The Reign of Relativity: Philosophy in Physics 1915–1925 Thomas Ryckman OXFORD UNIVERSITY PRESS THE REIGN OF RELATIVITY OXFORD STUDIES IN PHILOSOPHY OF SCIENCE General Editor Paul Humphreys, University of Virginia Advisory Board Jeremy Butterfield Peter Galison Ian Hacking Philip Kitcher Richard Miller James Woodward The Book of Evidence Peter Achinstein Science, Truth, and Democracy Philip Kitcher The Devil in the Details: Asymtotic Reasoning in Explanation, Reduction, and Emergence Robert W. Batterman Science and Partial Truth: A Unitary Approach to Models and Scientific Reasoning Newton C. A. da Costa and Steven French Inventing Temperature: Measurement and Scientific Progress Hasok Chang Making Things Happen James Woodward The Reign of Relativity: Philosophy in Physics 1915–1925 Thomas Ryckman THE REIGN OF RELATIVITY Philosophy in Physics 1915–1925 Thomas Ryckman 1 2005 1 Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Sa˜o Paulo Shanghai Taipei Tokyo Toronto Copyright # 2005 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press 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, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Ryckman, Thomas. The reign of relativity : philosophy in physics 1915–1925 / Thomas Ryckman. p. cm. - (Oxford studies in philosophy of science) Includes bibliographical references and index. ISBN 0-19-517717-7 1. Relativity (Physics) - History. I. Title. II. Series. QC173.52.R93 2004 530.11'09 - dc22 2004041576 987654321 Printed in the United States of America on acid-free paper for Pamela, light of my life This page intentionally left blank PREFACE T he theories of special and general relativity have been essential components of the physical world picture for now more than eight decades, longer than a generous span of human life. Among physicists, familiarity has not bred contempt. Both theories continue to challenge implicitly held notions in ways that even adepts can yet find surprising. The change in outlook occasioned by relativity theory thus has something of the character of ‘‘permanent revolution’’, continu- ally turning up things new, interesting and possibly disturbing. On the other hand, its revolutionary image would appear to be considerably dulled among philoso- phers of science, excepting, of course, certain philosophers of physics and others interested in space-time theories. To be sure, Einstein retains the halo of universal genius among the public at large. But today one can easily acquire the impression that it is the quantum theory, the other principal component of the current physical world-view, which has largely captured the contemporary philosophical imagination. No knowledgeable person would seriously question its revolutionary character or inherent philosophical interest. But while philosophers are generally aware of the vigorous epistemological debate that accompanied the quantum the- ory’s rise, was epitomized in the Einstein-Bohr dialogues, and still continues, rec- ognition seems altogether lacking that a corresponding controversy worthy of present philosophical scrutiny occurred in the early years of general relativity. In part this ignorance is traceable to a false, but understandable, impression that such philosophical engagement as took place principally involved supporters and opponents of general relativity, a conflict abating, and justly forgotten, as the opponents of the theory faded away into oblivion. A sallow bill of goods adapted and adopted by logical empiricism, it is still frequently found retailed within the literature of philosophy of science. This book was written to finally inter that insidious narrative, and to recover, if possible, something of the freshness of the philosophical encounter with that most beautiful of physical theories by two of its greatest masters, Hermann Weyl and Arthur S. Eddington. I am grateful to the National Science Foundation and the National Endowment for the Humanities for grants that relieved me from teaching duties in 1995–1996 in order to begin the project of the book. In relieving me of any further duties on my return, an interim dean at a private university on Chicago’s North Shore unwit- tingly furnished me with the requisite motivation to finish it. I should like to thank her, although readers will have to judge for themselves whether I have succeeded in following her injunction to ‘‘write more boilerplate’’. My largest scholarly debts are to Arthur Fine and Michael Friedman, for innumerable conversations, friendly criticism, and for authoring books in philosophy of science that have not ceased to inspire since I read them as a graduate student in the 1980s. It is largely due to them I became a philosopher of science. It was Howard Stein who awakened my interest in Hermann Weyl, long before this book was conceived. With such an introduction, it is small wonder that Weyl has been on my mind ever since. I owe the warmest thanks to Roberto Torretti, who read the penultimate version with his customary meticulousness, and whose expertise and judicious comments vastly improved it. Carl Hoefer’s firm but gentle criticisms of an earlier version played a decisive role in shaping the book’s final form and content. Over the years I also received encouragement, advice, or assistance from Guido Bacciagaluppi, Mara Beller, Yamima Ben-Menahem, Michel Bitbol, Katherine Brading, Harvey Brown, Jeremy Butterfield, Elena Castellani, Leo Corry, Steven French, Michel Ghins, Friedrich Hehl, Don Howard, Karl-Norbert Ihmig, John Krois, James Ladyman, John McCumber, David Malament, Paolo Mancosu, Yuval Ne’eman, John Norton, Norman Packard, Itomar Pitowsky, Rob Rynasiewicz, Simon Saunders, Hans Sluga, John Stachel, Rick Tieszen, Thomas Uebel, and Daniel Warren. Heartfelt thanks to all. Sadly, some who helped in meaningful ways are no longer with us. I cannot thank them, but mention them here to record debts that I shall find other ways to pay: Jim Cushing, Zellig Harris, Robert Weingard, and Richard Wollheim. Chapter 2 draws upon ‘‘Two Roads from Kant: Cassirer, Reichenbach and General Relativity’’ by T. A. Ryckman from Logical Empiricism: Historical and Contemporary Perspectives, edited by Paolo Parrini, Wesley C. Salmon, and Merrilee H. Salmon, # 2003 by University of Pittsburgh Press, 159–193. Reprinted by permission of the University of Pittsburgh Press. Chapter 4 includes material from my ‘‘Einstein Agonists: Weyl and Reichenbach on Geometry and the General Theory of Relativity’’, in The Origins of Logical Empiricism, edited by Ronald Giere and Alan Richardson (Minneapolis, University of Minnesota Press, 1996), 165– 209. Chapter 6 incorporates much of my ‘‘The Philosophical Roots of the Gauge Principle: Weyl and Transcendental Phenomenological Idealism’’, in Symmetries in Physics: Philosophical Reflections, edited by Katherine Brading and Elena Castellani (Cambridge: Cambridge University Press, 2003), 61–88. I am grateful to the editors and the publishers concerned for their permissions to reuse the material here. viii Preface Unpublished correspondence of Einstein was obtained from Albert Einstein: The Collected Papers, published by Princeton University Press (reprinted by permission of Princeton University Press). I thank the University of Pittsburgh Library System for permission to quote from unpublished correspondence of Hans Reichenbach, and Frau Dr. Yvonne Vo¨geli of the Wissenschaftshistorische Sammlungen of the Swiss Federal Institute of Technology (Zu ¨ rich) for providing me with photocopies of the unpublished letters of Eddington to Weyl. I am grateful to the following sources of the photos on the dust jacket: Dr. Matthias Neuber for locating the photograph of Moritz Schlick, and to Dr. George van de Velde-Schlick for permission to reproduce it here. Alain Guillard of the Interlibrary Loan Service at the Bibliothe ` que universitaire de Paris–XII–Val de Marne for permission to reproduce the photograph of Emile Meyerson from the Ignace Meyerson collection. All rights reserved. Brigitta Arden at the Archives of Scientific Philosophy, Special Collections, Hillman Library, University of Pittsburgh, for locating the photograph of Hans Reichenbach. Reproduction here is by permission of the University of Pittsburgh. All rights reserved. Professor John Krois for kindly lending his photograph of Ernst Cassirer and for giving permission to reproduce it here. Professor Dirk van Dalen of the University of Utrecht, and to Dr. Helmut Rohlfing of the Niedersa¨chsische Staats-und Universita¨tsbibliothek Go¨ttingen, for locating the photograph of Hermann Weyl. Reproduction by permission of the Niedersa¨chsische Staats-und Universita¨tsbibliothek Go¨ttingen. All rights reserved. The Emilio Segre ` Visual Archives at the American Institute of Physics for permission to reproduce the photograph of A. S. Eddington. Norbert Ludwig and Sabine Schumann of the Bildarchiv Preussischer Kultur- besitz, Berlin, for the photograph of Albert Einstein. Permission to reproduce the latter was also granted by the Albert Einstein Archives, Jewish National and University Library, Jerusalem. Many thanks to Barbara Wolff for her assistance. Preface ix [...]... values of the metric at a point can be determined through the use of freely falling neutral ‘‘test particles’’ and by observing the arrival of light at points in the immediate neighborhood of that point However, neither of these hypotheses, of ‘‘freely falling’’ test particles or of the behavior of light in a gravitational field, is independent of gravitational theory Both can be derived from the Einstein... knowledge’’, varying with the development of physical theory, whereas the ‘‘objective contribution to knowledge’’ is alone provided by experience The principle of general covariance is but one of a set of coordination principles for the general theory of relativity, having essentially the meaning of a generalized principle of relativity, ‘ the relativity of the coordinates’’ In any case, within a few years Reichenbach’s... form-and this includes not only the special theory of relativity but also the Newtonian theory.20 Perhaps the most widely read recent formulation of the received view, that of Michael Friedman (1983), maintains that in upholding general covariance as a principle of general relativity, Einstein illicitly mixed together distinct notions that pertain either to the form or to the content of the theory, but... objects are, Einstein noted in 1924, ‘ the aether of Newtonian mechanics’’ as well as that of ‘‘special relativity ’, in uencing matter and light propagation through inertial effects but not in uenced by ‘ the configuration 22 The Reign of Relativity of matter or anything else’’.43 Thereby picking out a theory’s ‘‘absolute objects’’, the invariance group of the theory identifies and constrains the space-time... and interloper in theoretical physics, Hermann Weyl, who looms disproportionately large in the following pages Weyl was an original Universally regarded as one of the premier mathematicians of the century, in the decade in question, his contributions to relativity theory ranked second only to Einstein’s, and in fact, it is from Weyl that the present mathematical formulation of the theory stems In the. .. articulation of a role for the relativized a priori has been rather amply confirmed in the subsequent development of physical theory Namely, Cassirer expressly pinpointed the specific ‘‘metaempirical’’ standing of invariance principles in physical theory, in particular, emphasizing that the principle of general covariance significantly transformed the concept of ‘‘objectivity’’ in physics In this role, principles... 0 from S in the same coordinate system by differently spreading the values of the metric field functions gmn over the spacetime manifold of points To take the scenario of the ‘‘hole argument’’, assume that S contains a ‘‘matter hole’’ H inside of which, by definition, 8x 2 H, Tmn ¼ 0 Then the values of the metric field gmn within H are determined, according to the Einstein field equations, by the matter-energy... solved’’.33 Then the striking statement situating physical reality in ‘‘point-coincidences’’ represents an attempt to distinguish clearly what is required for certain mathematical structures of the theory to have physical significance.34 It is not the positivist credo that, since the in- principle observable is found in the coincidence of points (intersections of world lines), only such coincidences as... Covariance In the first complete exposition of general relativity in 1916, Einstein introduced a ‘‘postulate of general relativity ’, deemed an extension of the principle of relativity: ‘ The laws of physics are to be of such a kind that they apply to systems of reference in any kind of motion’’ A few pages on, a condition of coordinate generality is posed: ‘ The general laws of nature are to be expressed through... include accelerating reference frames Indeed, Einstein had named his theory of gravitation a general theory of relativity because, by application of the principle of equivalence, the behavior of bodies freely falling in a gravitational field (of a highly artificial kind) is indistinguishable from that behavior observed in a frame of reference uniformly accelerated in a gravitation-free region.11 As there . audience of several thousand at the centenary meet- ing of the German Society of Natural Scientists and Doctors on the topic of ‘ The 4 The Reign of Relativity Theory of Relativity in Philosophy ’ in uence of the theory of relativity in shaping the fundamental core of its outlook. Since the rise of logical empiricism, from which stem the main trends in subsequent philosophy of science, if. violated in the standard operator formalism of quantum field theory. The most systematic articulation of the alternative to the new empiricism is to be found in the writings of the mathematician, and interloper