B u s i n e s s C u l i n a r y A r c h i t e c t u r e C o m p u t e r G e n e r a l I n t e r e s t C h i l d r e n L i f e S c i e n c e s B i o g r a p h y A c c o u n t i n g F i n a n c e M a t h e m a t i c s H i s t o r y S e l f - I m p r o v e m e n t H e a l t h E n g i n e e r i n g G r a p h i c D e s i g n A p p l i e d S c i e n c e s P s y c h o l o g y I n t e r i o r D e s i g n B i o l o g y C h e m i s t r y e WILEY B O O K WILEY JOSSEY-BASS PFEIFFER J.K.LASSER CAPSTONE WILEY-LISS WILEY-VCH WILEY-INTERSCIENCE T h e A c c e l e r a t i n g U n i v e r s e Infinite Expansion, the Cosmological Constant, and the Beauty of the Cosmos Mario Livio John Wiley & Sons, Inc. New York • Chichester • Weinheim • Brisbane • Singapore • Toronto To Sharon, Oren, and Maya, who I hope will find beauty in their own lives This book is printed on acid-free paper. Copyright © 2000 by Mario Livio. All rights reserved Published by John Wiley & Sons, Inc. Published simultaneously in Canada Illustrations by Jackie Aher No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photo- copying, recording, scanning, or otherwise, except as permitted under Sec- tion 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through pay- ment 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, e-mail: [email protected]. This publication is designed to provide accurate and authoritative informa- tion in regard to the subject matter covered. It is sold with the understand- ing 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 Livio, Mario The accelerating universe: infinite expansion, the cosmological constant, and the beauty of the cosmos / Mario Livio. p. cm. Includes index. ISBN 0-471-32969-X (alk. paper) 1. Cosmology. I. Title. QB981.L57 1999 523.1—dc21 99-22278 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Contents Foreword v Preface xiii 1 Prologue 1 2 Beauty and the Beast 14 3 Expansion 43 4 The Case of the Missing Matter 82 5 Flat Is Beautiful 105 6 When Inflation Is Good 139 7 Creation 171 iii Contents 8 The Meaning of Life 196 9 A Universe Custom Made for Us? 237 10 A Cosmological Aesthetic Principle? 254 Index 266 iv Foreword When the history of ideas is written four hundred years from now, the twentieth century will be known as the dawn of the great scientific idea of the origin of a changing universe that is still evolving. It recycles hydrogen and helium through the stars in its galaxies and manufactures there- from the heavier chemical elements that somehow can organize themselves into complex structures that contemplate themselves. Self-contemplation is but one of many miraculous things that the natural chemical elements do over the age of the universe. These ideas of origins and evolution have become part of scientific literacy of our age. The major ideas of this twentieth- century synthesis center around the understanding of the laws of physics, the life history of the stars, and the consequences of that history for mankind in an expanding universe. This book is about how such grand ideas have come about us- ing the cosmological discoveries made in astronomy and physics. But it is also about much more. It concerns the philosophy of sci- ence, of how one judges if a theory is fundamental and likely to last, about truth, about the definition of beauty, and about the connec- tion of science to art, literature, music, and the human endeavor. Imagine two authors, one an art and literature fanatic, and the other a theoretical physicist who is heavily involved in cosmology. Imagine a decision to write a book jointly that would attempt to bridge the two cultures. Could the two such authors make a syn- thesis that would ring true, each to his or her own tradition, yet also true to the other’s quite different creative style? Now imagine v Foreword that the two authors are not two, but are the same person. What you are about to read is that synthesis. Its author is that art fanatic and theoretical physicist. What could such a book be like? Near the middle third of the just-past century, a series of highly influential, semipopular, yet scientifically astute books were pub- lished that had a profound influence on the very young (and not so young), many of whom prepared themselves for a scientific life be- cause of them. Such books, especially by Sir James Jeans and Sir Arthur Eddington, were important for astronomy. Perhaps the most popular was The Mysterious Universe(1930) by Jeans, which Tallulah Bankhead, the American actress of multiple reputations, said con- tains “what every girl should know.” Other books of the same sort were The Stars in Their Courses(1931), Through Space and Time(1933), and the favorite of this writer, Physics and Philosophy (1943), all by Jeans. Similar central books by Eddington were The Nature of the Phys- ical World(1931), Science and the Unseen World(1929), The Expanding Universe(1933), and again a favorite of mine, Space, Time, and Gravi- tation (1920), which opened up general relativity and Riemannian manifolds to the layman. More recently, the books by Fred Hoyle such as The Nature of the Universe(1950), Frontiers of Astronomy(1955), and Highlights of Astronomy(1975) had the same merit. This book by Mario Livio is of that type. Not only is it a book on the new astronomy and cosmology, but it also is a book on the “old” philosophy—of art, and of culture. Livio’s deep purpose is to ex- plore the meaning of beauty in science, using the developments in twentieth-century cosmology as the subject with which to discuss a concept of beauty in general and beauty in science in particular. The author’s premise is that “beauty” is an essential ingredient in all truly successful theories in science, and especially “true” theo- ries of the nature of the universe. The aim of the book is to discuss whether the laws of physics are actually determined by aesthetic principles. Livio believes they are, and makes a compelling case through- out the book. He first defines what he means by beauty. He then vi Foreword shows that so much of the modern standard model of cosmology conforms to his stated definition. In the process he describes al- most every aspect of both the old and the new cosmology. This is the heart of the book, both for the young would-be scientist and for the fascinated layman. In the process he shows what beauty means in art, describing many paintings by many artists to illustrate both the beauty and the philosophy of human artistic endeavor. Said only this way, most hard-bench, experimental reduction- ist scientists would likely be put off by such an attempt. We scien- tists have generally been trained to regard art, literature, poetry, and anything else to do with the “humanities” as subjective and therefore not amenable to assessment by the scientific method. On the other hand, science, and especially physics and astronomy, is widely thought to refer to nature independently of subjective thought, feeling, and categories made by the mind. Beauty often is also placed outside that regime. This book is a revelation on how, and at what price (if any), this notion of objectivity with no con- cern for beauty is incompatible with modern science, especially in cosmology. In chapter 2, the author defines beauty as he will use it throughout the book. Although he agrees with the often-quoted definition by many that “beauty symbolizes a degree of perfection with respect to some ideal,” yet this definition is too diffuse and oversimplified to be of use. He also rejects the misquoted (out of context) definition by Keats that “beauty is truth, truth beauty,” and states that beauty defined by the poets is often a dangerous thing, as Paris found by his association with Helen. Livio does insist, as do many of the greatest scientists through- out history, that the laws of physics are exquisitely beautiful. Before defining beauty, he convinces us that in physics, the explanations of what once were mysteries but which now are “understood” is of- ten ineffably more beautiful than the questions, and that “beauty in physics and cosmology is not an oxymoron.” To proceed in a way that is precise enough so that in later chapters he can combine the vii Foreword concept of beauty with the most esoteric and profound elements of modern cosmology, Livio sets out his definition of beauty in this early, introductory chapter. Three requirements must be fulfilled if a theory is to be judged beautiful: 1. It must describe a symmetry (or a series of symmetries); other- wise its predictions will not be invariant to the two simplest trans- formations as to place (i.e., space) or time (it makes no difference if I do an experiment now or next week), or at a much deeper level by circumstances in the equations (i.e., such as coordinate trans- formations). 2. It must have simplicity in the sense of reductionism (i.e., many questions can be replaced by very few more basic questions that can be solved as puzzles and not be left as mysteries). 3. A theory must obey a generalized Copernican principle, by which is meant that we, or the circumstances, are nothing special, in time, space, or category. This last is probably the deepest requirement, and has the most profound implication for the ultimate cosmological mystery, de- scribed in the penultimate chapter as the Nancy Kerrigan ques- tion, whose solution can be given in terms of “quintessence,” which in fact provides an adherence to the postulated cosmological aes- thetic principle. This, and the final chapter, provide the climax to the full story of cosmology that has been set out in chapters 3 through 8. These six chapters contain the description of much of cos- mology of the twentieth century. The discovery of the expansion in 1929 is in chapter 3, with its implications for the hot big bang origin and the resulting prediction and subsequent discovery of the relic radiation and the formation of the earliest elements out of the gluon glue (once called the yelm), predictions made already viii Foreword in 1945 by George Gamow, Ralph Alpher, and Robert Herman. Here, the more modern ideas that combine the high-energy par- ticle physics of the 1980s with its Higgs fields and the grand unifi- cation theories of the four forces are made easy by the many sur- prising analogies from art, literature, and underground cultural jokes combined with the straightforward style of the author. The book itself has charm as well as beauty. Chapter 4 combines the problem of the missing mass with the question of the fate of the universe via the omega parameter. The method of inferences from indirect data is illustrated with the ex- amples of studies of the authenticity of Rembrandt paintings and the deductions by Sherlock Holmes on the alcoholism and mari- tal neglect of a client, and the discovery of the omega minus par- ticle (no relation to the omega density parameter) independently by Yuval Ne’eman after its prediction by Murray Gell-Mann. All this is tied up with beauty in the simplicity of the deductions as they ultimately relate to the fate of the expansion. The richness of the narrative and the fun of the author is kept throughout the book as it lays out even the most complicated of the cosmological problems. The prime example is in chapters 5 and 6 where non-Euclidean geometry, curved space as the mani- festation of gravity, and inflation via the behavior of the inflaton fields following the Planck time are all explained better than in any other semipopular book on this most profound of the cosmologi- cal subjects. These ideas are at the heart of the question of origins and the “cause” of the expansion, as well as the explanation of the dominance of matter over antimatter. Chapters 5, 6, and 7 are titled “Flat Is Beautiful,” “When Infla- tion Is Good,” and “Creation.” These contain the essence of mod- ern quantum cosmology as a theory of the origin, evolution, and fate of the universe (or many universes in the variant called “eter- nal inflation,” as invented by Alex Vilenkin and Andrei Linde). Here the author is most persuasive and powerful in attempting to ix