Daniel Kennefick - Traveling at the Speed of Thought: Einstein and the Quest for Gravitational Waves

TRAVELING AT THE SPEED OF THOUGHT

Traveling at the Speed of Thought

EINSTEIN AND THE QUEST FOR GRAVITATIONAL WAVES

Daniel Kennefick

Princeton University Press

Princeton & Oxford

Copyright 2007 by Princeton University Press

Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540

In the United Kingdom: Princeton University Press, 3 Market Place, Woodstock, Oxfordshire OX20 1SY

All Rights Reserved

ISBN-13: 978-0-691-11727-0

ISBN-10: 0-691-11727-6

Library of Congress Control Number: 2006938366

British Library Cataloging-in-Publication Data is available

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Printed on acid-free paper.

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Selection from Richard Feynmans letter printed with permission by Melanie Jackson Agency, LLC.

TO MY PARENTS

Dan and Maura Kennefick

CONTENTS

ILLUSTRATIONS

ACKNOWLEDGMENTS

The research that led to this book was the idea of my physics advisor at Caltech, Kip Thorne, who had been involved in some of the controversies discussed in it and saw that it was a story that someone should try to tell. I was fortunate in having an advisor who was so open to the idea that I should combine studies in physics with work in the history of science. I was doubly fortunate in finding a history advisor as able to facilitate my novice efforts in so many ways as Diana Buchwald, now the general editor of the Einstein Papers Project, engaged in editing the Collected Papers of Albert Einstein. After finishing my thesis work, I benefited greatly from a two-year period spent collaborating with Harry Collins, author of Gravitys Shadow, a history of experimental gravity wave physics, at Cardiff University.

Diana made sure I got much excellent advice at an early stage from the first editor of Einsteins papers, John Stachel. Another physicist turned historian, Peter Havas, who like Kip was centrally involved in much of the history I was studying, was initially skeptical that I could objectively tell this story, given my background and training. Yet he never let this prevent him from helping me in every way he could, in person and by correspondence.

I owe a particular debt of gratitude to the many physicists who agreed to be interviewed by me and would like to thank them all. At the end of the book I have provided a table of the interviews and when they took place. They all informed the text considerably, even when they are not quoted directly. Funding to conduct these interviews was provided by the National Science Foundation through a Doctoral Dissertation Improvement Grant.

A number of people kindly read the manuscript and offered much helpful advice, in particular Martin Krieger and Eric Poisson, as well as Tilman Sauer, Michel Janssen, and David Kaiser.

I would like to thank the Albert Einstein Archives at the Hebrew University of Jerusalem for permission to quote from the correspondence of Albert Einstein. The California Institute of Technology has kindly granted me permission to quote from correspondence of Howard Percy Robertson and from a letter of Richard Feynmans in their possession, for which I am also grateful. They have also kindly granted permission for the whole of Robertsons referee report of a paper by Einstein and Nathan Rosen to be reproduced in transcript in . I would also like to thank Michelle Feynman for her kind permission to quote from her fathers correspondence. The mathematician John Tate, Jr, graciously granted permission to quote from his fathers letters, for which I thank him, and also Nathan Rosens sons, Joe and David Rosen, who granted permission to quote from their fathers letters to Einstein.

My wife, Julia Kennefick, also critiqued the manuscript and provided constant encouragement and advice from the earliest days of this research up to the present. Finally I would like to thank my parents, Dan and Maura Kennefick, without whose love and encouragement I would never have properly begun this work and to whom I dedicate this book.

TRAVELING AT THE SPEED OF THOUGHT

The Gravitational Wave Analogy

In the early years of the twenty-first century, several large detectors designed to be the first observatories of gravitational waves went, one by one, into operation. These detectors trace their ancestry to around 1960, when Joseph Weber, an American physicist working at the University of Maryland, first began the experimental effort to detect gravitational waves. Until 1969 the field of gravitational wave detection consisted of Weber and his students, but when he claimed to have detected gravitational waves (Weber 1969), others (some of whom had previously considered working on this subject) began to build their own devices. It proved to be a false dawn. In a highly controversial episode lasting several years, the new detector groups all failed to replicate Webers results with their instruments (Collins 2004). Nevertheless, despite this controversial and turbulent start, most of these groups continued in the field, persisting through decades of hard effort and many different instruments. Today it is widely expected that the first direct detection of gravitational waves will take place within the decade.

As an illustration of how likely the detection of gravitational waves was thought to be in earlier years, one of the most dedicated boosters of the effort, Kip Thorne, had no difficulty in 1981 in finding a taker for a wager that gravitational waves would be detected by the end of the last century. The wager was made with the astronomer Jeremiah Ostriker, one of the better-known critics of the large detectors then being proposed. Thorne was one of the chief movers behind the largest of the new detector projects, the half-billion-dollar Laser Interferometer Gravitational Wave Observatory, or LIGO. He lost the bet, of course. One can see the record of it posted in the west corridor of the Bridge Building at the California Institute of Technology (Caltech), outside Thornes office. It stands beside more than half a dozen other such wagers between Thorne and his colleagues (the most famous of Thornes wagering friends is Stephen Hawking), most of which Thorne has won. On it is written his note of concession, I underestimated the time required to make LIGO a reality. It is actually more remarkable that he and others managed to make LIGO a reality at all, especially when one considers the controversial history of the field, for that controversy was not only on the experimental side. The theory of gravitational waves has an even longer history of disputes, false dawns, and setbacks. At one time or another, many theorists doubted whether such waves existed at all. Albert Einstein himself, who founded the theory of gravitational waves in 1916, numbered himself among the doubters on at least two occasions. How that controversy came to be replaced by the certainty and conviction necessary to motivate the great projects of today is the principal story of this book.