Peter C. Aichelburg and Roman U. Sexl (Eds.)

Albert Einstein

His Influence on Physics, Philosophy and Politics

With Contributions by

Peter G. Bergmann, Hiroshi Ezawa, Walther Gerlach, Banesh Hoffmann, Gerald Holton, BernulfKanitschneider, Arthur I. Miller, Andre Mercier, Roger Penrose, Nathan Rosen, Dennis W. Sciama,Joseph Weber, Carl-Friedrich von Weizsacker,John A. Wheeler and Wolfgang Yourgrau

Published under the auspices of the "International Society on General Relativity and Gravitation"

Friedr. Vieweg & Sohn Braunschweig/Wiesbaden

The papers of W. Gerlach and C. F. v. Weizsacker were translated by Dr. and Mrs. M. Skopec.

The paper of B. Kanitscheider was translated by R. U. Sexl.

The contribution of R. Penrose is a completely revised version of an article from "Cosmology Now", British, Broadcasting Corporation.

The copyright of the articles by J. A. Wheeler rests with the author.

Quotations from Einstein by kind permission of the Estate of Albert Einstein, Otto Nathan, Trustee, New York, N.Y., U.S.A.

All rights reserved © Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig, 1979 Softcover reprint of the hardcover 1 st edition 1979 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any informational storage and retrieval system, without written permission from the copyright owner.

Set by Vieweg, Braunschweig

ISBN 978-3-528-08425-7 ISBN 978-3-322-91080-6 (eBook)

DOI 10.1007/978-3-322-91080-6

Introduction

v

Dart nun, bei den Heiden, bei diesen wirkiich vorbild­

haften Menschen erscheint uns das Interesse fiir die Person, fiir den Namen, fiir Gesicht und Gebiirde er­

iaubt und natiiriich.

H. Hesse, "Das Giasperienspiel"

In 1979 the world celebrates the centenary of Albert Einstein's birth. This offers an occasion to review his life and his scientific work in retrospect, to survey his importance for our time, and to look forward to future years of scientific research.

Undoubtedly, Einstein was one of the key-figures in the intellectual history of our century. He influenced physics and philosophy, as well as politics. The creation of general relativity is one of the greatest scientific achievements of our time, as well as the apex of Einsteins's scientific work. Its full implications for the other fields of physics have become clear only in recent years. The technological possibilities offered by space research have enabled mankind to survey the universe for the first time unhindered by the earth's atmosphere. This has led to new discoveries and has shown that even some of the far-reaching conclusions derived from Einstein's theory are borne out by observation. General relativity, which has for a long time been viewed as an outsider among physical theories because of its mathematical difficulty and complexity, is considered now to be the prototype of theories in the fields of elementary particle physics and even solid state physics.

The contributions to this volume attempt to demonstrate Einstein's influence on the intellectual history of our century. Three of the contributors have been co-authors of Einstein, several others have had an intense exchange of ideas with him. The papers collected here demonstrate the far-reaching influence of Einstein's work and his personality on the physics, philosophy, theory of science and on the politics of our time.

The first papers survey Einstein's scientific work in the field of relativity and some of the problems which are of interest in this respect today. The President of the International Committee for General Relativity and Gravita­tion, Peter Bergmann, one of Einstein's collaborators, opens this series of papers with a short introduction to relativity and its confirmation by ex­periment. Of special interest are Bergmann's remarks on the various attempts which have been made to generalize relativity and the personal recollections of the au thor concerning his joint work with Einstein.

VI Introduction

General relativity has led to completely new answers to the old problem of the structure of the universe. The progress of relativistic cosmology, which started with Einstein's "Kosmologischen Betrachtungen zur Allgemeinen Relativitatstheorie", was hindered for several decades by the lack of ap­propriate observational material. The discovery of the Hubble law in the twenties led to the idea of an expanding universe which had its origin several billion years ago in a big bang. It was only the discovery of the cosmic back­ground radiation by Penzias and Wilson in 1965, however, which gave a further and probably decisive hint to the reality of the hot and dense initial phase of the universe. Dennis Sciama shows in his short introduction to relativistic cosmology how the experimental data slowly led to a more quantitative and exact history of the cosmic revolution.

It was already in 1920 that Einstein concluded from the field equations of general relativiry that gravitational waves should exist, which propagate with the velocity of light. At that time it seemed out of the question to detect these waves experimentally. All known mechanisms for the generation and discovery of gravitational waves led to effects which were too small to be measured. Therefore the scientific community was very sceptical when Joseph Weber began in 1950 first with theoretical considerations and later with practical attempts to improve gravitational wave antennas. The decisive improvement of the sensitiviry of these antennas, which is due to him, has encouraged other scientists. Currently there are about twenty groups working on the development and improvement of gravitational wave antennas. Weber surveys the present state of the art in his paper and shows that quantitative results may be expected within the next years.

An important source of gravitational waves is the gravitational collapse of stars. Depending on the mass of a star this collapse can lead either to a white dwarf, a neutron star or a black hole. While white dwarfs have been known to astronomy for a long time, the discovery of neutron stars came only in 1967. A research group at the University of Cambridge found periodic radio signals at that time, which were emitted by stars. Theoretical con­siderations showed that neutron stars were the only possible source of this radiation. Thus the second of the three possible final states of the gravita­tional collapse of a star had been found. The open and outstanding problem was now to discover a third possible form, black holes. At first it was not certain whether these singularities of space-time would actually be formed in the collapse of realistic stars. Theoretical considerations by Stephen Hawking and Roger Penrose showed however, that the complete annihilation of matter in gravitational collapse can be expected not only in improbable idealized cases, but as a general feature of the gravitational collapse of massive objects. This result initiated the development of methods for the search for black holes. The paper by Roger Penrose shows that several astronomical objects are known today which are likely to contain black holes. It is unfortunate that Einstein could not live to see this confirmation of the most daring con-

Introduction VII

elusion to be drawn from general relativity. In an imaginary dialogue John Wheeler tries to reconstruct Einstein's possible reaction to this discovery.

Einstein's contributions to physics were not restricted to the field of relativity, but dealt also with quantum theory and thermodynamics. The creation of the light quantum hypothesis in 1905 was one of the decisive steps towards quantum theory. I t initiated the wave-particle dualism which turned out to be one of the most difficult problems in interpreting the quantum theory. Einstein himself and some of the other leading physicists of the time remained sceptical towards the quantum theory. In a famous paper "Can the Quantum-mechanical Description of Reality be Considered Complete" by Einstein, Podolski and Rosen, he laid down the reasons for his dissatisfaction with the orthodox Copenhagen interpretation of quantum mechanics. This paper led to many comments and Nathan Rosen discusses his present position in his contribution.

Einstein's contributions to quantum theory are closely connected with his research on thermodynamics, which is analyzed by Hiroshi Ezawa. This analysis illustrates how Einstein's scientific work was guided by the fundamental postulate of the simplicity and unity of the universe. These postulates are taken up from a different point of view by Arthur I. Miller in his contribution analyzing the origin of special relativity and in Gerald Holton's studies of Einstein's approach to theory formation. It is interesting to see the similarities in the different treatments of one subject by various authors: the physicist Ezawa is mainly interested in Einstein's influence on the third development of thermodynamics and shows how Einstein tried again and again to "understand" Planck's law, thereby working his way towards quantum mechanics. Miller's study of the origin of relativity is written in a completely different style. The methodology of the history of science (which might seem to the physicist to be overly accurate in some places) proves that Einstein's research was opposed to the scientific fashions of his time and shows the variety of problems which have been solved by special relativity. On the other hand, Holton's paper leads to an analysis of Einstein's work from the point of view of the philosophy of science. Holton discusses Einstein's method of theory construction on the basis of a letter from Einstein to his friend Solovine. This letter reveals the full importance of the jump which leads from the field of experience to the formulation of the axioms of a theory: "There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them."

The philosophy of science on which Einstein's papers are based is also analyzed in the contribution by Bernulf Kanitscheider. It becomes apparent how much Einstein differed in his scientific work, but also in his methodologi­cal reflections, from the positivistic attitudes of the philosophy of science of his time. In an intuitive way Einstein's ideas anticipated several decades of developments in the philosophy of science, which led to a more liberal attitude towards the introduction of theoretical entities.

VIII Introduction

Carl-Friedrich von Weizsiicker's contribution deals with the connection between physics and philosophy, which is brought out by Einstein's work, but also with his importance for politics. "Einstein was a physicist not a philosopher. But the naive directness of his questions was philosophical". This naivite is also characteristic for Einstein's attitude towards politics, in which he was increasingly involved in his later years. The paper by Banesh Hoffmann shows how Einstein was won over to the idea of Zionism only slowly after 1920, but was deeply concerned with Jewish affairs thereafter. The concern for the fate of the Jews and the fear of a victory of Nazi­Germany in the Second World War were also decisive for Einstein's famous letter to President Roosevelt, in which he pointed out the possibility of an atomic bomb. This letter, written in August 1939, and a second one in March 1940, were crucial for the funding of the first controlled chain reaction and the atomic bomb.

The influence wh"ich political developments have even in the fields of pure and most abstract science such as general relativity and gravitation, is borne out by Andre Mercier's account of the history of the GRG-organization. The International Committee for General Relativity and Gravitation, which tried to co-ordinate the international research efforts in the field of general relativity, repeatedly had severe problems in overcoming the barriers be­tween different political systems and in encouraging a genuine world-wide collaboration.

The last contributions to this volume deal with personal recollec­tions. For Walter Gerlach Einstein's contribution to quantum theory was most important. In the early history of quantum mechanics one of the central problems was the real existence of photons. In a variety of experi­mental arrangements one tried to clarify whether the emission and absorption of photons was an instantaneous process or whether it corresponded rather to the continuous emission of waves, which was postulated by classical theory. The arguments were so heated, that frauds were used in order to prove the opposing points of view.

John Wheeler's recollections deal mainly with relativity. A visit at Einstein's house in 1953 and Einstein's last lecture, which took place on April 14, 1954, illustrate Einstein's search for a unified field theory. The detailed notes taken during Einstein's last lecture give an insight into the style of his lectures, in which he tried to present a synthesis of many fields of physics. Finally, Wolfang Yourgrau describes some personal meetings with Einstein which illustrate the lighter side of academic life.

* * *

Introduction IX

We are especially indebted to the authors whose contributions have made this publication possible. Furthermore, we are obliged to Dr. O. Nathan who gave us permission to quote from the Einstein Estate. We thank

Mrs. J. Aichelburg, as well as Dip!. Ing. E. Oberaigner, and Doz. Dr. A. Wehr! for their valuable help in revising the manuscripts, and Miss E. Klug and Mrs. F. Wagner for their untiring typing efforts. We especially want to mention the pleasant cooperation offered by the Vieweg Publishers, who were always willing to accommodate our wishes, despite the pressing dead­lines.

Peter C. Aichelburg Roman U. Sexl

Vienna, November 1978

x

Contributing Authors

Peter G. Bergmann

Professor of Physics at Syracuse University, USA; born in Berlin, he emigrated to the USA and became in 1936 assistant to Einstein at the Institute of Advanced Study in Princeton; numerous articles on special and general relativity; first attempts to quantize the gravitational field; author of the book "The Riddle of Gravitation"; President of the International Society on General Relativity and Gravitation.

Hiroshi Ezawa

Professor of Physics at Gakusuin University, Japan; research on quantum field theory and quantum statistics; author of the book "Who has seen the Atom?"

Walther Gerlach

Professor (Emeritus) for Physics, University of Munich, Bundesrepublik Deutschland; essential contributions to experimental quantum theory (Stern-Gerlach experiment for directional quantization); publications on radiation, spectroscopy, magnetism and history of science.

Banesh Hoffmann

Professor for Mathematics, Queens College, New York, USA; co-worker of Einstein and member of the Institute for Advanced Study; publications and research on relativity in particular on the motion of matter in a gravitational field, quantum theory, applications of tensor analysis to electrical engineering; author of a biography of Albert Einstein.

Gerald Holton

Professor of Physics and History of Science at the Massachusetts Institute of Technology, USA; research in history of science and philosophy of science; author of "Thematic origins of Scientific Thought: Kepler to Einstein" and "The Scientific Imagination: Case Studies".

Contributing Authors XI

Bernulf Kanitscheider

Professor for Philosophy of Science at the University of GieBen, Bundesrepublik Deutsch­land; studies on the concept of geometry and its meaning for physics; author of "Geo­chronometrie und Wirklichkeit" and "Vom absoluten Raum zur dynamischen Geo­metrie".

Arthur I. Miller

Assoc. Professor for Physics at Lovell University, USA; interdisciplinary research in the history of 19th century science.

Andre Mercier

Professor (Emeritus) for Theoretical Physics, also Philosophy at the University of Bern, Switzerland; research and numerous publications on mathematical methods of theo­retical physics, theories on the origin of the earth, the concept of time, theory of knowl­edge; author of the book "Analytical and Canonical Formalism in Physics" and others; former Secretary-General of the International Society on General Relativity and Gravita­tion.

Roger Penrose

F.R.S., Rouse Ball Professor for Mathematics, University of Oxford, England; formulated, together with S. Hawking the first theorems on the existence of space-time singularities in general relativity; research on black hole physics, techniques of differential topology

in relativity.

Nathan Rosen

Professor of Physics at the Israel Institute of Technology, Israel; colleague of Einstein's at the Institute for Advanced Study in Princeton; research in relativity and unified field theory, quantum theory, thermal diffusion, fundamental particle theory, gravitation and

cosmology.

Dennis W. Sciama

Fellow of All Souls College, Oxford, England; research in astrophysics, cosmology and general relativity; author of several books e.g. "Modern Cosmology".

Joseph Weber

Professor of Physics at the University of Maryland, USA; he developed the first detectors for gravitational waves; publications and research on relativity, microwave spectroscopy, irreversibility; au thor of "General Relativity and Gravitational Waves".

XII Contributing Authors

Carl-Friedrich von Weizsa'cker

Professor and Director of the Max-Planck-Institut zur Erforschung der Lebensbedingungen der wissenschaftlich-technischen Welt, Starnberg, Bundesrepublik Deutschland; numerous

publications and books on physics, philosophy and peace research; his book "Zum Welt­bild der Physik" was translated into ten languages, several distinctions, Max-Planck Medal and Pour Ie Merite.

John A. Wheeler

Professor in Physics at the University of Texas, Austin, USA; he worked many years in Princeton and was in friendly contact with Einstein; during the Second World War Advicer on atomic energy projects, co-worker on the Manhattan Project; creator of "Geometro­dynamics" where matter is described as topological properties of space-time; decorated with the Einstein Medal and several other awards; author of the books "Geometro­dynamics", "Einstein's Vision", "Gravitation" and others.

Wolfgang Yourgrau

Professor of Physics at the University of Denver, USA; studied in Berlin with Schrodinger, Einstein and v. Laue; research on quantum theory and the theory of measurement; editor of "Foundations of Physics".

XIII

Contents

Peter G. Bergmann

The Development of the Theory of Relativity 1

Dennis W. Sciama

Cosmology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17

Joseph Weber

Gravitational Radiation 25

Roger Penrose

Black Holes .............................................. 33

John A. Wheeler

The Black Hole: An Imaginary Conversation with Albert Einstein . . . .. 51

Nathan Rosen

Can Quantum-Mechanical Description of Physical Realty Be Considered Complete .................................... 57

XIV Contents

Hiroshi Ezawa

Einstein's Contribution to Statistical Mechanics. . . . . . . . . . . . . . . . . .. 69

Arthur I. Miller

"On the History of the Special Relativity Theory" 89

Gerald Holton

Einstein's Model for Constructing a Scientific Theory .............. 109

Bernulf Kanitscheider

Einstein's Treatment of Theoretical Concepts .................... 137

Carl Friedrich v. Weizsiicker

Einstein's Importance to Physics, Philosophy and Politics . .......... 159

Banesh Hoffmann

Einstein and Zionism ....................................... 169

Andre Mercier

Birth and Role of the GRG-Drganization and the Cultivation of International Relations among Scientists in the Field ............ 177

Contents xv

Walther Gerlach

Reminiscences of Albert Einstein from 1908 to 1930 .............. 189

John A. Wheeler

Mercer Street and other Memories ............................. 201

Wolfgang Yourgrau

Einstein - and the Vanity of Academia . . . . . . . . . . . . . . . . . . . . . . . .. 231