'Subtle is the Lord ...' Albert Einstein in 1896. (Einstein Archive) 'Subtle is the Lord...' The Science and the Life of Albert Einstein ABRAHAM PAIS Rockefeller University OXFORD UNIVERSITY PRESS OXFORD UNIVERSITY PRESS Great Clarendon Street, Oxford ox2 6DP Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Cape Town Dares Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Oxford University Press 1982 Foreword © Roger Penrose 2005 The moral rights of the author have been asserted Database right Oxford University Press (maker) First published 1982 First issued as an Oxford University Press paperback, 1983 Reissued with a new foreword, 2005 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organizations. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose this same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Pais, Abraham, 1918- Subtle is the Lord—. Bibliography: p. Includes index. 1. Einstein, Albert, 1879-1955. 2. Physicists– Biography. 3. Physics—History. I. Title. QC16.E5P26 530'.092'4 [B] 82-2273 AACR2 Printed in Great Britain on acid-free paper by Ashford Colour Press Ltd., Gosport, Hampshire ISBN 0-19-280672-6 ISBN 978-0-19-280672-7 02 XII The last known picture of Einstein, taken in March 1955, in front of 112 Mercer Street. (Einstein Archive, Courtesy United Press International) To Joshua and Daniel 'Science without religion is lame, religion without science is blind.' So Einstein once wrote to explain his personal creed: 'A religious person is devout in the sense that he has no doubt of the significance of those super-personal objects and goals which nei- ther require nor are capable of rational foundation.' His was not a life of prayer and worship. Yet he lived by a deep faith—a faith not capable of rational foundation—that there are laws of Nature to be discovered. His lifelong pursuit was to discover them. His realism and his optimism are illuminated by his remark: 'Subtle is the Lord, but malicious He is not' ('Raffiniert ist der Herrgott aber boshaft ist er nicht.'). When asked by a colleague what he meant by that, he replied: 'Nature hides her secret because of her essential loftiness, but not by means of ruse' ('Die Natur verbirgt ihr Geheimnis durch die Erhabenheit ihres Wesens, aber nicht durch List.'). Foreword The world of science is greatly fortunate that a theoretical physicist of the distinction of Abraham Pais should have discovered within himself not only a particular talent for scientific biography but also a passionate desire to convey to us his unique perspective on the momentous developments in 20th-century physics that he had witnessed. Himself a very significant later contributor, Pais had been well acquainted with most of the key figures in this highly remarkable period of scientific development, and he was able to combine his own deep understanding of the central physical ideas with a personal knowledge of these individuals. Pais had worked with Niels Bohr in 1946 and later wrote a comprehensive biography of Bohr's life and work.* Subsequently, he provided short biographies of many other outstanding figures of the time, with whom he had been personally acquainted, such as Paul Dirac, Wolfgang Pauli, John Von Neumann, and Eugene Wigner.** But the book that launched Pais's biographical career was his landmark biography of Einstein, entitled "Subtle is the Lord", the title being an English translation of part of a quotation from Einstein (inscribed, in 1930, in marble above the fireplace in the faculty lounge of the mathematics building in Princeton) which in the original German reads "Raffiniert ist der Herrgott aber boshaft ist er nicht." Pais translates this as "Subtle is the Lord, but malicious He is not". There have been numerous biographies of Einstein, both before and after this one, but what distinguishes Pais's book is the detail and insight into Einstein's scientfic contributions, with not so much emphasis on issues of a personal nature that have little bearing on his role as a scientist. This book was surely the biography that Einstein himself would have most valued.*** For whereas Pais does not at all *Niels Bohr's Times: In Physics, Philosophy, and Polity (Oxford University Press, 1991). **The Genius of Science: A Portrait Gallery of Twentieth Century Physicists (Oxford University Press, 2000). In his technical/historical book Inward Bound: Of Matter and Forces in the Physical World (Oxford University Press, 1986), he addressed the important aspects of 20th-century physics not covered in the current volume. ***It was clearly valued by others, as it became the winner of the 1963 American Book Award and was selected by The New York Times Book Review as one of the best books of the year. viii FOREWORD neglect Einstein's personal side—and an interesting picture of Einstein the man indeed comes through—the real strength of this work lies in its handling of the physical ideas. As Einstein had earlier commented: "The essential of the being of a man of my type lies precisely in what he thinks and how he thinks, not what he does or suffers". On the scientific side, there is, indeed, much to be said. For Einstein contributed far more to the physics of the early 20th century than just relativity. Apart from Max Planck, with his ground-breaking work of 1900 (on the spectrum of black- body radiation), Einstein was the first to break away from the classical physics of the time and to introduce the crucial quantum "wave/particle" idea—the idea that despite light being an electromagnetic wave, it sometimes had to be treated as a collection of particles (now called "photons"). Through this work Einstein discovered the explanation of the photo-electric effect, this eventually winning him a Nobel Prize. He provided (in his doctorate thesis) a novel method of determining the sizes of molecules, at a time when their very existence was still controversial. He was one of the first to understand the detailed nature of the tiny wiggling "Brownian" motion of small particles in suspension and to provide a beginning to the new statistical physics. He contributed key ideas that led to the development of lasers. And all this is not to mention his revolutionary theories of special and general relativity! In describing each of these contributions, Pais first sets the stage, lucidly describing the state of the relevant parts of physics at the time Einstein entered the scene, often explaining in significant detail the work of Einstein's precursors. Then we find Einstein's own fundamental contributions, introduced and discussed in depth, the essential novelty of Einstein's viewpoint being all very clearly set out, as is the profound influence that it had on subsequent work. This account indeed provides a wonderful overview of the developments in physics of the early 20th century, as there seems to be no major area of theoretical physics on which Einstein did not have some impact. This book is not a "popular" work, in the sense of the term that so often seems to involve distortions and oversimplifications in attempts to explain technical concepts to the lay reader. Instead, it comes seriously to grips with the physics involved in each major area that is treated and, where appropriate, mathematical equations are presented without apology. Yet this is by no means simply a cold scientific account in which personal influences are deemed irrelevant. Pais illuminates many facets of Einstein's life, some of which may at first seem almost paradoxical. Pais may not always provide answers, but he expounds these issues in insightful ways. The common picture of Einstein is as an unworldly almost saintly old man, with twinkling eyes, moustache, wild white hair, and attired in a floppy sweater. But this was the Einstein who spent the last twenty years of his life in Princeton on a certain approach to a unified field theory that the majority of physicists would now judge to be basically misconceived. How does this picture relate to that of the Einstein of the "miraculous" year 1905, with an apparently dapper appearance, working at