INVENTING REALITY EALITY “This Book Makes for Smooth Riding Over the Rough Terrain of
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“...a rich account of the dogged and often futile attempt of physicists to talk about nature.” —Alan Lightman Author of Time Travel and Papa Joe’s Pipe: Essays on the Human side of Science INVENTING INVENTING REALITY EALITY “This book makes for smooth riding over the rough terrain of ... PHYSICS AS modern physics... [Gregory] steers the reader unerringly to his provocative conclusion: reality is a function of language...” R —Lynn Margulis LANGUAGE Coauthor of Microcosmos, Five Kingdoms, and Origins of Sex Physicists do not discover the physical world. Rather, they invent a physical world—a story that closely fits the facts they create in ex- perimental apparatus. From the time of Aristotle to the present, In- venting Reality explores science’s attempts to understand the world by inventing new vocabularies and new ways to describe nature. Drawing on the work of such modern physicists as Bohr, Einstein, and Feynman, Inventing Reality explores the relationship between language and the world. Using ingenious metaphors, concrete examples from everyday life, and engaging, nontechnical language, Gregory color- fully illustrates how the language of physics works, and demonstrates the notion that, in the words of Einstein, “physical concepts are free creations of the human mind.” BRUCE GREGORY is an Associate Director of the Harvard- Smithsonian Center for Astrophysics. For over twenty years he has made science intelligible to audiences ranging from junior high school students to Members of Congress. B R U C E G R E G O R Y Back cover Front cover INVENTING INVENTING REALITY REALITY PHYSICS AS LANGUAGE ❅ Bruce Gregory For Werner PREFACE Physics has been so immensely successful that it is difficult to avoid the conviction that what physicists have done over the past 300 years is to slowly draw back the veil that stands between us and the world as it really is—that physics, and every science, is the discovery of a ready-made world. As powerful as this metaphor is, it is useful to Copyright © 1999 Bruce Gregory. All rights reserved. keep in mind that it is a metaphor, and that there are other ways of looking at physics and at science in general. Ways that may prove This book was originally published in 1988 by John Wiley & Sons, Inc. even more illuminating than the “obvious” view. Copyright returned by John Wiley & Sons to the author in 1999. This book tells the story of how physicists invented a language in This reproduction was created by Dag Forssell in May, 2001. order to talk about the world. In this sense, the book is not “about” This pdf-file “printed” on May 31, 2001. physics. Although I hope the reader will discover something about physics, my purpose is not to try to explain the discipline, but to ex- Bruce Gregory has granted permission to freely distribute this book in pdf-file form for personal use only. Not for commercial use or corporate distribution. plore the relationship between language and the world. Physicists use a very precise language, and this precision gives us an opportunity to For printed copies or commercial/corporate use, contact: see more clearly than is otherwise possible just how much of what we Bruce Gregory find in the world is the result of the way we talk about the world. 14 River Road Deep River, CT 06417 USA The physics discussed in this book is sometimes called fundamental physics, but this understandably offends physicists who feel what they are doing is every bit as fundamental. Much of fundamental physics is also called high energy physics or particle physics. Other branches of physics have had a much greater effect on our lives. For example, solid-state physics has had an immense impact as a result of the de- velopment of transistors and integrated circuits. The physics whose history I trace is concerned with understanding the ultimate constitu- ents of matter and the nature of the forces through which these con- stituents interact. It attempts to answer the question, What is the world v INVENTING REALITY PREFACE made of, and how does it work? These are clearly fundamental ques- believe the reader without a strong background in physics more likely tions, if not the only fundamental questions. I chose to focus on this would be confused than enlightened by a discussion of these esoteric branch because I think it has something particularly valuable to tell interpretations. Again the bibliography points to works that develop us about the general quest to understand the “furniture of the uni- these ideas in greater detail. verse”—the stuff we think of as real—and the role that language plays I owe my recognition of the way language commits us to what is in creating and supporting this conviction. real to the writings of W.V.O. Quine. My appreciation of the implica- I use the word language throughout the book, and it is helpful to tions of pragmatism was greatly enriched and deepened by the writ- know what I mean by it. I call any symbolic system for dealing with ings of Richard Rorty. the world a language. The language of physics is mathematics, and I It is a pleasure to acknowledge the people who made this book refer to particular domains of mathematics as the language of classi- possible. I benefited enormously from many conversations through- cal physics or the language of quantum mechanics. I also refer to the out the years with Bob and Holly Doyle that shaped and sharpened vocabulary of Newtonian physics, where I mean the Newtonian ap- my understanding of the issues raised in the book. Barbara Clark, proach to dealing with physical situations in terms of forces and Steve and Susan Gross, Linda Houck, James Jones and Gail Hughes, changing position with time. I take this approach to make it clear Ken and Linda Schatz, and Susan Thomas provided continuing sup- that physics is a language, a way of talking about the world. As to port and encouragement. In addition, the Schatzes introduced me to what else we can say about physics, this is something the book sets my agent, Michael Snell, who besides placing the book gave me tren- out to explore. chant advice on how to write clearly and effectively. The story I tell resembles physics itself in that it ruthlessly pares Myron Lecar read an early version of the manuscript, and Holly away the sort of detail historians rightly consider essential in under- Doyle, Don Lautman, Lynn Margulis, Matthew Schneps, Edward Tripp, standing a place and time. The obligatory details and caveats of a and Angela von der Lippe read later versions; they provided helpful truly historical exploration would obscure the story I want to tell. I suggestions and badly needed encouragement. Owen Gingerich, have tried to be historically accurate, but I have only touched on the Lawrence Krauss, and Alan Lightman read parts of later versions, point- high points, and the reader who wishes to savor the richness of the ing out ambiguities and mistakes and providing helpful guidance. I history is referred to works recommended in the bibliography at the also benefited greatly from the remarks of several anonymous readers. end of the book. I have also pared away a great deal of physics in the Suggestions and queries from my editor David Sobel resulted in a much effort to make what is central to my discussion more intelligible; more intelligible book than I would have otherwise written. The book more detailed discussions of the science are recommended in the would have been much less accurate and far more obscure were it not bibliography. for several careful readings of the manuscript by Irwin Shapiro. Any The reader is also entitled to know where the demarcation lies be- incoherencies or muddles that remain do so despite his admonitions. I tween what is broadly accepted by the community of physicists and deeply appreciate the time he gave to the project despite his unreason- the views that may be mine alone. By and large, the story as it is de- ably busy schedule. I am grateful to Marian Shapiro for providing the veloped here is not controversial. For example, the interpretation of impetus to seek a publisher for the book. quantum mechanics given here follows the lines laid down by the My wife, the poet Gray Jacobik, provided constant support, encour- orthodox or “Copenhagen” interpretation accepted by the great ma- agement, and unfailingly perspicacious editorial advice. Her keen un- jority of physicists. There are other ways of understanding quantum derstanding of the ways in which language works was indispensable mechanics, but in each case they are held by an extremely small, and to developing the approach I take in this book. I owe more to her than in some cases dwindling, minority. They are fun to think about, but I I can possibly express. I owe my appreciation of the immense power vi vii of the myth of “is” to Werner Erhard’s relentless commitment to mak- ing a difference in my life. Absent his unremitting efforts to uncover the role of speaking in shaping experience, this book never would have been written. CONTENTS Preface v Prologue 1 1 In the Beginning Was the Word 5 2 The Invaluable Concept of Force 19 3 The Indispensable Idea of Fields 35 4 The Ingenious Notion of Atoms 49 5 The Unimaginable Unity of Spacetime 59 6 The Imponderable Nature of Matter 71 7 The Intransigent Presence of Paradox 89 8 The Inexhaustible Fecundity of Space 101 9 The Improbable Prevalence of Symmetry 119 10 W, Z Fields 135 11 The Ineffable Color of Quarks 143 12 The Unquestionable Imagination of Physicists 157 13 The Inscrutable Essence of Mathematics 169 14 The Unspeakable Power of Language 179 15 The Last Word 193 Epilogue 201 Appendix A: Is There a Fact in the Matter? 203 Appendix B: Schroedinger’s Cat, the Problem of Measurement, and Language Domains 209 Notes 213 Bibliography 221 Index 225 viii ix To him who is a discoverer in this field, the products of his imagination appear so necessary and natural that he PROLOGUE regards them, and would like to have them regarded by others, not as creations of thought but as given realities.