The Accelerating Universe , livre ebook

The Accelerating Universe
Infinite Expansion, the Cosmological Constant, and the Beauty of the Cosmos
Mario Livio
 

John Wiley & Sons, Inc.
NewYork • Chichester • Weinheim • Brisbane • Singapore • Toronto
 
To Sharon, Oren, and Maya, who I hope will find beauty in their own lives
 
Copyright © 2000 by Mario Livio. All rights reserved
Illustrations copyright © 2000 by Jackie Aher
Published by John Wiley & Sons, Inc.
Published simultaneously in Canada
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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 (cloth: alk. paper)
ISBN 0-471-39976-0 (paper)
1. Cosmology. I. Title.
QB981.L57 1999
                              523.1—dc21           99-22278
Contents
Foreword
Preface
1
Prologue
2
Beauty and the Beast
3
Expansion
4
The Case of the Missing Matter
5
Flat Is Beautiful
6
When Inflation Is Good
7
Creation
8
The Meaning of Life
9
A Universe Custom Made for Us?
10
A Cosmological Aesthetic Principle?
Index
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 using the cosmological discoveries made in astronomy and physics. But it is also about much more. It concerns the philosophy of science, of how one judges if a theory is fundamental and likely to last, about truth, about the definition of beauty, and about the connection 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 synthesis that would ring true, each to his or her own tradition, yet also true to the other’s quite different creative style? Now imagine 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 published that had a profound influence on the very young (and not so young), many of whom prepared themselves for a scientific life because 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 contains “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 Physical World (1931), Science and the Unseen World (1929), The Expanding Universe (1933), and again a favorite of mine. Space, Time, and Gravitation (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 explore 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” theories 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 throughout the book. He first defines what he means by beauty. He then shows that so much of the modern standard model of cosmology conforms to his stated definition. In the process he describes almost 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 reductionist scientists would likely be put off by such an attempt. We scientists 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 concern 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 throughout 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 often 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 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) ; otherwise its predictions will not be invariant to the two simplest transformations 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 transformations).
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, described in the penultimate chapter as the Nancy Kerrigan question, whose solution can be given in terms of “quintessence,” which in fact provides an adherence to the postulated cosmological aesthetic 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 cosmology 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 (o