Table Of ContentTHE PHYSICIST'S CONCEPTION OF NA TURE
The Physicist's
Conception of Nature
Edited by
Jagdish Mehra
D. Reidel Publishing Company
Dordrecht-Holland / Boston-U. S.A.
1973
Library of Congress Catalog Card Number 73-75765
ISBN-13: 978-94-010-2604-8 e-ISBN-13: 978-94-010-2602-4
DOl: 10.1007/978-94-010-2602-4
Published by D. Reidel Publishing Company,
P.O. Box 17, Dordrecht, Holland
Sold and distributed in the U.S.A., Canada, and Mexico
by D. Reidel Publishing Company, Inc.
306 Dartmouth Street, Boston,
Mass. 02116, U.S.A.
All Rights Reserved
Copyright © 1973 by D. Reidel Publishing Company, Dordrecht, Holland
Softcover reprint of the hardcover I st edition 1973
No part of this book may be reproduced in any form, by print, photoprint, microfilm,
or any other means, without written permission from the publisher
Dedicated to
PAUL ADRIEN MAURICE DIRAC
on the occasion of his seventieth birthday
SYMPOSIUM ON THE DEVELOPMENT OF
THE PHYSICIST'S CONCEPTION OF NATURE
IN THE TWENTIETH CENTURY
Held at the International Centre for Theoretical Physics,
Miramare, Trieste, Italy, 18-25 September 1972
Sponsoring Committee:
Co-Chairmen: H. B. G. CASIMIR (Philips Research Laboratories, Eindhoven),
EUGENE P. WIGNER (Princeton University)
EDOARDO AMALDI (University of Rome),
PIERRE AUGER (Universite de Paris),
BRIAN FLOWERS (U.K. Science Research Council, London),
RUDOLF E. PEIERLS (University of Oxford),
FRANCIS PERRIN (College de France),
ISIDOR I. RABI (Columbia University),
GUNNAR RANDERS (NATO, Brussels),
LEON ROSENFELD (NORDITA, Copenhagen),
ABDUS SALAM (Imperial College, London, and International Centre
for Theoretical Physics, Trieste)
Symposium Director:
JAGDISH MEHRA (The University of Texas at Austin)
Financial Sponsorship:
The Science Committee, North Atlantic Treaty Organization (Brussels, Belgium);
Minna-James-Heineman Stiftung (Hanover, Germany);
Consortia of the City and the Region of Trieste (Trieste, Italy);
The Lorentz Foundation (Haarlem, The Netherlands)
Contents
page
Preface XI
Contributors xv
Opening remarks at the symposium XIX
1 Development of the physicist's conception of nature, by P. A. M. DIRAC 1
Part I Space, Time, and Geometry
2 The universe as a whole, by DENNIS W. SCIAMA 17
3 A chapter in the astrophysicist's view of the universe,
by s. CHANDRASEKHAR 34
4 Fundamental constants and their development in time, by P. A. M. DIRAC 45
5 The expanding earth, by PASCUAL JORDAN 60
6 The nature and structure of spacetime, by JVRGEN EHLERS 71
7 Einstein, Hilbert, and the theory of gravitation, by JAGDISH MEHRA 92
8 Theory of gravitation, by ANDRZEJ TRAUTMAN 179
9 From relativity to mutability, by JOHN ARCHIBALD WHEELER 202
Part II Quantum Theory
10 The wave-particle dilemma, by LEON ROSENFELD 251
11 Development of concepts in the history of quantum theory,
by WERNER HEISENBERG 264
12 From matrix mechanics and wave mechanics to unified quantum mechanics,
by B. L. V AN DER W AERDEN 276
13 Early years of quantum mechanics: some reminiscences,
by PASCUAL JORDAN 294
14 The mathematical structure of elementary quantum mechanics,
by JOSEF M. JAUCH 300
15 Relativistic equations in quantum mechanics, by EUGENE P. WIGNER 320
16 The electron: development of the first elementary particle theory,
by FRITZ ROHRLICH 331
17 The development of quantum field theory, by RUDOLF E. PEIERLS 370
18 Quantum theory of fields (until 1947), by GREGOR WENTZEL 380
19 Development of quantum electrodynamics, by SIN-ITIRO TOMONAGA 404
20 A report on quantum electrodynamics, by JULIAN SCHWINGER 413
x CONTENTS
21 Progress in renormalization theory since 1949, by ABDUS SALAM 430
22 Some concepts in current elementary particle physics,
by CHEN NING YANG 447
23 Crucial experiments on discrete symmetries, by v. L. TELEGDI 454
24 Superconductivity and superfluidity, by H. B. G. CASIMIR 481
Part III Statistical Description of Nature
25 Problems of statistical physics, by GEORGE E. UHLENBECK 501
26 Phase transitions, by MARK KAC 514
27 Approach to thermodynamic equilibrium (and other stationary states),
by WILLIS E. LAMB, JR. 527
28 Kinetic approach to non-equilibrium phenomena, by E. G. D. COHEN 548
29 Time, irreversibility and structure, by IL Y A PRIGOG INE 561
30 The origin of biological information, by MANFRED EIGEN 594
Part IV Physical Description, Epistemology, and Philosophy
31 Classical and quantum descriptions, by c. F. VON WEIZSACKER 635
32 Wavefunction and observer in the quantum theory, by LEON N. COOPER 668
33 The problem of measurement in quantum mechanics, by JOSEF M. JAUCH 684
34 Subject and object, by J. S. BELL 687
35 Subject, object, and measurement, by R. HAAG 691
36 Measurement process and the macroscopic level of quantum mechanics,
by IL Y A PRIGOGINE 697
37 Why a new approach to found quantum theory?, by G. LUDWIG 702
38 A process conception of nature, by DA VID FINKELSTEIN 709
39 Quantum logic and non-separability, by BERNARD D'ESPAGNAT 714
40 Physics and philosophy, by c. F. VON WEIZSACKER 736
Part V Memorial Lectures
41 Recollections of Lord Rutherford, by P. L. KAPITZA 749
42 W. Pauli's scientific work, by CHARLES P. ENZ 766
43 Remarks on Enrico Fermi, by s. CHANDRASEKHAR 800
Part VI Celebration of P. A. M. Dirac's 70th Birthday
44 The banquet of the symposium - in honour of Paul Dirac,
including an address on: The classical mind, by c. P. SNOW 805
Appendix 1 Programme of the symposium 820
Appendix 2 Participants 823
Index of names 830
Preface
The fundamental conceptions of twentieth-century physics have profoundly influenced
almost every field of modern thought and activity. Quantum Theory, Relativity, and
the modern ideas on the Structure of Matter have contributed to a deeper understand
ing of Nature, and they will probably rank in history among the greatest intellectual
achievements of all time. The purpose of our symposium was to review, in historical
perspective, the current horizons of the major conceptual structures of the physics of
this century.
Professors Abdus Salam and Hendrik Casimir, in their remarks at the opening of
the symposium, have referred to its origin and planning. Our original plan was to hold
a two-week symposium on the different aspects of five principal themes: 1. Space,
Time and Geometry (including the structure of the universe and the theory of gravita
tion),2. Quantum Theory (including the development of quantum mechanics and
quantum field theory), 3. Statistical Description of Nature (including the discussion
of equilibrium and non-equilibrium phenomena, and the application of these ideas to
the evolution of biological structure), 4. The Structure of Matter (including the discus
sion, in a unified perspective, of atoms, molecules, nuclei, elementary particles, and
the physics of condensed matter), and finally, 5. Physical Description and Epistemo
logy (including the distinction between classical and quantum descriptions, and the
epistemological and philosophical problems raised by them).
These themes, taken together, might be regarded as constituting almost the whole
of modern physics, and as a programme for one symposium it would have seemed to
be too ambitious. It was, however, not all that insane. Our intention was not to
cover the details of all the problems that come under these themes. Rather we had
hoped to discuss the historical development of the principal conceptions, and the
current horizons which have arisen from them, which would emphasize the structural
and conceptual unity of the body of physical knowledge about Nature. These would be
presented by some of their most authentic exponents.
The Sponsoring Committee came to the conclusion that the programme, even for a
two-week symposium, would be too heavy. They thought that it would be advisable
to hold two symposia to cover the intended programme, and that it could be done
without damaging the unity of the general theme. They decided that we should deal
with four themes in the first symposium, leaving the Structure of Matter to the second.
Our financial sponsors also thought that this was a good idea, that based upon the
success of the first symposium the second one could be held with confidence a couple
of years later. We thus finally adopted the programme which is reproduced in
Appendix 1.
xu PREFACE
With a programme so rich in scientific and historical fare, and with many stars
among the lecturers, every occasion at the symposium represented a highlight. Yet,
there were several exceptional occasions which many of us will specially cherish.
Dirac's evening lecture on the 'Development of the Physicist's Conception of
Nature' was such an occasion. In pin-drop silence, all ears attuned to his words,
Dirac developed his theme. He talked about classical mechanics and relativity, about
quantum mechanics and the quantum theory of fields, and about how the development
of physics could be pictured as a rather steady development with many small steps,
superposed on which were a number of big jumps, the latter consisting usually of over
coming prejudices. Dirac wondered about the present state of physical theory and
invoked the twin principles of 'beauty and logic' as the guidelines for the developing
architecture of physics. He declared his belief that the physicist's conception of Nature
has not stopped in growing: it is at an interim state at present and fundamental
developments will occur in the future that will change it.
As he spoke, his voice feeble but firm, the sentences perfectly formed as only Dirac's
sentences can be, his spirit grew and filled the hall. The audience shrank in size if not
in numbers. As he finished his talk, one felt the presence of only this frail man who
had the strength of character to match his wisdom, a man who, with a few kindred
spirits, had created the language of modem theoretical physics, and who now enjoined
his audience of distinguished physicists to cast away prejudice and seek a deeper
understanding of Nature.
In his beautiful historical talk, dealing with a period of a few weeks in March and
April 1926 when the passage took place from matrix mechanics and wave mechanics
to a unified quantum mechanics, B. 1. van der Waerden discussed at length a letter
from Pauli to Jordan, written in April 1926, in which Pauli had referred to Lanczos'
work on the integral equations. Van der Waerden pointed out in delectable detail how
Pauli and SchrOdinger had imperfectly understood the work of Lanczos, and how the
latter's integral equation was equivalent to Schrodinger's. At the end of this talk,
which had shown how deep and original had been Lanczos' understanding of the
mathematical structure of quantum mechanics, it was pointed out that Professor
Cornelius Lanczos was in the lecture hall and had listened to this forceful vindication
of his early work against Pauli's criticism of it. As Lanczos got up to acknowledge the
announcement of his presence Van der Waerden, who did not know him personally,
was shocked with pleasant surprise, and the audience broke into sustained applause.
It was a thrilling moment for all.
Another occasion with enormous impact came on Wednesday morning, 20 Septem
ber 1972. This was just the fact that the speakers that morning, one after the other,
were Paul Dirac, Werner Heisenberg, and Eugene Wigner. An occasion with such a
succession, in one session of a conference, of speakers who had participated in the
creation of quantum theory had probably not occurred since the first and the fifth
Solvay conferences, and the audience was conscious of a sense of history. This was
the veritable celebration of the seventieth birthday of physics in the twentieth century.
An evening we will all remember and cherish was the banquet of the symposium in
PREFACE XJII
honour of Dirac. The gracefulness of the occasion was highlighted by both the com
pany present and the remarks that were made. Lord Snow's address on 'The Classical
Mind' underscored the joy and pride of the occasion which we were allowed to share.
The impromptu telling of the 'Dirac stories' by several people, and Dirac's own story
about David Hilbert, delighted all who were present. These remarks have been gathered
in a chapter in this volume, and hopefully many a reader will enjoy them.
Many of those who attended the symposium have written to me how 'successful,
beautiful, historic, unique, etc.' this symposium was. It gives me great pleasure to
thank those who contributed to the uniqueness, beauty, and success of this event.
First of all, the members of the Sponsoring Committee, all of whom helped at one
time or another during the organization. Professors Edoardo Amaldi, Pierre Auger,
Brian Flowers, Rudolf Peierls, Francis Perrin, I. I. Rabi and Leon Rosenfeld gave
much wise counsel and help. Professor Gunnar Randers' encouragement, cooperation,
and assistance were invaluable throughout. Professors Hendrik Casimir, Abdus Salam,
and Eugene Wigner encouraged, helped, and sustained me at every step of the way in
the effort to organize the symposium, and it was their continuous support that made
this task both possible and a joy. The association of all these distinguished scientists
with the symposium had assured its success, and every expression of gratitude will be
inadequate to acknowledge the significance of their sponsorship.
The distinguished lecturers were most cooperative. The subject of the lecture was
not of their choice at times, yet they accepted their assignments graciously. They made
wonderful contributions to the programme and it is what they delivered that gave
content and meaning to the symposium. Their papers, often with the discussions that
followed the talks, are reproduced here. Also reproduced in this volume are the papers,
prepared for other occasions, of those who were invited to give talks but preferred
not to do so (Wentzel), and of those whom circumstances prevented from attending
(Kapitza, Tomonaga). We can be truly grateful for the treat which the contributors
to this volume have offered us.
The chairmen of sessions preserved a relaxed atmosphere throughout. The par
ticipants in the symposium were just marvellous. They braved a heavy programme,
participating fully in all sessions and contributing to the discussions. The lecturers,
chairmen, and participants stayed throughout the symposium, which was also a unique
experience, deserving of the gratitude of the organizers.
The holding of the symposium was made possible by the financial sponsorship
of NATO's Scientific Committee. The Minna-James-Heineman Foundation of
Hanover, Germany, also contributed funds. At the request of Professor Casimir, the
Lorentz Foundation made a timely contribution. Several friends of the Symposium
Director, who wish to remain anonymous, rendered financial help, and the Consortia
of the City and the Region of Trieste gave invaluable support for the social events,
as did the Prince of Torre e Tasso. The publishers of this volume have supported
the symposium enormously, and have cooperated in meeting our wishes regarding
the publication. We are grateful for all this wonderful support.
The symposium was held at the beautiful premises of the International Centre for
