict dietary
cure.
With kindest regards, also to you wife and to Margot.
Yours
Max Born
I enclose an outline of the contents of a book Rumer intends to
write.
I continued to find Rumer's six-dimensional theory of relativity alarming.
Later on we wrote a short paper together on nuclei; its purely speculative
nature was more representative of his mentality than of mine.
The hostile attitude of official Communist philosophy towards the theory
of relativity continued for a long time. Perhaps Rumer's fate was connected
with this. When I flew to Moscow as a member of the English delegation
to the 25th Jubilee celebrations of the Soviet Academy in June 1945, soon
after the end of the war, and enquired after Rumer, it was hinted that he
was in disgrace and had disappeared. I heard nothing from him until
he sent me congratulations on my 75th birthday, from Novosibirsk.
I wrote asking what had happened to him, and he replied with a long
letter saying that he had been deported and had lived for many years
in one of the terrible camps near the Arctic Ocean. He had managed to
survive only because of the help of a kindly nurse, who was now his
wife. After the death of Stalin he received a telegram, which not only
gave him back his freedom but also recalled him to Moscow, where he
was appointed head of the Institute of Physics at the new scientific
centre in Novosibirsk. He is now one of the most important men in
Soviet science.
The strange thing is that his long period of suffering in northern Siberia had
aroused no bitterness, no hostility towards the regime. on the contrary,
he wrote me long letters in which he tried to convince me that the Soviet
system is superior to Western institutions, not only politically and econo-
mically, but also morally.
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60
Institute for Theoretical Physics
Gottingen
Bunsenstr. g
13 January, igsg
Dear Einstein
The upheavals of the beginning of the university term have
prevented me from answering your good long letter until
now. I also wanted to discuss your remarks with Jordan and
he has only recently arrived here. We are very grateful to
you for your criticism, and have altered the relevant passage in
our book accordingly. You are, of course, absolutely right that
an assertion about the possible future acceptance or rejection
of determinism cannot be logically justified. For there can
always be an interpretation which lies one layer deeper than
the one we know (as your example of the kinetic theory as
against the macroscopic theory shows). Jordan and I are not
much inclined to beUeve in anything like that, but of course we
should not claim anything for which we have no rigorous proof,
and therefore we have altered the passage in question ac-
cordingly. . .
I am now reading the theory of relativity, not only because 1
have to teach it to my students, but also to feel at home again
in this field. I hope to progress as far as your most recent papers,
and will then study them carefully and let you know my opinion.
Rumer is staying here in Gottingen. He has obtained a grant
from Warburg in Hamburg, which enables him to study here
a little longer.
My wife is now quite well again; but she would very much
like Margot to come here for a visit. I would like to enter into
a conspiracy with you. Hedi's birthday is on December 14th,
and I wonder if it would be possible for Margot to pay us a
surprise visit on that day ? That would give us a lot of pleasure.
With kindest regards to your wife and to Margot.
Yours
Max Bom
The letter in which Einstein criticises a passage in our book seems
unfortunately to have been lost. But the gist of his remarks is clear from
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BORN-EINSTEIN LETTERS
my letter. At this point I would like to say a few words about that book.
Shortly before the discovery of quantum mechanics, I had published a
book in collaboration with Friedrich Hund (then my assistant) . ** This book
was still based on the Bohr-Sommerfeld theory, which grafts 'quantum
conditions' on to the classical laws of mechanics; it has recently been
re-issued in America in an English version by Fisher and Hartree. In the
introduction it says: 'I have called this book Volume one; the second
volume is to contain a closer approximation to the "ultimate" atomic
mechanics. I realise that it is rash to promise such a second volume, as
for the time being there are only a few vague indications as to the nature of
the changes which must be made to the classical laws in order to explain
the properties of the atoms.' But before the end of that same year, papers
by Heisenberg, Jordan and myself were published, laying the foundations
for the new mechanics. Thus I was soon able, with Jordan's assistance,
to tackle the writing of the promised second volume. In the introduction to
this volume it says : 'My hope that the veil then still obscuring the essential
structure of the atomic laws would soon fall h£is been realised with sur-
prising speed and thoroughness'. It took several years to write the second
volume. In the meantime, Schroedinger's wave mechanics appeared,
and won the approbation of theoretical physicists to such an extent that
our own matrix method was completely pushed into the background,
particularly after Schroedinger himself had shown the mathematical
equivalence of wave and matrix mechanics.
Jordan and I, however, were convinced that our method was the better
one, and that Schroedinger's wave equation was preferred because it
took as its point of departure traditional ideas of mathematical physics
(eigenvalue problems of oscillating systems). Schroedinger himself even
claimed, and maintained throughout his lifetime, to have eliminated
quantum theoretical peculiarities such as quantum jumps by his theory. In
our opinion Heisenberg's method was more deeply penetrating. Wave equa-
tions in more than three dimensions are no 'return to classical concepts'. It
is true that I had supported my statistical interpretation of quantum
mechanics (1926) by the argument, inter alia, diat I considered the
collision of particles with other particles as a scattering of waves. But this
was only a simple borderline case, where the three-dimensional, intuitive
description could be used. Jordan and I regarded quantum mechanics,
as developed by us in Gottingen and independently by Dirac in Cam-
bridge, as the implementation of Bohr's correspondence principle; that
is why our book is dedicated to Niels Bohr. We planned a third volume
which was to put wave mechanics into its rightful place, but we did not
get that far. The completion of the second volume took much longer than
we had expected, and then our ways parted. Because of the general
predisposition in favour of Schroedinger, our second volume was not
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BORN-EINSTEIN LETTERS
favourably received. I recall in particular a review published by Pauli,
which was utterly destructive.
Now the situation seems to be changing. At the conference of Nobel
prizewinners for physics in Lindau in the summer of 1965, Dirac said in
a lecture that he believed the reason for the great difficulties with the
quantum field theory, which were leading to almost grotesque tricks such
as infinite renormalisation, to he partly in the fact that Schroedinger's
ideas, and not those of Heisenberg, were used as a starting point. He went
so far as to say, 'For the purpose of setting up quantum electro-dynamics,
Schroedinger's is a bad theory, Heisenberg's a good one.' I believe that
Dirac is right, and that the preference for Schroedinger is based only on
the fact that he works with familiar thought processes. Our old book may
thus enjoy a renaissance. Almost all the textbooks published in the
meantime deal principally with wave mechanics.
After this digression into physics, I return to Einstein's letter. Jordan
and I had apparently sent him the proofs of our book, possibly in the hope
of changing his negative attitude towards quantum mechanics. But it did
not succeed. He particularly objected to a passage in the book (presumably
in the introduction) in which we called the statistical interpretation of
physics the final one. We gave in to his request to alter this passage,
although we did not change our opinion. Today this view is probably
shared by the vast majority of physicists.
61
14 December, igsg
Dear Bom
Your lucid letter gave me much pleasure. The complete
person is revealed by both important and unimportant actions.
I liked Rumer very much. His idea of using a multidimen-
sional treatment is original, and formally well developed. Its
weakness lies in the fact that the known laws are incomplete,
and there seems no logical way of completing them.
In any case, it would be gratifying if one could make it
possible for him to do scientific work, and this could, of course,
best be done by giving him some routine job which would leave
him enough spare time for independent work. Unfortunately,
such opportunities do not exist. Would it really be impossible
to create grammar school teaching posts or similar official
appointments for this kind of case, with a reduced number of
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BORN-EINSTEIN LETTERS
teaching hours and pay? This would be definitely more
satisfactory than grants for a limited period, for the stork is
Bohemian when it comes to intellectual births, and refuses to
accept a fixed delivery date.
Kind regards,
Yours
[no signature]
62
Institute for Theoretical Physics
Gdttingen
Bunsenstrasse g
ig December^ igsg
Dear Einstein
I am very pleased that you want to take Rumer under your
wing. The idea of giving him some sort of routine job which
would leave him enough spare time for his scientific work is,
of course, good in theory but extremely difficult to implement
in practice. The establishment of grammar school teaching
posts with reduced hours of teaching and lower pay is desirable,
but would of course be very difficult to achieve, and then
probably only after years of preparatory work. My own
relations with the Ministry are far too tenuous for me to be able to
effect anything in this direction. But perhaps your influence would
be successful. This seems to me a practical problem where you
could well use the full weight of your name to benefit young
people. Would it be possible for you to make an appointment
with Richter, the permanent head of the ministerial department,
and put the case to him ?
But such wild hopes as these will not help Rumer at this
moment. Incidentally, he has completed a technical training
course at the Technical School in Oldenburg, and passed his
finals there. He could therefore look for a job in practice, but
while there is so much unemployment a foreigner has practically
no chance of finding a job in Germany. In my opinion we can
do nothing else now but get him a grant, for at least one year.
My wife told me that you and Ehrenfest had offered to do
this, and to obtain it from the Rockefeller Foundation. I do
not want to approach them under any circumstances just now,
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BORN-EINSTEIN LETTERS
as they have treated me rather badly. Tisdale was here last
spring, and when he saw how badly my nerves were playing me
up he suggested that he would have me sent to California for
a few months, at the expense of the Rockefeller Foundation. At
the time I declined his offer because I hoped to recover suffi-
ciently during the holidays. But when I was not very much
better after the long vacation, I wrote to Tisdale again and
reminded him of his proposal. Thereupon he refused rather
brusquely to support my application at Head Office. I can
really only think of one explanation for this, and that is that
the Rockefeller people have something against Gottingen.
Maybe something I don't know about happened when the
Mathematical Institute was being established. Therefore I
should not like to put a proposal to him just at the moment.
Please, therefore, be kind enough to write to Tisdale (The
Rockefeller Foundation, 20 rue de la Baume, Paris), and apply
for a grant for Rumer for a year's stay with you, or with me
perhaps, or someone else, and please add that Ehrenfest and I
would wholeheartedly support it. But I will not conceal the
difficulties from you: generally the Rockefeller people strictly
obey the rule to hand out stipends only to those who can prove
that they have a definite salaried position in their own country.
This does not apply in Rumer's case. But it is just possible that
your name may be enough to have an exception made in this
case.
Laue has sent me an attractive invitation to lecture to the
Physical Society [Physikalische Gesellschaft] in Beriin in January.
I accepted with pleasure, as I have not seen any of you for such
a very long time. I'm afraid I have no very special news for you
as regards physics.
Hedi sends her best wishes to you all, and particularly to
Margot.
Yours
Max Born
Einstein expressed over and over again the thought that one should not
couple the quest for knowledge with a bread-and-butter profession, but
that research should be done as a private spare-time occupation. He
himself wrote the first of his great treatises while earning his Uving as an
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BORN-EINSTEIN LETTERS
employee of the Swiss Patent Office in Berne. He believed that only in
this way could one preserve one's independence. His proposal to create a
part-time grammar school teaching post for Rumer was in accordance
with this. What he did not consider, however, was the organisational rigidity
of almost all professions, and the importance which individual members
of a profession attach to their work. No professional pride could develop
without it. To be able successfully to practice science as a hobby, one has
to be an Einstein.
63
Pasadena
5 February, igji
For the last five weeks we have been loafing in this paradise
without, however, forgetting our friends.
Kind regards
Yours
A.E.
64
Gottingen
Wilhelm Weberstrasse 4s
22 February, zgji
Dear Einstein
When Hedi saw your entry into California on film, she thought
of you as completely caught up in the hectic turmoil of American
life. We were all the more pleased to receive your card, which
arrived today. It is nice to feel that you think of us from time
to time. I expect you are brooding on cosmology, expansion of
the universe, and similar matters. We were lectured on these
questions in the astronomy seminar, where Weyl intervened
with explanatory comments. Weyl is altogether a most valuable
addition to our circle. He often attends the physics colloquium,
regularly visits my theoretical seminar, frequently takes part
in the discussion, and everything he has to say is, as a rule,
tremendously lively, intelligent and ingenious. My young
people have learned a great deal from him, but then the seminar
has inspired him to write two short papers about the application
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of group theory to molecules and valencies for the Gottinger
J^achrichten. Our personal relationship with the Weyls is also very
pleasant, as both of them have a variety of literary interests,
and this brings them into contact with Hedi.
I am glad that the term will soon be at an end, for I have
been working extremely hard. I worry about quantum electro-
dynamics; I feel I have made a promising start, but it is
abominably difficult. The problem is to eliminate the infinite
self energy of the electron and everything connected with it. In
addition I have been writing up my optics lectures, which I
want to publish some day in order to earn some money. Apart
from that, there is little to report from Gottingen. Occasionally
we go to the cinema to see how beautiful it is elsewhere, and
your card with the orange trees has reawakened our longing
for faraway places. A few years ago, in Como, I think, Millikan
asked me if I would like to go to Pasadena for six months. At
that time I replied that I did not want to be separated from my
children for such a long time when they were so young. Now the
girls are almost grown-up, and we could get away easily in a
few years' time. Could you please ask Millikan, when the
opportunity arises, whether he could perhaps use me in eighteen
months' or two years' time? I could not do it earlier than that
for other reasons; from next October I have to be Dean for
a year. For all of ten years I have shirked this office by my
partly genuine, partly feigned blockheadedness in official
business matters, but it will not do any longer. Well, I hope to
get through this year, too. My collaborator Rumer, on whose
behalf I once wrote to you, will now be able to remain with me
for another year as my assistant. Heitler is going to America
this summer to Columbus, Ohio, and Rumer is going to replace
him. I have scrounged some money for the winter.
At Christmas I spent twelve days in Switzerland as the guest
of an industrialist friend of mine, and visted Zurich on the way
back. I gave a lecture there at the invitation of the student body,
and afterwards, when we continued our session in a local pub, I
met your son. I liked him very much; he is a fine, intelligent
fellow and laughs in exactly the same wonderful way as you do.
Well, what else is there to tell you? Things in Europe do not
look pleasant, either politically or economically. We also have
personal worries, like so many other people about 'displaced'
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BORN-EINSTEIN LETTERS
relatives. But things must surely improve in spite of Hitler and
his consorts. I know all sorts of things about California, as I am
just reading Ehrenfest's wonderfully vivid, descriptive letters
about his travels which he has sent to Hedi. How well that
fellow observes and describes his experiences. While reading I
can quite clearly see the Californian landscape in front of me,
as well as the dear people there; particularly the Tolmans,
Epstein and the Millikans. Please give them all my warmest
regards. I expect Hedi will want to add a few words of her own.
This letter is meant to be a birthday greeting, so will have to
reach you at approximately the right time.
Best wishes to your wife. From Margot, the young wife, we
hear little.
Yours
Max Bom
Dear Einsteins
I just want to add my loyal good wishes. Keep well, both of you.
I am always very amused to see and hear you in the weekly
newsreel - being presented with a floral float containing lovely
sea-nymphs in San Diego, and that sort of thing. The world
has, after all, its amusing side. However crazy such things may
look from the outside, I always have the feeding that the dear
Lord knows very well what he is up to. In the same way as
Gretchen sensed the Devil in Faust, so he makes people sense in
you - well, just the Einstein. For none of them will ever be
able to really know you - however thoroughly they may have
studied the theory of relativity.
God bless you all. Our little Margot remains silent - silent -
silent.
In warmest friendship.
Yours
Hedi Bom
I do envy you the orange trees and the blue skies.
The allusion to cosmology and expansion of the universe refers to the
discovery by the American astronomer Hubble, which created a sensation
in those days. He showed that the more distant star systems, called
1X0
BORN-EINSTEIN LETTERS
galaxies, which all resemble our own Milky Way, are moving apart with a
velocity which is greater the further away they already are. It was as a
result of this discovery that the renewed interest in cosmology initiated
by Einstein's theory of relativity, gained further momentum.
Hermann Weyl, who had been a student and private lecturer in Gdttingen
at the same time as I was, became Hilbert's successor. Weyl was one of the
last of the great mathematicians to concern himself with theoretical physics
and astronomy. He made important contributions to both. When Hitler
came to power he went to Princeton, to the 'Institute for Advanced
Study', where Einstein too had gone.
The year I was Dean was one of the worst of my academic life. The
German Cabinet, under Chancellor Briining, was forced to take extreme
economic measures as a result of the crisis in Europe caused by the collapse
of the American financial system. An order thus went out to the univer-
sities to dismiss immediately a large proportion of the younger assistants and
other paid staff. Many members of our scientific faculty found this shocking :
firstly, because it was cruel to single out the young, struggling ones, many
of whom were married, for dismissal, and to deprive them of their already
meagre incomes; furthermore, it would paralyse the activities of the
institutes, practically bringing them to a standstill. We formed a com-
mittee and decided to propose to the faculty that we would pay most of
the people affected out of our own pockets by offering to make a volun-
tary contribution which amounted to less than lo per cent of our salaries.
The battles this caused within the faculty still make me shudder. In the
course of an interminable meeting we won with a considerable majority.
But those who were outvoted displayed an animosity we had never
before experienced; amongst them were some historians, but most of them
were agriculturalists and forestry people. Six months later we knew what
they really were : disguised Nazis, who considered solicitude for the indi-
vidual just as superfluous as the existence of scientific institutes. The
only bright spot occurred when I personally told the Curator of the
University, Geheimrat Valentiner, the faculty's decision. He was so
moved that tears came to his eyes; he said something Uke, 'if all corporate
bodies acted as unselfishly as your faculty, our country would soon be
rid of its problems.'
Walter Heitler was my assistant for many years, together with Lothar
Nordheim. While the latter went to America (California) during the Hitler
period, Heitler first went to England, and later became Professor at the
Institute for Advanced Studies in Dublin. He eventually became pro-
fessor in Zurich as a result of his significant work with F. London on the
quantum theory of chemical components and on cosmic radiation, as well
as his splendid book about the quantum theory of radiation.
The industrialist friend mentioned in the letter was Carl Still, from
III
BORN-EINSTEIN LETTERS
Recklinghausen, whom I mentioned before (commentary to letter No. 30).
As regards my optimism about the political situation, this letter must
have been written during one of my momentary spells of hopefulness.
But I remember very well that I was just as prone to moments of complete
despair. The poor condition of my nerves, frequently mentioned in these
letters, was due not only to overwork but also to other worries, mainly
political ones. At the beginning of the year 1929, I think, I was sent to a
sanatoriimi at Constance on Lake Constance; there I was kept in bed
at first, but was later allowed to sit in the lounge and talk to people. But
the conversation of the patients, who were manufacturers, doctors,
lawyers, or at any rate all people from the upper middle classes, was
almost wholly about Hider and the high hopes they had of him, inter-
spersed with virulent attacks on the Jews. This drove me back to my room
again. I was only able to recover completely when I escaped from the
sanatorium and went to Konigsfeld in the Black Forest. During lone
treks on skis I got the better of my worries, and towards the end of my
stay I got to know Albert Schweitzer. While walking past a church I
heard wonderful organ music, and went inside. There at the organ I
found Dr Schweitzer, well-known to me from photographs. I spoke to
him during an interval in his playing. In the course of several long walks
he told me about his life and his work in Lambarene. This helped me to
recover my equilibrium. The political optimism displayed in my letter
may well have been connected with this. The American friends mentioned
in connection with Ehrenfest's letters from the United States are all high-
ranking physicists : Tolman, who was mainly known for his work on the
theory of relativity and cosmology; Epstein, through his contributions to
Bohr's theory of atomic structure; Millikan, for his final confirmation of
the corpuscular structure of electricity and his exact measurement of the
charge of the electron.
65
Institute for Theoretical Physics
Gottingen
Bunsenstr. g
6 October, 1Q31
Dear Einstein
By the same post I am sending you a new paper by Rumer,
which shows, it seems to me, real progress in the direction he
has pursued for many years. I am well aware that you are
occupied with an entirely different range of ideas, but perhaps
you will find time to have a look at Rumer's paper. I think his
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BORN-EINSTEIN LETTERS
Statement is quite correct; the assumption of a Riemann space
leads inevitably to certain assumptions about the matter
tensor and fairly necessarily to a curious new kind of field
theory of matter. The question is, should one continue in this
direction and elaborate this field theory, or should one - as you
are trying to do - change over to a wholly new geometry ? I have
no opinion on this. However, I think that every avenue should
be explored.
With kind regards, also from my wife.
Yours
M.Bom
There are about eighteen months between this letter and the next, during
which time so much happened that scientific matters receded into the
background. Several elections for the Reichstag were held, which increa-
sed the number of Nazi delegates, and Hitler's power grew accordingly.
His brown hordes terrorised the country. Then came Hitler's seizure of
power. And one day (at the end of April, 1933), I found my name in the
paper amongst a list of those who were considered imsuitable to be civil
servants, according to the new 'Laws'. Franck was not amongst them; as
a front-line warrior during the first world war he was excused for the time
being.
Einstein was in the United States during this period. He returned to
Europe in the spring of 1933, but went to Belgium and England and not
to Germany, where his life could have been in danger.
After I had been given 'leave of absence', we decided to leave Germany at
once. We had rented an apartment for the summer vacation in Wolken-
stein in the Grodner valley (Selva, Val Gardena in Italian), from a farmer
by the name of Peratoner. He was willing to take us immediately. Thus
we left for the South Tyrol at the beginning of May (1933) ; we took our
twelve-year old son, Gustav, with us, but left our adolescent daughters
behind at their German schools. From Selva I apparently wrote to
Einstein via Ehrenfest in Holland, and this is his reply:
66 Oxford
30 May, 1933
Dear Bom
Ehrenfest sent me your letter. I am glad that you have resigned
your positions (you and Franck). Thank God there is no risk
"3
BORN-EINSTEIN LETTERS
involved for either of you. But my heart aches at the thought of
the young ones. Lindemann has gone to Gottingen and Berlin
(for one week). Maybe you could write to him here about
Teller. I heard that the establishment of a good Institute of
Physics in Palestine (Jerusalem) is at present being considered.
There has been a nasty mess there up to now, complete char-
latanism. But if I get the impression that this business could be
taken seriously, I shall write to you at once with further details.
For it would be splendid if something good were to be created
there; it could develop into an institute of international renown.
But for the time being I have not much faith in it.
Two years ago I tried to appeal to Rockefeller's conscience
about the absurd method of allocating grants, unfortunately
without success. Bohr has now gone to see him, in an attempt
to persuade him to take some action on behalf of the exiled
German scientists. It is to be hoped that he'll achieve something.
Lindemann has considered London and Heitler for Oxford.
He has set up an organisation of his own for this purpose, taking
in all the English universities. I am firmly convinced that all
those who have made a name already will be taken care of.
But the others, the young ones, will not have the chance to
develop.
You know, I think, that I have never had a particularly
favourable opinion of the Germans (morally and politically
speaking). But I must confess that the degree of their brutality
and cowardice came as something of a surprise to me.
I originally intended to create a university for exiles. But it
soon became apparent that there were insurmountable obstacles,
and that any efforts in this direction would impede the exertions
of individual countries.
I do hope I shall soon be able to write to you with more
concrete news. Meanwhile I wish you and your family a peace-
ful time in the mountains.
Yours
Einstein
I've been promoted to an 'evil monster' in Germany, and all
my money has been taken away from me. But I console myself
with the thought that the latter would soon be gone anyway.
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BORN-EINSTEIN LETTERS
Lindemann, a thorough-going Englishman despite his Grerman name,
was well known to me, almost a friend, since my days as a lecturer. He
studied with Nernst in Berlin, and often came to Gottingen. His work was
so good that he rose quickly: Fellow of Christ Church College, Oxford,
Professor of Experimental Philosophy and Head of the Clarendon Labora-
tory. In the second world war he was Churchill's most influential scientific
adviser. It was his idea to break the fighting spirit of the German people by
air attacks on the centres of the large cities. In 1933 he came to Germany
to get the dismissed German scholars for England. He was especially keen
on promoting physics in Oxford. Oxford was traditionally given over to
the humanities, while at Cambridge, Newton's university, the sciences
blossomed. And so Lindemann travelled all over Germany trying to
obtain physicists of note for Oxford. In July he even came to Selva
(Gardena) to negotiate with me. I had, however, just accepted an invita-
tion to go to Cambridge. Einstein's letter also says that Lindemann had
considered Heitier and London for Oxford. Heitler had, as already
mentioned, been my assistant in Gottingen for many years. London, the
son of one of my mathematics professors from my student days in Breslau,
had studied mainly with Sommerfeld in Munich. London and Heitler
jointly published a fundamental work in which the chemical (non-polar)
valency forces were for the first time explained in physical terms by means
of quantum mechanics. This theory has since been successfully developed
by the American chemist Linus Pauling; he was awarded the Nobel Prize
for chemistry for this, but Heitler and London did not get the prize
for physics. Neither went to Oxford. Instead, Lindemann got Franz
Simon, Professor of Physical Chemistry at Breslau, and some younger
research workers, Mendelssohn, Kurti and Kuhn inter alia. They soon
brought the Clarendon Laboratory to full bloom. In the end Simon
became Lindemann's successor, was knighted and so became Sir
Francis. The main research effort at his institute was in low temperature
studies.
It is evident from Einstein's letter that at that time I was trying
to do something for Edward Teller, but I cannot remember it. He
had been in Gottingen for some time and had helped me to write one
of the chapters in my book on optics (the theory of the Raman effect).
He later became famous in America as the 'father of the hydrogen
bomb' and has always tried passionately to influence public opinion in
favour of power politics and against any compromise between East and
West.
Einstein's severe judgment of the Germans would no doubt have been
subscribed to by all of us who had been expelled by Hitler, as well £is our
friends in other countries. But what we experienced then was child's play
in comparison with what happened later. And yet I am now living in
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BORN-EINSTEIN LETTERS
Germany again. These pages will show how this came about. Einstein
himself never again set foot on German soil.
one of Einstein's letters appears to have been lost between this letter and
the one that follows.
67
Selva-Gardena
Villa Blazzola
2 June, 1933
Dear Einstein
Many thanks for your kind letter. I wish I could help you to
look after the young exiled physicists and others like them, but
I am in the same position myself. I spend my time trying to
improve my rather run-down nerves (sleep is still a problem),
and thinking about physics a little. I do have, after all, one
advantage: for quite some time now I have had plenty of time
at my disposal. But it is not too easy without a library. one of
my pupils, an Englishman, has come here and I do a little
work with him.
Many thanks for your concern about my - or rather our -
future. I see my task as being more to make my children's lives
worth living, rather than to spend the rest of my days in pleasure
and comfort. I have not given up, by any means, but I share
Ehrenfest's opinion that those who are younger have a better
chance of achieving something. It is all the more sad that their
prospects in life are so poor. As regards my wife and children,
they have only become conscious of being Jews or 'non- Aryans'
(to use the delightful technical term) during the last few months,
and I myself have never felt particularly Jewish. Now, of course,
I am extremely conscious of it, not only because we are con-
sidered to be so, but because oppression and injustice provoke
me to anger and resistance. I would like my children to become
citizens of a Western country, preferably England, for the
English seem to be accepting the refugees most nobly and
generously. Also, I studied in England 26 years ago, know the
language, and have many friends there. But I do not know
whether it will be possible for anything as good as that to
happen. You seem to have it in mind to recommend me (or
Franck?) to the Institute of Physics to be created in Palestine.
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BORN-EINSTEIN LETTERS
In the interests of my wife and children I would rather not
do that, though I admit that I know next to nothing about life
and conditions in Palestine.
Meanwhile I have already received several invitations for
the immediate future : one to go for a few months to Columbus,
Ohio, where Lande is, and one to go to Paris for a whole year,
free from teaching obligations. The latter, of course, would
appeal to me greatly, and even more to Hedi; but the salary
offered is too small to live on with a wife and three children for a
whole year. once I got to Paris, I expect the same thing would
happen to my money as has happened to yours : you would then
be the big monster, I the small monster. But if it could be
arranged, we would be very pleased : just imagine, Paris after
ten years in Gottingen! There is yet another possibility: I have
been informed that I have received (or am going to receive) a
post in Belgrade (Yugoslavia); however, the letter was not
official. Hedi is attracted to anything adventurous and strange.
I am put off by the scientific wasteland which probably still
exists there, and the language. I have absolutely no talent for
languages, and to learn a Slav language seems almost impossible
to me. But if nothing else comes along, I would undertake it.
But younger people should really be picked for such posts,
people who would find it easier to adapt themselves.
I am going to write to Lindemann about the Teller business,
and will also ask him to take care of this letter, as you did not
give any address. I received direct news from Gottingen
through my English pupil the other day about Franck, Weyl and
my daughter Irene, who is staying with the Weyls there and is
enjoying her life, without taking much notice of current events.
Happy youth that makes that possible! And yet she is not at
all superficial in her emotions. Courant spent a few days
with H. Bohr in Copenhagen and his condition seems to have
improved a little. Franck is resolutely determined not to go
abroad while he has the slightest prospect of finding work
in Germany (though not as a civil servant). Although there is,
of course, no chance of this, he remains in Gottingen and waits.
I would not have the nerve to do it, nor can I see the point of
it. But both he and Courant are, in spite of their Jewishness
which is far more pronounced than in my case, Germans at
heart.
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BORN-EINSTEIN LETTERS
Hedi sends her kind regards to you and yours. I am most
deeply grateful to you for all you are doing on our behalf
Yours
M.Bom
The pupil who looked me up in Selva was Maurice Blackman, a South
African Jew; he did valuable work later on, and is now professor at
Imperial College, London, and a Fellow of the Royal Society. Soon another
EngUsh pupil of mine, Thomson from Oxford, also arrived. I gave them
little lectures on a bench in front of our house or in the woods of the narrow
valley, Val Lunga. We were very proud of this Uttle Selva University.
I never seriously considered going to Jerusalem, for the reasons mentioned
in the letter, to which I should Uke to add a few words of explanation.
My parents were both of Jewish extraction. My mother died while I was
still a child. My father, who was Professor of Anatomy and Embryology
at the University of Breslau, was a member of the Jewish community; he
was a liberal of the previous century, for whom religious tolerance was
natural. Though he suffered professionally more than once from anti-
semitism, he refused to change his religion, for merely practical reasons.
The atmosphere in his house was one of urbanity and tolerance. I grew up
in this and have tried to preserve it in my own home. An involvement with
Judaism can hardly be said to have existed. It was even less so in the case
of my wife; although her father, the well-known lawyer Viktor Ehrenberg,
was of Jewish descent, her mother was of Frisian stock, a daughter of the
world-famous lawyer Rudolf von Ihering. My wife was in later years a
Christian in more than name. In Edinburgh her conviction became even
more strongly rooted when she joined the Religious Society of Friends
(Quakers) . Neither she nor our children had any ties with Judaism, other
than love for Jewish relatives, and certainly none with Zionism or with
Palesdne.
We took the call to Yugoslavia seriously. I wrote to a colleague in Vienna
whom I knew to be famiUar with the Balkan countries. His reply was a
humorous description of the situation in Belgrade : how everything de-
pended on personal relations, and that it was far more important to
entertain a Minister of State with a few amusing stories over a glass of
wine than to do research, and so on. This deterred us.
Shortly afterwards came the invitation to England. The next letter, again
from myself to Einstein, was written from Cambridge, where my wife had
rented a small house.
ii8
BORN-EINSTEIN LETTERS
Cambridge
8 March, ig34
Dear Einstein
I have had news of you from time to time through Weyl, just
as you have probably heard in the same way about us from him.
Today I am writing to you direct, because I would like to know
if there is any prospect of assistance for exiled German scholars,
and for physicists in particular, from America. You, with your
warm heart, are no doubt following all these disastrous events
in detail, but from a distance, after all. Here, where I am, it is
all very real indeed. Almost every week some unfortunate wretch
approaches me personally, and every day I receive letters from
people left stranded. And I am completely helpless, as I am my-
self a guest of the English and my name is not widely known;
I can do nothing except advise the Academic Assistance
Council in London and the Notgemeinschaft [Emergency Aid
Society] in Zurich. But neither of these institutions has any
money. As a result of your address in the Albert Hall, Ruther-
ford had hoped to get a movement under way which would
produce greater amounts ; but nothing much seems to have come
of it. Most of the grants from the Academic Assistance Council
come to an end in the autumn, and cannot be renewed. In the
meantime many more have arrived in need of help, for whom
nothing is available.
What I would like to know is this:
1 . Is America still able to take people, and particularly younger
people ? In which professions ? Could teachers of physics be
placed? To whom would one have to apply? (Dugan
Committee ?)
2. Would it be possible for you to collect a really large sum by
making use of your popularity, and to send it to Rutherford
for the Academic Assistance Council? I would then devote
my entire time and energy to make sure that it is used
sensibly. (You would have to write to Rutherford and suggest
that I should be asked to do this.) Frequently it is not the
most capable but the most pushing who are given preference.
3. What other possibilities are there? Could one not start a
publicity campaign in South America ? What is the position
in regard to Jerusalem ?
"9
BORN-EINSTEIN LETTERS
The Notgemeinschaft in Zurich has, partly with my assistance,
established connections with Russia and India, which offer
good prospects.
I myself have been asked by Raman whether I would accept
a professorship in Bangalore. But because of my predisposition
to asthma, I would rather avoid any such abrupt change in
climate as long as the Cambridge people want to keep me on.
I feel very much at home here, and can work better than in
Gottingen. Hedi has not settled down as well; her health,
particularly her nervous condition, is not at all satisfactory.
My daughters are arriving in England in a fortnight's time and
want to stay at home for the time being. Hedi will then enter a
sanatorium.
The other day I sent you my paper which appeared in the
Proceedings of the Royal Society. It is not yet satisfactory. I am
very satisfied, however, with a second paper which is at present
being printed; it contains a 'classical' treatment of my field
theory, in which everything happens to fall into place most
splendidly. You may not agree with it, as I have not dealt with
gravitation at the same time. This is a matter of principle, in
which I differ from the ideas expressed in your papers on the
unified field theory. I hope soon to be able to develop my idea
about gravitation. I have made some progress with the quanti-
sation of my field equations, but I still face towering difficulties.
Are you going to come to Europe in the summer ? I expect I
will have to remain here for financial reasons. Hedi would very
much like to know Margofs address. How is your wife ? Please
give my sincere regards to her and our colleagues at Princeton.
Yours
Max Bom
While Einstein occupied a firm, highly paid academic teaching post at
Princeton, my employment in Cambridge was only provisional. But I
was soon given the 'degree' of Master of Arts (MA.) . and the title of
'Stokes lecturer'; I had a small room in the Cavendish Laboratory and
did not have to give many lectures, which left me enough time for my own
work. Our economic position was, however, very tight. I spent a great
deal of my time in correspondence or discussions to try to accommodate
exiled scholars.
Parting from Gottingen, and from all I had built up there, was bound to
1 20
BORN-EINSTEIN LETTERS
weigh heavily upon me. But I found some compensation in my scientific
life, which flourished under Rutherford's leadership at the Cavendish
Laboratory. I was also granted the hospitality (dinner rights) of two col-
leges, Gonville and Caius (of which I had been a member years ago as an
'advanced student'), and St. Johns (where Dirac was one of the Fellows).
My wife had none of these things. She had been torn away from every-
thing she knew and loved - landscape, language, friends, and the home-
town where her parents and grandparents had lived. Cambridge offered
her nothing but heavy domestic drudgery, and well-meaning invitations
to afternoon tea. There is no letter from her to Einstein during this
period.
As regards my research, the investigations mentioned in the letter concern
an attempt, begun in Selva, to modify Maxwell's electrodynamics so
that the self energy of the point charge is finite. In Cambridge I was
fortunate in getting the Polish physicist Leopold Infeld as my colleague.
The theory is usually referred to as the 'Born-Infeld theory' now. We gave
it a generally relativistic look without pursuing this aspect of it any further.
Einstein rejected the idea right from the beginning. We tried very hard to
reconcile it with the principles of the quantum theory. But we did not
succeed, and today, possibly with good reason, the whole thing has been
forgotten. I then warmly recommended Infeld to Einstein, and he became
his collaborator and assistant. They published a popular book. The
Evolution of Physics,^ which is brilliantly written and has helped to bring
Einstein's ideas to a much wider public. The pinnacle of their scientific
collaboration was the reduction of the laws governing the movements of
celestial bodies to Einstein's field equations. These will be mentioned
again.
69
Princeton, N.J.
22 March, 1934
Dear Bom
It gives me great pleasure to see your handwriting again, even
if the main cause of your letter is so regrettable. Unfortunately
I can see no possibility of being able to contribute directly to
the health of the English Assistance Fund, as I was able to do
last year. I regret that, for a variety of reasons, it is impossible
for me to hold travelling lectures in America.
It is particularly unfortunate that the satiated Jews of the
countries which have hitherto been spared cling to the foolish
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BORN-EINSTEIN LETTERS
hope that they can safeguard themselves by keeping quiet and
making patriotic gestures, just as the German Jews used to do.
For the same reason they sabotaged the granting of asylum to
German Jews, just as the latter did to Jews from the East. This
applies just as much in America as in France and England.
I am greatly interested in your attempt to attack the quantum
problem of the field from a new angle, but I am not exactly
convinced. I still believe that the probability interpretation
does not represent a practicable possibility for the relativistic
generalisation, in spite of its great success. Nor has the reasoning
for the choice of a Hamiltonian function for the electromagnetic
field, by analogy with the special theory of relativity, convinced
me. I am afraid that none of us will Uve to see the solution of
these difficult problems.
If at all possible, I am going to fritter away the summer
somewhere in America. Why should an old fellow like me not
enjoy relative peace and quiet for once? I hope that your
position in England is now ensured for some time to come.
Conditions are very difficult here, as the universities, which in
the main have to live from hand to mouth on a combination of
private contribution and diminishing capital, have to struggle
for their existence, and for this reason many capable young
local people are unemployed.
Kind regards
Yours
A. Einstein
Margot's address: 5 rue du Docteur Blanche, Paris i6me.
Einstein's objections to my ideas were twofold. The first was based on his
rejection of the probability of quantum mechanics. This concerns a matter
of principle. It did not really apply to the theory devised by Infeld and
myself, because we ourselves did not in fact manage to make it fit in with
quantum mechanics ; he judged our efforts in this direction to be wrong
in principle. Einstein's second objection concerned our original classical
field theory, which was complete in itself and free from inconsistencies. It
was based on the following analogy: in the special theory of relativity the
kinetic energy of a particle, which in classical mechanics is proportional
to the square of its velocity, is represented by a rather complicated expres-
sion; for velocities which are small compared with that of light it tends to
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the classical ｅxpression, but deviates from it when the velocity approaches
that of light. In Maxwell's electrodynamics the energy density is a
quadratic ｅxpression containing the field intensity. I replaced this with a
general ｅxpression which approximates to the classical ｅxpression whenever
the strength of the field is small compared with a certain field intensity,
but diverges from it when this is not the case. From this it followed auto-
matically that the total energy of the field of a point charge is finite, while
it becomes infinite in the Maxwellian field. The absolute field has to be
regarded as a new natural constant. Einstein did not find this analogical
construction convincing. Infeld and I found it attractive for a long time.
We abandoned the theory for completely different reasons, namely,
because we did not succeed in reconciling it with the principles of the
quantum field theory. In any case this constituted the first attempt to
overcome the difficulties of microphysics by means of a non-linear theory.
Heisenberg's theory of elementary particles, which is much talked about
today, is also non-linear. But I am guessing.
70
'Haus Simon', Neue Wiese
Karlsbad
24 August, igsG
Dear Einstein
Please let me know as soon as possible how one should evaluate
the work of Prof. Y. He has approached me and seems to be in
great distress. I understand nothing of his work, but he seems
to have had closer contact with you (and indeed has even
written a book about you). My personal impression is that he is
a poor wretch who rather overrates himself But I may be
wrong, and in any case I would like to help him. Please write
to me completely objectively.
I am here to take the cure; my gall-bladder pains have already
disappeared. I will be back in Cambridge in a fortnight's time
(address : 246 Hills Road) ; please write to me there.
We are moving to Edinburgh shortly, where I have been
appointed Darwin's successor.
During my holidays I spoke to many Americans (Franck,
Ladenburg, Courant), who all talked to me about you. I am
extremely sorry to hear that your wife is ill. My family are all well .
With kind regards
Max Bom
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BORN-EINSTEIN LETTERS
My chief memory of my stay at this spa is my meeting with Chaim
Weizmann, the Zionist leader. He accompanied me almost daily on the
early morning constitutionals which were part of my cure, and I learned
a great deal about the Zionist movement. The beneficial effect of the cure,
however, lasted only a short time. A few years later I had to undergo a
gall-bladder operation in Edinburgh.
My appointment to the University of Edinburgh is mentioned here for the
first time. To us it meant the end of uncertainty, and the beginning of a
new life in Scotland.
71
[undated]
Dear Born
Y. is a somewhat pathological case. He has an independent but
unfortunately not very clear mind. His papers about surfaces
contain much that is useful, even if it has unfortunately never
been put in order or given clear form. He is a little difficult as a
person. For example, he made use of our very casual personal
acquaintance over many years to make money by writing a
biographical book about me, though I had expressly forbidden
him to do so. But he was having a very difficult time, and was
constantly in some kind of distress; always, or almost always,
without employment. At the same time his exaggerated
opinion of himself makes it hard to help him, particularly as I
am not sure whether he would do well in a subordinate position.
But it is quite possible that his hard experiences have made him
more amenable. Therefore, help him if you can, but be cautious
with your recommendations to save yourself from possible
reproach. He is able to do experimental and technical work,
and seems at times to have supported himself by it in the past.
Some time ago I tried to put a word in on his behalf with
J. Franck. But he refused quite brusquely, on the grounds that
one should make efforts to help more valuable people. But I
believe that this attitude towards an older man, who is in
great distress and who, after all, has certain merits, is far too
harsh.
I am quite extraordinarily pleased that you have found a
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BORN-EINSTEIN LETTERS
permanent and highly respected chair in Edinburgh, and that
you and your family are well. My wife is unfortunately very
seriously ill. I personally feel very happy here, and find it
indescribably enjoyable really to be able to lead a quiet fife. It
is, after all, no more than one deserves in one's last terms,
though it is granted to very few.
Next term we are going to have your temporary collaborator
Infeld here in Princeton, and I am looking forward to discus-
sions with him. Together with a young collaborator, I arrived
at the interesting result that gravitational waves do not exist,
though they had been assumed a certainty to the first approxi-
mation. This shows that the non-linear general relativistic field
equations can tell us more or, rather, limit us more than we
have believed up to now. If only it were not so damnably
difficult to find rigorous solutions. I still do not beUeve that the
statistical method of the quantum theory is the last word, but
for the time being I am alone in my opinion.
With best wishes
Yours
A. Einstein
At the end of the letter, Einstein again rejects the statistical quantum
theory, with the admission that he is alone in this. At the time I was
quite certain that I was in the right on this question. All theoretical
physicists were in fact working with the statistical concept by then; this
was particularly true of Niels Bohr and his school, who also made a
vital contribution to the clarification of the concept. However, I
consider it unjustified that this is usually cited as having originated in
Copenhagen.
72
S4 Grange Loan
Edinburgh
24 January, ig^y
Dear Einstein
Today I have to ask for your help in two different matters:
I. Prof. R. Samuel, a pupil of Franck's and mine from Got-
tingen; we did not regard him as outstanding in those days
J 25
BORN-EINSTEIN LETTERS
(more than ten years ago), but he has developed well. He
went to India, to the MusHm University of Aligarh, and
created an up-to-date institute there under extraordinary
difficulties (such as one could not imagine here). A new
vice-chancellor (my wife calls him the most amiable rogue
she has ever met) is getting rid of all non-Mohammedans;
as a result, Samuel has to leave on April ist. The beautiful
institute, which we inspected last winter, is going to sink
back once more into the lap of Allah. Samuel has been a
convinced Zionist from his youth; his dearest wish is to
live in Palestine. His wife, also a Zionist of long standing,
and his son, are already there. Samuel is applying for a
position as experimental physicist in Jerusalem (or elsewhere
in the country).
As regards his suitability, it is like this: he is no genius, but
intelligent and extremely energetic. The establishment of
the institute in Aligarh is a considerable achievement. His
papers are based on ideas of Franck's (the Unking together
of chemistry and spectroscopy). During the last few years he
has tried hard to demonstrate experimentally that the ori-
ginal valency interpretation by Heitler and London is
better than the so-called 'improvements' by Hund, Herzberg
and Millikan.
At first I was very sceptical, but have become more and
more convinced that Samuel's empirical material proves
him right. London, who is very sceptical, shares my opinion.
Be that as it may, the experimental material is valuable in
itself because of the systematic selection of the materials
and clean workmanship.
My motive for interceding so energetically on Samuel's
behalf is as follows: a convinced Zionist of long standing,
provided he is otherwise suitable, should be given precedence
over people who want to go to Palestine for purely personal
reasons. Moreover: a most unpleasant clique seems to be in
control at the university in Jerusalem; people who lead
rather lazy lives, and do not want to be disturbed. They
object to Samuel as not being sufficiently distinguished; I
believe the opposite to be true - he is too energetic for them.
I think your word will still have influence there. I hope you
did not take it amiss that I did not go there myself. I am
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BORN-EINSTEIN LETTERS
just not a Zionist. I do not belong there; but Samuel wants
to go there, and is entirely suitable. He wrote to me that, if
all else failed, he would even settle there as a bricklayer or
shoecleaner. I had a very detailed discussion with Weizmann
this summer. He also takes Samuel's part; but this does not
seem to be enough.
Please do something in this matter, if you think it right
to do so.
2. Dr Hans Schwerdtfeger: young mathematician from Got-
tingen. Lone wolf, earned his university education by doing
factory and similar work. Pure 'Aryan'. Was not popular
with Weyl and Courant, as he used to go his own way. I
believe him to be talented, but lacking in self-criticism; his
enthusiasm has up to now been greater than his achieve-
ment. Herglotz had a good opinion of him; but he does
nothing for his people. Schwerdtfeger is married to a young
chemist of whom my wife is very fond, and they have a baby.
Schwerdtfeger was a violent opponent of the Nazis right
from the beginning, and has therefore no chance of a
position in Germany in spite of his 'spotless' ancestry. It is
people such as this whom we should help.
A friend of his, Cohn-Vossen, went to Russia and obtained
a good post in Moscow in 1933. He tried to get Schwerdt-
feger to follow him. Negotiations got under way; to facilitate
them, S. went to Prague (one risks one's life in Germany if
one has any contact with Russia). Hardly had he arrived
there when he received the news that Cohn-Vossen had
died. Thereupon the negotiations gradually came to an end.
Schwerdtfeger and his wife and child were in considerable
trouble. We helped a little, as did the Notgemeinschaft in
London. Eventually, after a year, I succeeded in establishing
a direct link with the Russians through my former pupil
Weisskopf, who is now with Bohr and who went on a trip to
Russia. He wrote of the great fear of German 'spies' which
prevails there. But, in spite of this, the employment of S.
might possibly be considered if someone like you or Lan-
gevin put in a word for him. I have written to Langevin,
but have not received a reply. Therefore I address myself to
you: could you write to Molotov, to Prof. Schmidt or to
Garbunov, to the effect that S. has been highly recommended
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BORN-EINSTEIN LETTERS
to you (you can use my name) as an absolutely honest,
decent person, who has a burning desire to work in Russia;
he as a mathematician, his wife as a chemist. Both would be
satisfied with nominal positions. But if you do not want to
do this, please say so openly; I can well understand that no
one gladly gets involved in Russian affairs. The new trial
against Radek and associates seems to me extremely dis-
gusting.
My wife, who is beginning to get on to her feet again, sends her
warmest regards. She would very much like to hear from
Margot.
With kind regards
Yours Max Bom
This letter is an example of the voluminous correspondence I carried on
not only with Einstein, but with many people all over the world, on the
subject of help for exiled scientists.
Samuel, as far as I know, did go to Palesdne. After many vain attempts
I eventually managed to place Schwerdtfeger in Australia, with the help
of the great physicist Sir William Bragg, who came from there.
Weisskopf was one of my best pupils and one of the last of those who were
working for their doctor's degree in Gottingen. He subsequently had a
distinguished career, and was for many years head of the European
Institute for Nuclear Research, CERN, in Geneva.
73
[undated]
Dear Born
First of all, I am extremely delighted that you have found such
an excellent sphere of activity, and what's more in the most
civiUsed country of the day. And more than just a refuge. It
seems to me that you, with your well-adjusted personality and
good family background, will feel quite happy there. I have
settled down splendidly here: I hibernate like a bear in its cave,
and really feel more at home than ever before in all my varied
existence. This bearishness has been accentuated still further
by the death of my mate who was more attached to human
beings than I.
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BORN— EINSTEIN LETTERS
The tasks you gave me are no simple matter.
1. Palestine is unquestionably the right place for Samuel. But
from the university's point of view, the first priority is to
obtain a proficient theoretician, preferably London. I
cannot appear on the scene with Samuel until this has been
accomplished, because it would only add to the confusion.
There is as yet no proper theoretician there, and while this
is so it is going to remain a desolate place. But when the time
comes, I am quite prepared to put in a word for Samuel,
particularly as his organising ability could prove to be of
great importance there.
It is really rather a comforting thought that in India, too,
the all-too-human trait of knavery predominates. After all,
it would be just too bad if this were to be the privilege of the
proud white race. I believe that all creatures who can have
young ones together are very much the same.
2. Schwerdtfeger. Nothing can be done for him here. This is
because Weyl and Courant are up in arms at the suggestion.
Besides, I have had a closer look at one of his papers, and
have the impression of a lack of really profound questioning.
Because of the widespread unemployment amongst local
people, it is, in any case, very difficult to place anyone here,
and if one does succeed, it usually means a lowering of status.
But in this case I cannot even attempt it with a clear conscience.
Now Russia. After a certain amount of to-ing and fi:o-ing I
was able to place one of my former assistants there satisfactorily,
and am going to try and get in another very able and original
man there, whose position here is threatened by the very con-
siderable antisemitism in academic circles. But should I ever
recommend a mediocrity to them, even just once, my credit
there would be at an end, and I would never again be able to
help. It is sad that one is forced to treat human beings like
horses where it matters only that they can run and pull,
without regard to their qualities as human beings. But what can I
do ? In the last resort it is precisely humane considerations which
compel me to adopt this kind of attitude.
This would, however, not prevent me from giving a friendly
account of Schwerdtfeger to Russia, if they could be induced to
ask me. This is how it should be done. This is frequently more
effective than if one takes the initiative oneself.
lag
BORN-EINSTEIN LETTERS
By the way, there are increasing signs that the Russian trials
are not faked, but that there is a plot among those who look
upon Stalin as a stupid reactionary who has betrayed the ideas
of the revolution. Though we find it difficult to imagine this
kind of internal thing, those who know Russia best are all more
or less of the same opinion. I was firmly convinced to begin
with that it was a case of a dictator's despotic acts, based on
lies and deception, but this was a delusion.
Margot is spending the week in New York, and is hewing
stone with unrivalled enthusiasm. She has really been saved by
art, she could hardly have born her grievous human losses as
well as her divorce without it. She often speaks of you with
affection.
Kind regards to you and your family
Yours
A. Einstein
P.S. Infeld is a splendid chap. We have done a very fine thing
together. Problem of astronomical movement with treatment of
celestial bodies as singularities of the field. The institute has
treated him badly. But I will soon help him through it.
The incidental way in which Einstein announces his wife's death, in the
course of a brief description of his bear-like existence, seems rather strange.
For all his kindness, sociability and love of humanity, he was nevertheless
totally detached from his environment and the human beings included in
it.
For me the most remarkable passage in the letter is the one about the
all-too-human trait of knavery which ends with the confession : I believe
that all creatures who can have young ones together are very much the
same; a typical formulation of Einstein's rejection of racial discrimination
and national pride.
It is typical of his kindness that he apparently suffered because he could
only advance exceptionally able people by his recommendation as if they
were horses. For my wife and myself it was brief remarks such as these which
were, time and again, a source of renewed affection for Einstein the man.
The Russian trials were Stalin's purges, with which he attempted to
consolidate his power. Like most people in the West, I believed these
show trials to be the arbitrary acts of a cruel dictator. Einstein was
apparently of a different opinion: he believed that when threatened by
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BORN-EINSTEIN LETTERS
Hitler the Russians had no choice but to destroy as many of their enemies
within their own camp as possible. I find it hard to reconcile this point of
view with Einstein's gentle, humanitarian disposition.
The 'good thing' which he and Infeld had done has been mentioned
before. It concerns a fundamental simplification of the foundations of the
general theory of relativity. Infeld described in a short autobiographical
sketch of his^ how the idea seemed so daring to him at first that he did
not want to believe in it. At that time, the theory had two pillars. Firstiy,
the movement of mass points is determined by the geodetic lines of the
space-time world; secondly, the metrics of this world satisfy Einstein's
field equations. Now Einstein asserted that the first of these assumptions
is redundant, because it follows from the field equations by going to the
limit of infinitely thin, mass-covered world lines, on which the field becomes
singular. The calculations were at first so extensive that only excerpts
could be published, and the massive manuscript was deposited in the
Institute for Advanced Study in Princeton. ShorUy afterwards, and quite
independentiy, the Russian physicist W. Fock (who had collaborated with
me on several papers in Grottingen) and his students tackled the same
problem in a somewhat different manner. This work was later incorporated
in his well-known book on relativity. Einstein's theory, as elaborated by
Infeld and Hoffman, was presented in an improved form after Einstein's
death by Infeld and Plebanski in their brilliant hook Motion and Relativity.'^
In his short autobiography, Infeld tells how Einstein had said to him
more than once: 'here in Princeton I am considered an old fool'. He was
regarded as an historical relic, and this at a time when he was engaged
upon this great work.
74
84 Grange Loan
Edinburgh
II April, igj8
Dear Einstein
Your paper with Infeld and Hofmann has impressed me
enormously. I will not say that I understand it - that would
need long and intensive study, for which I have not got time
at present. But I believe I have understood the concept, the
manner of approximation and the method of development,
which treats the time and space components in different ways.
In any case, the result is beautiful ; it is the first really satisfactory
deduction of the equations of motion from field equations.
You know I have never concerned myself particularly with
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BORN-EINSTEIN LETTERS
the theory; just enough to be able to lecture to average
students.
Except for your fundamental work, it all seemed excessively
formalistic to me, and, apart from a few papers by Weyl, not
very profound. But this new work is both profound and beautiful,
I shall keep studying it until I understand the details better.
Infeld wrote to me the other day and said you were interested
in my reciprocity speculations, and he would like material
for a lecture. But I did not have anything decent available,
and did not want to part with what I did have. This may not
have been terribly nice. But this work is still in the early stages,
quite unfinished, and over there you have, after all, so many
terribly clever people who can do everything so much more
quickly than my frayed old brain. on the other hand, I would
have no hesitation about writing something on it for you
personally, which you may also show to Infeld. It is like this :
The cosmic rays demonstrate the existence of a physical
world in which the energy of the particles is many times that of
their mass when at rest. The velocities are therefore almost c
because
P =
mv
E=-
mc^
J{i-v^lc^)' J{i-v'/c^)
This means that the v are not suitable physical parameters;
so much can happen in a minute range of v, which contains
an enormous range of /> and E values. I interpret this in the
sense that p and E cannot be reduced to, or measured by, v,
but have an independent significance. There are other indi-
cations in support of this, but we cannot go into this here.
[Nuclei with v of the order c/5 to c/io (for protons or neutrons)
are an intermediate stage.] The problem is to extend classical
mechanics so as to include this hypothesis. I use the fact that
the canonical transformations are symmetrical in x and p;
e.g. if they are defined through the Poisson brackets:
(«, v) ■■
-y(—
dv
Sp,c
du
3xJ
then the transformation {x, p) -^{X, P) is canonical when
(Z„ZO=o, (P*,PO=o, {Xu,Pi)-^u .
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BORN-EINSTEIN LETTERS
If one now takes a line element d5* =^ gi^ dx^. dxi
in ;c-space and carries out a canonical transformation, it
becomes the eight-dimensional
di^ =X [Em dxj dxi +Fki dx^ dpi + G« d/>4 dxi + H„i dp„ dpi)
kl
where Ej^ and //^j are symmetrical and F^i^Gi^. But this is, of
course, not the most general case! There are four identities
between the matrices E, F, G, H. They are best found as
follows: first establish that canonically the following invariant
equations exist between E, F, G, H; I am using matrix notation
(matrices of matrices) :
H-G>
■F E)
/E FN / H-GN_/A o\
VG hJ'Uf EJ~Vo A/
where A is a 4 by 4 diagonal matrix. It is now very easy, viz.
by A=o, to characterise the case where d5* is reducible to the
four-dimensional Ar-space. But if A i^o one has a general case!
This is precisely what I want. For, if A is small (in c.g.s. units)
it becomes conceivable that A ^^ o applies to the 'real' mechanics,
but that for less precise observations the limiting case A=o
applies.
Fuchs and I are busy developing this new hyper-dynamics.
We hope it will work. The characteristic feature is the appear-
ance of a new natural constant for, since x and p are always
treated as equivalent, a constant (H) of the dimension [P] arises.
Planck's constant (A) has the dimension [x p]. If we now equate
j^
H=-p-, h=XoPo,
then X^ = J{Hh) and Po = J{hlH) define an absolute length
and an absolute momentum. A pure 'momentum mechanics'
would be valid wherever p'^Po, i-e. ds^ — Yjykidp^dpi (to a
good approximation). *'
I have discussed this case in my papers (manuscript accepted
for Proc. R. Soc.) and in the letter to Nature,^ where I singled out
rather arbitrarily a closed spherical /(-space and discussed some
of the conclusions. These are so reasonable that they have
encouraged me in my delusions. In any case, I think it good
fun to pursue them further; so please do not pour too much
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BORN-EINSTEIN LETTERS
cold water on my head. When one Hves in Europe - even here
in far Caledonia - one has to have something which diverts one
from political anxieties. How disgusting it all is. You are lucky
to be over there.
Hedi is very well, having got over her eye operation. She is
attending a Quaker meeting on the west coast with our son
Gustav, and I am going to meet her there tomorrow for a few
days' rest by the sea. Our elder daughter is happily married
and living in the south of England ; the second one is still studying
in Vienna, and hopes to be able to hold out until her final
exams in June. My brother was fortunately able to obtain a
small post in St. Louis as Professor of Fine Arts. How is Margot?
Kind regards to her, and to the Infelds, as well as to all our
friends at the Institute, the Weyls, v. Neumanns, Veblens,
Ladenburgs. Also please tell Robertson that I liked his papers
very much. I wish he did not still bear me a grudge. I suppose
he has reason, as I treated him badly when he was in Gottingen.
In old friendship
Yours
Max Bom
My speculations about reciprocity, which I explain in this letter, have
occupied me and a variety of collaborators for many years. The one
mentioned here is the same Klaus Fuchs who later became notorious as
an 'atom spy'. He spent many years at my Institute in Edinburgh, did
excellent work and, if I remember rightly, obtained two doctorates, a
Ph.D. and a D.Sc. (doctorate of philosophy and of science, of which the
latter was more difficult to get and rated more highly). He was a quiet,
friendly, likeable man. My wife and I are convinced that he acted from
purely idealistic motives in the spy affair. He was a convinced Communist,
and believed it to be his duty to prevent capitalist America from being
able to dominate the whole world as the sole possessor of the atom bomb.
As regards my reciprocity theory, this is based on a demand for symmetry,
requiring the fundamental laws of nature to remain unaltered when the
four quantities - space coordinates and time - are interchanged with the
four quantities - momentum components and energy.
All the efforts I made in Edinburgh at that time to deduce from this
postulate concrete conclusions which could be proved experimentally
were in vain. Later it was shown that this was due to the lack of suitable
experimental material. Meanwhile great progress has been made in
experimental research into elementary particles, and to my surprise and
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joy my old reciprocity principle now plays an important part in the
interpretation of phenomena. Relations of that kind have been discovered
quite independently in three different places, in the United States, Japan
and Australia. Among the scientists involved is Yukawa, the great
Japanese physicist and Nobel prizewinner, who predicted the existence of
mesons. My former collaborator H. S. Green, Professor at the University
of Adelaide, is working successfully in this direction and keeps me up to
date. But I am unfortunately too old to be able to follow this line of
research.
75
84 Grange Loan
Edinburgh
2 September, igjS
Dear Einstein
I would very much like to send you another peaceful letter
about my physical and geometrical phantasies, but things
pohtical occupy my mind to such an extent that I feel com-
pelled to write about them first of all. We hear such horrible
things from Germany, and particularly firom Vienna, where
people are literally starving. Until recently I still had property
and income in Germany, and we were able to use this to help
not only a few of our relatives but others as well. Hedi, who has
become a Quaker, has achieved a lot with the help of these good
people. A short time ago, however, I learnt that my property
in Germany had been confiscated by the secret police. Thus,
even this chance of helping people has come to an end. This
depresses me more than the general political situation and the
threat of war. For you are probably right in your confidence in
the deep-rooted stupidity of our one-time fellow-countrymen:
they will once again succeed in having the whole world against
them, and then attack - if not this year against the Czechs, then
next year against the Poles or whoever it may be. And that will
be the end of them. But what a horrible thought: all those
hundreds of thousands of young men, who will perish as a result.
I have two English sons-in-law, fine, peace-loving people
(you know one of them, Maurice Pryce, who has become
engaged to our Gritli). But one is unable to change the course of
these events. They run their course Uke a thunderstorm.
I have in mind, however, another matter, where one might
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BORN-EINSTEIN LETTERS
perhaps be able to do something. Mussohni has passed a 'law',
according to which all Jews who have settled in Italy since 1919
are required to leave the country within six months. It is not
clear whether he did this in order to grovel before Hitler, or to
do a favour to the Arabs in Palestine. I think this offers America
a chance to take reciprocal action. Surely a certain amount of
Italian emigration to America is still going on. Could one not
get the American government to use this in order to apply
some pressure on the Itahans? And could you not address
President Roosevelt? Simply to send back the same number of
Italians as there are Jews forced to leave Italy would, I fear,
hardly be possible. But it should be possible to construct some
means of applying pressure. Of course, innocent people are
bound to suffer again as a result, and I feel inwardly ashamed
even to think of such a thing. But in the present situation there
is really no other method but force against force. If the Western
powers would only show by example that the methods of the
dictators can also be used against them, they would probably
have second thoughts.
Forgive me for disturbing the peace of your holiday by
writing to you about these things. We are so close to these
matters and events here that one cannot find peace. Hedi and
I are alone at home at present, as the children are staying in
different parts of Scotland. But we intend to go away for a short
time in about a week to the west coast.
My idea of reciprocity pursues me constantly, although no-
one else is taking it seriously. However, we did not succeed in
giving it a useful form. one of Heisenberg's more recent papers
in the ^eitschrift fur Physik shows that he, too, has now realized
that it is essential to hmit the 'moment' p by an absolute con-
stant. I was in Cambridge the other day at the meeting of the
British Association, where I had a thorough discussion with
Niels Bohr amongst others. The nuclear theory, which can be
formulated in so beautifully unrealistic a way, gives him so
much satisfaction that for the moment he is putting aside the
question of the nature of the elementary particle, which I find
so fascinating. Let us hear from you some time.
With kind regards, also to Margot, from Hedi and myself.
Yours
Max Bom
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BORN-EINSTEIN LETTERS
A political letter. The prediction that the folly of the Germans would
drive them into wild adventures and eventually to their ruin was confirmed
by events.
My proposal to use the Italian immigrants to America as a means of
applying pressure on Mussolini to mitigate the persecution of the Jews
was somewhat naive. What I find of interest in this paragraph today is
the shame I felt because it was not the real culprits who would be likely
to be hit by such measures, but innocent people. It is precisely this which is
so horrible about foreign politics, and what makes it so repulsive to any
decent person.
The subject of the principle of reciprocity comes up again at the end, and
in this connection a new paper of Heisenberg's is considered. Since those
days he has switched from 'purely critical' observations to constructive
ones. His non-linear spin theory of matter is a great gamble which has led
to a number of successes. But time alone will show whether it is the real
thing.
76
Department of Natural Philosophy
The University
Drummond Street
Edinburgh
31 May, 1939
Dear Einstein
I saw a report in the paper yesterday about a speech of yours
on Palestine, and seize this opportunity to write to you once
again. I quite agree with what you are supposed to have said,
according to this report. Without wishing to defend the
wavering and unrehable British poUcy, I am of the opinion
that the Jews could do nothing more stupid than to assume an
antagonistic attitude towards the English. The British Empire
is still a place of refuge and protection for the persecuted, and
particularly for Jews. I also completely subscribe to what you
are reported to have said concerning the need for and the
possibility of coming to an understanding with the Arabs. I am
glad that you said what you did; your voice will be heard. I can
only think my own thoughts in silence.
Hedi, at least, is doing something for the refugees. Her
domestic servant office flourishes; she has already succeeded in
saving many people from the Nazis, unfortunately virtually only
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women. My sister and other relatives have also escaped -
except for a few unfortunate cousins. What can one do with a
55-year-old dentist? Unless he emigrates soon, the Gestapo will
put him in a concentration camp. But his American registration
number is 60,000 !
My children are well provided for. I had an operation for
removal of my gall bladder last April. The operation was a
success, I have no more pain and am feeling fine, and I am
able to work again. My Department is growing, I have a
capable staff; next term there will be nine of them. We are
working on a variety of things, nuclear structure, crystals, etc.
I have written a paper about melting, which I have sent to
Bridgman in America for publication, as I considered his high
pressures in it. This is a new way of treating the thermodynamics
of crystals (statistical mechanics), which is applicable up to
very high temperatures and pressures. This work is being
continued by some of my pupils. I hope also to be able to work
on a new treatment of the soHdity problem. I have not heard
from Infeld for a long time; I do not even know his address.
Franck wrote to me the other day quite contentedly from
Chicago.
With kind regards, also from Hedi,
Yours
Max Bom
There is litde to say about this. P. W. Bridgman was Professor of Physics
at Harvard University, the leading expert in the generation and handling
of extremely high pressures, for which he received the Nobel Prize.
77
Department of Natural Philosophy
The University
Drummond Street
Edinburgh
10 April ig4o
Dear Einstein
At the beginning of the war I wrote a letter to Niels Bohr in
order to get news from Heisenberg. Today I have to write to
you for news, if possible, about Niels himself I am terribly
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worried. A year ago Niels was here - he received the Copley
Medal of the Royal Society, our highest honour, and came to
Edinburgh, where he stayed with us and gave us a lecture. He
was quite excited and shocked by the indifference of most of
the British people to the imminent danger of war, and he tried
to convince all people he met (he met important people, of
course) about the danger. He said to me confidentially that he
believed his own little country to be in much greater danger than
Great Britain, since it is so small and helpless, but that nobody
would be spared to fight for its existence - though at that time
many people here denied this and still beUeved in 'appease-
ment'. Well, he was right. You might be able to get news from
him and his family. Let me know if you hear anything.
We are well so far. Hedi works very hard, as maternity nurse
in a slum quarter in the morning, and in refugee and Quaker
committees in the afternoon. At present she is in the country
for a short holiday. We had both our daughters here for longer
visits, one with her husband (M. Pryce, whom you know),
the other with her fat and merry baby. My son is studying
medicine here. I continue my work undisturbed; soon my
department will be the only spot in Great Britain where
theoretical work is still done.
My chief interest is concentrated on my 'reciprocity' idea;
Fuchs and I have made nice progress, and PauU, the super-
critical man, wrote to me the other day: 'I think you are on the
right track'. A series of papers will appear in June or July; but
we have refrained from publishing short notes, as Lande does.
He is working along the same lines (though with very primitive
methods and rather unclear ideas). I am sure you will be
interested in the thing because it is the proper way of unifying
wave mechanics and relativity. There are many interesting
mathematical features, but one of the main points is the
discovery of representations of the Lorentz group by infinite
(not finite) matrices which belong nevertheless to the Hilbert
space (square integrable). I think that Wigner has some
similar results in a very abstract way; but what we are trying
to do is to show that these representations are connected with
the 'structure' of the elementary particles. A letter is much too
restricted a space for indicating these things even superficially.
In the summer term (starting next week) I am going to
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lecture to my advanced students on general relativity, concen-
trating my attention on Fock's (the Russian) most interesting
paper on the derivation of the equations of motion for finite
bodies from the field equations. We have further quite inter-
esting results on the thermodynamics of crystals, melting, etc.
Fiirth, from Prague, who is here as my guest, has found a most
surprising connection between the tensile strength (breaking)
of a solid and the heat of melting. The agreement of his formula
with the empirical facts is perfect; the theoretical derivation
is amusing, but will be criticised.
It is sometimes not easy to work under the strained con-
ditions of war. But it is the best way to avoid worrying. We hear
very little from American friends. Sometimes I think they
consider us as lost outposts of civilisation. But I think that is
quite wrong. This nation and France as well are tremendously
strong and internally sound. But most of what we hear about
American opinion seems to us strange. I am convinced that
you look at the present struggle with the same attitude as I do.
Remember me to all friends in Princeton, Weyls, Veblens.
Ladenburg, v. Neumann and the others.
Yours ever
Max Bom
Pauli writes: 'I just got a letter from Guido Beck. He is in a
camp (Camp de Chamberau, 27e Compagnie, Isere, France).
He lost his post in Lyon (with Thiband) and needs money very
urgently. Perhaps one could make a collection for him; it
would facilitate his position very much. I shall try this here in
Zurich.' I cannot do anything (export of money is not permitted,
and we have innumerable liabiUties).
Can you do it ?
M.B.
This is the first letter in English. I was not more fluent in it than in German
m those days, but after the outbreak of war it was more in accordance
with my frame of mind.
My anxiety about Niels Bohr was well founded. After Hitler's army
marched into Denmark, he was left in peace at first (as I found out later).
When measures were taken in Denmark, as elsewhere, to exterminate the
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Jews, he was warned in time (he was half Jewish) and escaped to Sweden.
From there he went to America and, under a pseudonym, took part in
the 'Manhattan Project', which led to the producdon of the first atomic
bomb.
The work of the Quakers in saving Jews and other victims of persecution,
in which my wife had a great interest, deserves the greatest praise.
The progress Fuchs and I made in the reciprocity investigations was
probably, in spite of Pauli's approval, merely formal; as mentioned
above, it has only quite recently (1965) really become physics.
Fock's paper on the deduction of the equations of motion in the general
theory of relativity from the field equation was mentioned in connection
with the paper by Einstein, Infeld and Hoffmann deahng with the same
problem (commentary to letter No. 73) .
Reinhold Furth, Professor of Theoretical Physics in Prague, escaped to
Great Britain with his wife after Hitler's invasion of Czechoslovakia, and
was taken on by my institute, where he worked successfully and helped
me with the teaching.
In my assessment of the strength of France and Great Britain, I was very
much mistaken about France (which is understandable, as I did not
know it well) ; but I was right where Great Britain was concerned.
Guido Beck was a gifted theoretical physicist. As far as I know, he was
rescued when France was threatened, and found asylum in South America.
78
Department of Natural Philosophy
The University
Drummond Street
Edinburgh
10 May, 1943
Dear Einstein
A geographical colleague of mine, Dr Arthur Geddes, has
asked me to write to you about the following matter: he has
found a short essay of yours on the 'Meanders of Rivers in
Alluvium, and the Earth's Rotation' [Life as I see it, Library
Ed.). He is deeply interested in this problem and wishes to
know whether you have published a full account of your
considerations, or whether other people have followed your
ideas. He could find no reference in the (rather scarce) literature
in French, English, German which is available here. You would
oblige me very much by letting me know what you are able to
tell me. I take this opportunity to tell you about ourselves. Hedi
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had a serious operation last October and has recovered extreme-
ly slowly. But now she is almost well. Our son is now a doctor
in a hospital and will join the forces in August. Our daughters
both have two children each, and their husbands are in the
Air Force and in the Admiralty. So we are four-fold grand-
parents. My department consists now only of Furth and two
half-time research students. But I have quite a lot of elementary
teaching.
I have not done much research, but I watch what Schroe-
dinger is doing with great interest. He writes to me regularly
and I hope to visit him in Dublin during the summer. He has
taken up an old paper of yours, from 1923, and filled it with
new life, developing a unified field theory for gravitation,
electrodynamics and mesons, which seems to me promising.
But I suppose he has written to you about it.
I have just been informed that Joh. v. Neumann is in this
country and will visit me next week, accompanying a man from
the Admiralty for whom he will do some war research.
How is Margot? Give her our love.
Kind regards from both of us.
The war looks much better now, and I hope it will be over
before Europe is completely destroyed. I had just a letter from
Brillouin (Providence USA) .
Yours
Max Born
I myself had once observed the meanderings of the great rivers, which is
the subject I wrote to Einstein about at Dr Geddes' suggestion. It was
during the Russian congress when we travelled down the length of the
Volga.
I can no longer remember the towns, which now lie a few kilometres
from the river, while it is quite obvious that they were originally built
on its banks. The explanation of the phenomenon by means of the so-
called 'Coriolis forces', which the rotation of the earth exerts upon bodies
which have a component of motion in a south-north or north-south
direction, is trivial and universally known. I cannot quite understand what
induced Einstein to write anything on this subject, or why Dr Geddes
should have been interested in it.
I can no longer remember anything about the contents of Schroedinger's
unified field theory. My correspondence with him was sporadic and
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explosive. It would languish for a while; then there would be an out-
break of letters from him, often one every day, so that I found it difficult
to keep in step with my repHes. I have a clear recollection of the series of
letters about the general theory of relativity and its generalisation, but
I cannot remember their contents. In the end, when I left Edinburgh
(''954)> I bad a mountain of Schroedinger's letters and have destroyed
most of them - because of lack of space in my tiny study in Bad Pyrmont.
Today I realise how silly this was; for even if there was much chaff"
amongst the corn, there were also some precious grains, turns of phrase
which were truly characteristic of Schroedinger.
John von Neumann was a Hungarian mathematician who spent some time
in Gottingen soon after the discovery of quantum mechanics. He then
published a book which today is regarded as a standard work on the sub-
ject. It contains the rigorous proof of the mathematical concepts and
methods used by Heisenberg, Jordan and myself He represents the
matrices I introduced as operators in an infinite dimensional space, the so-
called 'Hilbert-space'. For this I used results of Hilbert's, although I was
aware that the basic premises made in physics were less than those cus-
tomary in the mathematics of this space up to that time. Von Neumann
succeeded in the anything but easy task of finding rigorous proof amongst
the further suppositions. His book contains other results of importance
and useful creative concepts. During the Nazi period he emigrated to
America, became professor at the Institute for Advanced Study at
Princeton and worked there with Einstein and Weyl. He was considered
to be the greatest mathematician in America, and possibly in the whole
world. Unfortunately he contracted an incurable disease while still
comparatively young, and died an agonising death.
79
2 June, 1 943
Dear Born
My remark about the influence of the curvature of rivers and
of the Coriolis force on the erosion of waterways was only a
casual one. I have not published anything further on the subject,
as I am convinced that the idea must have been known for a
long time. I have, however, never searched the literature.
I was very interested in your news about yourself and your
family. The multifariousness of our destinies is really remarkable.
Schroedinger was kind enough to write to me himself and tell
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me about his work. At one time I was rather enthusiastic about
this trend of thought. Its weakness lies in its rather artificial and
weak construction from the point of view of affinitive space.
Moreover, the connection between the antisymmetrical curve
and the electrical properties of space results in a linear relation
between electric fields and charge densities. I have of course
written to Schroedinger about it in detail.
I myself am engaged in a rather daring attempt to get to a
unified physics, after trying vainly so many times before.
Certainly, to make real progress will require a mighty leap
forward in our thinking.
Kind regards to you and yours
Yours
A.Einstein
80
84 Grange Loan
Edinburgh
Dear Einstein
Our newspaper. The Scotsman, had a note about you : that you
have called upon intellectual workers to unite and organise
some protection against new wars of aggression and to secure
their influence in the political field. I was very glad when I
read that, for I feel that you are the only man who could do
anything in this direction, as your name is known to everybody
in the world. Of course, we are all getting old and have the
desire to rest and to be left alone, and there are not many
younger fellows.
Concerning myself, I had a kind of breakdown last winter
from which I have not quite recovered. It was the result of
many causes : a little overwork, the stress of the war in general
and the extinction of the European Jews, the transfer of my son
to the Far East (he is after many adventures quite safe on a
pathological course in Poona, India), etc. But the most de-
pressing idea was always the feeling that our science, which is
such a beautiful thing in itself and could be such a benefactor
for human society, has been degraded to nothing but a means of
destruction and death. Most of the German scientists have
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collaborated with the Nazis, even Heisenberg has (I learned
from reliable sources) worked full blast for these scoundrels -
there are a few exceptions, e.g. v. Laue and Hahn, The British,
American, Russian scientists are fully mobiUsed and rightly so.
I do not blame anybody. For under the given circumstances
nothing else can be done to save the rest of our civilisation. Yet
I think that we must have an international organisation and,
even more important, an international code of behaviour or
ethics (like the very strict rules which the British physicians
have inside their profession), by which our scientific com-
munity could act as a regulating and stabilising power in
the world, not, as at present, being no more than tools of
industries and governments. There is a definite ethical standard
upon which all religions agree. Christian, Jewish, Moslem and
Hindu. But some branches of biological science, logically
backward and based on poor evidence, have been tools in the
hand of criminal politicians for throwing us back in the state
of the jungle. There must be a way of prohibiting a repetition
of such things. We scientists should unite to assist the formation
of a reasonable world order. If you have any definite plans please
let me know. I am rather powerless, sitting at this pleasant but
backward place. But I should try my best. Fowler, who would
be the proper man to take the initiative in this country, is
unfortunately very ill; he had a breakdown much worse than
mine. I do not know where Niels Bohr is at present. I should
like to get in touch with him. Here in Britain it is very difiicult
to keep up connections with people. Travelling is possible only
in the most urgent cases, and meetings in the South are res-
tricted by the flying bombs.
But the military situation is excellent and we hope the Euro-
pean part of the war will be over soon.
Hedi is quite well and sends her best wishes to you and
Margot. My son is a medical officer in the army and has seen a
lot of India. My daughters and their families are all right,
though one of them is living in an area over which the flying
bombs are passing and occasionally dropping.
I have tried, together with my Chinese pupil Peng, an
excellent man, to improve the quantum theory of fields, and I
think we are on the right track. Schroedinger on the other hand
has improved your and other people's attempts to unite the
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different fields in a classical way. I think the next step should
be a combination and merging of these two approaches. But I
am too old and worn out to try it.
With kind regards and best wishes
Yours ever
Max Bom
In writing about the responsibility of the scientist I have said more than
once that the news of Hiroshima affected the issue decisively. This is true
in so far as a new situation existed from that day on. It was no longer
merely a question of ethics, whether political differences can ever
justify technical mass murder, but of the continued existence of civili-
zation itself, perhaps even of life on the earth. This letter shows that the
ethical question, and the abhorrence of war waged with technical means,
had been occupying me for a long time.
I would like to add a few more words on this subject here. It was during a
meeting of the British Association that I first learnt of the possibility of
developing a weapon of enormous effectiveness by splitting uranium
nuclei with the help of a chain reaction, a technique which had just
been discovered by Hahn and Strassmann. Before that, Leo Szilard, a
Hungarian physicist who had worked with Einstein for some time, had
appeared on the scene. He was completely obsessed with the idea of a
nuclear explosion. As the discovery of the splitting of the atom had taken
place in Germany, he was haunted by the fear that Hitler might be able
to develop this horrible weapon, and he talked of nothing else. This was
the first occasion I heard of fission, chain reactions, neutron exploitation,
and so on. It alarmed me but, for all that, seemed a long way off.
Then the war really started. After Dunkirk, all Germans in Great Britain
were interned, irrespective of whether they were Nazis or victims of Nazi
persecution. I escaped this fate, as I had become a British subject a few
weeks before the outbreak of the war. But my German collaborators,
Klaus Fuchs among them, were interned, and had to spend the next few
months in camps, first on the Isle of Man and later in Canada. There
their political reliability was investigated, and those who passed the test
were sent back to England.
Thus, Fuchs returned to my Institute after a few months and took up his
work again. But a little later he received a letter from Peierls, a German
physicist who had emigrated and had become a professor in Birmingham.
He asked Fuchs whether he would like to collaborate on an important,
top-secret war project. I knew at once that this could only mean one thing;
nuclear fission. As the possible consequences of the development of such
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a means of destruction filled me with horror, I tried as hard as I could to
dissuade Fuchs, but in vain. His hatred of the Nazis was boundless, and he
was glad to be able to do something against them. So he went to Peierls
in Birmingham, and later accompanied him to the United States; what
followed is common knowledge.
I myself was never directly invited to take part in the fission project. I
had never done any work in nuclear physics; but so many other branches
of physics were tied up with it that I could certainly have collaborated if I
had offered my services.
Thus I was spared any real temptation to participate; this is where my
fate was different from Einstein's. At the time I wrote this letter to
Einstein, about a year before Hiroshima, we still knew next to nothing
about the Manhattan Project. It was not until much later that I found out
that it was Einstein who, under pressure from Szilard and a number of
other physicists, had written a letter to President Roosevelt which had set
the whole thing in motion. I assume that Einstein, too, did not subsequentiy
receive much further information about the progress of the project.
Einstein, like Szilard, was motivated by the idea that Hider must be
prevented from being the first to use this weapon. That it should then be
used against defenceless people was a horrible thought for him and one
which cast a shadow over the evening of his life. Einstein's fate shows more
clearly than almost any other in history that even the greatest intellectual
powers and the purest of intentions are no protection against having to
make a decision between two possible courses of action, both equally
detestable.
Had all this been known to me, I would hardly have written the preceding
letter. I had been under the impression that Einstein was an absolute
pacifist, like the Quakers, with whom I came into frequent contact
through my wife, who had become a member of the Society of Friends.
But this he was not. He hated the use of force, particularly when it was
directed against non-combatant, defenceless people. He considered no
political or economic ideology, no state, no constitution to be worth the
sacrifice of masses of human lives. But the events of our lifetime had taught
him, and me, that the ultimate ethical values, on which all human
existence is based, must, as a last resort, be defended even by force and
with the sacrifice of human lives. We never again had an opportvmity of
exchanging our ideas on the subject. But I am convinced that we would
have understood one another. The following letter, his answer to my
suggestion, confirms this.
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8i
7 September, ig44
Dear Bom
I was so pleased about your letter that to my surprise I feel
compelled to write to you, although no one is wagging a finger
at me to do so. But I cannot write in English, because of the
treacherous spelling. When I am reading, I only hear it and am
unable to remember what the written word looks like.
Do you still remember the occasion some twenty-five years
ago when we went together by tram to the Reichstag building,
convinced that we could effectively help to turn the people
there into honest democrats ? How naive we were, for all our
forty years. I have to laugh when I think of it. We neither of us
realised that the spinal cord plays a far more important role than
the brain itself, and how much stronger its hold is.
I have to recall this now, to prevent me from repeating
the tragic mistakes of those days. We really should not be
surprised that scientists (the vast majority of them) are no
exception to this rule, and if they are different it is not due to
their reasoning powers but to their personal stature, as in the
case of Laue. It was interesting to see the way in which he
cut himself off", step by step, from the traditions of the herd,
under the influence of a strong sense of justice. The medical
men have achieved amazingly little with a code of ethics, and
even less of an ethical influence is to be expected from pure
scientists with their mechanised and specialised way of thinking.
It is, of course, quite correct for you to allot the relevant priest-
hood to Niels Bohr. For there is some hope that he would dis-
sociate his priestly side from physics, and use it in some other
way. Apart from this, I do not, however, expect much from such
an undertaking. The feeling for what ought and ought not to
be grows and dies like a tree, and no fertilizer of any kind
will do very much good. What the individual can do is to
give a fine example, and to have the courage to uphold ethical
convictions sternly in a society of cynics. I have for a long
time tried to conduct myself in this way, with a varying degree
of success.
Your 'I feel too old. . . .' I am not taking too seriously,
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because I know this feeling myself Sometimes (with increasing
frequency) it surges upwards and then subsides again. We can
after all quietly leave it to nature gradually to reduce us to dust
if she does not prefer a more rapid method.
I have read your lecture against Hegelianism with great
interest. It represents to us theoreticians the quixotic element, or
should I say the seducer? Where this evil or, rather, vice is
altogether missing, the inveterate philistine rules. I am therefore
confident that 'Jewish Physics' is not to be killed. Moreover I
have to confess that your deliberations remind me of the beauti-
ful proverb : 'Junge Huren - alte Betschwestern' [Young whores
- old bigots] particularly when I think of Max Born. But I
cannot really believe that you have completely and honestly
struggled your way through to the latter category.
We have become Antipodean in our scientific expectations.
You believe in the God who plays dice, and I in complete law
and order in a world which objectively exists, and which I, in a
wildly speculative way, am trying to capture. I firmly believe,
but I hope that someone will discover a more realistic way, or
rather a more tangible basis than it has been my lot to find. Even
the great initial success of the quantum theory does not make me
believe in the fundamental dice-game, although I am well
aware that our younger colleagues interpret this as a consequence
of senility. No doubt the day will come when we will see whose
instinctive attitude was the correct one.
With kind regards to you and your family (now freed
from flying bombs)
Yours
A. Einstein
The incident of twenty-five years ago, which Einstein remembers here, was
as follows: when the German Supreme Command suddenly capitulated
towards the end of 191 8 and the revolution broke out all over (rermany, I
was in bed with influenza and thus only witnessed the events in Berlin
from a distance. Just after I had recovered, Einstein rang me up (the
telephone functioned even during the wildest days) and reported that a
student council had been formed at the university, modelled on the
workers' and soldiers' councils (German Soviets). one of its first actions
had been to depose and lock up the Rector and some of the other digni-
taries. Einstein, because of his left-wing political views, was believed to
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have some influence with the more radical of the students, and he was
asked to negotiate with the 'council' in order to bring about the release
of the prisoners and the restoration of reasonable order. Einstein had
discovered that the student council met in the Reichstag building, and
asked me whether I would accompany him. I accepted despite the weak
state I was in after my bout of influenza.
First there was the long march from my house in the Grunewald to
Einstein's in the Bavarian quarter, for there were no trams or buses
running in our district; then three of us - Einstein had asked the psycholo-
gist Max Wertheimer to come too - went by tram to the Reichstag. I will
not go into the difficulties we had in penetrating the dense crowds which
surrounded the Reichstag building and the cordon of revolutionary soldiers,
heavily aimed and red-beribboned. Eventually someone recognised
Einstein, and aU doors were opened.
once in the Reichstag building, we were escorted to a conference room
where the student councU was in session. The Chairman greeted us
politely, and asked us to sit down and wait until an important point in the
new statutes for the university had been dealt with. So we patiently
waited and listened. Eventually the point at issue was settled and the
Chairman said: 'Before we come to your request, Professor Einstein, may
I be permitted to ask what you think of the new regulations for the
students?' Einstein thought for several minutes, and then said something
like this: 'I have always thought that the German universities' most
valuable institution is academic fireedom, whereby the lecturers are in no
way told what to teach, and the students are able to choose which lectures
to attend, without much supervision and control. Your new statutes
seem to abolish all this and to replace it by precise regulations. I would be
very sorry if the old freedom were to come to an end.' Whereupon the
high-and-mighty young gentleman sat in perplexed silence. Then our
business was discussed; but the student council decided that it had no
authority in the matter, and referred us to the new Grovernment in the
Wilhelmstrasse, issuing us with a pass for this purpose.
Accordingly we walked on to the Reich Chancellor's palace. This was
a hive of activity. The footmen of the Emperor's time still stood in
corners of the passageways and stairs but, apart from them, the people
running about the corridors were more or less shabbily dressed and
carrying briefcases - socialist delegates and delegations from the workers'
and soldiers' councils. The main hall was full of excited people talking in
loud voices. But Einstein was recognised at once, and we had no difficulty
in getting through to the newly appointed President Ebert, who received
us in a small room and said that we would appreciate that he was unable
to pay attention to minor matters that day, when the very existence of the
Reich itself was in the balance. He wrote a few words on our behalf to
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the appropriate new minister, and in no time at all our business had been
concluded.
We left the Chancellor's palace in high spirits, feeling that we had taken
part in a historical event and hoping to have seen the last of Prussian
arrogance, the Junkers, and the reign of the aristocracy, of cliques of
civil servants and of the military, now that German democracy had won.
Even the long journey back to the Grunewald, mostly on foot, could not
dampen my elated mood.
In those days we believed in the triumph of reason, of the 'brain'. We had
yet to learn that it is not the brain which controls human beings but the
spinal cord - seat of the instincts and of blind passions. Even scientists are
no exception to this.
Einstein had criticised Max Laue earlier on (Letter No. 3) but in this
letter he gladly acknowledges his bravery towards the Nazis.
Einstein did not think much of an 'ethical code'. The words contained in
this letter about Bohr, about 'the feeling for what ought to be, and what
ought not to', and about the role of the individual in the society of
cynics, are of profound wisdom.
Finally, Einstein concerns himself with my lecture 'Experiment and
Theory in Physics'. ^^''^ Scientifically, we had indeed drifted far apart. He
concentrated on speculations about his unified field theory, while I tried
to keep a tight reign on my inclination to speculate. My little book is a
sharp attack against certain papers by the astronomers Eddington and
Milne, who both, though in completely different ways, tried to solve the
enigma of the world of atoms and of the cosmos by means of pure thought
alone. I still, to this day, believe my arguments to be reasonable but, on
the other hand, Einstein is quite right in that empiricism alone, without
bold ideas, does not get one anywhere. He is a master who finds the
right proportions.
The last paragraph deals again with the fundamental dice-game in
quantum mechanics, and is probably the best and most lucid formulation
of Einstein's point of view. I have discussed it thoroughly in my book
J^atural Philosophy of Cause and Chanc^^ and there is no need to go into it
again.
82
84 Grange Loan
Edinburgh
g October, 1944
Dear friend Albert Einstein
It was wonderful to get a letter from you; that is, it was Max
who got it. I have read it several times, and once again had
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that feeling of liberation which I used to get from our talks
during the war. Somehow all the essentials are said in it, and I
feel as if I were standing in crystal clear air on the top of Mount
Everest. In the last few years, I have thought again and again
about two things you once said to me. When I asked you
whether you were at all afraid of death (when you were so
serene during your serious illness), you said: 'I feel such a sense
of solidarity with all living things that it does not matter to
me where the individual begins and ends'. You also said:
'There is nothing in the world which I could not dispense with
at a moment's notice'. For me these are very 'religious' remarks
in the idiom of the twentieth century. I hope you do not mind
my calling them that. It is a joyous consciouness of submission
to a law allied with a stem sense of responsibility for ethical
convictions. As to the latter: to live one's ethical convictions
before one is reduced to dust again is something which you
simply cannot renounce. I hope you will not regard this as a
sermon - the Quakers (I've been one for the last six years)
have no sermons. Nor have I become a Betschwester [bigot]. I
am very bad at praying, as I think that we have no right to it.
once we have recognised how we should live, we can pray
through the very quaUty of our life; and if the quality of our
lives is not up to that level, in spite of our awareness, then we
are even less entitled to pray with words. But usually there is
this awareness of unity with God and with all living things. I,
too, am unable to believe in a 'dice-playing' God, nor am I
able to imagine that you believe - as Max has just told me
when we were discussing it - that your 'complete rule of law'
means that everything is predetermined, for example, whether
I am going to have my chUd inoculated against diphtheria or
not, etc. . . .
Things would then be as in Omar the tentmaker:
'That I would drink during my lifetime
God has known for all eternity. . . .'
I have forgotten what follows, but it must have been: where
then is ethics, the consciousness of striving?
You could probably explain this to me with just a few of
those vigorous words of yours.
Just a fortnight ago I wrote two remaining sonnets to add to
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BORN-EINSTEIN LETTERS
the three I wrote in India in 1935, where I try to express the
thought that love alone binds and liberates one (from the ego)
at one and the same time. They came into being from Indian
'non-attachment'. It seems to me that you have achieved such
non-attachment - but how? You have landed yourself in a
fine pickle with that letter of yours ! I hope it has been pre-
determined that you are going to answer me on this !
You are quite right in your attitude towards ageing - that
we can simply leave it to nature to reduce us to dust again.
What Max was trying to express must have been that feeling of
being 'used up' which we are both constantly aware of now,
and which is constantly being confirmed by certain facts:
for example, by the fact that neither of us is any longer
physically capable of coping with the constant calls for help
from our daughters, who want us to put them up with their
babies for weeks on end. I have just had one such visit, lasting
four weeks, from Gritli and Sylvia (eighteen months old) which
led to a mighty breakdown on my part. Gritli wanted to have a
rest, just when I was entirely without help in the house; then
too, Maurice came home on leave, and I had to do absolutely
everything (and wanted to do it) - cooking, washing-up,
shopping and queuing, looking after the baby, etc. etc. . . .
Also, I can draw lip quite a list of illnesses and operations since
we came to Edinburgh - six months of pleurisy, an operation
for detachment of the retina, and finally, less than two years
ago, a major gynaecological operation for the removal of (your
ｅxpression) my complete production centre with all accessories.
You once said: 'where you females are concerned, your pro-
duction centre is not situated in the brain' - you see how well
all your shameful sayings are fixed in my memory! Yes, all
these illnesses, together with the constant wear and tear caused
by the vastly increased difficulties of everyday life, as well as
three years of voluntary nursing service, have all contributed
to the feeling of 'being used up'. This feeling of being old and
tired is different from the 'normal' ageing process, which still
seems to exist in America, far removed from the war. To
recover from our kind of 'ageing', it would have to be peace-
time again, with one's children and friends once more in peace-
time occupations, when one would no longer have to be a
constant witness of suffering.
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Your letter -just as in the old days, during the last war, your
cheerful objectivity - has done me a power of good. I wish I
could hear you roar with laughter once again ! How is my little
Margot? Did she ever receive my letter with the Hiddensee
photos ? Wish I could see you all again sometime !
God bless !
Your old friend
Hedi
My wife's answer to Einstein's letter was written a few days before mine,
but both were apparently sent off at the same time. She uses the familiar
'Du' to address Einstein here, which she had never done before. This
familiarity may have been brought about by their feeling of mutual
affinity. This letter, recollecting some of Einstein's remarks and contem-
plating on his philosophy of life, is indeed a testimony to our friendship
and accord.
Although my wife had not been schooled in philosophy, her reservations
about Einstein's attitude to nature hit the nail exactly on the head.
Strict determinism seemed to us then, as it still does today, to be irrecon-
cileable with a belief in responsibility and ethical freedom. I have never
been able to understand Einstein in this matter. He was, after all, a highly
ethical person, in spite of his theoretical conviction about predetermina-
tion. As far as I am concerned, the discrepancy between ethical freedom and
strict natural laws - which even modern physics does not deny but merely
conceives of in a different way - only became intelligible with the help
of Niels Bohr's complementarity principle. How much longer will it be
before the professional philosophers come to understand and adopt these
ideas? I also mention the 'dice-playing God' in my letter. Today I still
consider my objection, that Einstein's way of thinking in physics could not
do without the 'dice-playing God', to be absolutely correct. For in classical
physics the initial conditions are not determined by natural laws, and in
every prediction one either has to assume that the initial conditions have
been determined by mesisurement, or else one has to be content with a
statement of probability. I basically believe that the first case is illusory;
even the best of measurements offer only statistical evidence, which is
more or less restricted by the scatter of the initial configuration. The
letters which follow deal with this subject in greater detail.
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83
10 October, 1344
Dear Einstein
Your letter gave both Hedi and myself great pleasure, and
Hedi was so excited and stimulated by it that she replied
straight away. In my case it takes a little longer.
I have not held any lectures for the last nine months, as I
suffered a collapse in January from which I recovered very
slowly, and today I lectured again for the first time after this
long interval. I had to prepare myself for it, and eventually
one single student turned up, whom I gave a private lesson.
All the other fellows are somewhere in the army and navy or
the R.A.F. Our expedition to the Reichstag building is still
quite fresh in my memory. (Wertheimer was there, too, wasn't
he?). In those days, I must admit, we completely misjudged
the forces in German politics. But it was, after all, only by a
hair's breadth that everything went as wrong as it did. Of
course I agree with you completely that all human actions
spring from the depths of an ethical feeling which is primary
and almost completely independent of reason. But after
agreeing with you on this point, I must now switch over to our
disagreement in physics. For I am unable to separate the two
and I cannot understand how you can combine an entirely
mechanistic universe with the freedom of the ethical individual.
Hedi, who knows nothing about physics, has all the same
formulated it excellently in her enclosed letter to you. To me a
deterministic world is quite abhorrent - this is a primary
feeling. Maybe you are right, and it is as you say. But at the
moment it does not really look like it in physics - and even less
so in the rest of the world. I also find your ｅxpression, the 'dice-
playing God', completely inadequate. You have to throw dice
as well in your deterministic world; this is not the difference.
You know what that difference really is, as well as I do, and if
you are not in possession of all the arguments at the moment,
give Pauli a cue, and he will trot them all out. I think first of all
that you underestimate the empirical fundamentals of the
quantum theory (I attach less importance to the mass of 'proof
than to single blatant instances, such as Gibb's paradox or the
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BORN-EINSTEIN LETTERS
Stern-Gerlach experiment) ; and secondly that your philosophy
somehow manages to harmonise the automata of lifeless objects
with the existence of responsibility and conscience, something
which I am unable to achieve.
Now with regard to my anti-Eddington and Milne essay, it
was written in accordance with the British style of courtesy. I
myself would have summed it up as 'rubbish'. But something
of that kind had to be written as Eddington is regarded as a
kind of prophet in this country. I believe, though, that you have
the right to speculate, but that other people do not, myself
included. Did I sin so in days gone by (or rather, as you put it,
whore) ?
I have always appreciated your good Jewish physics, and
have greatly enjoyed it; but I have done it myself on only one
occasion, in the case of non-linear electrodynamics, and this
was hardly a success. It is my honest opinion that when average
people try to get hold of the laws of nature by thinking alone,
the result is pure rubbish. Schroedinger may be able to do it. I
would like to know what you think of his affine field theory.
I find it all beautiful and ingenious, but is it true? He has now
published his lectures about statistical thermodynamics (auto-
graphed) ; I find them better and more substantial.
In spite of the war, I still have a small group of people doing
scientific research here. Fiirth too has done some experimenting;
he has built a photoelectric microphotometer, as well as an
harmonic analyser, which is also photoelectric. At the moment
he is constructing a Fourier transformer which I have invented ;
this produces the Fourier coefficient curve for any given curve
on the screen of an oscillograph. It would amuse you. We are
also working on crystals and X-rays, but mainly on the improve-
ment of the quantised field theory. You are, of course, absol-
utely right if you detest this in its present form. But I think
that we (that is, my Chinese collaborator Peng and I) have
already improved it considerably, and we are fairly certain that
we will be able to discard everything unsatisfactory (diverging
integrals, etc.). I believe it is going to be at least as beautiful
as any respectable classical theory.
Unfortunately I am still unable to get much work done. My
heart cannot stand the slightest exertion. For this reason I am
not going to do anything further vwth regard to the matter which
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BORN-EINSTEIN LETTERS
was the subject of my last letter to you and of your reply,
particularly as your reply was not encouraging. Moreover, I
do not know where Niels Bohr is, and therefore cannot appoint
him referee in this business. You are probably right in saying
that it is even more difliicult for scientists than for ordinary
people to develop a conscience and a sense of right and wrong.
In regard to Laue, I have also heard that his conduct was
decent and courageous. one can only hope that he will survive
the last, and presumably the most gruesome, period of the war.
I hope that you will write again from time to time. A letter
from you gives us the very greatest pleasure. It causes long
discussions; for Hedi, as a Quaker, often interprets your remarks
very differently from the way I do, old heathen that I am (I am
not one really, in fact I am quite devout; it is only in compari-
son with Hedi). Give my regards to our friends in Princeton -
Neumann, Ladenburg, Weyl and the caustic Pauli.
In old friendship
Yours
Max Born
Fiirth's experimental work contained only one idea of mine; this was the
photoelectric Fourier transformer. Later on the Edinburgh branch of
Ferranti developed this further, but it was not, however, introduced in
practice.
84
3 March, ig4y
Dear Born
If I were not a confirmed old rogue, with a fossilised bad
conscience, I would not have been able to go for such a long
time without writing to you. For firstly, your wife's poem about
the Indian ideal of life made so deep an impression on me that
I would not have been surprised if it had been written by old
Goethe himself; secondly, I was very impressed with your
contribution to that peculiar schoolmaster Schilpp's volume
which is dedicated to me. It has so much warmth and proves
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SO clearly that you consider my attitude towards statistical
quantum mechanics to be strange and archaic. Finally, I
particularly like your soUcitude for your Chinese protege's
transportation; fortunately he has happily and silently slipped
away from you without my intervention. I had consulted Weyl
about him, and we both agreed that we would not have been
able to solve the problem in the way you had suggested, and
that I should approach the EngUsh ambassador, who would
bring the matter honourably to a satisfactory conclusion.
Fortunately I avoided making this step for several days, and
then your letter arrived, releasing me.
I cannot make a case for my attitude in physics which you
would consider at all reasonable. I admit, of course, that there
is a considerable amount of validity in the statistical approach
which you were the first to recognise clearly as necessary given
the framework of the existing formalism. I cannot seriously
believe in it because the theory cannot be reconciled with the
idea that physics should represent a reality in time and space,
free from spooky actions at a distance. I am, however, not yet
firmly convinced that it can really be achieved with a continuous
field theory, although I have discovered a possible way of doing
this which so far seems quite reasonable. The calculation diffi-
culties are so great that I will be biting the dust long before I
myself can be fully convinced of it. But I am quite convinced
that someone will eventually come up with a theory whose
objects, connected by laws, are not probabilities but considered
facts, as used to be taken for granted until quite recently. I
cannot, however, base this conviction on logical reasons, but can
only produce my little finger as witness, that is, I offer no
audiority which would be able to command any kind of respect
outside of my own hand.
I am glad that your life and work are fruitful and satisfying.
This helps one to bear the craziness of the people who deter-
mine the fate of homo sapiens (so-called) on the grand scale.
Maybe it has never been any better, but one did not see it as
clearly in all its wretchedness, nor were the consequences of
the bungling quite as catastrophic as under present conditions.
Best wishes to you and your family
Yours
A. Einstein
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My wife's 'Indian Sonnets' have been published in an anthology of her
poems,33 'Stille Gauge' [Silent Corridors]. 'Schoolmaster' Schilpp's
volume is one of the series published in the United States called The
Library of Living Philosophers, under this title: Albert Einstein, Philosopher-
Scientist. Each volume of this collection begins with a short autobiography
of the philosopher concerned; this is followed by critical reviews of his
work by different authors, and ends with the subject's reply to his critics.
I had undertaken to write about Einstein's statistical theories; this essay
is also published in German in my book Physik im Wandel Meiner y^eit.
Towards the end of the article I go into Einstein's attitude towards
quantum mechanics, and contrast the empirical creed of his youth with
his later inclination towards speculation. In an obituary that Einstein
wrote for Ernst Mach,^* he says: 'concepts which have proved useful for
ordering things easily assume so great an authority over us, that we forget
their terrestial origin and accept them as unalterable facts. They then
become labelled as "conceptual necessities", "a priori situations", etc.
The road of scientific progress is frequently blocked for long periods by
such errors. It is therefore not just an idle game to exercise our ability
to analyse familiar concepts, and to demonstrate the conditions on which
their justification and usefulness depend, and the way in which these
developed, little by little, from the data of experience. In this way they
are deprived of their excessive authority. Concepts which cannot be
shown to be valid are removed. Those which had not been coordinated
with the accepted order of things with sufficient care are corrected, or
they are replaced by new concepts when a new system is produced which,
for some reason or other, seems preferable'. In my article in the Schilpp
book I contrast this creed of his with his attitude towards quantum
mechanics, by quoting from his earlier letters. The present letter can
equally well serve as paradigm, particularly the paragraph which begins :
'I cannot make a case for my attitude which you would consider at all
reasonable.' The decisive sentence is the one where he says: 'that physics
should represent a reality in time and space, free from spooky actions
at a distance'. I too had considered this postulate to be one which
could claim absolute validity. But the realities of physical experience had
taught me that this postulate is not an a priori principle but a time-
dependent rule which must be, and can be, replaced by a more general
one.
My article in the Schilpp book is not by any means the only one which
deals with this subject. There is, for example, an article by Niels Bohr,
in which he reports on some detailed discussions he had with Einstein.
In the course of it he picks to pieces Einstein's ingenious thought-experi-
ments, which were intended to refute quantum mechanics.
But even this difference of opinion in print did not interfere with our
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friendship in the slightest degree. Einstein expressly acknowledges the
warm tone of my article.
I cannot now remember what was the point about the transportation of
my Chinese protege. I had a number of extremely gifted Chinese colla-
borators, who presumably wanted to return home because of the con-
stantly increasing threat of war without having to pass through either
Germany or Russia, but by way of America.
The last paragraph of the letter is a resigned complaint about the craziness
and wretchedness of homo sapiens, which at that time (end of 1947) was
becoming more and more obvious.
85
Magdalen College, Oxford
4 March, ig48
Dear Einstein
A few days ago I saw a film here about atomic energy, and
there you were, as large as life, talking with that familiar and
well-loved voice, and smiling your amiable, half-serious, half-
cynical grin. I was quite moved - it will soon be twenty years
since we last saw you. And when I vwote about this experience
to Hedi in Edinburgh, she replied at once that she wanted to
see the film as well. I am going to try and persuade the atomic
physicists here to send the film there. It also contained some
fine shots of J. J. Thomson and Rutherford but, though I have
always greatly admired them, they are nowhere near as close
to my heart as you are. As to the rest of the film, it is quite good,
but it will not alter the course of world history very much.
We've really put our foot in it this time, poor fools that we are,
and I am truly sad for our beautiful physics! There we have
been trying to puzzle things out, only to help the human race to
expedite its departure from this beautiful earth! I no longer
understand anything about politics: I understand neither the
Americans, nor the Russians, nor any of the numerous little
stinkers who are now, of all times, becoming nationalistic. Even
our good Jews in Palestine have discredited their cause in this
way. It is better to think about something else.
Today I gave the last of my Waynflete Lectures, in which
inter alia I produced certain passages from your letter to me. I
assumed that you would have no objection, as you did not return
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my manuscript in protest. My stay in a luxurious Oxford
college was very pleasant. The (relatively) good food does not
mean much to me; but the many conversations with a variety of
intelligent people did, as well as the beautiful old town itself
with its grey old buildings; visits to my daughter Gritli (her
husband, Maurice Pryce, was unfortunately ill for almost the
whole time) and playing with my grandchildren. Occasionally
we played music on two pianos - all delightfiil things. I have
prepared the lectures for printing in book form. Hedi stayed at
home in order to re-arrange our house: moving the kitchen
upstairs, to save us old people from having to climb so many
stairs. She is happy because a religious (and very fine) article of
hers has appeared in an Indian periodical. Could you not
arrange to have her poems printed in a German periodical in
America ? They are very beautiful, aren't they, but here in Eng-
land nobody understands German, and in Germany there are
enough poets, more than the country can suppert. Much of
Hedi's time is taken up with sending parcels to starving people in
Germany. It is particularly the anti-Nazis who are suffering
again at the moment. But then, we are rationed ourselves and
so cannot do much to help.
What we are doing in physics will not interest you very much.
We concluded our kinetic theory of liquids with a paper about
the crazy helium II (which has not yet been published).
one of my Chinese pupils is working on superconductivity,
and I consider his theory (which is based on a few suggestions
of mine) to be better than Heisenberg's. My collaborator
Green is hard at work on elementary particles; he is a brilliant
man, the best I have had since Pryce. All this keeps me reason-
ably young. I still have five more years in office, and then I
have to retire on a pension, which is not enough to live on (it
is a kind of insurance, and the amount depends on one's length
of service), so I will probably have to go on working, right to
my blissful end. Not a bad fate, really.
Although a letter from you gives me great pleasure, you need
not reply unless you really feel like it. All the best, and kind
regards to Margot.
Yours
Max Bom
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When I wrote 'we've really put our foot in it', I apparently still did not
know that it was Einstein who, through his letter to President Roosevelt,
had started it all off. Had I known, I would hardly have written this
passage.
This letter comes from Oxford. The Vice-Chancellor of the old university,
Sir Henry Tizard, known for his conflict with Lindemann-Cherwell over
the technical conduct of the war, had personally invited me to hold the
Waynflete Lectures while on a visit to Edinburgh. It was an honour I
gladly accepted, although it meant a considerable amount of work for me.
The lectures have been published under the title: Natural Philosophy of
Cause and Chance.*^ They contain a report about the advance of the
probability concepts into causal physics, which culminated in quantum
mechanics. It also contains quotations from Einstein's letters which will
be the subject of further comments.
The statistical mechanics of condensed systems, devised by Green and
myself, which was intended to lead to a kinetic theory of liquids, has been
summed up in a booklet called A General Kinetic Theory of Liquids,^ and has
made some contribution towards the development of this field. But the
use of helium, which has a Hquid phase that behaves curiously, was not
as successful as we had hoped. The theory accepted today originated with
the Russian Nobel prizewinner of 1962, L. D. Landau.
86
18 Marchy ig48
Dear Born
Today I was looking for something in my igloo, that is, on my
desk in the Institute. I did not, however, find what I was looking
for, but your letter instead, which I had taken to be printed
matter (because of the large envelope), and had therefore left
unopened together with many others. Now I have read it, of
course, and moreover with such interest that I arrived home an
hour late for lunch.
There are several misunderstandings in your quotations from
my letters, presumably caused by my illegible handwriting,
which distort the meaning as you will see from my marginal
notes. But even if it has already been printed it is not a disaster
because the 'patience of paper' will certainly be preserved
in this case as well. I have got my own back by means of several
caustic marginal comments, which will delight you; for I
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BORN-EINSTEIN LETTERS
believe that you enjoy rough language, which after all goes with
the Scottish climate.
It is really rather a pity that we cannot spend some time
together at leisure. For I really understand very well why you
consider me an impenitent old sinner. But I feel sure that you
do not understand how I came by my lonely ways; it would
certainly amuse you, even if there is not the slightest chance of
your approving of my attitude. I would enjoy picking your
positivistic philosophical attitude to pieces myself. But this is
hardly likely to happen during our lifetime. I have greatly,
although belatedly, enjoyed your and your wife's letters, and
remain, with kind regards,
Yours
A. Einstein
I am only going to quote a few of the 'caustic comments' here. In the last
chapter of my book ('Metaphysical Conclusions') I assembled some of
the fundamental concepts of physics, which cannot be traced back to
other more fundamental ones, but have to be accepted as an act of faith. I
then continue: 'Causality is such a principle if it is defined as the belief in
the existence of mutual physical dependence of observable situations.
However, all specifications of this dependence in regard to space and time
(contiguity, antecedence) and to the infinite sharpness of observation
(determinism) seem to me not fundamental but consequences of the actual
empirical laws'.
Einstein's marginal comment was: 'I am well aware that no causality
exists in relation to the observable ; I consider this realisation to be conclu-
sive. But in my opinion one should not conclude from this that the theory,
too, has to be based on fundamental laws of statistics. It is, after all,
possible that the (molecular) structure of the means of observation
involves the statistical character of the observable, but that it is expedient
in the end to keep the basis of the theory free from statistical concepts.'
My text then continues: 'Another metaphysical principle is incorporated
in the notion of probability. It is the belief that the predictions of statis-
tical calculations are more than an exercise of the brain, that they can be
trusted in the real world.'
Einstein comments briefly: 'I agree with this, of course.'
These comments are calm and matter-of-fact. But there are also some
short, sharp remarks. My text deals with the question of whether the
beauty and simplicity of a theory are of importance; it reads as follows:
'With regard to simpUcity, opinions will differ in many cases. Is Einstein's
law of gravitation simpler than Newton's? Trained mathematicians will
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answer yes, meaning the logical simplicity of the foundations, while others
will say emphatically no, became of the horrible complications of the
formaUsm.'
Einstein's comment on this is simply:
'The only thing which matters is the logical simphcity oi the foundations'.
I agree with this, as a trained mathematician, but I am unable to condemn
the other point of view entirely. After all, what really matters in the end
is whose formulae do more justice to the observations, Newton's or
Einstein's.
I then discuss what I call the 'principle of objectivity' : 'It provides a
criterion for distinguishing subjective impressions from objective facts,
namely by substituting for given sense data others which can be checked
by other individuals'. I have recently dealt in detail with this favourite
idea of mine in an essay entitled: 'Symbol and Reality'.** Einstein's brief
comment was simply: 'Blush, Bom, Blush!'
Elsewhere I try to explain that the application of the objectivity principle
can sometimes be out of place by using a work of art as an example (a
Bach fugue), and he just comments: 'Ugh!'
At the end he adds a somewhat longer passage in his elegant handwriting,
which I reproduce in its entirety: 'Remark: you should not interpret the
omission of marginal comments in the latter part of your article as agree-
ment. The whole thing is rather sloppily thought out, and for this I must
respectfully clip your ear. I just want to explain what I mean when I say
that we should try to hold on to physical reality. We all of us have
some idea of what the basic axioms in physics will turn out to be.
The quantum or the particle will surely not be amongst them; the
field, in Faraday's and Maxwell's sense, could possibly be, but it is
not certain. But whatever we regard as existing (real) should somehow
be localised in time and space. That is, the real in part of space A should
(in theory) somehow 'exist' independently of what is thought of as real in
space B. When a system in physics extends over the parts of
space A and B, then that which exists in B should somehow exist indepen-
dently of that which exists in A. That which really exists in B should
therefore not depend on what kind of measurement is carried out in part
of space A; it should also be independent of whether or not any measure-
ment at all is carried out in space A. If one adheres to this programme, one
can hardly consider the quantum-theoretical description as a complete
representation of the physically real. If one tries to do so in spite of this,
one has to assume that the physically real in B suffers a sudden change as a
result of a measurement in A. My instinct for physics bristles at this.
However, if one abandons the assxmiption that what exists in different
parts of space has its own, independent, real existence, then I simply
cannot see what it is that physics is meant to describe. For what is thought
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to be a 'system' is, after all, just a convention, and I cannot see how one
could divide the world objectively in such a way that one could make
statements about parts of it.'
According to his letter, Einstein believes that I would disapprove of this
attitude, even if we had the opportunity to discuss it personally. He calls
my philosophical ideas 'positivistic', and would love to pull them to pieces.
I myself certainly do not regard my philosophy as a variety of positivism if
this implies that only sensory impressions have any claim to reality, and
that everything else, not only scientific theories but also one's ideas about
real things of daily life, is merely constructed, created for the purpose of
establishing reasonable relationships between the various impressions of
the senses. My reply to Einstein's comments is contained in a later letter.
87
84 Grange Loan
Edinburgh
31 March, ig48
Dear Einstein
Many thanks for the return of my manuscript with your
marginal comments, and for your letter. It takes some time to
get things printed here. Meanwhile the manuscript is nowhere
near completion, and even if I should send it to the publishers
in May it is unlikely to appear before January '49. This will
enable me to make any corrections which seem necessary.
I am very grateful to you for allowing me to reprint the two
passages from your letters. I will make the corrections you
suggest in their text, even though the wording of your original
version was absolutely clear, while the second is entirely
ambiguous. I have made a careful copy of your words; here is
the result:
1 . 'I firmly believe, but I hope that. . . .'
The words are curious, I admit. But the 'believe' has been
underlined by you. I am leaving it out, and am going to replace
it by: 'I hope. . . .'
2. Skin - as you are talking about the little finger, I took it to
be 'hand'. But your reading is equally justified, particularly as
it is in accordance with the writer's interpretation.
As to the rest, I will bear your earclipping and scolding with
humility. There is nothing to be done. But in order fully to
understand what you are criticising, one has to be familiar, of
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course, with the six preceding lectures as well. But I am quite
sure that they would not have helped to convert you to my
point of view either. I will make good use of your remarks and,
if I can find the time, improve my wording. I am very sorry
indeed that you do not like my 'observational invariants'. They
are descendents of Wertheimer's Gestalt, in a new form. I think
quite highly of it. But I am annoyed that you reproach me
for my positivistic ideas; that really is the very last thing I am
after. I really cannot stand those fellows. Again, my sincere
thanks.
Hedi and I are travelling to France the day after tomorrow.
First to Bordeaux, where a congress on light dispersion and the
Raman effect is taking place. Raman and I are to receive
honorary doctorates there. This is very funny, as for the last
three years we have been engaged in a violent feud about
crystal theory. That is, he has encouraged his pupils to attack
me in Nature, and I have answered back rather energetically at
times. Now we shall have to keep the peace and allow ourselves
to be honoured. He is used to it, I am not. In the case of quantum
mechanics, which you think so Httle of, the adulation has
aUghted entirely on Heisenberg and Schroedinger. And yet
Heisenberg did not even know what a matrix was in those days
(he was my assistant, that is how I know). By the way, he
visited us last December, as pleasant and intelligent as ever, but
noticeably 'Nazified'. I have recently talked to him again in
Oxford. once more we are on the same trail: superconductivity.
He has published a theory which we consider absolute rubbish.
We first of all carefully deduced the kinetic theory of dense
matter (liquid and solid bodies), and then explained helium II
very satisfactorily, and are at present engaged in producing a
decent theory of superconductivity. It all seems to work out
quite well. Do you really believe that the whole of quantum
mechanics is just a phantom ?
Do come over to Europe some time. In England and Scotland
little has been destroyed, and even in France enough has been
left intact. How beautiful are the ancient towns, churches
and castles of pre-machine days ! Hedi and I were in Switzerland
last summer, and were completely intoxicated with the loveli-
ness not only of the landscape but also of the small towns such
as Berne, Lucerne, Thun, etc. Oxford, too, is not to be despised.
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BORN-EINSTEIN LETTERS
Or have you, with your leaning towards puritanism, lost the
ability to enjoy such impressions ?
With kind regards, also from Hedi
Yours
Max Born
When I used the ｅxpression 'observational invariants' in my book, I
meant the following: when one sees a bird flying away, what one really
perceives is usually a bird, recognisable as such, which then becomes
smaller and smaller until one can no longer distinguish any details and
finally sees only a small point. All the same, one is aware that one is
looking at the same bird all the time. Thus there is something constant
and invariable in totally different sensual perceptions, which one's
brain deals with unconsciously. This is what I call the 'observational
invariant'.
Wertheimer was the same man who accompanied Einstein and me to the
Reichstag during the revolution, as described in the commentary to letter
No. 8i. He was one of the founders of the Gestalt theory, together with
Kdhler, Hornbostel and others, which teaches that perception consists,
not of sense perceptions which coexist side by side, but of the recognition
of complete and meaningful Gestalten.
The meeting with Sir C. V. Raman in Bordeaux was most dramatic.
At his invitation we had spent the winter of 1935-36 at the Indian
Institute of Science in Bangalore, where I gave some lectures. Wc had
got on well together, apart from some minor differences of opinion, and
had become friends, or so I thought. He even tried to obtain a permanent
position for me there, but spoilt this plan by some rather clumsy manoeuv-
ring. Although he had regularly attended almost all my lectures on the
dynamics of crystal lattices, he developed a very primitive theory of his
own about lattice vibration, and induced his pupils to attack me in Nature.
In Bordeaux, after a friendly greeting, we clashed almost immediately;
he was running down the theoreticians who want to make experiments,
when I said: 'And what about experimentalists who try their hand
at theory?' This made him see red; during the banquet, at which my
wife sat next to him, he declared that I had insulted him to such an
extent that he would have to leave, and she had great difficulty in
dissuading him. The tension persisted for the whole of the congress. And
even later, during a meeting of Nobel prizewinners in Lindau, he cut us
as much as possible.
My opinion of Heisenberg was probably not justified. Later on he explained
to me what his work had been during the Hitler period and how this had
governed his relations with the regime. In the meantime (1969) objective
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evaluations of German work on the splitting of the atom during the
war have appeared, in particular that by the EngUsh historian David
Irving,* which confirms Heisenberg's statement and justifies his behaviour.
As I have said before, nothing much came of our theory of the super-
fluid phase of helium, and of the superconductivity of metals.
88
5 April, jg48
Dear Bom
I am sending you a short essay which, at Pauli's suggestion, I
have sent to Switzerland to be printed. I beg you please to
overcome your aversion long enough in this instance to read
this brief piece as if you had not yet formed any opinion of your
own, but had only just arrived as a visitor from Mars. I am not
asking you to do this because I imagine that I can influence your
opinion, but because I think that it will help you to understand
my principal motives far better than anything else of mine you
know. However, it tends to express the negative aspect, rather
than the confidence I have in the relativistic group as represent-
ing a heuristic limiting principle. In any case, I will be extreme-
ly interested to hear your counter-arguments, beyond the
obvious fact, of course, that quantum mechanics alone has up
to now been able to encompass the wave-particle character of
light and matter.
With kindest regards
Yours
A. Einstein
Quantum Mechanics and Reality
In what follows I shall explain briefly and in an elementary
way why I consider the methods of quantum mechanics
fundamentally unsatisfactory. I want to say straight away,
* David Irving, The Virus House''' (pseudonym of a German nuclear research
laboratory in Berlin). Also the issue oi Bulletin of the Atomic Scientists" devoted to
the 'German atom bomb', which, in addition to a leading article by the editor,
E. Rabinovich, contains contributions by Heisenberg himself and by Hans Suess
(once a member of the German nuclear research team, now Professor of Chemistry
in the University of California at San Diego).
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BORN-EINSTEIN LETTERS
however, that I will not deny that this theory represents an
important, in a certain sense even final, advance in physical
knowledge. I imagine that this theory may well become a part
of a subsequent one, in the same way as geometrical optics is
now incorporated in wave optics: the inter-relationships will
remain, but the foundation will be deepened or replaced by a
more comprehensive one.
I consider a free particle described at a certain time by a
spatially restricted ^-function (completely described - in the
sense of quantum mechanics). According to this, the particle
possesses neither a sharply defined momentum nor a sharply
defined position. In which sense shall I imagine that this represen-
tation describes a real, individual state of affairs ? Two possible
points of view seem to me possible and obvious and we will
weigh one against the other :
(a) The (free) particle really has a definite position and a
definite momentum, even if they cannot both be ascertained by
measurement in the same individual case. According to this point
of view, the i^-function represents an incomplete description of
the real state of affairs.
This point of view is not the one physicists accept. Its accept-
ance would lead to an attempt to obtain a complete description
of the real state of affairs as well as the incomplete one, and to
discover physical laws for such a description. The theoretical
framework of quantum mechanics would then be exploded.
{b) In reality the particle has neither a definite momentum nor a
definite position; the description by i/«-function is in principle a
complete description. The sharply-defined position of the par-
ticle, obtained by measuring the position, cannot be interpreted
as the position of the particle prior to the measurement. The
sharp localisation which appears as a result of the measurement
is brought about only as a result of the unavoidable (but not
unimportant) operation of measurement. The result of the
measurement depends not only on the real particle situation
but also on the nature of the measuring mechanism, which in
principle is incompletely known. An analogous situation arises
when the momentum or any other observable relating to the
particle is being measured. This is presumably the interpretation
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preferred by physicists at present; and one has to admit that it
alone does justice in a natural way to the empirical state of
affairs expressed in Heisenberg's principle within the framework
of quantum mechanics.
According to this point of view, two ^-functions which differ
in more than triviaHties always describe two different real
situations (for example, the particle with well-defined position
and one with well-defined momentum).
The above is also valid, mutatis mutandis, to describe systems
which consist of several particles. Here, too, we assume (in the
sense of interpretation lb) that the ^-function completely
describes a real state of affairs, and that two (essentially)
different ^-functions describe two different real states of affairs,
even if they could lead to identical results when a complete
measurement is made. If the results of the measurement tally,
it is put down to the influence, partly unknown, of the measure-
ment arrangements.
II
If one asks what, irrespective of quantum mechanics, is charac-
teristic of the world of ideas of physics, one is first of all struck
by the following: the concepts of physics relate to a real outside
world, that is, ideas are estabhshed relating to things such as
bodies, fields, etc., which claim a 'real existence' that is inde-
pendent of the perceiving subject - ideas which, on the other
hand, have been brought into as secure a relationship as
possible with the sense-data. It is further characteristic of these
physical objects that they are thought of as arranged in a space-
time continuum. An essential aspect of this arrangement of things
in physics is that they lay claim, at a certain time, to an existence
independent of one another, provided these objects 'are situated
in different parts of space'. Unless one makes this kind of
assumption about the independence of the existence (the
'being-thus') of objects which are far apart from one another in
space — which stems in the first place from everyday thinking -
physical thinking in the famiUar sense would not be possible.
It is also hard to see any way of formulating and testing the
laws of physics unless one makes a clear distinction of this
kind. This principle has been carried to extremes in the field
theory by localising the elementary objects on which it is
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based and which exist independently of each other, as well as
the elementary laws which have been postulated for it, in the
infinitely small (four-dimensional) elements of space.
The following idea characterises the relative independence
of objects far apart in space (A and B) : external influence on A
has no direct influence on B; this is known as the 'principle
of contiguity', which is used consistently only in the field
theory. If this axiom were to be completely abolished, the idea
of the existence of (quasi-) enclosed systems, and thereby the
postulation of laws which can be checked empirically in the
accepted sense, would become impossible.
Ill
I now make the assertion that the interpretation of quantum
mechanics (according to lb) is not consistent with principle 11.
Let us consider a physical system S12, which consists of two
part-systems Si and 83. These two part-systems may have been
in a state of mutual physical interaction at an earlier time.
We are, however, considering them at a time when this inter-
action is an at end. Let the entire system be completely described
in the quantum mechanical sense by a i/(-function ^12 of the
coordinates qx, • • • and q^, . . . of the two part-systems (^^a
cannot be represented as a product of the form ^^ ^^ but only
as a sum of such products). At time t let the two part-systems be
separated from each other in space, in such a way that t/(i2 only
differs from o when q^, • • ■ belong to a limited part Ri of space
and q^,... belong to a part Rg separated from Ri.
The i/f-functions of the single part-systems Si and Sg are then
unknown to begin with, that is, they do not exist at all. The
methods of quantum mechanics, however, allow us to deter-
mine 1^2 of S2 from ^12. if a complete measurement of the part-
system Si in the sense of quantum mechanics is also available.
Instead of the original i^ij of S12, one thus obtains the ^-
function ifj^ of the part-system Sj.
But the kind of complete measurement, in the quantum
theoretical sense, that is undertaken on the part system Si, that
is, which observable we are measuring, is crucial for this deter-
mination. For example, if Si consists of a single particle, then
we have the choice of measuring either its position or its
momentum components. The resulting ^^ depends on this
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choice, so that different kinds of (statistical) predictions
regarding measurements to be carried out later on Sj are
obtained, according to the choice of measurement carried out on
Sj. This means, from the point of view of the interpretations of
lb, that according to the choice of complete measurement of
Si a different real situation is being created in regard to Sg,
which can be described variously by ^2> 'Pz, '/'2> etc.
Seen from the point of view of quantum mechanics alone,
this does not present any difficulty. For, according to the
choice of measurement to be carried out on Si, a different real
situation is created, and the necessity of having to attach two
or more different i/t-functions ifi^, ^2, . . . to one and the same
system Sg cannot arise.
It is a different matter, however, when one tries to adhere
to the principles of quantum mechanics and to principle II, i.e.
the independent existence of the real state of affairs existing in
two separate parts of space Ri and Rj. For in our example the
complete measurement on Sj represents a physical operation
which only affects part Ri of space. Such an operation, however,
can have no direct influence on the physical reaUty in a remote
part Rg of space. It follows that every statement about Sg
which we arrive at as a result of a complete measurement of
Si has to be valid for the system S^, even if no measurement
whatsoever is carried out on Si. This would mean that all
statements which can be deduced from the settlement of ^^
or ^ must simultaneously be valid for Sg. This is, of course,
impossible, if ip^, ^ etc., should represent different real states
of affairs for Sg, that is, one comes into conflict with the lb
interpretation of the i/r-function.
There seems to me no doubt that those physicists who regard
the descriptive methods of quantum mechanics as definitive in
principle would react to this line of thought in the following
way: they would drop the requirement II for the independent
existence of the physical reality present in different parts of
space; they would be justified in pointing out that the quantum
theory nowhere makes expHcit use of this requirement.
I admit this, but would point out : when I consider the physical
phenomena known to me, and especially those which are being
so successfully encompassed by quantum mechanics, I still
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cannot find any fact anywhere which would make it appear
likely that requirement II will have to be abandoned.
I am therefore inclined to believe that the description of
quantum mechanics in the sense of la has to be regarded as an
incomplete and indirect description of reality, to be replaced
at some later date by a more complete and direct one.
At all events, one should beware, in my opinion, of commit-
ting oneself too dogmatically to the present theory in searching
for a unified basis for the whole of physics.
A. Einstein
This short article" is so closely linked with the letter that I had to include
it here. Also, my reply cannot be understood without it. The discussion
is, of course, comprehensible only to those who have some knowledge of
the development of modern physics and of its philosophical basis.
89
84 Grange Loan
Edinburgh
g May, 1948
Dear Einstein
I am very sorry not to have replied at once to your letter of
April 5th with the manuscript. I was in Oxford for two months,
then at home for only a fortnight, and off again to France with
Hedi to take part in two meetings, one in Bordeaux and one in
Paris. After my return I had to look after my long neglected
pupils, prepare my Oxford lectures for the printer, and write an
official obituary on Planck for the Royal Society, a considerable
task which has to be completed by the middle of June. This is
why I am only just getting around to answering your letter. I am
pleased that you seem to attach some importance to my opinion.
I have the feeling that I hardly deserve it. But, if you like, you shall
hear what came into my mind while reading your manuscript.
Let me begin with an example. A beam of light falls on to a
plate of doubly refracting crystal, and is split into two beams.
The direction of polarisation of one of the beams is determined
by measurement: it is then possible to deduce that that of the
second beam is perpendicular to the first. In this way one has
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been able to make a statement about a system in a certain part
of space as a result of a measurement carried out on a system in
another part of space. That this is possible depends on the
knowledge that both beams have originated from one beam
which has passed through a crystal; in the language of optics,
that they are coherent. It seems to me that this case is closely
related to your abstract example, which is apparently connected
with collision theory. But it is simpler and shows that such
things happen within the framework of ordinary optics. All
quantum mechanics has done is to generalise it.
It seems to me that your axiom of the 'independence of
spatially separated objects A and B', is not as convincing as
you make out. It does not take into account the fact of coherence;
objects far apart in space which have a common origin need
not be independent. I believe that this cannot be denied and
simply has to be accepted. Dirac has based his whole book on
this. You say: The methods of quantum mechanics enable
one to determine ip^ of S^ from ip^^, provided a complete
measurement, in the quantum mechanical sense, of the spatial
system Si exists as well. You evidently assume that ^^ is
already known. Therefore a measurement in S^ does not really
give any information about events occurring in far distant Sj,
but only in association with the information about ^12, that is,
with the help of additional earlier measurements. In the optical
example, we have the information that both partial beams are
produced from one single beam by one crystal.
Your example is too abstract for me and insufficiently precise
to be useful as a beginning. 'Measurement' is often loosely
defined in quantum mechanics. It means either the deter-
mination of the possible eigenvalues of a quantity, or the
determination of the actual state corresponding to the particular
eigenvalue of a system, or, more generally, the determination
of the weight \an\^ corresponding to the different eigenvalues
K = I, 2, ... in the mixture tfi{x) =X„fl„i/'„ (x). It is not clear to
me what you mean by 'measurement' in your example. I
would find it more convenient to consider a real collision
process, in which two originally independent particles collide and
are deflected. The wave functions after the collision would then
correspond to your ip^ and i/t^- Moreover, it is relevant whether
you mean a stationary current of falling particles or just two
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particles, one of each kind. In the latter case, nothing normally
happens. But in addition to the direction of collision the times
must be accurately known, and if they are so adjusted that
deflection does occur, then it seems plausible to me that the
particles are not independent after the collision. For in order
for anything to happen at all, one must know and arrange so
much before the collision. But if we are dealing with a stationary
current of particles, with statistical arrival times at the place of
collision, it is obvious that the statistics must have an effect
on the distribution after the collision, i.e. the two partners
are still not independent. I cannot really find any particular
difficulty.
But I feel that I am not expressing my opinion as lucidly as I
would like to do. Basically I am coming back again to the fact
of coherence, which cannot be denied. But as the usefulness of
mechanical analogues cannot be denied either, one must be
content with a formalism which covers both. This does not go
too much against the grain with me. I am therefore inclined to
make use of the formalism, and even to 'beHeve' in it in a
certain sense, until something decidedly 'better' turns up. I have
expounded all this in some detail in my Oxford lectures, which
you may have the chance to see one of these days. As for my
expectation of 'something better' I am, of course, of a com-
pletely different opinion from you. For progress in physics
has always moved from the intuitive towards the abstract. And
this will probably remain so. Quantum mechanics and the
quantum field theory both fail in important respects. But it
seems to me that all the signs indicate that one has to be prepared
for things which we older people will not like. I believe that
even the days of the relativistic group, in the form you gave it,
are numbered ; the transportability of the line element is fine
mathematically but, to my mind, physically unsatisfactory.
Now, the divergencies in quantum mechanics seem to indicate
that an absolute length does in fact exist in the world. I presume
that this will have to be included in the general transformation
group. We have gone to a great deal of trouble over this.
My pupil Green, a highly gifted man (whom I am going to
send to you in Princeton next year), may possibly make some
progress with it; he has good ideas and great mathematical skill.
We are at present working on superconductivity, and I
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think our theory is the right one. It is not so terribly com-
plicated.
With kind regards, also from Hedi.
Yours
Max Born
The root of the difference of opinion between Einstein and me was the
axiom that events which happen in different places A and B are inde-
pendent of one another, in the sense that an observation of the state of
affairs at B cannot teach us anything about the state of affairs at A. My
argument against this assumption is taken from optics, and is based on the
concept of coherence. When a beam of light is split in two by reflection,
double-refraction, etc., and these two beams take different paths, one can
deduce the state of one of the beams at a remote point B from an observa-
tion at point A. It is curious that Einstein did not admit this objection to
his axiom as valid, although he had been one of the first theoreticians to
recognise the significance of de Broglie's work on wave mechanics and had
drawn our attention to it. The axiom cert£iinly does not apply to light; but
if the movement of matter can be described as 'wave motion' - and it was
Einstein himself, after all, who supplied some powerful arguments for
this - then the concept of coherence can be applied to beams of matter:
from this it follows that, as in the case of light, one can under certain
circumstances draw conclusions about the state at B by determining the
state at A. Einstein declared that any theory which could lead to such
conclusions was incomplete. Therefore, in his eyes, the theory of light must
be considered to be incomplete as well. He looked forward to the creation
of a more profound theory which would do away with this state of
imperfection. So far his hopes have not been realised, and physicists have
good reasons for believing this to be impossible, based mainly on studies
carried out by J. von Neumann (see commentary to letter No. 78).
Department of Mathematical Physics
90 TTie University
Drummond Street
Edinburgh 8
22 May, ig48
Dear Einstein
Unlike my last letter, which I hope you received, this one has
nothing to do with quantum theory, but with Palestine. You
will say : 'Why does this concern you ?' Indeed, when you wrote
to me in 1933 suggesting that I should go to Palestine, I refused
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BORN-EINSTEIN LETTERS
for the sake of my wife and children, who are entirely without
any Jewish tradition. Also I had no clear picture of the situation
in Europe. Later, I was in daily contact with Weizmann in
Karlsbad for a number of weeks. I learned a great deal. How-
ever, I do believe that he could have saved many more Jews if
he had accepted the offer of the English to give them a part of
Kenya in East Africa. As things are now, Palestine is the only
possible place of refuge. I was very sad when the Jews started to
use terror themselves, and showed that they had learned a lesson
from Hitler. Also I was so grateful towards my new 'fatherland',
Britain, that I expected nothing evil from it. But it gradually
dawned on me that our Mr Bevin is playing a wicked game : first
the Arabs are supphed with arms and trained; then the British
army pulls out and leaves the dirty business of liquidating the
Jews to the Arabs. Of course, I have no proof that it is so.
Moreover, I detest nationalism of every kind, including that of
the Jews. Therefore I could not get very excited about it. But
gradually it has become quite obvious to me that my worst
suspicions were correct. A leading article in today's Manchester
Guardian openly attacks Bevin for doing precisely what I had
suspected. I am feeling very depressed, for I am completely
powerless and without influence in this country. The main
purpose of this letter is to tell you that you have my whole-
hearted support if you take any action to help. Could you not
induce the American government to act before it is too late?
The Russians would cooperate and this could perhaps help to
reduce the tension between America and Russia. Let me know
what people think of this business in your part of the world.
With kind regards, also from Hedi
Yours
Max Bom
91
/ June, 1948
Dear Bom
Your Palestine letter has moved me very deeply. Without any
doubt, you have summed up Bevin's policy correctly. He seems
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to have become infected with the infamy germ by virtue of the
post he occupies. You have, however, rather too optimistic an
idea of the opportunities I have to influence the game in
Washington. The latter can be summed up with the maxim:
never let the right hand know what the left is doing. one
thumps the table with the right hand, while with the left one
helps England (by an embargo, for example) in its insidious
attack.
Your letter about the interpretation of the quantum theory
goes into quite a lot of detail but does not keep to my logical
system, so that I am unable to reply without fatiguing you with
tiresome repetitions. Perhaps one day we will have that personal
discussion after all. I should just like to add that I am by no
means mad about the so-called classical system, but I do consider
it necessary to do justice to the principle of general relativity in
some way or other, for its heuristic quality is indispensable to
real progress.
Kind regards
Yours
A. Einstein
My Palestine letter and Einstein's reply hardly require comment. The
assessment of Bevin's Palestine policy was quite correct. But he did not
take into account the toughness and desperate determination of the Jews,
who succeeded in getting the better of the Arabs.
As regards Einstein's remarks about physics at the conclusion of his letter,
his reproach that I had not kept to his logical system seems to me quite
unjustified. He was so thoroughly convinced that his ideas were right that
he could not accept any different method, while he for his part reproached
me for doing the same. We had come to different philosophical points of
view between which there could be no bridge. But, even so, I believe that I
followed the teaching of the young Einstein, as defined by him in his
obituary for Ernst Mach, which I mentioned in the commentary to letter
No. 84.
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92
84 Grange Loan
Edinburgh
23 January, ig4g
Dear Einstein
This communication is intended mainly in reply to Margot's
letter to Hedi. Please pass my enclosed letter on to her - you
can, of course, read it. We are very pleased to hear that you
are feeling better. Look after yourself and take it easy.
By the way, what has happened to the Schilpp book? I sent
off my contribution to it more than two years ago, and it has
still not been published.
I worked very hard during the last term and, I think, with
success. Green and I have developed a theory for elementary
particles, and I am convinced that it is correct, though I
express myself a little more cautiously in the literature. You
will not believe in it, however, for we use the quantum-mechani-
cal 'spook' which you so much dislike. There are going to be
two short letters of ours in the next issue o? Nature.
Our idea is as follows :
Previously one knocked together a Lagrange function for each
kind of particle (photons, electrons, protons, mesons, etc.) as
best one could, introducing the mass arbitrarily as a character-
istic constant. We beUeve that a completely different approach
should be made. For it is certain that the number of different
mesons is very large, probably infinite. The huge unknown is
the Lagrange function L itself, not the solution of the associated
mechanical problem. We find it from a very general principle:
the laws of nature are invariant with respect not only to the
relativistic transformations but also to the substitutions x'-^p^,
jf*. -»■ - ^" where r- denotes space-time coordinates and p^ energy
and momenta. Classically this is of course meaningless, but
quan turn-mechanically it makes sense because now p^= -ih — .
OX'
It boils down to the fact that your fundamental invariant
x^x^ =Ris replaced by the symmetrical quantity S=R + P where
P=P°Pa- ^ is an operator, the integral eigenvalues of which are
the distances and the eigenfunctions of which are substantially
the Lagrange functions L. {x^ and/, must of course be measured
in 'natural' units.) This indeed produces infinitely many Ls,
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BORN-EINSTEIN LETTERS
and the masses of the known mesons are calculated correctly.
No offence!
Kindest regards
Yours
Max Bom
Margot's letter contained the news of Einstein's serious illness.
The Schilpp book did eventually appear in the same year {1949).
The physical information which comprises the greater part of my letter
is based on the idea which I had already submitted to Einstein in an
earher letter, and which we called the 'reciprocity principle'. But our
considerations went off in a new direction, and this, as previously stated,
has recently assumed renewed importance in connection with the theory
of elementary particles.
93
[undated]
Dear Bom
Thank you very much for your friendly words. I am once again
crawling about quite cheerfully. But the machinery isn't much
good any longer. The Schilpp affair is temporarily buried be-
cause Schilpp is at present busying himself somewhere in Ger-
many. When he returns, something will happen. I am truly sorry
to hear that your wife's nerves are in such a bad state. Her poem
about the Indian philosophy of life made such a deep impression
on me at the time. It shows a noble mind and a genuine poetic
talent. I am sorry to hear that you are worried about the mean
pension. However, this sort of thing is virtually an obligation in
Scotland, for the sake of all those jokes about the nation's
thrifty habits. Here, too, the pensions are none too generous
nowadays, as a result of inflation. I have more or less under-
stood your theoretical hints. But our respective hobby-horses
have irretrievably run off in different directions - yours, how-
ever, enjoys far greater popularity as a result of its remarkable
practical successes, while mine, on the other hand, smacks of
quixotism, and even I myself cannot adhere to it with absolute
confidence. But at least mine does not represent a blind-man's
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BORN-EINSTEIN LETTERS
buff with the idea of reality. My whole instinct rebels against it
irresistibly. My hope of talking it over with you once more
before my departure is unlikely to be fulfilled. Perhaps I can
still arrange for the institute to send you an invitation.
Kind regards and wishes
Yours
A.E.
Einstein's handwriting in this letter clearly shows the effect of his illness,
and is difficult to read in parts. But in spite of his premonition of death he
lived for another six years.
His remark about retirement pay is funny, but unjustified. There is no
pension to professors in the whole of Great Britain, except for a kind of
compulsory insurance, to whose premiums the universities make quite
considerable contributions. Anyone who serves for a long period of time
thus receives a more or less adequate old age pension. As I became a pro-
fessor at Edinburgh rather late in Ufe, that is, at the end of my fiftieth year,
I could only expect a small pension. The university was no doubt unable to
make an exception by increasing the amount in my case, to avoid creating
a precedent. As regards the parsimony of the Scots, we never encountered
it anywhere. It only exists as a subject for jokes, and probably originated
during the time when ScoUand, in comparison with England, was rela-
tively poor and forced to economise.
Einstein's hope that we would see one another once more before his
'departure' and discuss things was not to be fulfilled.
94
12 April, 1949
Dear Boms
I was delighted with the wonderful photographs, the con-
tributions on causality and probability, and the interesting
article on how to overcome the moral decay of contemporary
life. You, dear Born, have exposed to public view the frivolous
remarks I made in my letter. The entire subject dealt with in
your book has been very well integrated into the framework of
development, and I understand your point of view very well.
All the same, I am convinced that your principles, which are
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BORN-EINSTEIN LETTERS
at present shared by almost everyone, will not stand the test of
time. You did the right thing in your letter when you expressed
the wish that you could be invited to the institute for a longish
period. As a matter of fact, I did advocate this, but I lack
influence, as I am generally regarded as a sort of petrified
object, rendered blind and deaf by the years. I find this role
not too distasteful, as it corresponds fairly well with my temper-
ament.
Your thesis, Mrs Born, that liberation from the bondage of
the self constitutes the only way towards a more satisfactory
human society, I regard as absolutely right. But is it not also a
fact that one cannot put everything down to the individual, as
the social orientation of the individual is bound to wither in a
society geared to ruthless competition? The effort to improve
must therefore take both these sources of human behaviour
into account.
Now you ask me what my attitude is towards the simple life.
I simply enjoy giving more than receiving in every respect, do
not take myself nor the doings of the masses seriously, am not
ashamed of my weaknesses and vices, and naturally take things
as they come with equanimity and humour. Many people are
like this, and I really cannot understand why I have been made
into a kind of idol. I suppose it is just as incomprehensible as
why an avalanche should be triggered off by one particular
particle of dust, and why it should take a certain course.
Kind regards and wishes
Yours
A.E.
Einstein explains the failure of his efforts to obtain an invitation to his
institute for me, by claiming that he was regarded as a kind of petrified
object. I am sure that I, too, was regarded as the fossilised relic of a bygone
epoch. Two fossils at the same time were too much for the up-to-date
gentlemen at the institute.
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BORN-EINSTEIN LETTERS
95
The Institute for Advanced Study
Princeton
New Jersey
8 January, IQ50
Dear Bom
The mischief in the press about my latest paper is very annoying.
I have no copies of the manuscript, which is to be reprinted in
the course of the next few weeks as an appendix to my booklet.
Meaning of Relativity.*^ I will send you an offprint.
Meanwhile, my warmest greetings to you, as one of my
favourite antipodes,
from Your
A. Einstein
At that time the American papers, and consequendy many European
ones as well, made much of a statement Einstein had made in one of his
papers to the effect that the unified field theory expounded in it was, in
his opinion, satisfying and probably conclusive.
I received a newspaper cutting on a postcard, dated 12th January 1950,
which, together with some unintelfigible 'elucidations' (in English),
contains the four basic equations :
gik = o; r = o; Rik = o; g'=o
+ - 1 ••
This is a typical example of the Einstein-idolatry, which he rejected at
the conclusion of his previous letter with words little short of desperation.
Q^ Dpt. of Mathematical Physics
{Applied Mathematics)
The University
Drummond St.
Edinburgh 8
J September, igjo
Dear Einstein
The periodical Xature has sent me your book Out of my later
years to review. I was not going to write to you until I had
finished reading it. But I would like to tell you straight away
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BORN-EINSTEIN LETTERS
how much I enjoy reading those beautifully lucid and concise
articles. Hedi was wondering whether they exist in a German
edition; she thinks it most likely that you wrote them originally
in German, and that no translation could possibly do justice to
your characteristic style. I have just read the 'open letters'
between you and four Russians. one wonders whether these
four gentlemen are now beginning to see that you are right
that international anarchy is bound to lead to a terrible
catastrophe, beside which all conflicts about social and economic
issues appear trivial by comparison. But most likely they are so
entirely cut off from everything non-Russian that they can
form no independent opinion. I am acquainted with the state of
mind of committed Communists from examples in this country.
A local doctor is one of them. He is a very good doctor, good-
natured and wilUng to help, and would not hurt a fly; but
he is apt to remark glibly that no sacrifice is too great in
order to achieve the realisation of Marxist ideals, not even the
destruction of miUions of human lives. To him everything
printed in our newspapers, including the Manchester Guardian,
is American propaganda, while his Communist rag, the Daily
Worker, proclaims absolute truth. It is useless to argue with
such people. It is unfortunate, however, that they are right in
so many things: for example, that America, with us in tow,
always supports governments in Asia which are reactionary
and corrupt, bombs civiUan populations, and never does any
of the things which the economically backward countries them-
selves need and desire. The world is enough to make one
despair. But it is possible that we are experiencing the crisis of
the illness, and that recovery will follow. Churchill said in one
of his last cautionary speeches: 'It is a miracle that the enormous
Red Army has not yet overrun the whole of Europe, in spite of
the atom bomb'. I think that maybe it is not a 'miracle' at all.
It looks to me as if the Russians really do not want a major war;
their peace overtures are not pure humbug. I have the feeling
that neither the Russians nor the Americans can go on ir-
ritating each other much longer, without the Europeans getting
tired of it and going their own way. No one here wants to fight
for Chiang Kai-Shek. I would very much like to hear your
comments on world events.
I have also read the articles on physics in your book and en-
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BORN-EINSTEIN LETTERS
joyed them very much, apart from our well-known difference
of opinion on the subject of quantum mechanics. I have
defined my position in regard to the argument of 'the incomplete
description' in an article which I am going to send to you. In it I
have the audacity to refer to you by claiming that this incom-
pleteness is sometimes necessary, as, for example in the case of
the theory of relativity.
Hedi and I spent three weeks in England, first in a small
town called Lewes from where we paid a visit to Glyndebourne,
and were allowed to see a rehearsal o^ Figaro, Then we went to
Guernsey, one of the Channel Islands, where the weather was
warm and southerly. Now we are back in cold Scotland once
more, but enjoy the warming Festival of Music and Drama.
We saw here the finished performance of Figaro given by the
Glyndebourne Opera, and various other things. Our son
Gustav married, in July, a Catholic girl from the Highlands.
Hedi, by her tact and intelligence, managed to iron out various
difficulties with her strictly orthodox and snobbish parents. My
son-in-law, Maurice Pryce, will arrive in Princeton in October
with his entire family, except for one son, and I hope you will
get to know him and my daughter Gritli.
I am at present working on the completion of a book I began
a year ago on the quantum mechanics of crystal lattices,
together with a Chinese collaborator. The subject matter is
completely beyond me by now, and I am glad if I can under-
stand any of what young Kun Huang writes in both our names.
But most of the ideas in it date back to my younger years. I see
from the newspapers that Blackett has once again announced
the discovery of several new short-Uved mesons to the British
Association in Birmingham. There is a paper of mine in the
issue of Rev. of Modem Physics dedicated to you, where I make
the existence of masses of short-lived particles of this sort seem
plausible. The details of these calculations are probably wrong
but the principle seems to have proved itself.
Hedi sends her kindest regards to you and Margot. once
more, many thanks for the book.
Yours
Max Bom
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BORN-EINSTEIN LETTERS
4 September, 1Q50
Before I send this letter off, I want to add two comments.
one of them concerns a paragraph in your book, where you
explain the responsibility of the whole German people for the
monstrous crimes of the Nazis. I did share your opinion, but
have now come to another conclusion. I think that in a higher
sense responsibility en masse does not exist, but only that of
individuals. I have met a sufficient number of decent Germans,
only a few perhaps, but nevertheless genuinely decent. I assume
that you, too, may have modified your wartime views to some
extent.
The other remark concerns your interpretation of the i/r-
function; it seems to me that it completely agrees with what I
have been thinking all along, and what most reasonable
physicists are thinking today. To say that ifi describes the
'state' of one single system is just a figure of speech, just as one
might say in everyday life: 'My life expectation (at 67) is 4.3
years'. This, too, is a statement about one single system, but does
not make sense empirically. For what is really meant is, of course,
that you take all individuals of 67 and count the percentage
of those who live for a certain length of time. This has always
been my own concept of how to interpret |^|^. Instead you
propose a system of a large number of identical individuals -
a statistical total. It seems to me that the difference is not
essential, but merely a matter of language. Or have I misunder-
stood you, do you mean something much more fundamental?
If we were able to reach agreement on this point, there would
seem to me also some hope of our reaching agreement on the
question of 'incompleteness' as well. But more of this later.
M.B.
Since this was written, there have been so many crises that it is hardly
likely that anyone will remember the one of 1950. The state of the world
is still just as 'desperate'. Perhaps the difficulty in communicating with
Communists has been somewhat reduced. I still believe now, as I did
then, that the Russians do not intend to overrun Europe without extreme
provocation.
I had begun the book on crystals at the outbreak of war, in order to build
up the theory of crystal lattices systematically on a quantum-mechanical
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BORN-EINSTEIN LETTERS
basis. But the task proved beyond my strength; I had to put the manu-
script aside. Later I gave it to one of my talented Chinese collaborators,
Dr Kun Huang, to read, and he declared himself willing to help me with
its completion. As it happened, it was he who bore the main burden of the
work, as described in my letter. It was only in the final stages that this once
more fell to my lot. He was an enthusiastic Communist and, when the
news of Mao Tse-Tung's victory over Chiang Kai-Shek was received, he
wanted to take part in whatever happened, and he returned to China with
his (English) wife, taking the last, still unfinished chapters of the book
with him. After many exhortations he eventually returned it to me. I
then had to get the large manuscript ready, check all the calculations, and
read the proofs, etc., all by myself, which was not easy for me at the age of
70. The book. Dynamical Theory of Crystal Lattices,*^ is widely known and is
fulfilling its purpose.
The news of the existence of many short-lived particles pleased me, as our
reciprocity theory had predicted something of this kind. Today this theory
seems also to contribute to their classification and to an understanding of
their properties.
The postscript contains first of all an observation about the reponsibility
of the masses. Einstein's reply to this is in the next letter. Then follows an
attempt to put an end to the difference of opinion between us about the
interpretation of quantum mechanics, by saying that it was due to an
inaccurate, abbreviated ｅxpression. But this observation misses Einstein's
most essential point, as the following letter clearly shows.
97
75 September, ig^o
Dear Born
I am sorry that you have been bothered with my series of
articles. Nothing they contain can lay any claim to originality;
they are only jottings which I wrote, not because I wanted to,
but in answer to certain demands made on me.
People such as your Bolshevik doctor come by their fantastic
attitude as a result of their objection to the harshness, injustice
and absurdity of our own social order (escape from reality) .
If he happened to be living in Russia, no doubt he would be a
rebel there as well, only in that case he would take care not to
tell you about it. Nevertheless it seems to me that our own
people here make an even worse job of their foreign policy than
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BORN-EINSTEIN LETTERS
the Russians. And the idiotic pubUc can be talked into any-
thing. And they really are very shortsighted, for technological
superiority is transitory, and if it comes to an all-out conflict,
the decisive factor is sheer numerical superiority.
There is nothing analogous in relativity to what I call
incompleteness of description in the quantum theory. Briefly
it is because the ^-function is incapable of describing certain
qualities of an individual system, whose 'reality' we none of us
doubt (such as a macroscopic parameter) .
Take a (macroscopic) body which can rotate freely about an
axis. Its state is fully determined by an angle. Let the initial
conditions (angle and angular momentum) be defined as pre-
cisely as the quantum theory allows. The Schroedinger equation
then gives the i/r-function for any subsequent time interval. If
this is sufficiently large, all angles become (in practice) equally
probable. But if an observation is made (e.g. by flashing a
torch), a definite angle is found (with sufficient accuracy). This
does not prove that the angle had a definite value before it was
observed - but we believe this to be the case, because we are
committed to the requirements of reality on the macroscopic
scale. Thus, the i/r-function does not express the real state of
affairs perfectly in this case. This is what I call 'incomplete
description'.
So far, you may not object. But you will probably take the
position that a complete description would be useless because
there is no mathematical relationship for such a case. I do not
say that I am able to disprove this view. But my instinct tells me
that a complete formulation of the relationships is tied up with
complete description of its factual state. I am convinced of this
although, up to now, success is against it. I also believe that the
current formulation is true in the same sense as e.g. thermo-
dynamics, i.e. as far as the concepts used are adequate. I do not
expect to convince you, or anybody else - 1 just want you to
understand the way I think.
I see from the last paragraph of your letter that you, too, take
the quantum theoretical description as incomplete (referring to
an ensemble). But you are after all convinced that no (complete)
laws exist for a complete description, according to the posi-
tivistic maxim esse est percipi. Well, this is a programmatic
attitude, not knowledge. This is where our attitudes really
1 88
BORN-EINSTEIN LETTERS
differ. For the time being, I am alone in my views - as Leibniz
was with respect to the absolute space of Newton's theory.
There now, I've paraded my old hobby-horse once again.
But it is your own fault, because you provoked me. I am glad
to hear that your children are going to visit our dovecote. I
have not changed my attitude to the Germans, which, by the
way, dates not just from the Nazi period. All human beings are
more or less the same from birth. The Germans, however, have
a far more dangerous tradition than any of the other so-called
civihzed nations. The present behaviour of these other nations
towards the Germans merely proves to me how little human
beings learn even from their most painful experiences.
Kind regards
Yours
A.E.
This IS probably the clearest presentation of Einstein's philosophy of
reahty. The last but one paragraph is particularly reveaUng. He calls my
way of describing the physical world 'incomplete'; in his eyes this is a
flaw which he hopes to see removed, while I am prepared to put up with
It. I have in fact always regarded it as a step forward, because an exact
description of the state of a physical system presupposes that one can make
statements of infinite precision about it, and this seems absurd to me
It seems to me that I have followed Einstein's own way of thinking in accor-
dance with his theory of relativity, which recognises the impossibility of
locating any point in time and space absolutely, and therefore concludes
that the concept of absolute place and time determination does not make
sense. This is at the base of the whole of his mighty edifice. But he did not
want to acknowledge the analogy of the situation in the quantum theory.
98
4 May, ig^s
Dear Einstein
As you can imagine, the death of Ladenburg grieves me very
much. He was my oldest and, until fate cast us into different
countries, my closest friend, with whom I have corresponded all
the time. Since we came to Scotland I have only seen him once
briefly in London. Else Ladenburg wrote that you had spoken
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BORN-EINSTEIN LETTERS
very movingly at the cremation ceremony. It is very painful
to me that I was unable to be present. I hope that Else is
materially well provided for. Perhaps you could give me some
information about this some time.
A few days ago more sad news reached me — of Kramer's
passing. He had of course been ill for a long time, and was not
as strong and robust a man as Ladenburg. With him, too, I was
on terms of close, though not quite as intimate, friendship. The
last time I saw him was three years ago during a congress in
Florence, when he was not at all well, and spent most of his
time in bed. I had hoped to meet him in June at a conference on
thermodynamics. So we old fellows become more and more
lonely, and I am writing to you in order to keep intact the few
remaining Unks with our contemporaries which still exist. Hedi
and I have come throught the winter rather well. It is already
the second time that we have spent the Christmas holidays in
the Bavarian Alps (Oberstdorf), and the sun, snow, good food
and Bavarian beer have worked like a fountain of youth. We
intend to return there again next summer. My pension in
Germany has been restored to me (as Professor Emeritus), and
so I can afford these hoUdays. While there, we live entirely for
ourselves, and only see close friends and simple people, such as
maids, waitresses, peasants, who, there as elsewhere, are still
pleasant and unspoilt.
I am engaged in completing two books, one with my Chinese
collaborator, Dr Huang Kun, on crystal theory, and one about
optics with a Czech, Dr E. Wolf The American 'Custodian of
Alien Property', who appropriated my German book on optics
without paying any compensation, has actually demanded that
we should apply for a licence for the new book (which is going
to be much larger and more up-to-date). But the British
government has taken up my case, and my pubUsher, Dr
Rosbaud, whom you may remember, now hopes to fight it out
with their assistance.
Freundlich was here yesterday and gave us a very lucid
lecture about the state of light-deflection by the sun. It really
looks as if your formula is not quite correct. It looks even worse
in the case of the red shift; this is much smaller than the
theoretical values towards the centre of the sun's disk, and much
larger at the edge. What could be the matter here? Could it be
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BORN-EINSTEIN LETTERS
a hint of non-linearity? (The scattering of light by light?)
Have you done anything about this problem? Schroedinger is
pursuing these ideas - I have given them up.
Hedi sends her best wishes; also to Margot.
In old friendship
Yours
Max Bom
Since those days when I lamented the death of two dear friends, thirteen
more years have gone by. In the meantime many more have died, in-
cluding Einstein himself. Working on this correspondence helps me to
combat increasing loneliness.
The new book on optics was written at the instigation of the principal
of the University of Edinburgh, Professor Edward Appleton, himself a
physicist who had made a great name for himself by investigating the
upper layers of the atmosphere with the help of radio beams. He received
the Nobel Prize for this work. He told me that my old optics book of 1933
was being reprinted photomechanically in the United States and had sold
widely during the war because it contained material important to the war
effort - the spreading of radar waves along the earth's surface, for example.
I was unable to accept his suggestion that I should have the book trans-
lated into English, because it seemed to me to be out of date. So I decided
to write a new book in English, based on the old one, and I succeeded
in finding an excellent collaborator in Dr E. Wolf, now (1965) Professor
in Rochester, N.Y., U.S.A. This book, Principles of Optics,*^ was very
successful; the first edition of 8000 copies was sold out within a year, and
the third is now in preparation. The negotiations with the Custodian
of Alien Property in Washington had to be continued for several more
years. I had, after all, become a British citizen at the beginning of the war,
and I alone owned the copyright. The confiscation of the book was there-
fore completely unjustified. But several more years went by before I
received justice and compensation.
The astronomer Freundlich tried right from the start to obtain proof of
Einstein's theory of gravitation with the help of astronomical observations;
he first worked at the Einstein Tower telescope in Potsdam, and later,
after his enforced emigration in 1933, at St Andrews, a small university
not far from Edinburgh. At that time (1952) it did not really seem that the
predictions of the theory about the bending of light by the sun, and about
the red shift of the spectral lines, were correct. More recent observations,
however, have eliminated these difficulties. But this is not the place to
enlarge on them. A brief report can be found in the latest edition of my
book Die Relativitatstheorie Einsteins.^"
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BORN-EINSTEIN LETTERS
99
12 May, 1Q52
Dear Bom
First of all I must express my admiration for your wife's poems.
Most of them are among the most beautiful I have ever come
across. My compliments! You are right. one feels as if one were
an Ichthyosaurus, left behind by accident. Most of our dear
friends, but thank God also some of the less dear, are akeady
gone. Ladenburg was taken very suddenly - apparently by a
virus infection of the internal organs. He was a good man who
did not take things lightly. During the last few years he even
avoided reading the newspapers because he could not bear all
the hypocrisy and mendacity any longer. Over there with you
things seem on the whole to be cleaner and less wild.
It really is sweet of the Germans to pay you a pension which
you can convert on the spot into sausages and beer. The victory
over the cunning publisher is also rather gratifying. The general-
isation of gravitation is now, at last, completely convincing and
unequivocal formally unless the good Lord has chosen a totally
different way of which one can have no conception. The proof
of the theory is unfortunately far too difficult for me. Man is,
after all, only a poor wretch. Freundlich, however, does not
move me in the slightest. Even if the deflection of light, the
perihelial movement or line shift were unknown, the gravitation
equations would still be convincing because they avoid the
inertial system (the phantom which affects everything but is
not itself affected). It is really rather strange that human beings
are normally deaf to the strongest arguments while they are
always incUned to overestimate measuring accuracies.
Have you noticed that Bohm believes (as de Broglie did, by
the way, 25 years ago) that he is able to interpret the quantum
theory in deterministic terms? That way seems too cheap to me.
But you, of course, can judge this better than I.
Kindest regards to you both
Yours
A. Einstein
1 9a
BORN-EINSTEIN LETTERS
My report on Freundlich's doubts about the astronomical confirmation of
the theory of relativity left Einstein quite cold. He considered the logical
foundations of his theory of gravitation to be imshakeable. The latest
observations have proved him right.
It is curious that he does not acknowledge the analogy with quantum
mechanics. He condemns the term 'inertial system' as a 'phantom'
which affects everything but is not affected by anything. This must surely
mean: as a hypothesis, produced ad hoc and uncheckable. But he would
not admit that processes in the atomic world can be described by means of
things which can be fixed in time and space, which are sturdy and real
according to the standards of the everyday world, and which obey deter-
ministic laws. The remark he makes about David Bohm's theory is connected
with this. Although this theory was quite in line with his own ideas, to
interpret the quantum mechanical formulae in a simple, deterministic
way seemed to him to be 'too cheap'. Today one hardly ever hears about
this attempt of Bohm's, or similar ones by de Broglie.
100
sg May, 1932
Dear friend Albert Einstein
This is just a little thank-you for your dear, kind words about
my poems; after all, their sole significance and purpose is to
give a little pleasure to someone. How happy I would be if I
could see you and Margot again; but I'm afraid that wish will
never be fulfilled, for if we old folks travel it is either to visit
children and eight grand-children or to the tranquillity of moun-
tains, meadows and forests. In Germany we live mostly very
much by ourselves, but have several times invited children and
children-in-law. And I have formed many connections with
German Quakers. I also have my brother and his family still
living in Germany, as well as two old aunts almost ninety years
old and many cousins of both sexes. There are now 500 German
Quakers; last July I took part in their annual meeting held
in Bad Pyrmont, a really beautiful experience. This year Max is
coming with me, provided he gets 'permission', to attend some
of the sessions, but apart from that will just be 'holiday-making'.
The German Quakers still address each other with 'Du' while
the EngUsh and American ones have abandoned 'Thou'.
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Germany is and will remain a cause for concern. I, at least,
have not torn up my roots so completely that I no longer feel
'responsible'. In some ways, surely, everyone shares the respon-
sibiUty for everything. There can be no true 'world-citizen-
ship' until everybody becomes very much more aware of this.
The German Quakers fully realise this. It is, of course, the most
decent of the Germans who are most profoundly conscious of
German guilt. And there are many circles and classes of people
working for reconstruction from the inside. Seen from outside,
it is always the loud-mouthed and brutal which attract at-
tention. By sinking one's roots into new ground one has, of
course, grown away from it all in many essential respects, but
one feels all the more responsible. It is a pity that one is so old
and has insufficient energy for anything but a very modest effort.
By the way. Max is reading aloud to me from a very delightful
book just now: the biography of Adolf v. Harnack, written by
his daughter Agnes Zahn-Harnack, Do you know it? Harnack
was undoubtedly a fine, energetic and upright man,
I hope that you and Margot are in good health. Old age is
not so bad really, provided one does not have too many twinges.
What have you got against being an Ichthyosaurus ? They were,
after all, rather vigorous little beasts, probably able to look back
on the experiences of a very long lifetime.
In any case, we two old ones will go on thinking of you and
Margot with unchanging loyalty, even if we should never be
able to meet again.
With all my heart
I remain
Your old Hedi
lOI
28 October, 1Q52
Dear Einstein
A few days ago I received a book by Dr Carl Seelig about you
and Switzerland. As I happened to be in bed with a cold, I had
time to read it right through, and liked it very much. Dr
Seelig had written to ask me for a contribution to the book.
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BORN-EINSTEIN LETTERS
and when he had assured me that you had agreed I copied
some characteristic sentences from your letter, which he has now
printed. I do hope that it is really all right by you, I have written
to him to draw his attention to several inaccuracies (for example,
he credited me with honours I do not have, and calls Wertheimer
Paul instead of Max, etc.). The book took me back to old times
and rekindled the desire to see you again. I met Courant in
Gottingen this summer; he would very much like to invite me
to New York, but I am afraid that will not be possible - for as I
was born in Breslau, on the far side of the Iron Curtain, I am
excluded from the U.S,A. by your 'McCarthy Act',
I would like to know what you think of contemporary
politics, particularly American. Seen from here, it all seems
horrible - British politics included (for example, the Mau Mau
uprising in Kenya). And then on the other side, the trial of
tried and trusted Communists in Prague, with its strong anti-
semitic overtomes; I am being bombarded with propaganda
from China, wildly anti-American, My sensible Chinese col-
laborators, dear, fine fellows that they are, seem from their
letters to have gone crazy poUtically since they returned to
China. What a lovely, promising world! As I have eight grand-
children, it matters to me; it could be a matter of indifference
to you, were it not for your kind heart.
Next week I am due to hold a series of lectures at the Univer-
sity of London, Schroedinger was supposed to come for a public
discussion that week. He dishkes the statistical concept of
quantum mechanics, just as you do, but believes that his waves
constitute the final deterministic solution. It is not quite as
simple as that, however, and I'm afraid I would have been very
hard on him had this discussion taken place. But unfortunately
he had to undergo a serious operation for a perforated appendix,
was in great danger, and is not strong enough to travel to
London. Instead, there is now going to be a discussion with
several philosophers, which promises to be a somewhat wishy-
washy adventure. Afterwards we are going to celebrate my
70th birthday in Cambridge with the children and grand-
children.
Hedi and I are going to spend our holidays in Oberstdorf
again. Life in Germany is very pleasant after the austerity in
this country (for those who have some money - I receive my
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pension). Nice, fine, good people exist there, too; most of them
have suffered terribly during the Hitler period. I will have to
retire from my academic chair in another 9 months' time, and
then we are going to five for six months in Germany and six
months here, for financial reasons. I want to finish two books
before then. one of them, about crystals (with my Chinese
collaborator), has just gone off to the Oxford University Press.
The other one, about optics, is going to be ready in a year's
time. Maybe it is silly to put so much work into these things.
But for the bigger problems I am too old and too stupid. By
the way, it causes me some amusement that Heisenberg has
taken up my old idea of non-linear electrodynamics, and has
applied it, mutatis mutandis, to meson fields.
Let me know from time to time what you are doing and how
you are.
With kindest regards, also from Hedi
Yours
Max Born
The discussion with philosophers in London did in fact take place, and in
Schroedinger's absence turned out to be wishy-washy as I had predicted.
The discussions have been published in E. Schroedinger's 'Are there
Quantum Jumps?'** and my own 'The Interpretation of Quantum
Mechanics'.*^
Schroedinger was, to say the least, as stubborn as Einstein in his conservative
attitude towards quantum mechanics; indeed, he not only rejected the
statistical interpretation but insisted that his wave mechanics meant a
return to a classical way of thinking. He would not accept any objection
to it, not even the most weighty one, which is that a wave in 3n-dimen-
sional space, such as is needed to describe the n particles, is not a classical
concept and cannot be visualised.
Heisenberg's non-linear theory was intended to serve not only for meson
fields but for all elementary particles. Today it is the centre of a great
deal of interest.
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BORN-EINSTEIN LETTERS
102
84 Grange Loan
Edinburgh
26 September, igj3
Dear Einstein
Very often I feel the need to write to you, but I usually suppress
it to spare you the trouble of replying. Today, though, I have
a definite reason - that Whittaker, the old mathematician,
who lives here as Professor Emeritus and is a good friend of
mine, has written a new edition of his old book History of the
Theory of the Ether, of which the second volume has already
been published. Among other things it contains a history of
the theory of relativity which is pecuUar in that Lorentz and
Poincare are credited with its discovery while your papers
are treated as less important. Although the book originated in
Edinburgh, I am not really afraid you will think that I could
be behind it. As a matter of fact I have done everything I could
during the last three years to dissuade Whittaker from carrying
out his plan, which he had already cherished for a long time
and loved to talk about. I re-read the originals of some of the
old papers, particularly some rather oflf-beat ones by Poincare,
and have given Whittaker translations of German papers (for
example, I translated many pages of PauU's Encyclopaedia
article into English with the help of my lecturer, Dr Schlapp,
in order to make it easier for Whittaker to form an opinion).
But all in vain. He insisted that everything of importance had
already been said by Poincare, and that Lorentz quite plainly
had the physical interpretation. As it happens, I know quite
well how sceptical Lorentz was and how long it took him to
become a relativist. I have told Whittaker all this, but with-
out success. I am annoyed about this, for he is considered a
great authority in the English speaking countries and many
people are going to believe him. It is particularly unpleasant in
my opinion that he has woven all sorts of personal information
into his account of quantum mechanics and that my part in it is
extolled. Many people may now think (even if you do not)
that I played rather an ugly role in this business. After all,
it is common knowledge that you and I do not see eye to
eye over the question of determinism. What is more, I have
written a small article which is shortly to appear in which I
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BORN-EINSTEIN LETTERS
give a theoretical interpretation of an idea of Freundlich's about
stellar red shift, which could, if correct, cause difficulties for
the relativistic interpretation. Therefore my feeling towards
you is that of a cheeky urchin who can get away with certain
liberties without offending you, But it may well seem less
harmless to other people. Well, I had to write this and get it
off my chest.
Hedi and I have just returned from Germany. We have been
in Gottingen, attending the town's thousandth anniversary,
when Nohl, Franck, Courant and I were given the freedom of
the city. It was a harmonious celebration. Franck and Courant
will be able to tell you about it. Afterwards we went to Bad
Pyrmont, where we are building a small house where we can
settle down and spend our old age. I am about to retire from
my academic post. Life in Germany is quite pleasant again;
the people have been thoroughly shaken up and anyway there
are many fine, good people. We have no choice, as I receive
a pension in Germany but not here. Hedi sends kindest regards
to you and Margot.
In old friendship
Max Bom
Sir Edmund Whittaker's book is a brilliant and historic philosophical
work which I found extremely useful in my early years. During my time in
Edinburgh we had become very close friends. It grieved me all the more
that he should dispute Einstein's merits in the special theory of relativity.
As far as Lorentz is concerned my account is, if anything, too kind; he
probably never became a relativist at all, and only paid lip service to
Einstein at times in order to avoid argument.
The celebration in Gottingen caused us quite a headache to begin with.
Franck at first did not want to accept the invitation under any circumstances.
Courant and I were in two minds; when we eventually decided to go,
plain curiosity played a certain part in our decision, and Franck even-
tually joined us. Our choice of Bad Pyrmont as the place where we would
spend our old age was really due to sentimental memories. During our
engagement my fiancee's parents in Leipzig had sent her, together with
two of her girl friends, to Bad Pyrmont for the sake of her health. At that
time it was known specifically as a spa for women, renowned for the treat-
ment of anaemia and so on. I was then a private lecturer in Gottingen and
travelled every weekend by train to Pyrmont. There we spent some delight-
ful days together, which we liked to remember later on. When we decided
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BORN-EINSTEIN LETTERS
to return to Germany in 1953 we looked around for a quiet and beautiful
place in the Black Forest and elsewhere. Finally we remembered the period
of our engagement that we spent in Bad Pyrmont. We stayed there for a
few weeks of our summer holidays and, as we liked it, searched for and
found a plot on which to build our small house.
103
12 October, ig^s
Dear Bom
Don't lose any sleep over your friend's book. Everybody does
what he considers right or, in deterministic terms, what he
has to do. If he manages to convince others, that is their own
affair. I myself have certainly found satisfaction in my efforts,
but I would not consider it sensible to defend the results of
my work as being my own 'property', as some old miser might
defend the few coppers he had laboriously scraped together.
I do not hold anything against him, nor of course against you.
After all, I do not need to read the thing.
If anyone can be held responsible for the fact that you are
migrating back to the land of the mass-murderers of our
kinsmen, it is certainly your adopted fatherland - universally
notorious for its parsimony. But then we know only too well
that the collective conscience is a miserable Uttle plant which
is always most likely to wither just when it is needed most.
For the presentation volume to be dedicated to you, I have
written a little nursery song about physics, which has startled
Bohm and de Broglie a little. It is meant to demonstrate the
indispensability of your statistical interpretation of quantum
mechanics, which Schroedinger, too, has recently tried to
avoid. Perhaps it will give you some amusement. After all,
it seems to be our lot to be answerable for the soap bubbles we
blow. This may well have been so contrived by that same 'non-
dice-playing God' who has caused so much bitter resentment
against me, not only amongst the quantum theoreticians but
also among the faithful of the Church of the Atheists.
Best regards, also to your wife
Yours
A. Einstein
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Einstein's reaction to my complaint about Whittaker's account of the
theory of relativity proves his utter indifference to fame and glory.
Then follows the harsh ｅxpression 'land of mass-murderers'. This was his
opinion, and he never deviated from it. He was never able to understand
why I returned to Germany, and never approved of it.
It may thus be appropriate to say something about it here. During the war
and for some time afterwards, particularly when the atrocities of Ausch-
witz, Buchenwald and Belsen became known, we were of the same opinion.
But when we began to re-establish connections with our relatives and
friends in Germany the matter took on a different aspect. Many of them
had undergone terrible experiences and sufferings. My wife tried to
help as much as the scarcity in Great Britain permitted.
My post in Edinburgh came to an end in 1953. The fact that I could not
look forward to an adequate provision in my old age was not, as Einstein
thought, due to 'Scottish parsimony' ; all over England, as well as Scotland,
there are no pensions for professors. There are only contributory insurance
schemes whose yield depends on the length of one's service, which in my
case had been too short. My income would have been less than that of an
unskilled labourer. Another factor which influenced us was the tough
Scottish climate, which for anyone not brought up there is hard to bear.
During this time (1947) I was offered the directorship of the Dublin
Institute of Advanced Studies as successor to Schroedinger, who had been
recalled to Vienna, his native town. I declined after lengthy negotiations,
because I did not feel confident that my strength was equal to taking on a
new task; besides, after five years in office I would still have reached
retirement age and would have faced the same problem once again. In the
meantime I had been reinstated in Gkittingen as Professor Emeritus on full
salary. Quite some time went by before it was decided to allow this to be
paid in foreign countries.
The first sortie into Germany was to be made by my wife. She had been
invited to Gottingen by the philosopher Herman Nohl to give a talk there
on British democracy as we had experienced it. But she was prevented
from making the journey, which would have been subsidised by the Foreign
Office in London, because on her arrival at King's Cross station in London
all her luggage was stolen.
In 1948 I was awarded the Max Planck medal of the Deutsche Physi-
kalische Gesellschaft (German Physical Society). This had been founded
at Max von Laue's and my instigation a short time before we emigrated.
The annual general meeting of the society was held in September 1948
in Clausthal-Zellerfeld. We took part and were given a friendly reception,
but we were at that time still regarded as visitors from England, watched
over and taken care of by the occupying power.
The impression made on us by the Harz moimtains, and the small towns
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BORN-EINSTEIN LETTERS
such as Goslar which had not been destroyed, was deep and moving.
In the following few years we spent our summer holidays in Oberstdorf
in the Allgau.
In 1953 the town of Gottingen celebrated its thousandth anmversary.
Franck, Courant and I were among those who were to be given the free-
dom of the city on this occasion. Franck wanted to turn it down at first,
but after a lengthy correspondence we decided not to reject this gesture
of reconciUation. The celebrations took place with due solemnity and
friendliness, and even the sceptical Franck found no reason to complain. He
paid frequent visits to Gottingen later on, and it was during one of these
that he died (in 1964) .
After these experiences we decided to settle down m Germany. In
choosing Bad Pyrmont we took into account its beautiful situation sur-
rounded by wooded hills, the fact that as a watering place it was quiet and
well cared for, the close proximity of Gottingen and, most important of all,
the Quaker house, the headquarters of the ReUgious Society of Friends m
Germany. My wife had joined this society in Edinburgh, and she had my
full sympathy in this respect. The Quakers' creed had been one of strictest
pacifism for many centuries, and because of this they had suffered greatly
under the Nazi regime. We were certain not to find any mass-murderers
amongst them. We wanted to five the quiet life, indoors with books and
music, out-of-doors in the garden, the Spa's park and in the forests. But
it turned out rather differently, because in the year we moved to our new
home (1954) I was awarded the Nobel Prize. In this way my name
became known all over Germany, and my voice was listened to. This
resulted in a new task for the rest of my life.
Many of my German colleagues shared my anxiety about the future of
mankind, because of the atomic bomb. Foremost among these were
Otto Hahn, the discoverer of atomic fission. Max von Laue, G. F. von
Weizsacker and Walter Gerlach. They succeeded in bringing about the
well-known 'Declaration of the Eighteen from Gottingen', which was
directed against the atomic re-armament of the Federal Repubkc. My
name appears on the document, and I had some part in its accomplish-
ment, if not in its formulation. I felt it to be my duty to continue the
task of enlightenment about the dangers of nuclear war and other
technical developments, and the fight against war and militarism. I
tried to do this by means of lectures, radio talks, television discussions
and books. There would not have been any point in doing this in England.
The British people are poUtically mature, and need no advice from an
immigrant. The Germans however, have destroyed their national
tradition by two lost wars, and the misdeeds of a criminal government.
Here there was the chance of making one's influence felt. I regarded this
work as my duty, but it also gave me pleasure. But today (at the end of
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1965) it seems more than doubtful to me whether it has had any success.
The unteachable are in the ascendancy again.
The matter of the presentation volume was as follows. on my retirement
from my chair in Edinburgh the university organised a small celebration,
where a presentation volume was handed over to me: 'Scientific Papers,
presented to Max Born on his retirement from the Tait Chair of Natural
Philosophy in the University of Edinburgh'.« It contains papers by
friends and former pupils of mine. Among these, however, were not only
adherents of my statistical interpretation of quantum mechanics, but
also four outspoken opponents. The first of these was Schroedinger,
although he dealt with a different theme. Our differences had akeady
been thrashed out in the papers from the British Journal for the Philosophy
of Science that I mentioned in my commentary to letter loi. Contribu-
tions also came from de BrogUe, David Bohm and Einstein, which dealt
with the interpretation of quantum mechanics. As these questions play
quite an important role in the correspondence with Einstein which follows,
I should like to enlarge upon them here so that I can deal briefly with
them thereafter.
Schroedinger's point of view is the simplest; he thought that by his develop-
ment of de Broglie's wave mechanics the whole paradoxical problem of
the quanta had been settled: there are no particles, no 'quantum
jumps' - there are only waves with their well-known vibrations, charac-
terised by integral numbers. The particles are narrow wave-packets. The
objection to this is that one generally (i.e. for processes which are classi-
cally described with the help of several particles) needs waves in spaces of
many dimensions, which are something entirely different from the waves
of classical physics, and impossible to visualise; that wave packets
representing solutions of the Schroedinger equations do not propagate
without change of shape, but disperse; and other similar objections.
Schroedinger's point of view has, I think, definitely been abandoned
today.
De Broglie, the creator of wave mechanics, and Bohm accepted the
results of quantum mechanics just as Schroedinger did, but not the
statistical interpretation. They tried to develop ideas in which the
deterministic character of the elementary processes were preserved,
assuming that concealed mechanisms exist which were hidden by the waves'
or suggesting that the formulae should be re-written so that they looked
like deterministic mechanical laws. These attempts did not get far; it
seems to me that today (1965) they have virtually disappeared. Even
Einstein considered this point of view 'too cheap' (letter 99).
His ideas were more radical, but 'music of the future'. He saw in the
quantum mechanics of today a useful intermediate stage between the
traditional classical physics and a still completely unknown 'physics of
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BORN-EINSTEIN LETTERS
the futiu-e' based on general relativity, in which - and this he regarded as
indispensable for philosophical reasons - the traditional concepts of
physical reality and determinism come into their own again. Thus he
regarded statistical quantiun mechanics to be not wrong but 'incomplete'.
His reasons were essentially philosophical and therefore difficuU to
shake, least of all by purely physical arguments. Nevertheless I tried to
answer him, and thus a sharp but always friendly dispute arose, which
is expressed in the following letters.
At the end of his letter, Einstein talks about the effect of his phrase, the
'non-dice-playing God', and uses the ｅxpression so typical of him, 'Church
of the Atheists'. He had no beUef in the church, but did not think that
reUgious faith was a sign of stupidity, nor unbeUef a sign of intelligence;
he knew, as did Socrates, that we know nothing. one should tell this to
the Communists when they claim that he shared their beliefs.
104
Department of Mathematical Physics
{Applied Mathematics)
The University
Drummond Street
Edinburgh 8
8 November, 1953
DearEinstein
Your kind letter of 12.10.53 has reassured me that old Whit-
taker's peculiar pranks do not trouble you particularly. You
say that it is unreasonable to behave like some old miser m
defence of his property, who tries to hold on to the few pence
he has managed to scrape together. I agree with you whole-
heartedly, and I too have tried to keep my mouth shut when-
ever my own few coppers have disappeared into other people's
pockets. But I have sinned against this good doctrine a little
lately. I am sending you several of my papers on general themes,
including my Guthrie lecture (given to the Physical Society,
London), in which I have explained my contribution to
quantum mechanics with as much modesty as I was able to
muster, not only with regard to the statistical interpretation but
also to the theory itself. That Heisenberg's matrices bear his
name is not altogether justified, as in those days he actually had
no idea what a matrix was. It was he who reaped all the
rewards of our work together, such as the Nobel Prize and that
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sort of thing. I do not begrudge it him in the least, but for the
last twenty years I have not been able to rid myself of a certain
sense of injustice. Purely practical matters are involved, such
as the return to Germany, for example, which you clearly regard
with a certain amount of suspicion. You are wrong in casting
aspersions on my dear Scots; the inadequate provision for the
old age of teachers and professors is quite general all over Bri-
tain, and is just as wretched in Oxford and Cambridge. If
anyone is to blame it is the Swedes, who could quite well have
found out about my contribution to quantum mechanics. But
that happened in the year of Heil-Hitler, 1933. Now they have
realised it, apparently, for six months ago they made me a
member of their academy. Though this does not help me with
my practical problems such as the choice of a place to live. But
to be quite honest, I must admit that I would probably return to
Germany even if I had the chance to remain here. Hedi is still
homesick for the Weser mountains and I, too, love the beautiful
countryside around Pyrmont, where we are building a small
house (which will have central heating, of course, which does
not exist here, because the Scots are such hardy fellows that
they do not worry about chilblains and arthritis). As for the
people, I only want to teU you that the German Quakers have
their headquarters in Pyrmont. They are no 'mass-murderers',
and many of our friends there suffered far worse things under
the Nazis than you or I. one should be chary of applying
epithets of this sort. The Americans have demonstrated in
Dresden, Hiroshima and Nagasaki that in sheer speed of ex-
termination they surpass even the Nazis.
I must wait a little longer for the presentation volume to
which you have contributed. It is to be ceremoniously presented
to me on November 24th. I am keenly looking forward to your
treatment of the assertions by Schroedinger and Bohm. You will
find my comments on them in a small package of papers which
IS on its way to you. After the confession of my weaknesses
contained in this letter, there is no need to tell you how much
pleasure I derive from being thus honoured by the most
distinguished members of my profession.
Hedi is in a nursing home at the moment. She suffered a
Uttle breakdown, caused by all kinds of family worries and an
excessive burden of domestic and social obligations. I am all
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alone in the house and am muddling through somehow. She is
improving, and may well return home in a few day's time.
If she knew that I was writing to you she would want to add
her kindest regards to you and Margot.
Yours
Max Bom
I have nothing to add to this 'confession of my weaknesses', except to wish
that its publication today, when I am almost 86 years old and have been
decorated with various honours, will not be held too much against me.
I still fully subscribe today to my reply to Einstein's 'the land of mass-
murderers.' one would have to have been brought up in the 'spirit of
militarism' to understand the difference beiween Hiroshima and Nagasaki
on the one hand, and Auschwitz and Belsen on the other. The usual
reasoning is the following : the former case is one of warfare, the latter of
cold-blooded slaughter. But the plain truth is that the people involved
are in both instances non-participants, defenceless old people, women and
children, whose annihilation is supposed to achieve some political or
military objective. The first of the terrible attacks on Dresden was carried
out by British bombers; the Americans came later. I mentioned the
Americans in my letter as Einstein was living in America. I am certain
that the human race is doomed, unless its instinctive detestation of
atrocities gains the upper hand over the artificially constructed judgment
of reason.
105
26 November, igjj
Dear Einstein
The presentation of the volume was made yesterday during a
little celebration at the university. It gives me tremendous
pleasure that so many of my old friends and colleagues have
contributed to it. For the time being I have read only a few of
the articles - yours was the first, of course, and you are also the
first to receive my heartfelt thanks.
Your philosophical objection to the statistical interpretation
of quantum mechanics is particularly cogently and clearly
expressed. But even so I must take the liberty of asserting that
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BORN-EINSTEIN LETTERS
your treatment of the example (that of a ball rebounding
between two walls) does not prove what you say it does: namely,
that in the limiting case of macroscopic dimensions, the wave-
mechanical solution does not become the classical motion.
This is due to the fact that - forgive my cheek - you have chosen
an incorrect solution which is inappropriate to the problem.
When it is done according to the rules, it results in a solution
which, in the Hmiting case (mass^-oo), becomes exactly the
classical, deterministic motion; although it always, of course,
produces statistical statements of enormous probability only
for finite (large) values of the mass. If one wants to describe
a sequence of events, one has to use the 'time-dependent*
Schroedinger equation:
2m ox^ dt
where ^ = hji-n (Planck's constant) , and m = mass ; and not, as you
are doing, the special case, that ^ is proportional to e'"* (^ =£) ;
for this is appropriate to sharply defined energy, hence an
indeterminate position.
The right solution in the range o <x <l is :
00
ip {x, = 2 An eK« sin b„x
where <On
2ml*'
TTtl
"T
and A„ =j ip{x, o) sin -j- x dx.
ili{x, o) is the arbitrary initial state. This has to be selected
to express: at the time t=o the ball is close to point x^, with
the approximate velocity v. Therefore ip{x, o) has to be zero
everywhere except within the small range about point Xq, and
it also has to be asymmetrical about Xq, so that the value to be
expected for the velocity _L * ■"•
.fjV.
m
[V^dA:
has a predetermined
value. one can easily add these ifi{x, o); with three arbitrary
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BORN-EINSTEIN LETTERS
constants, one for normalisation, one for y and one for imprecision
of the range about x^. For example:
i/i{x, o) =x{l-x){<x+px) e-('-*<>>'/2«
(I do not know whether this function is convenient for calcu-
lations). The result is certain to be (one can see it qualitatively
without calculations) that the wave packet ^(;c, t) bounces to
and fro in exactly the same way as a particle, while it becomes
a little more indeterminate in the process. But these imprecisions
become infinitesimally small as m-^oo.
I am convinced that in this sense quantum mechanics also
represents the motion of macroscopic single systems according
to deterministic laws. I am going to carry out a thorough
calculation of it with my collaborator (which is not easy to do
formally), and will send you the result. Ultimately you will
certainly admit that I am right, and when that happens it will
somehow have to be made known to the readers of the pre-
sentation volume.
I more or less agree with what you said about de Broglie,
Bohm and Schroedinger. Incidentally, Pauli has come up with
an idea (in the presentation volume for de Broglie's 50th birth-
day) which slays Bohm not only philosophically but physically
as well.
Another letter of mine is on its way to you by ordinary mail.
With sincerest thanks and kindest regards, also from Hedi,
Yours
Max Bom
Every quantum theoretician would probably recognise that my objection
to Einstein's example was correct. It formed the basis for my printed
reply which was subsequently published, and which will be the subject
of further discussion. But, as Einstein pointed out in his next letter, it
misses the point of his basic philosophical thoughts.
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BORN-EINSTEIN LETTERS
io6
3 December, igjj
Dear Bom
Today I received (and read) your letter, as well as your printed
material, which I intend to read thoroughly too. I was very
pleased that you have taken my simple ideas seriously and did
not dismiss them with a few superficial remarks like most
people.
I must say first of all that your point of view surprised me.
For I thought that an approximate agreement with classical
mechanics was to be expected whenever the relevant de
Broglie wavelengths are small in relation to the other relevant
spatial measurements. I see, however, that you want to relate
classical mechanics only to those i/r-functions which are narrow
with respect to coordinates and momenta. But when one
looks at it in this way, one could come to the conclusion that
macro-mechanics cannot claim to describe, even approxi-
mately, most of the events in macro-systems that are con-
ceivable on the quantum theory. For example, one would then
be very surprised if a star, or a fly, seen for the first time,
appeared even to be quasi-localised.
But should one now adopt your point of view in spite of this,
one should at least demand that a system which is 'quasi-
localised' at a certain time should remain so according to the
Schroedinger equation. This is a purely mathematical problem,
and you expect that the calculations would bear out this
expectation. But this seems quite impossible to me. The easiest
way to realise this is to consider the three-dimensional case (of a
macro-body), which is represented by a 'narrow' Schroedinger-
function in relation to position, velocity and direction. There it
seems obvious, even without a mathematical 'microscope',
that the position must become more and more diffuse in the
course of time. The one-dimensional case is similar, as the
group-velocity depends on the wavelength. I think it would be
a pity to waste your assistant's time when the result can never
be in doubt. But if you are not convinced, by all means have
the calculations done. Oppenheimer has extricated himself by
claiming that the time required by the process of getting more
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BORN-EINSTEIN LETTERS
and more out of focus would be on a 'cosmic' scale, and that
one could ignore it for that reason. But one could easily quote
some quite pedestrian examples where the divergence time is
not all that long. I consider it too cheap a way of calming
down one's scientific conscience. All the same it is not difficult
to regard the step into probabalistic quantum theory as final.
one only has to assume that the ^-function relates to an en-
semble, and not to an individual case; then one can use my
example to describe, with the expected approximation (statisti-
cally conclusive), what classical mechanics also describes.
According to the interpretation which you support in your letter,
one has to regard this circumstance as a kind of coincidence.
The interpretation of the ^-function as relating to an ensemble
also eliminates the paradox that a measurement carried out in
one part of space determines the kind of expectation for a
measurement carried out later in another part of space (coupling
of parts of systems far apart in space) .
one can safely accept the fact that, according to this concept,
the description of the single system is incomplete, if one assumes
that there is no correspondingly complete law for the complete
description of the single system which determines its develop-
ment in time.
Then one need not become involved with Bohr's interpreta-
tion that there is no reality independent of the probable subject.
I do not believe, however, that this concept, though consistent
in itself, is here to stay. But I maintain that it is the only one
which does justice to the mechanism oftheprobabilisticquantum
theory.
I am very much looking forward to reading the rest of your
ideas on matters of principle. You call these thoughts 'philoso-
phical', but unjustifiably so in my opinion. I am quite satisfied
if one has the machinery for making predictions, even if we
are unable to understand it clearly.
Kindest regards
Yours
A.E.
This letter marks the beginning of the period of mutual misunderstanding.
Even today it seems to me that Einstein's reflections resulted from his
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BORN-EINSTEIN LETTERS
inadequate knowledge of quantum mechanics. His statement that
'approximate agreement with classical mechanics is to be expected
whenever the relevant de Broglie wavelengths are small in relation to
the other relevant spatial measurements' is, of course, correct. The
example he used to point out the weaknesses in quantum mechanics was
that of a particle which bounces to and fro between two parallel, elastic
and reflecting walls. He regards the distance between the walls to be the
only relevant length to be taken into account. But this is only the case
when nothing else is known about the position of the particle. Einstein
now wants to compare the quantum mechanical with the classical
treatment of this situation, where in the latter case it is taken for granted
that the initial condition is known. The situation is somewhat different
in the case of the analogous quantum-mechanical treatment, because
of Heisenberg's relation of indeterminacy; the point of origin and the
initial velocity can only be prescribed to an accuracy which is limited
by this relation. But this one can and must do if one wants to compare the
quantum-mechanical with the classical treatment. It is therefore both
necessary and possible to state the range within which the particle
initially lies; and this constitutes a second 'relevant measurement'.
The next consideration, concerning the question of whether a particle
which is 'quasi-localised' at a certain time must remain precisely locaUsed
according to the Schroedinger equation, is based on a simple misunder-
standing. I never expected this to be so for a moment. The initial impre-
cision of the velocity brings about an imprecision which increases in the
course of time. It was precisely this point which was of such importance
to me from the beginning, for it is equally valid for classical mechanics,
and shows that the usual assertion, that this is deterministic, only applies
when one admits infinitely precise statements about the initial position
and the initial velocity; and this seems to me metaphysical nonsense.
Einstein admits that one can regard the 'probabilistic' quantum theory as
final if one assumes that the i/^-function relates to the ensemble and not to
an individual case. This has always been my assumption as well, and I
consider the frequent repetition of an experiment as the realisation of the
ensemble. This coincides exactly with the actual procedure of the experi-
mental physicists, who obtain their data in the atomic and sub-atomic
area by accumulating data from similar measurements.
The last sentence of this letter is characteristic of Einstein in his old age.
The 'it does not make sense' itself only makes sense when related to a
definite philosophy. The same argument was used by the opponents of
the young Einstein, who alleged that the consequences of the relativity
theory did not make sense ; as for instance that if one of two twins goes
on a journey through space while the other remains at home, the first,
on his return, is younger than the other.
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BORN-EINSTEIN LETTERS
107
Goldsborough Hotel
Hills Road
Cambridge
S2 December, igj3
Dear Einstein
It was very nice of you to write to me again and to go into the
details of my letter. As a matter of fact, I was very impressed by
your article in my 'presentation volume', and could not rest
until I had found a final answer to it. Your example needed to
be calculated exactly from beginning to end at some time or
other. The learned gentlemen at your institute and in other
places do not concern themselves with such trivial problems
But it is not at all easy, and I really had to rack my brain.
Then too we started to move house at the same time, and en-
countered considerable difficulties with both the German and
British financial authorities, and so on. In the end I finished
the work here in Cambridge, in an ice-cold hotel (as they all
are in this country), where one is roasted in front by the fire
while one's back freezes. But even so I managed to finish it
and, what is more, all by myself, without the help of an assistant.
You see, I have taken your warning to heart, but not out of
sympathy for the man (or to prevent him from working in
vain) but because I had the ambition to accomplish it by
myself. It all turned out exactly as I had thought, and as I
indicated in my last letter. The result is completely rigorous
and incontrovertible, and it overcomes your objections, which
are due only to the fact that these simple problems have not
been considered thoroughly in any of the literature. You cannot
do anything about it. But I hope to be able to convince'you at
last that quantum mechanics is complete and as realistic as the
facts permit.
I am going to have the paper typed, and will hand it over to
the Royal Society. I will send you a copy on thin paper and
I will ask the publications assistant to accept anything you
want to insert. His address is: Dr D. C. Martin, Assistant
Secretary, The Royal Society, Burlington House, Piccadilly,
London W. 1 .
I would be very pleased if you would like to add a few lines
or pages, if you agree, or have some new objections; the old
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BORN-EINSTEIN LETTERS
ones have, I believe, finally been settled. For many years your
critical dissociation from the general business of quantum
mechanics has been quite unbearable to me. Much happens
there which is contestable, particularly in Princeton; but the
foundations laid down by Heisenberg and myself are quite in
order, and there is no other way. Perhaps it is presumptuous of
me to contradict you, as you did not concede anything to
Niels Bohr. But Bohr's ｅxpressions are frequently nebulous and
obscure. I am simpler and possibly clearer. Well, do not hold
it against me.
Kind regards from Hedi, also to Margot, and good wishes
for Christmas and the New Year.
Your old
Max Born
1 08
/ January, 1954
Dear Bom
Your concept is completely untenable. To demand that the
i/r-function of a macro-system should be 'narrow' in relation to
the macro-coordinates and momenta is incompatible with
the principles of quantum theory. A demand of this kind is
irreconcilable with the superposition principle for i/<-functions.*
As against this the following objection, which also appHes in
almost every case, is only of secondary importance: that the
Schroedinger equation in time leads to a dispersion of the
narrowness
You claim that the latter does not apply to the system I have
been considering. But I am convinced that this result (not
very important when seen from the point of view of the problem
in general) is based on a mistaken conclusion. I do not want to
take part in any further discussion, such as you seem to envisage.
I content myself with having expressed my opinion clearly.
With best regards and wishes for 1954
Yours
A. Einstein
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BORN-EINSTEIN LETTERS
♦Leti/riand^abe two solutions of the same Schroedinger equations.
Then ip='l'i + 4'i also represents a solution of the Schroedinger
equation, with an equal claim to describing a possible real state.
When the system is a macro-system, and when ipi and ifr^ are
'narrow' in relation to the macro-coordinates, then in by far
the greater number of cases this is no longer true for ^.
Narrowness in regard to the macro-coordinates is a require-
ment which is not only independent of the principles of quantum
mechanics but, moreover, incompatible with them.
109
ic Howitt Road
Belsize Park
London JV. W.3
2 January, 1954
Dear Einstein
I enclose a short paper of mine, which links up with your
contribution to the presentation volume. I am grateful to you
for having forced me to think your simple example over
thoroughly in my own way. That I have thereby arrived at a
result which is different from yours, you will have to accept
into the bargain. Presumably you will stick to your own way of
thinking. I am going to hand over the papers to be published in
the Proceedings of the Royal Society and will, as I mentioned, tell the
Secretary, Dr Martin, that you might want to add a reply. I would
be pleased if you did, even if you are going to contradict me.
These considerations have provided the impetus for me to
make a new advance in the direction of the elementary particles,
with the help of the reciprocity principle which I formulated
years ago. Nothing has come of it up to now, but this time it
seems to be working, thanks to the simple realisation which I
have drawn from the inspiration you gave me.
I am in London visiting my nephew, but am shortly going to
return to Edinburgh, where I still have quite a lot to do. I am
going to live with our doctor. Hedi is in Germany and I am
going to follow her in four weeks' time. Our household in
Edinburgh has been disbanded.
With bestwishesfor a happy New Year, and kindest regards
Yours Max Bom
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BORN-EINSTEIN LETTERS
BORN-EINSTEIN LETTERS
IIO
12 January, igj4
Dear Born
Thank you for sending me your paper for the Royal Society,
from which I see that you entirely missed the point which
matters to me most of all. As I do not feel inclined to appear
before the circus publicum in the role of fencing master, but as
on the other hand I wanted to give you an answer, I herewith
send you the kind of reply I could have made. In this way, too,
there may be some hope of your thinking the matter over
dispassionately, a hope which has already melted away
considerably.
With best regards
Yours
A.Einstein
The above paper by M. Born merely shows me that my
contribution to the presentation volume dedicated to him did
not succeed in formulating the problems I posed with sufficient
clarity. In particular, I did not intend to raise objections
against the quantum theory, but to make a modest contribution
to its physical interpretation.
In the quantum theory the state of a system is characterised
by a 0-function which, in its turn, represents a solution of the
Schroedinger equation. Each of these solutions (i/r-functions)
has to be regarded, within the sense of the theory, as a descrip-
tion of a physically possible state of the system. The question is :
in what sense does the (/(-function describe the state of the system ?
My assertion is this: the i/«-function cannot be regarded as a
complete description of the system, only as an incomplete one.
In other words: there are attributes of the individual system
whose reality no-one doubts but which the description by
means of the ^-function does not include.
I have tried to demonstrate this with a system which contains
one 'macro-coordinate' (coordinate of the centre of a sphere of
I mm diameter). The ^-function selected was that of fixed
energy. This choice is permissible, because our question by its
very nature must be answered so that the answer can claim
\
validity for every 0-function. From the consideration of this
simple special case, it follows that - apart from the existing
macro-structure according to the quantum theory - at any
arbitrarily chosen time, the centre of the sphere is just as likely
to be in one position (possible in accordance with the problem)
as in any other. This means that the description by (/(-function
does not contain anything which corresponds with a (quasi-)
localisation of the sphere at a selected time. The same applies
to all systems where macro-coordinates can be distinguished.
In order to be able to draw a conclusion from this as to the
physical interpretation of the (/(-function, we can use a concept
which can claim to be valid independently of the quantum
theory and which is unlikely to be rejected by anyone: every
system is at any time (quasi-) sharp in relation to its macro-
coordinates. If this were not the case, an approximate descrip-
tion of the world in macro-coordinates would obviously be
impossible ('localisation theorem'). I now make the following
assertion : if the description by a ^-function could be regarded
as the complete description of the physical condition of an
individual system, one should be able to deduce the 'local-
isation theorem' from the ^-function, and indeed from any
^-function belonging to a system which has macro-coordinates.
It is obvious that this is not so for the specific example which has
been under consideration.
Therefore the concept that the (/(-function completely describes
the physical behaviour of the individual single system is
untenable. But one can well make the following claim: if one
regards the ^-function as the description of an ensemble, it
furnishes statements which - as far as we can judge - cor-
respond satisfactorily to those of classical mechanics and, at the
same time, account for the quantum structure of reality. In my
opinion the 'localisation theorem' forces us to regard the
0-function generally as the description of an 'ensemble', but
not as the complete description of an individual single system.
In this interpretation the paradox of the apparent coupling
of spatially separated parts of systems also disappears. Further-
more, it has the advantage that the description thus interpreted
is an objective description whose concepts clearly make sense
independently of the observation and of the observer.
A.E.
214
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BORN-EINSTEIN LETTERS
BORN-EINSTEIN LETTERS
III
20 January, ig54
Dear Einstein
Your letter of January 12th gave me pleasure and relieved me
of the anxiety which your last letter had caused me. Its tone
was irritable and angry, as if you had regarded the difference of
opinion between us as a personal attack. I am glad that you
have now given me an objective reply, even if I by no means
agree with your opinion and, what's more, for reasons which are
objective and completely 'dispassionate'. I have understood
your ideas, but I am convinced that your starting point is an
untenable one: the ^-function, which you rely on, is inappro-
priate to the problem you intend to deal with. Although it
represents a solution of the Schroedinger equation and fulfils
the boundary conditions, it does not satisfy the initial conditions.
Indeed, it lacks, in your own words, the properties required for
the description of an individual system. But other solutions
produced by superposition exist which satisfy the initial
conditions required when one wants to follow an individual
system. This can, of course, only be done approximately, but
the greater the mass m, the more accurate it is. I have just
calculated this limiting transition m^-oo, by using your example,
and have found that it leads exactly to the classical description.
The calculation is free from difficulty, and has been confirmed
not only by my collaborators, but also by my successor. Prof.
Kemmer, and by the critical and sceptical Schroedinger.
If you are in any doubt, ask Johann V. Neumann to read the
manuscript, or Weyl, who is probably now in Princeton.
You were probably affronted because I used the opportunity
to hit out at classical determinism. But I am convinced that
even this will eventually seem plausible to you too, if you take
plenty of time to read it, and discuss it with Weyl and Neumann.
In any case, you must not be angry with me. My intentions are
sincere and objective, and my respect for you is undiminished,
even if I do not share your opinion. But you need not write to
me any more if you consider me a hopeless case. Should that
be so, write to Hedi, who is delighted with every line she
receives from you. She suffers from constant noise in one ear,
216
and cannot sleep for this reason; she is taking a cure in the
Harz mountains, where I am also going shortly.
I am taking part in another piece of heresy in company with
Erwin Freundlich. It has already been printed, and I am going
to send you a copy. Incidentally, Freundlich has been seriously
ill, arterial thrombosis of the heart.
Hoping that you are not angry with me, with sincere
regards
Yours
Max Bom
The preceding letters show how two intelligent people can misunderstand
each other while discussing concrete problems. Each was convinced that
he was right and the other wrong. This happened because each proceeded
from a different point of view, which he regarded as incontestable, and
was thereby prevented from accepting that of the other.
In this situation it was fortunate that a third person intervened and acted
as intermediary: Wolfgang Pauli. I have included three of his letters to
me below. He has already appeared in this correspondence as my assis-
tant in Gottingen, the first of a series of outstanding young people. He
had then, when barely twenty years old, already written a great work, the
article about the theory of relativity in the Encyclopaedia, which was for
a long time the best representation of the theory of relativity and is
today still regarded as one of the authoritative sources. Pauli became a
professor in Zurich. He went to America during the second world war,
as he feared that Switzerland, like other small countries such as Belgium,
Holland and Norway, would also be overrun by Hitler's armies. He became
a close friend of Einstein's and regarded himself, probably with some
justification, as the designated 'successor' in theoretical physics. With me,
too, he remained in constant contact, although mainly by letter.
112
Princeton, N.J.
The Institute for Advanced Study
3 March, 1934
Dear Mr Born
I am here on a brief visit. I intend to be back in Zurich by the
middle of April. In my spare time I have read many things,
including the 'Scientific Papers' which were dedicated to you
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BORN-EINSTEIN LETTERS
on the occasion of your retirement. They contain some inter-
esting contributions, and I think the photograph of you is very
good. Einstein's article arrested my attention, of course,
particularly as I was able to talk it over with him in person,
which is much easier than a discussion by letter. He also told me
that there had been some correspondence with you on this
subject. I believe I am fairly well able to understand what he
means, as I know both Einstein and quantum mechanics, but
what jowr point of view was I could not quite see from Einstein's
remarks. As I am interested in this matter in general, and in the
discussion between you and Einstein in particular, I would be
grateful if you could write a brief summary for me of the point
of view represented by you (details are not important to me).
It is clear that quantum mechanics must, in principle, be
able to claim validity for small macroscopic spheres; their finer
structure (atomic constitution) clearly does not come into
play.
Now from my conversations with Einstein I have seen that
he takes exception to the assumption, essential to quantum
mechanics, that the state of a system is defined only by specification
of an experimental arrangement. [By the way, Einstein says instead of
'specification of the experimental arrangement' : 'that the state
of a system depends on the way one looks at it'. But it boils down
to the same thing. M. Born.] Einstein wants to know nothing of this.
If one were able to measure with sufficient accuracy, this would
of course be as true for small macroscopic spheres as for electrons.
It is, of course, demonstrable by specifying thought experiments,
and I presume that you have mentioned and discussed some of
these in your correspondence with Einstein. But Einstein has the
philosophical prejudice that (for macroscopic bodies) a state
(termed 'real') can be defined 'objectively' under any circum-
stances, that is, without specification of the experimental
arrangement used to examine the system (of the macro-bodies),
or to which the system is being 'subjected'. It seems to me that
the discussion with Einstein can be reduced to this hypothesis
of his, which I have called the idea (or the 'ideal') of the
'detached observer'. But to me and other representatives of
quantum mechanics, it seems that there is sufficient experi-
mental and theoretical evidence against the practicability of
this ideal.
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BORN-EINSTEIN LETTERS
For the rest, however, I believe that it represents pure logic.
Now I would very much like to know what you think of it.
Kind regards
Yours
W.Pauli
113
Bismarckstrasse g
Bad Pyrmont, Germany
77 March, igj4
Dear Einstein
A letter inviting me to contribute to a collection of congratula-
tory messages for your 75th birthday arrived here too late.
Please overlook the fact that my congratulations are too late
as well - I wish you health, cheerfulness and the strength to
work. I would so much like to see you again some time! For
there is no one in the world for whom I have more profound
admiration, and to whom I am more indebted, than you. This
is not at all affiected by our temporary difference of opinion. I
have had several invitations to come to America recently, one
for example to give the Messenger Lectures at Cornell Univer-
sity. But I was unable to accept any of them. We are only just
settling down here, and cannot leave again so soon. Moreover, I
have two books in preparation : one about the theory of crystals
is at the proof stage, and the manuscript of the other on optics is
almost completed. I cannot take on any further obligations such
as the invitation to Cornell would inevitably involve. In
addition I was born on the other side of the Iron Curtain and
am a member of the Russian Academy of Sciences. This would
mean that one would be treated rather horribly at the con-
sulates. My successor in Edinburgh, Kemmer, did not get a visa
for a short visit to America because he was born in St Petersburg
more than forty years ago. But it is still possible that Hedi and I
may one day come to the United States and visit you.
Pauli has written to me to say that you have talked to him
about our correspondence. But it was not clear to him what it is
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BORN-EINSTEIN LETTERS
I am asserting, and he asked for information. Could you perhaps
give him my manuscript? That would save me a great deal of
trouble.
With best wishes and kind regards,
Yours
Max Bom
This letter came from Bad Pyrmont, where we had moved at the beginning
ofi954.
Among the invitations to America was one from the University of California
at Berkeley (perhaps it arrived after this letter had been sent off). This
tempted me, as I had come to know and love this area during previous
visits, with its blue skies, orchards, mighty mountain ranges, magnificent
coastline and friendly people. one of the reasons why I refused this
invitation was that Edward Teller Uved there. He used to work with
me in Gkittingen, but had in the meantime risen to become 'father of the
atom bomb'. I did not want to have anything to do with him.
114
1 2 March, igj4
Dear friend Albert Einstein
There can never be enough opportunities to wish other people
well, especially when the other person has meant so much and
been so helpful as you were to me during our years in Berlin.
You may not even be aware of this yourself. But whenever the
war really got me down and I came to see you, something of
your Olympian outlook on life rubbed off on me and, happy
once more, I went on my way. Now we are all of us approaching
those years of which Henriette Feuerbach in her Altersgedanken
[Thoughts of Old Age] wrote that 'the spirit floats above still
waters'. I now wish you, in unchanging loyalty and friendship,
many years of peaceful old age and the spirit to enjoy them.
When Max reached seventy, I was reminded of a poem which
our then eight-year-old Irene wrote for my father's seventieth
birthday. It began like this:
'Merkwiirdig ist's auf dieser Welt
Wie lang ein Menschenkind doch halt! . . .'
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BORN-EINSTEIN LETTERS
['It is a strange thing in this world of ours that a human being
lasts for such a long time' !]
But when one gets old oneself, it does not seem such a long time
at all; particularly when, unlike you, one cannot look back
upon so long a chain of products of one's mind as you are able
to do, as one has spent so much of one's time dreaming and
vegetating as I have done.
Give a kiss to dear Margot on my behalf.
As always
oldHedi
115
Princeton, The Institute for
Advanced Study
31 March, 1954
Dear Bom
Thanks for your letter. I am writing from here after all, for
when I get back to Zurich on April nth I will probably find
work waiting for me and will have no time. Also, Einstein gave
me your manuscript to read; he was not at all annoyed with you,
but only said you were a person who will not listen. This agrees
with the impression I have formed myself insofar as I was un-
able to recognise Einstein whenever you talked about him in
either your letter or your manuscript. It seemed to me as if you
had erected some dummy Einstein for yourself, which you then
knocked down with great pomp. In particular, Einstein does
not consider the concept of 'determinism' to be as fundamental
as it is frequently held to be (as he told me emphatically many
times), and he denied energetically that he had ever put up a
postulate such as (your letter, para. 3) : 'the sequence of such
conditions must also be objective and real, that is, automatic,
machine-like, deterministic'. In the same way, he disputes that
he uses as criterion for the admissibility of a theory the question :
'Is it rigorously deterministic ?'
Einstein's point of departure is 'realistic' rather than 'deter-
ministic', which means that his philosophical prejudice is a
different one. His train of thought can be reproduced briefly
thus:
I. A preliminary question: Do all mathematically possible
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BORN-EINSTEIN LETTERS
X,
solutions of the Schroedinger equation, even in the case of a
macro-object, occur in nature under certain conditions
{in my opinion this question has to be answered in the affirmative
whatever happens) or only in those special cases where the
position of the object is 'exactly', 'sharply' defined ?
Comment: If the latter class of solutions (which we denote
[Axf <Ll) is described by K», it has the following attributes :
i. When ^^{x) and ^a(x) also belong to K», but their mean
positions
are widely separated, that is to say {xz-x;f>Ll, then
{A) Ci-^i [x) + C2<^2 {x) =4>{x) does not belong to K".
ii. If ^i(Ar, to) belongs at a certain time ^o to K", then (^i {x, t)
no longer belongs to K" when \t-to\ is sufficiently large.
It therefore seems impossible to me to confine oneself in
principle to the solutions of the Schroedinger equation of the
special class K", and this cannot in principle be different for
a macro-body than, let us say, for an H atom or for a single
electron. For if quantum mechanics is correct, then a macro-
body has in principle to show diffraction (interference)
phenomena, and the difficulties are only going to be technical
because of the small size of the wavelength.
In that case, however, one also needs the superpositions of
type (A) from solutions of class K" which do not themselves
belong to K". This is, for example, the case with interference
phenomena, when a particle passes through two (or more)
openings (in this case it does not matter whether they are
'spheres which are visible under the microscope' or 'elec-
trons').
Up to this point, it seems to me, there is agreement.
2. Now to Einstein's essential question: How are those solutions of
the Schroedinger equation which do not belong to class K^ {for
example, macro-objects) to be interpreted in physical terms ?
Here Einstein's reasoning is as follows :
A. When one 'looks at' a macro-body, it has a quasi-
sharply-defined position, and it is not reasonable to invent a
causal mechanism according to which the 'looking' fixes
the position.
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BORN-EINSTEIN LETTERS
Comment: Instead of 'looking at', I would say 'illuminating
with convergent light', and instead of the further 'looking', I
would say 'a suitable experimental arrangement'. Apart
from that I am still in agreement, because in this case I do
not consider that the appearance of the definite position or,
what amounts to the same thing, its appearance as a result of
the observation, can be deduced by natural laws.
Einstein's reasoning continues :
B. Therefore a macro-body must always have a quasi-
sharply-defined position in the 'objective description of
reality'. As those i/r-functions which do not belong to class K"
cannot in principle be 'thrown away', and must also be in
accordance with nature, the general ^-function can only be
interpreted as an ensemble description. If one wants to assert
that the description of a physical system by a i^i-function is
complete, one has to rely on the fact that in principle the natural
laws only refer to the ensemble-description, which Einstein
does not believe (not only in those at present known to us).
What /do not agree with is Einstein's reasoning B (please note
that the concept of 'determinism' does not occur in it at all!). I
believe it to be untrue that a 'macro-body' always has a quasi-
sharply-defined position, as I cannot see any fundamental
difference between micro- and macro-bodies, and as one always
has to assume a portion which is indeterminate to a considerable
extent wherever the wave-aspect of the physical object concerned
manifests itself. The appearance of a definite position Xo during
a subsequent observation (for example, 'illumination of the
place with a shaded lantern') above the opening in the figure*
on the previous page, and the statement 'the particle is there', is
then regarded as being a 'creation' existing outside the laws' of
nature, even though it cannot be influenced by the observer.
The natural laws only say something about the statistics of these
acts of observation.
As O. Stern said recently, one should no more rack one's
brain about the problem of whether something one cannot
know anything about exists all the same, than about the ancient
question of how many angels are able to sit on the point of a
needle. But it seems to me that Einstein's questions are ul-
timately always of this kind.
* The figure was not with the letter.
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BORN-EINSTEIN LETTERS
Einstein would not agree with this, and he would demand
that the 'complete real description of the system' even before the
observation must already contain elements which would in
some way have to correspond with the possible differences in the
results of the observations obtained by 'illumination with a
shaded lantern'. / think, on the other hand, that this postulate
is inconsistent with the freedom of the experimenter to select
mutually exclusive experimental arrangements (for instance,
radiation with long parallel light wavelengths !) .
To summarise I should like to say this : while I have no objection
to the formal calculations your manuscript contains - which
incidentally, were not unknown to me - it completely bypasses
the problems which are of interest to Einstein. In particular it
seems to me misleading to bring the concept of determinism
into the dispute with Einstein.
A further remark here, independently of Einstein, to illus-
trate the difference between classical mechanics and quantum
mechanics when 'measuring' a 'path'.
A. Classical mechanics. Let us consider, for example, the deter-
mination of the path of a planet. one should measure the
position repeatedly (at different moments of time to, ^, . . •)
always with the same accuracy Axq. If one is in possession of the
simple laws for the motion of the body (for example, Newton's
law of gravitation), one is able to calculate the path (also position
and velocity at any given time) of the body with as high an
accuracy as one likes (and also to test the assumed law again at
different times). Repeated measurements of the position with
limited accuracy can therefore successfully replace one measure-
ment of the position with high accuracy. The assumption of
relatively simple laws of force Uke that of Newton (and not
some irregular zig-zag motion or other on a small scale) then
appears as an idealisation which is permissible in the sense of
classical mechanics.
B. Quantum mechanics. The repetition of positional measurements
in sequence with the same accuracy Ax(, is of no use at all in
predicting subsequent positional measurements. For every
positional measurement to an accuracy Axg at the time f„
implies the inaccuracy
234
BORN-EINSTEIN LETTERS
Axt.
mAx,
iUl-tn)
at a later time, and destroys the possibility of using all previous
positional measurements within these limits of error \ (If I am not
mistaken, Bohr discussed this example with me many years
ago.)
The main difference between the theories A and B, which is
that in B information obtained as a result of earlier measure-
ments can be lost after one measurement, has not been ex-
pressed clearly enough in your manuscript.
With kind regards
I remain
Yours
W.Pauli
Pauli's discussion of the fundamental difTerence between classical and
quantum mechanics is now probably the common property of all physi-
cists. But his formulations are so simple and striking that they deserve to
be preserved here.
His next, shorter letter comes from Zurich. It is even more technical than
the last one, but deserves to be reproduced here for the same reasons.
ii6
Physikalisches Institut der Eidg.
Technischen Hochschule
Zurich
15 April, 1 954
Dear Mr Born
Having returned home safely, I found your letter of April loth.
I doubt, however, whether there is much more to be said.
I . Einstein. I entirely agree with your opinion that Einstein has
'got stuck in his metaphysics'; though I would call his meta-
physics 'realistic', not 'deterministic'. It is always those wave
functions which do not belong to the special class K»* from
which he wants to make a rope to hang quantum mechanics
by, claiming: those solutions which do not belong to K» (which
* An example: \ji=Ae^'^ cos Cx. 'Class K"' is just my abbreviation.
225
BORN-EINSTEIN LETTERS
are the case in general) are 'only' an 'incomplete' ensemble-de-
scription of 'reality' because, according to his metaphysics, the
place of a macro-object must always be 'quasi-sharply-defined'
in the objectively real state (in quantum mechanics, however,
this is only the case for the special solutions of class K", and only
for limited time intervals) .
Thus I have already tried in my last letter to explain Ein-
stein's point of view to you. It is exactly the same in Einstein's
printed work and in what he said to me. What is more, on the
occasion of my farewell visit to him he told me what we
quantum mechanicists would have to say to make our logic
unassailable (but which does not coincide with what he himself
believes): 'Although the description of physical systems by
quantum mechanics is incomplete, there would be no point in
completing it, as the complete description would not agree with the
laws of nature.' I am not, however, altogether satisfied with this
formulation, as it seems to me to be one of those metaphysical for-
mulations of the 'angels on the point of a needle' type (whether
something exists which nobody can know anything about).
2. Independent of Einstein. The solutions Q^^ {x)+C^2 W>
where ^^ {x) and ^g (x) do not coincide: Jf(x) <j>i{x) (fi^ix) dx
'^o in the x-space results in nothing other than classical mech-
anical ensembles (which can be described by densities P), but
does so (after Fourier decomposition) in the p-space, as long as the
phase a in Ci^Cjt^" is well defined. There is, of course, no
difficulty in this; on the contrary, it is satisfactory. After
averaging over a one obtains a mixture (which cannot be de-
scribed by a single wave-function, but - as in wave mechanics -
by a density matrix P, after v. Neumann), which is then quite
indistinguishable from a mixture in classical mechanics.
Einstein has, of course, no objection to ensembles in classical
mechanics, as these admittedly represent an incomplete
description of the system in the sense oi classical mtchdimcs. He is
only interested in his assertion that the characterisation of a
state by a wave-function ('pure case' after v. Neumann) is
also 'incomplete', as the 'true objective state of reality' always
has a quasi-sharp location (even when the wave-function does
not have it).
Sincerely
Yours P.
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BORN-EINSTEIN LETTERS
These letters of Pauli's clearly show that my draft for a reply to Einstein'^
paper in my presentation volume was completely inadequate. I had
failed to understand what mattered to him. When now, twelve years later,
I try to think how this was possible, I can find only one explanation: as
an unconditional follower and apostle of the young Einstein, I swore by
his teachings; I could not imagine that the old Einstein thought differently.
He had based the theory of relativity on the principle that concepts
which refer to things that cannot be observed have no place in physics:
a fixed point in empty space is a concept of this kind, in the same way as
the absolute simultaneity of two events happening in different parts of
space. The quantum theory came into being when Heisenberg applied
this principle to the electronic structure of atoms. This was a bold and
fundamental step which made sense to me immediately and which
caused me to concentrate all my efforts in the service of this idea. It was,
then, clearly incomprehensible to me that Einstein should refuse to accept
the validity of this principle, which he himself had used with the greatest
success, for quantum mechanics, and that he insisted that the theory should
supply information about questions of the type of 'how many angels can
sit on the point of a needle'. For this is what Einstein's requirement, that
a physical state must have an objective real existence even when it
proves impossible to postulate a principle for it, amounts to, as Pauli
clearly explains. And he claims, moreover, that any theory which
offends against this is incomplete. In an earlier letter he expressed this
by saying that he was opposed to the philosophy ofesseestpercipi.
Pauli's analysis of our fundamental difference of opinion was the correct
answer to Einstein's paper; I had to leave it to him to publish a reply.
As far as I know he has never done so.
My own manuscript seemed to me to contain certain thoughts which I
had not yet come across elsewhere. I rewrote it completely, with only
casual allusions to Einstein's article; I did this by proceeding from his
example of the particle oscillating between two elastic reflecting walls,
developing it further mathematically, and using it to explain my own
philosophical ideas about relativity and determinism.
At this time I received an invitation from the Danish Academy to contri-
bute to a volume of the Academy's reports, which was to be published on
the occasion of Niels Bohr's seventieth birthday. I therefore sent my paper
not to the Royal Society in London, as previously planned, but to the
Danish Academy in Copenhagen. It was published there under the title
'Continuity, Determinism and Reality'. In a letter from Zurich of nth
December 1955, in which he first of all tells me about the sudden death of
Hermann Weyl, Pauli then writes as follows: 'Your paper in the Danish
presentation volume to Bohr makes very pleasant reading now; its
epistomological content has now become very clear, and I agree with all
227
BORN-EINSTEIN LETTERS
of it. I had used the mathematics of the example of the mass point between
two walls, and of the wave-packets which belong to it, in my lectures in
such a way that the transformation formula of the theta-function comes
into play. But that is a mere detail.' It is more than a detail. It shows that
PaxiH had long been familiar with all I had to say. But this did not embar-
rass me. For ever since the time he had been my assistant in GJottingen, I
had been aware that he was a genius, comparable only with Einstein
himself. Indeed, from the point of view of pure science he was possibly
even greater than Einstein, even if as an entirely different type of person
he never, in my opinion, attained Einstein's greatness.
His remark about the theta-function made me take up this example later
when I had moved to Bad Pyrmont. In a paper that I wrote with W.
Ludwig,*' the movement of the oscillating particle was represented not only
by the superposition of Schroedinger waves (wave representation) but
also by a solution in the form of integrals, which could be regarded as
superposition of Gaussian distributions of decreasing sharpness (particle
representation). The first form corresponds to the quantum domain
proper, the second to the almost classical domain. Each of them can be
transformed into the other by means of the theta transformations men-
tioned by Pauli. Up to this point it was certainly familiar to Pauli. What
we added to it was a method which could be used to transform these two
separate descriptions into a single one, which can be used and is valid for
all velocities and all masses. I was familiar with this method from the
theory of crystals, where it had been used with great success by P. P.
Ewald to calculate electrostatic and electromagnetic potentials.
Although this problem deals with a case which is physically trivial and
unimportant in practice, it gives a clear insight into the connection between
classical and quantum mechanics, and seems to me to be more useful
than any philosophising about the question. It should be brought into, and
discussed in, every elementary lecture about quantum mechanics.
In the letters which follow, the controversy which has been described here
is merely hinted at. In spite of its occasional bitterness, it did not leave
even the slightest stain on our relationship.
117
112 Mercer Street
Princeton, New Jersey
U.S.A.
Dear Bom
I was very pleased to hear that you have been awarded the
Nobel Prize, although strangely belatedly, for your fundamental
228
BORN-EINSTEIN LETTERS
contributions to the present quantum theory. In particular, of
course, it weis your subsequent statistical interpretation of the
description which has decisively clarified our thinking. It seems
to me that there is no doubt about this at all, in spite of our
inconclusive correspondence on the subject.
And then the money in good currency is not to be despised
either, when one has just retired. With sincerest regards to you
and your wife.
Yours
A. Einstein
The fact that I did not receive the Nobel Prize in 1932 together with
Heisenberg hurt me very much at the time, in spite of a kind letter from
Heisenberg. I got over it, because I was conscious of Heisenberg's superior-
ity. By the time we returned to Germany this wound had long healed.
My surprise and joy were thus all the greater, especially as I was awarded
the prize, not for the work done jointly with Heisenberg and Jordan, but
for the statistical interpretation of Schroedinger's wave function, which
I had thought of and substantiated entirely by myself. It is not surprising
that this acknowledgement was delayed for twenty-eight years, for all the
great names of the initial period of the quantum theory were opposed to
the statistical interpretation: Planck, de Broglie, Schroedinger and, not
least, Einstein himself. It cannot have been easy for the Swedish Academy
to act in opposition to voices which carried as much weight as theirs;
therefore I had to wait until my ideas had become the common property
of all physicists. This was due in no small part to the cooperation of
Niels Bohr and his Copenhagen school, which today lends its name
almost everywhere to the line of thinking I originated.
118
Dr Earner'' s Sanatorium
Braunlage, Harz
28 November, 1954
Dear Einstein
I read in the paper recently that you are supposed to have said:
'If I were to be bom a second time, I would become not a
physicist, but an artisan'. These words were a great comfort
to me, for similar thoughts are going around in my mind as well,
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BORN-EINSTEIN LETTERS
in view of the evil which our once so beautiful science has
brought upon the world. Now they have given me the Nobel
Prize, essentially for the statistical interpretation of the >p-
function, work which dates back twenty-eight years. I can really
only think of one explanation for this: the intention was to
honour something which has no immediate practical appli-
cation, something purely theoretical. Linus Pauling received
the chemical prize at the same time, a man known for his up-
right political conduct and his rejection of the misuse of
scientific discoveries. (It was even rumoured here that he had
not received an exit permit from the United States, but this
does not seem to be true.) This could be chance, but it does
appear to have been done on purpose, and that would be
gratifying. It is for this reason that I am glad to go to Stockholm,
although neither Hedi nor I will feel any the better for it. For we
both suffer from heart complaints, and are only free from pain
when we live very quietly. Hedi is at present in a clinic in
Gottingen, in order to be revitalized a little; I am up here in the
Harz mountains for the same reason. It is unlikely that I will
manage to do any more scientific work (except for my optics
book, begun eight years ago), and I am thinking of using my
present popularity in two countries (here I am the 'German',
over there the 'British' physicist) to try and arouse the con-
sciences of our colleagues over the production of ever more
horrible bombs. Even before I knew anything about the Nobel
Prize I had written an article in this vein for the Physikalischen
Blatter, which is widely read here. I am reading a book at the
moment with the nice title Kapitza, the Atom Tsar, which
contains a dramatic description of the development of
nuclear explosives in Russia. It makes one feel quite sick.
Kapitza himself comes out of it quite well; in those days he
tried everything he could to put the brakes on and to take
delaying action, in much the same way as his opposite number
R. O. [Robert Oppenheimer] did on your side (if my information
is correct).
Someone wrote and told me that you were ill. Please accept
my best wishes for a speedy recovery, and do not trouble to reply.
We understand one another in personal matters. Our difference
of opinion about the incompleteness of quantum mechanics is
quite insignificant by comparison.
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BORN-EINSTEIN LETTERS
If Hedi were here, she would join me in sending you her
sincere regards.
In old friendship
Yours
Max Bom
Even today I cannot say with any certainty whether I was right
that the simultaneous award of the Nobel Prize to Linus Pauling and
myself had anything to do with the fact that neither of us had had any-
thing to do with the practical application or the misuse of science for
political purposes. For, after all, other scientists besides ourselves were
honoured with the prize at the same time. The physicist Walther Bothe
was one, and my assumption hardly applies to him.
We found the Nobel celebrations in Stockholm tiring but extremely
enjoyable, and sustained no injury to our health as a result. The Nobel
Prize has helped me a great deal in public appeals for reason in the use of
scientific discoveries.
The book Kapitza, the Atom Tsar apparently did not circulate widely in
Germany, in spite of its fetching title. I have never met anyone who knew
it, and did not see it reviewed in any paper or periodical. The greater
part of it is probably pure invention, for those few features of Kapitza's
life which we knew about in detail were either not mentioned at all or
misrepresented.
The next letter, the last I had from Einstein, refers to the beginning of my
previous one where I mention a newspaper report according to which
Einstein said that if he were to be born a second time, he would
become not a physicist, but an artisan. I thought at the time that he was
referring to the atom bomb. Here is Einstein's brief reply (typewritten;
apparently he was already seriously ill) .
119
/; January, 1955
Dear Bom
I enclose the text of my letter to the Reporter, which you have
asked for. Just one comment. The hired hacks of an accom-
modating press have tried to tone down the impact of this
statement, either by making it appear as if I regretted having
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BORN-EINSTEIN LETTERS
been engaged in scientific endeavour, or by trying to give the
impression that I had attached little value to the practical
occupations I mentioned.
What I wanted to say was just this: In the present circum-
stances, the only profession I would choose would be one where
earning a living had nothing to do with the search for know-
ledge.
Kind regards from
Yours
A.E.
Unfortunately I no longer possess the letter to the Reporter. When I gave
an account of Einstein's letters (my own letters to him were not at my
disposal at that time) to the meeting of Nobel Laureates in Lindau this
svunmer (1965), I still believed, as I have just mentioned, that Einstein's
remarks referred to the atomic bomb. In the meantime I have heard from
the executor of Einstein's estate, Dr Otto Nathan in New York, that this
is not so. Einstein's statement referred to the crisis of civil rights, which had
been brought about by the appearance of Senator McCarthy. Any teacher
or scientist who dared to express his poHtical opinion freely and openly
risked being asked to appear before the Committee of the Senate presided
over by Senator McCarthy, and the loss of his position, if not worse.
Anyone interested in this can read about it in the notes by Otto Nathan in
the book Einstein on Peac^ (pages 613, 614), which also contains the
letter to the Reporter with the sentence that has since become famous
because of its incorrect interpretation: 'rather to become a plumber or a
peddler than a physicist'.
120
Bad Pyrmont
Marcardstrasse 4
West Germany
29 January, 1955
Dear Einstein
Many thanks for sending me the text of your letter to the
Reporter so promptly. I can well imagine that the press people
have tried to tone down the impact of your words.
I myself am forced to say that your text is not free of ambi-
guity. I took it to mean something other than you explained,
but even this explanation does not satisfy me. For even when one
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BORN-EINSTEIN LETTERS
selects a method of making a living which is independent of the
search for knowledge, one must then also decide to keep one's
knowledge to oneself, or to interchange ideas only privately
amongst friends, as was customary during the 17th and i8th
centuries, for otherwise others are still going to misuse the
results for evil purposes, and I feel that one would then never
be free of responsibility.
I think a great deal about these things, and have got in
touch with Bertrand Russell. He has made an effective state-
ment over the British radio, which is printed in the Listener of
December 30th. I will let you know whether this discussion
leads to any conclusions, of either a personal or a more far-
reaching nature. A Japanese periodical has asked me to agree
to the publication of my correspondence with Yukawa about the
atom bomb, etc., and sent me a letter by Y. This did in fact
actually appear, together with my reply (I am unable to read
it, as I do not know any Japanese). It will not have amused any
Americans who read it. But this is only a miserable beginning.
With kindest regards, also from Hedi
Yours
Max Bom
This letter contains my attitude towards the 'plumber and peddler'
question. It goes beyond Einstein's; even if one does not earn one's
living by science, but publishes the results of one's research, one cannot
rid oneself of the responsibility for the use which is made of them. I have
stuck to this point of view right up to the present.
Hideki Yukawa is a brilliant theoretical physicist, the only Japanese
Nobel prizewinner. He received this in 1949 for his prediction of the
existence of a new kind of particle, called a meson (with a mass which is
between that of an electron and a proton). I correspond with him and
see him from time to time, for example at the meeting this year of Nobel
prizewinners in Lindau (1965). We are united not only by our ideas
about physics -he recognised my reciprocity principle as the leading
heuristic idea in the theory of elementary particles -but also by our
attitude towards the misuse of scientific research resvJts for the purposes
of war and destruction.
Einstein died soon after this last exchange of letters between us (on the i8th
of April, 1955). In a letter to my wife, his step-daughter Margot describes
her last visit to his sickroom: 'Did you know that I was in the same
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BORN-EINSTEIN LETTERS
hospital as Albert? I was allowed to see him twice more and talk to him
for a few hours. I was taken to him in a wheel-chair. I did not recognise
him at first - he was so changed by the pain and blood deficiency. But his
personality was the same as ever. He was pleased that I was looking a
httle better, joked with me, and was completely in command of himself
with regard to his condition; he spoke with a profound serenity -even with
a touch of humour -about the doctors, and awaited his end as an imminent
natural phenomenon. As fearless as he had been all his life, so he faced
death humbly and quietly. He left this world without sentimentality
or regrets.'
With his death, we, my wife and I, lost our dearest friend.
234
REFERENCES
1. Einstein, A., 'on the electrodynamics of moving bodies', in Ann.
Phjs.Lpz., 17, 8gi {igo^).
2. Einstein, A., 'on a heuristic viewpoint concerning the production
and transformation of light', in Ann. Phys. Lpz., 17, 132 (1905).
3. Einstein, A., 'The presumed movement of [suspended particles in
static fluids', in Ann. Phys. Lpz., 17, 549 (1905)-
4. Born, M., Der Matkematische und Maturwissenschaftliche Unterricht, 9, 97
(1956).
5. Born, M., Ausgewahlten Aghandlungen, Gottingen Akademie.
6. Born, M., Physik im Wandel meiner Zeii> Braunscheweig, 1957, 1966.
6a. Born, M., Physics in my Generation, Longmans, 1970.
7. Born, M., Von der Verantwortung des Naturwissenschaftlers (The Scientist's
Responsibility), Nymphenburger Verlagshandlung, Munich, 1965.
8. Born, M., and Born, H., Der Luxus des Gewissens (The Luxury of
Conscience), Nymphenburger Verlagshandlung, Munich, 1969.
9. BoTn,M., PhysikalischeZeitschriJi, 17,51 (1916).
10. Born, M., Die Relativitatstheorie Einsteins, Springer, Berlin, 1920.
1 1 . Born, M., Einstein's Theory of Relativity, Dover Publications, New York,
1962.
12. Born, M., Enzyklopadie der Mathematik, Teubuer, Leipzig, 1920.
13. Herneck, F., Albert Einstein, Bookpublishers der Morgen, Berlin,
1933.
14. Rabindranath Tagore, The Home and the World, Macmillan, 1919.
15. A. Einstein, A. Sommerfeld Briefwechsel,SchvfaheT, Basel, 1968.
16. Bom,M., Physikalische Zeitschrift, II, 1234-1257 (1910).
17. SeeUg, C, Albert Einstein, Europa Verlag, Zurich, i960.
18. Haldane, R. B., The Reign of Relativity, JohnMuira.y, London, 1921.
19. Born, M., and Jordan, P., Z^tschriftfiir Physik, 33, 32 (1925)-
20. van der Waerden, B. L., Sources of Quantum Mechanics, North Holland,
Amsterdam, 1967; see also Hund, F., Geschichte der Quantentheorie,
Bibliographisch. Mannheim, 1967.
21. Heisenberg, W., ^eiteAn/i/urPAj5fA:, 35, 879 (1925).
22. Born, M., and Hund, F., Vorlesungen iiher Atommechanik, Springer,
Berlin, 1925.
22a. Born, M., and Hund, F., The Mechanics of the Atom, tr. J. W. Fisher,
G. Bell and Sons Ltd, London, 1927; Fredk. Ungor, New York,
i960.
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BORN-EINSTEIN LETTERS
23. Einstein, A., and Infeld, L., The Evolution of Physics, Simon and
Schuster, New York, 1938.
24. Infeld, L., Bulletinof the Atomic Scientists, Feb. 1965.
25. Infeld, L., and Plebanski, Motion and Relativity, Pergamon Press,
Oxford, i960.
26. Born, M., Nature, 141, 328 (1938).
27. Einstein, A., Mein Weltbild, Amsterdam, 1934.
28. von Neumann, J., Mathematische Grundlagen der Quantenmechanik,
Springer, Berlin, 1932.
29. Nathan, O., and Norden, H., Einstein on Peace, Simon and Schuster,
New York, i960.
30. Born, M., Experiment and Theory in Physics, University Press, Cambridge,
1943; reprinted by Dover Publications, New York, 1956.
31. '&OTn,'M..,ExperimentundTheorieinderPhysik,yi.oshdL<^, 1969.
32. Born, M., Natural Philosophy of Cause and Chance, Clarendon Press,
Oxford, 1949.
33. Born, H., Stille Gdnge (Silent Corridors), Leonard Friedrich, Bad
Pyrmont.
34. Einstein, A., Physikalische Z^itschrift, I'j, loi (1916).
35. Born, M., and Green, H. S., A General Kinetic Theory of Liquids,
Cambridge University Press, 1949.
36. Born, M., Physikalische Blatter, 20, 554 (1964) ; 21, 53 (1965).
37. Irving, D., The Virus House, New York, 1968.
38. Bulletin of the Atomic Scientists, June 1 968.
39. Einstein, A., 'Quantum Mechanics and Reality', in Dialectica, 320
(1948).
40. Einstein, A., Meaning of Relativity, 4 lectures translated by Edwin
PUmpton Adams, Methuen & Co., London, 1922, 6th ed. 1956.
41. Einstein, A., Out of my Later Tears, translated by Alan Harris, Watts
& Co., London, 1940.
42. Born, M., and Huang, K., Dynamical Theory of Crystal Lattices,
Clarendon Press, Oxford, 1954.
43. Bom, M., and Wolf, E., Principles of Optics, Pergamon Press, Oxford,
1959-
44. Schroedinger, E., The British Journal for the Philosophy of Science, 109,
Aug. 1952; 233, Nov. 1952; 95, Aug. 1953.
45. Scientific Papers presented to Max Born on his retirement from the Tail Chair
of Natural Philosophy in the University of Edinbrugh, Oliver and Boyd,
Edinburgh/London, 1953.
46. Born, M., Kong. Dansk Videnskabernes Selskah, Matematiskfysiske
Meddelelser, 30, 1 (1955).
47. Bom, M., and Ludwig, W., Zeitschriftfur Physik, 150, 106 (1958).
236
Index
Althoff,F., 12
Andersen, H. C, 5
Appleton, E. V., 191
Auerbach, 56
Bachmann, 59
Beck, G., 140, 141
Becker, C. H., 27, 71
Bergson, H., 79
Berliner, A., 24, 30
Bevin, E., 177, 178
Bhagavantam, S., 54
Bieberbach, L., 12,98, 100
Blackett, P. M. S., 185
Blackman, M., 118
Blaschke,W.,67
Boguslawski, 43-4, 45, 49, 50
Bohm, D., 192, 193, 199, 202-3,
207
Bohr, H., 96, 99
Bohr, N., 27, 53-104 pofjim, 117,
125, 127, 136-59 passim, 212,
225,227,229
Boltzmann, L., 41, 62, 86
Bolza, O., 45, 49
Bormann, E., 54
Born, G., 56, 1 13, 134
Bose,J. C.,83,86,88
Bothe,W.,65, 231
Bragg,W.,78,i28
Bridgman, 138
Brillouin, L., 142
Brod, M., 3
Brody, E., 53, 56, 58, 68-9, 70-1
Broglie, L. de, 64, 83, 86, 176, 192,
i93> 199, 202, 207, 208, 210, 229
Brouwer, L. E. J., 79, 97-9, 100
Byk, A., 50, 52
Carathdodory, C, 53, 55
Clemenceau, G., 22
Cohn-Vossen, 127
Compton, A. H., 83, 86
Coudenhove-Kalergi, 76
Courant, R., 55, 58, 67, 74, 75, 85,
97, 98, 117, 123, 127, 129, 195,
198,201
Curie, M., 79
Darwin, C, 123
Davisson, C. J., 86
Debye, P., 25, 27, 28, 46, 49, 59
Dehlinger, 23
Descartes, 23
Dirac, P. A. M., 104, 121, 174
Drill, 18, 19
Duane, W., 83, 86
Ebert, F., 150
Eddington, A. S., 24, 65, 78, 85,
151,156
Ehrenberg, V., 1 18
Ehrenfest, P., 41-2, 44, 65, 71, 83,
85,96,106, 107, 112
Ehrenfest, T., 41, 43, 72, 84, no,
113,116
Ehrlich, P., 100
Elsasser,W.M.,83,86
Engels, F., 24
Epstein, P. S., 32, 45, 49, 71, 84,
no, 112
Erzberger, M., 22
Euclid, 23
Ewald, P. P., 8, 228
Fajans, K.,21,24
Faraday, M., 164
Fitzgerald, G. F., i
Fock,V.,3, 131,140,141
Fokker, A. D., 43, 71
Fowler, R., 145
237
INDEX
Franck, J., 20, 27, 31, 53-76
passim, 80, 84, 86, 113, 116, 117,
123,124,126,138,198,201
Frank, P., 85, 88
Freundlich, E., 21, 39, 190, 191,
192, i93> 198,217
Fuchs,K., 134, 139, 141, 146-7
Fiirth, R., 140, 141, 142, 156
Garbunow, 127
Geddes, A., 141, 142
Gehrcke, E., 39
Geiger, H., 65
Gerlach, W., 24, 53, 71, 72, 85, 201
Gibbs,J.W.,i55
Glaser, D. A., 59
Gleich,G.v.,8i
Godel, K., 100
Goens, 81
Goldman, H., 77
Grebe, L., 59
Green, H. S., 161, 162, 175, 179
Griineisen, 58, 69, 81
Haber, F., 6, 7, 12, 19, 20, 21, 24,
49.81
Hahn, O., 145, 201
Haldane, R. B., 75, 77-8
Harnack, A. v., 194
Hasenohrl, F., 41
Heisenberg, W., 63, 75, 78, 84, 87,
88, 89, 104, 105, 136, 137, 138,
143, 161, 166, 167-8, 170, 196,
203, 210, 212, 227, 229
Heitler, W., 109, in, 114, 115, 126
Hellinger, E., 17
Herglotz, 127
Hertz, G., 27, 69, 76
Herzberg, G., 126
Hilbert, D., i, 17, 25, 44, 45, 55,
63-79 /xMjJm, 93, 97-9, 100, III,
139, 143
Hitler, A., 24, 63, 77, no, in, 112,
ii3> ii5> i3i> 136, 140, 146,
167, i77> 196,217
Hoffj J. H. van't, 2
Hofmann, 131, 141
Hornbostel, E. M. v., 167
Hubble, E. P., no
Hiickel, E., 74
Hume, D., 7, 8
Hund, F., 84, 87, 104, 126
Infeld, L., 121, 122, 125, 130, 131,
141
Irving, D., 168
Jacobi, K.,47
JofK,A.T.,85,88, 100
Jordan, P., 84-5, 87, 103, 104-5,
143,229
Kant, I., 7, 8
Kapitza, P. L., 85, 88, 230, 231
Karmin, T. v., 2, 49
Kemmer , 216,219
Kienle, H., 85, 88
Klein, F., 45
K6hler,W., 167
Koppel, A., 12
Kossel, A.,31,46
Kramers, H., 85, 88, 190
Krutkow, G., 44
Kuhn, H., 115
Kun Huang, 185, 187, 190
Kiirti, 1 1 5
Kiistner, F. K., 57
Ladenburg, R., i, 2, 123, 134, 140,
157,189-90,192
Lagrange,J.L., 179
Landau, E., 100
Landau, L. D., 162
Land6,A.,46,85, 117, 139
Langevin, P., 41, 42, 44, 78, 80, 127
238
INDEX
Langmuir,J., 62
Larmor, J., i
Laue, M. v., 5, 6, 31, 40, 42, 63,
68, 71, 81, 145, 148, 157, 200, 201
Leibniz, G. W. v., 189
Lenard,P.,36,39,4i,44,63
Lenin, W. L, 24
Lenz,W.,3i,58,62,69
Lertes, P., 20, 27
Lewis, G. N., 45, 49
Lindemann, F., 114, 115, 117, 162
London, F., in, 114, 115, 126
Lorentz, H. A., i, 27, 41-2, 44, 51,
73> 139, 197, 198
Lorenz, R., 19, 31
Loria, S., i
Ludendorff, E., 1 1
Ludwig, W., 228
Lummer, O., i
Mach,E., 159, 178
Madelung,G.,46,52,54
Marx, K., 24n
Maxwell, J. C, 46, 50, 51, 62, 71,
79, 121, 164
McCarthy, J., 232
Meitner, L., 81
Mendelssohn, E., 1 15
Michelson, A., 73, 74
Mie, G., 76
Miller, 74., 90
Millikan, R. A., 71, 109, no, 112
Milne, E. A., 151, 156
Minkowski, H., i, 62
Minot, G. R., 100
Mises, R. v., 98, 100
Molotow, W. M., 127
MuUiken, R. S., 126
Nathan, O., 232
Nernst, W., 58, 115
Neumann, J. v., 134, 140, 142, 143,
157, 176,216,226
Newton, L, 6, 64, 1 15, 189, 224
Nikolai, 22
Nohl, H., 189,200
Nordheim, L., in
Nordstrom, 6, 7
Oppenheim, 12, 18,35,52
Oppenheimer, R., n, 34, 208,
230
Pauli, W., 21, 53-75 passim, 105,
139, 141, 155, 157, 168, 198,
207,217,219,225,227,228
Pauling, L. K., 1 15, 230, 231
Peierls, R., 146-7
Peng,H.W., 145, 156
Planck, M., 5, 6, 18, 34, 40, 44,
45, 48, 51, 55, 72, 76, 81, 133,
173,200,229
Plebanski, 131
Pohl,R.,25,26-7,57,6i,74
Poincare, H., i, 53, 60, 75, 78, 198
Polanyi, M., 58, 62, 63
Prandtl, L., 85
Pringsheim, A., i, 50, 51
Pryce,M., 135, 139, 161,185
Radek,K.B.,22, 128
Raman, G. V., 1 15, 120, 166, 167
Ramsauer, K., 46, 62, 64
Reiche, F., 1,31
Richter, 27, 106
Riecke, E., 25
Riemann, B., loi, 1 13
Robertson, 134
Rontgen, W.,42
Roosevelt, F. D., 136, 147, 162
Rosbaud, 190
Rubens, O., 71, 72
Rumer, G., 101-12 passim
Runge, C, 44, 55
Russell, B., 99, 233
Rutherford, E., 78, 119, 121, 160
239
INDEX
Samuel, R., 125-7, 128, 129
Schilpp, P. A., 157, 179, 180
Schlapp, R., 197
Schlick, M., 18, 19
Schmidt, E., 98, 100, 127
Schoenflies, A., 31
Schroedinger, E., 96, 104-5, 142-4)
145, 156, 166, igi-22g passim
Schur, I., 68
Schweizer, A., 112
Schwerdtfeger, H., 127-8, 129
Seelig, C, 74, 194
Simon, F., 115
Soldner, J. G., 63, 64
Sommerfeld, A., 11, 23, 59, 65,
72,75,104,115
Spengler, O., 22
Stark,J., 36, 50,51,52
Stern, O., 12, 23, 24, 31, 32, 45-6,
51,52,71,72,223
Still, C, 55, III
Still, K.F., 55
Strassmann, F., 146
Strindberg, A., 12
Szilard, L., 146, 147
Tagore, R., 34
Teller, E., 1 14, 1 15, 1 1 7, 220
Thiband, 140
Thomson,J.J., i, 160
Tisdale, 107
Tizard, 162
Toeplitz, O., 17
Tolman, no, ii2
Undset, S., 94
Vasmer, M., 49
Veblen, T., 134, 140
Vegard, 68
Voigt, W., 25, 26-7, 52
Wachsmuth, F. B. R., 24, 31, 32, 46
Waerden,B. L.,86,87
Warburg, E., 103
Weiss, P., 41, 42, 44
Weisskopf, V. F., 127, 128
Weizmann, C, 124, 127, 177
Weizsacker, C. F. v., 201
Wende, 26-7
Wertheimer, M., 150, 155, 166,
167, 195
Weyl, H., 21, 100, 108-9, "I, "7>
"9, 127, 129, 132,134, 140, 143,
157,158,216,227
Weyland, P., 35, 39, 43
Whittaker, E., 197, 198, 200, 203
Widman,J. v., 32
Wien, M. E., 41, 43, 44, 53
Wiener, N., 52
Wolf, E., 191
Yukawa, H., 88, 233
Zahn-Harnack, A. v., 194
Zeiss, C, 54
240
' 'You believe in the God who plays dice,
and I in complete law and order in a world
which I, in a wildly speculative way, am
trying to capture.' Thus Einstein, writin;
to Max Born in 1944, summed up two
utterly contrasted attitudes to science
which were never reconciled throughout
this long series of letters. Born, in holdin
that the basis of the material world was
the purely random behaviour of the
constituent particles of atoms, shared the
majority viewpoint among quantum
scientists; yet Einstein persisted in
thinking that every event must have its
cause, and searched constantly for a
deeper explanation which might bring
order into the seemingly chaotic sub-
atomic world. Their conflicting views
provide the intellectual stimulus of
much of this correspondence.
But at a time when politicians were
realizing the terrifying power of atomic
physics to provide weapons of unforeseen
destructiveness neither Born nor Einstein
could turn their backs on the social
implications of the new science. At first
their letters share atone of concern; in
the end, when the atomic bomb has been
used and the innocence of science has
been left far behind, they can only regret
'the evil which our once-so-beautiful
science has brought upon the world'.
The wider effects of war dominate many
of the letters, for both Born and Einstein
were fd'rced to flee from Germany during
the Hitler regime, and the scars of the
experience lasted so long with Einstein
that he never felt able to return.
In spite of their scientific differences
Born and Einstein sustained a rare and
close friendship for more than forty years,
until Einstein's death in 1955 (Max Born
was to live until 1970). For long periods
these letters were the only link between
them. Whether they are commiserating
over the plight of German Jews in exile,
or delighting in the plays and poems of
Born's wife Hedwig, or exchanging sharp
and often witty comments about their
scientific colleagues, the two men reveal
throughout the essential warmth and
generosity of their personalities. As
Bertrand Russell writes in his foreword:
'In an age of mediocrity and moral pygmies,
their lives shine with an intense beauty.
Something of this is reflected in their
correspondence, and the world is richer
for its publication'.
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