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Page i The Bit and the Pendulum From Quantum Computing to M Theory—The New Physics of Information Tom Siegfried Page ii This book is printed on acid-free paper. Copyright © 2000 by Tom Siegfried. All rights reserved Published by John Wiley & Sons, Inc. Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4744. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850- 6008, email: . [email protected] This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold with the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional person should be sought. Library of Congress Cataloging-in-Publication Data: Siegfried, Tom. The bit and the pendulum : from quantum computing to m theory— the new physics of information / Tom Siegfried. p. cm. Includes index. ISBN 0-471-32174-5 (alk. paper) 1. Computer science. 2. Physics. 3. Information technology. I. Title. QA76.S5159 1999 004—dc21 99-22275 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Page iii Contents Preface vii Introduction 1 1 13 Beam Up the Goulash 2 37 Machines and Metaphors 3 57 Information Is Physical 4 77 The Quantum and the Computer 5 95 The Computational Cell 6 115 The Computational Brain 7 133 Consciousness and Complexity 8 155 IGUSes 9 177 Quantum Reality 10 195 From Black Holes to Supermatter 11 213 The Magical Mystery Theory 12 235 The Bit and the Pendulum Notes 249 Glossary 264 Further Reading 268 Index 275 Page v Preface In the course of my job, I talk to some of the smartest people in the universe about how the universe works. These days more and more of those people think the universe works like a computer. At the foundations of both biological and physical science, specialists today are construing their research in terms of information and information processing. As science editor of the Dallas Morning News, I travel to various scientific meetings and research institutions to explore the frontiers of discovery. At those frontiers, I have found, information is everywhere. Inspired by the computer as both tool and metaphor, today's scientists are exploring a new path toward understanding life, physics, and existence. The path leads throughout all of nature, from the interior of cells to inside black holes. Always the signs are the same: the world is made of information. A few years ago, I was invited to give a talk to a regional meeting of MENSA, the high-IQ society. I decided to explore this theme, comparing it to similar themes that had guided the scientific enterprise in the past. For it seemed to me that the role of the computer in twentieth-century science was much like that of the steam engine in the nineteenth century and the clock in medieval times. All three machines were essential social tools, defining their eras; all three inspired metaphorical conceptions of the universe that proved fruitful in explaining many things about the natural world. Out of that talk grew this book. It's my effort to put many pieces of current science together in a picture that will make some sense, and impart some appreciation, to anyone who is interested. Specialists in the fields I discuss will note that my approach is to cut thin slices through thick bodies of research. No doubt any single chapter in this book could easily have been expanded into a book of Page vi its own. As they stand, the chapters that follow are meant not to be comprehensive surveys of any research area, but merely to provide a flavor of what scientists at the frontiers are up to, in areas where information has become an important aspect of science. Occasional passages in this book first appeared in somewhat different form in articles and columns I've written over the years for the Dallas Morning News. But most of the information story would never fit in a newspaper. I've tried to bring to life here some of the subtleties and nuances of real-time science that never make it into the news, without bogging down in technicalities. To the extent I've succeeded in communicating the ideas that follow, I owe gratitude to numerous people. Many of the thoughts in this book have been shaped over the years through conversations with my longtime friend Larry Bouchard of the University of Virginia. I've also benefited greatly from the encouragement, advice, and insightful questions over dinner from many friends and colleagues, including Marcia Barinaga, Deborah Blum, K. C. Cole, Sharon Dunwoody, Susan Gaidos, Janet Raloff, JoAnn Rodgers, Carol Rogers, Nancy Ross-Flanigan, Diana Steele, and Jane Stevens. I must also express deep appreciation for my science journalist colleagues at the Dallas Morning News: Laura Beil, Sue Goetinck, Karen Patterson, and Alexandra Witze, as well as former News colleagues Matt Crenson, Ruth Flanagan, Katy Human, and Rosie Mestel. Thanks also go to Emily Loose, my editor at Wiley; my agent, Skip Barker; and of course my wife, Chris (my harshest and therefore most valuable critic). There are in addition countless scientists who have been immensely helpful to me over the years, too many to attempt to list here. Most of them show up in the pages that follow. But I sadly must mention that the most helpful scientist of all, Rolf Landauer of IBM, did not live to see this book. He died in April 1999, shortly after the manuscript was completed. Landauer was an extraordinary thinker and extraordinary person, and without his influence and inspiration I doubt that this book would have been written. TOM SIEGFRIED MAY 1999 Page 1 Introduction I think of my lifetime in physics as divided into three periods. In the first period . . . I was in the grip of the idea that Everything is Particles. . . . I call my second period Everything is Fields. . . . Now I am in the grip of a new vision, that Everything is Information. —John Archibald Wheeler, Geons, Black Holes, and Quantum Foam John Wheeler likes to flip coins. That's not what he's famous for, of course. Wheeler is better known as the man who named black holes, the cosmic bottomless pits that swallow everything they encounter. He also helped explain nuclear fission and is a leading expert on both quantum physics and Einstein's theory of relativity. Among physicists he is esteemed as one of the greatest teachers of the century, his students including Nobel laureate Richard Feynman and dozens of other prominent contributors to modern science. One of Wheeler's teaching techniques is coin tossing. I remember the class, more than two decades ago now, in which he told all the students to flip a penny 50 times and record how many times it came up heads. He taught about statistics that way, demonstrating how, on average, heads came up half the time, even though any one run of 50 flips was likely to turn up more heads than tails, or fewer.* *Wheeler taught a class for nonscience majors (I was a journalism graduate student at the time) at the University of Texas at Austin. In his lecture of January 24, 1978, he remarked that a good rule of thumb for estimating statistical fluctuations is to take the square root of the number of events in question. In tossing 50 coins, the expected number of heads would be 25; the square root of 25 (footnote continued on next page) Page 2 Several years later, Wheeler was flipping coins again, this time to help an artist draw a picture of a black hole. Never mind that black holes are invisible, entrapping light along with anything else in their vicinity. Wheeler wanted a special kind of picture. He wanted it to illustrate a new idea about the nature of information. As it turns out, flipping a coin offers just about the simplest possible picture of what information is all about. A coin can turn up either heads or tails. Two possibilities, equally likely. When you catch the coin and remove the covering hand, you find out which of the two possibilities it is. In the language that computers use to keep track of information, you have acquired a single bit. A bit doesn't have to involve coins. A bit can be represented by a lightbulb—on or off. By an arrow, pointing up or down. By a ball, spinning clockwise or counterclockwise. Any choice from two equally likely possibilities is a bit. Computers don't care where a bit comes from—they translate them all into one of two numbers, 0 or 1. Wheeler's picture of a black hole is covered with boxes, each containing either a zero or a one. The artist filled in the boxes with the numerals as a student tossed a coin and called out one for heads or zero for tails. The resulting picture, Wheeler says, illustrates the idea that black holes swallow not only matter and energy, but information as well. The information doesn't have to be in the form of coins. It can be patterns of ink on paper or even magnetic particles on a floppy disk. Matter organized or structured in any way contains information about how its parts are put together. All that information is scrambled in a black hole's interior, though—incarcerated forever, with no possibility of parole. As the cosmologist Rocky Kolb describes the situation, black holes are like the Roach Motel. Information checks in, but it doesn't check out. If you drop a coin into a black hole, you'll never know whether it lands heads or tails. But Wheeler observes that the black hole keeps a record of the information it engulfs. The more information swallowed, the bigger (footnote continued from previous page) is 5, so in tossing 50 coins several times you would expect the number of heads to vary between 20 and 30. The 23 of us in the class then flipped our pennies. The low number of heads was 21, the high was 30. Average for the 23 runs was 25.4 heads. Page 3 the black hole is—and thus the more space on the black hole's surface to accommodate boxes depicting bits. To Wheeler, this realization is curious and profound. A black hole can consume anything that exists and still be described in terms of how much information it has digested. In other words, the black hole converts all sorts of real things into information. Somehow, Wheeler concludes, information has some connection to existence, a view he advertises with the slogan "It from Bit." It's not easy to grasp Wheeler's idea of connecting information to existence. He seems to be saying that information and reality have some sort of mutual relationship. On the one hand, information is real, not merely an abstract idea. On the other hand reality—or existence—can somehow be described, or quantified, in terms of information. Understanding this connection further requires a journey beyond the black hole (or perhaps deep inside it) to glimpse the strange world of quantum physics. In fact, Wheeler's black hole picture grew from his desire to understand not only information, but also the mysteries of the subatomic world that quantum physics describes. It's a description encoded in the elaborate mathematical rules known as quantum mechanics. Quantum mechanics is like the U.S. Constitution. Just as the laws of the land must not run afoul of constitutional provisions, the laws of nature must conform to the framework established by quantum mechanics' equations. And just as the U.S. Constitution installed a radically new form of government into the world, quantum requirements depart radically from the standard rules of classical physics. Atoms and their parts do not obey the mechanics devised by Newton; rather, the quantum microworld lives by a counterintuitive code, allowing phenomena stranger than anything Alice encountered in Wonderland. Take electrons, for example—the tiny, negatively charged particles that swarm around the outer regions of all atoms. In the world of large objects that we all know, and think we understand, particles have well- defined positions. But in the subatomic world, particles behave strangely. Electrons seem to be in many different places at once. Or perhaps it would be more accurate to say that an electron isn't anyplace at once. It's kind of smeared out in a twilight zone of possi- Page 4 bilities. Only a measurement of some sort, an observation, creates a specific, real location for an electron out of its many possible locations. Particles like that can do strange things. Throw a baseball at a wall, and it bounces off. If you shoot an electron at a wall, it might bounce off, but it also might just show up on the other side of the wall. It seems like magic, but if electrons couldn't do that, transistors wouldn't work. The entire consumer electronics industry depends on such quantum weirdness. Wall-hopping (the technical term is tunneling) is just one of many quantum curiosities. Another of the well-known quantum paradoxes is the fact that electrons (and other particles as well) behave sometimes as particles, sometimes as waves. (And light, generally thought of as traveling in waves, sometimes seems to be a stream of particles instead.) But light or electrons are emphatically not both particles and waves at the same time. Nor are they some mysterious hybrid combining wave and particle features. They simply act like waves some of the time and like particles some of the time, depending on the sort of experiment that is set up to look at them. It gets even more bizarre. Quantum mechanics shows no respect for common notions of time and space. For example, a measurement on an electron in Dallas could in theory affect the outcome of an experiment in Denver. And an experimenter can determine whether an electron is a wave or particle when it enters a maze of mirrors by changing the arrangement of the mirrors—even if the change is made after the electron has already passed through the maze entrance. In other words, the choice of an observer at one location can affect reality at great distances, or even (in a loose sense) in the past. And so the argument goes that observers, by acquiring information, are somehow involved in bringing reality into existence.