Table Of Content

R L R H H. G U T H THE IHf lRTIOHRRY UNIVERSE T H E QU E S T F O R A NEW THEORY OF COSMIC ORIGINS WITH A FOREWORD BY ALAN LIGHTMAN ~+ - c . Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book and Addison-Wesley was aware of a trademark claim, the designations have been printed in initial capital letters. Library of Congress Cataloging-in-Publication Data Guth, Alan H. The inflationary universe : the quest for a new theory of cosmic origins / Alan H. Guth. p. cm. Includes bibliographical references and index. ISBN 0-201-14942-7 (hardcover) ISBN 0-201-32840-2 (paperback) 1. Inflationary universe. l. Title. QB991.I54G88 1997 96-46117 523 .1 '8-dc2 l CIP Copyright © 1997 by Alan H. Guth Foreword copyright © 1997 by Alan Lightman Al! 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 written permission of the publisher. Printed in the United States of America. Addison-Wesley is an imprint of Addison-Wesley Longman, Inc. Cover design by Suzanne Heiser Text design by Jean Hammond Set in 10-point Sabon by Argosy 1 2 3 4 5 6 7 8 9-MA-0201009998 First printing, March 1997 First paperback printing, February 1998 Find Helix Books on the World Wide Web at http://www.aw.com/gb/ To my family CONTENTS Foreword ix Preface xiii The Ultimate Free Lunch 1 2 The Cosmic Vista from Ithaca, New York 17 3 The Birth of Modern Cosmology 33 4 Echoes of a Scorching Past 57 5 Condensation of the Primordial Soup 85 6 Matters of Matter and Antimatter 105 7 The Particle Physics Revolution of the 1970s 115 8 Grand U nified Theories 131 g Combatting the Magnetic Monopole Menace 14 7 1 O The Inflationary Universe 167 11 The Aftermath of Discovery 189 1 2 The New Inflationary Universe 201 1 3 Wrinkles on a Smooth Background 213 v111 e o N T E N T s 1 4 Observational Clues from Deep Below and Far Beyond 237 1 5 The Eternally Existing, Self-Reproducing Inflationary Universe 245 1 6 Wormholes and the Creation of Universes in the Laboratory 25 3 1 7 A Universe Ex Nihilo 2 71 Epilogue 2 77 A P P ¡ HO 1 H A Gravitational Energy 289 A P P ¡ HO 1 H B Newton and the Infinite Static Universe 295 A P P ¡ HO 1 H [ Blackbody Radiation 299 A P P ¡ HO 1 H O Units and Measures 305 Notes 311 Glossary 325 Credits 345 Index 347 FOREWORD very culture has had its cosmology, its story of how the universe carne Ei nto being, what it is made of, and where it is going. Astoundingly, cosmology in this century has become a science, a well-defined area of research within astronomy and physics. In the 1970s, the study of cosmology went through a majar conceptual change. Prior to this time, modern cosmologists asked such questions as: What is the composition of galaxies and where are they located in space? How rapidly is the universe expanding? What is the average density of matter in the cosmos? After this time, in the "new cosmology," cosmologists began seriously asking questions like: Why does matter exist at all, and where did it come from? Why is the universe as homogeneous as it is over such vast distances? Why is the cosmic density of matter such that the energy of expansion of the universe is almost exactly balanced by its energy of gravitational attraction? In other words, the nature of the questions changed. The questions became more fundamental. "Why?" was added to "What?" and "How?" and "Where?". Alan Guth was one of the young pio- neers of the new cosmology, asking the Whys, and his Inflationary Universe theory provided many answers. Sorne of the why questions had been asked earlier but not pursued with great stamina, mainly because there seemed no hope of answers, no explanatory theories had been proposed. The standard Big Bang theory, in hand since the work of Einstein and Friedmann and Lemaitre in the 1920s, offered no explanations. As a result, working cosmologists simply assumed as givens sorne of the most interesting observed features of the universe, such as its homogeneity and its very precise balance of energies. Indeed, x FOREWORD before the 1970s and early 1980s, many cosmologists took the attitude that sorne of these features of the universe had to be accepted as "initial condi- tions," present at the beginning, perhaps mere accidents, perhaps incalcula- ble even in principie. In any case, these features, observed but unexplained, were not taken as serious shortcomings of the standard big bang theory. The benign neglect of certain observed facts, or anomalies, that cannot be explained within the reigning theory is not uncommon in science. For example, prior to the work of Alfred Wegner in 1912 and his theory of "continental drift, " the conceptual framework in which geologists worked held that landmasses could move only vertically. In this picture there was no explanation of the observed remarkable similarity of shapes of the opposite coasts on the two sides of the Atlantic. South America and Africa, in particular, are shaped as if they were two fitting pieces of a jigsaw puzzle. Geolo- gists commented on this peculiar feature of geography but mainly accepted it as a curiosity, scarcely a puzzle waiting for a solution. After Wegner proposed his new theory, which offered a natural mechanism for how the continents could have drifted horizontally apart after once being joined in a single landmass, the fit of the continents was recognized as a major problem in the old theory. Another example comes from biology, namely the lack of adaptation of certain organisms to their environments. There are ducks with feet designed for swimming that do not swim; there are animals, like the dark-cave rat Neotoma, that have eyes but never use them; there are birds, like the pen- guin, that have wings but never fly. Before Darwin's theory of natural selection, these anomalous facts were observed but swept under the rug in the prevailing creationist framework , which held that each species is exquisitely designed for its habitat and never changes. However, nonadaptation as well as adaptation is explained in Darwin's theory because natural selection requires evolution and change. An organism that has adapted to a particular environment may change environments but still pass clown the previously adapted trait, such as a long line of rats that move from the daylight to a dark cave. After Darwin's work, the nonadaptation of some animals was seen as a major flaw in the creation theory. Such is the conservative nature and the psychological forces of the scientific enterprise. Similarly, the observed homogeneity of the universe and the precise balance of its energies were considered by most of the scientific community to represent serious deficiencies in the standard Big Bang model only after the Inflationary Universe theory was proposed. The conception of that new theory was made possible by a new stock of ideas from theoretical physicists who, in the past, had concerned themselves with the fundamental particles and forces of nature. In the early 1970s, new theories of particle physics called Grand Unified Theories proposed that three of the four fundamental FO RE wo RO XI forces of nature-the strong and weak nuclear forces and the electromag- netic force-were actually manifestations of a single, underlying force. (Uni- fication and simplicity have been the eternal Holy Grail of physicists and artists. Aristotle wanted to reduce ali substance to five elements; Picasso said that a painter should work with as few elements as possible.) According to the new theories, the temperature at which the single force would become 29 evident was an incredible 10 degrees centigrade, far higher than any temperature that existed on earth or even at the centers of stars. Such a fantasti- cally high temperature could have existed at only one place, or more precisely at one time: in the very young universe, shortly after its big bang beginning. Thus the particle physicists became interested in cosmology. One of the most well known and accomplished particle physicists to combine Grand Unified Theories with cosmology at this time was Steven Weinberg. One of the younger scientists was Alan Guth. Guth's great achievement was the proposal that, as a natural conse- quence of the properties of the Grand Unified Theories, the very young universe would have gone through a brief period of extremely rapid expansion, after which it would return to the more leisurely rate of growth dictated by the standard Big Bang theory. Guth's proposed modification of the older theory has been called the Inflationary Universe theory. That theory, and its various improved versions, provide explanations for sorne of the previously unexplained "anomalies" observed by cosmologists. In my view, the Infla- tionary Universe theory is the most significant new development in cosmological thinking since the foundational work in the 1920s. Because the key phenomenon of the Inflationary Universe theory, the extremely rapid cosmic expansion, purportedly happened so long ago, we will probably never know with certainty whether that event in fact occurred. (The theory also makes sorne precise predictions about the universe toda y but cannot be proven true on the basis of these predictions.) However, like the notion that the continents were once joined in a single landmass, the "infla- tion" idea has such explanatory power that it has become an underlying assumption of many working cosmologists today. Thus, an intellectual revolution has occurred in cosmological thinking. In the language of the late MIT historian of science Thomas Kuhn, we have a new paradigm in cosmology. This book that Alan Guth has written is extraordinary for severa] rea- sons. lt explains complex scientific ideas without the use of equations. lt is written with the same clarity and elegance as Guth's original, pathbreaking scientific paper in the Physical Review of 1981. lt is thorough and thought- ful. lt gives an honest portrait of a personal career in science, as well as the human and scientific history of a major discovery. But what is most extraordinary is that this book, like James Watson's Double Helix, is unique in its field. It has been written by a key scientist involved with the discovery. Xll FO RE wo RO Although other physicists played various roles in the discovery and development of the Inflationary Universe theory, Alan Guth is internationally recognized as the leading actor. Other popular books may be written (and have been written) about the subject, but only one book can be written by Alan Guth. This is the book. Alan Lightman Cambridge, Massachusetts May 1997