Steven Weinberg - Lake Views: This World and the Universe

LAKE VIEWS

This World and the Universe

STEVEN WEINBERG

The Belknap Press of

Harvard University Press

Cambridge, Massachusetts

London, England

Copyright 2009 by Steven Weinberg

All rights reserved

Jacket art: Marsha Miller

Jacket design: Lisa Roberts

First Belknap Press of Harvard University Press paperback edition, 2011

Library of Congress Cataloging-in-Publication Data

Weinberg, Steven, 1933

Lake views : this world and the universe / Steven Weinberg.

p. cm.

ISBN 978-0-674-03515-7 (cloth : alk. paper)

ISBN 978-0-674-06230-6 (pbk.)

1. Science. I. Title.

Q171.W4194 2009

500dc22 200917607

To Louise, Elizabeth, and Gabrielle

Contents

This book is a collection of essays published in various periodicals and books in the years 2000 to 2008. Its title reflects the fact that these essays, like my research articles, were all written in my study at home, on the shore of Lake Austin, at a desk by a window overlooking the lake.

It isnt really a lake. Like virtually all so-called lakes in Texas, Lake Austin is a segment of a dammed up river, in this case the Texas Colorado. It is twenty miles long and, at my house, less than a quarter of a mile wideso narrow, that the Lower Colorado River Authority requires boats on the lake to keep to the right. Especially in summer, one can see party boats and ski boats going up or down the lake, and hear their engines and their music. So, though most of my work as a physicist is mathematical and impersonal, through my window I am continually reminded, like some lakeside Lady of Shalott, of the human world outside.

The twenty-five essays in this collection are presented here in chronological order. They express my views on topics ranging from problems of cosmology to issues of this worldmilitary, political, and religious. Although many of these topics range far outside the bounds of science, in one way or another they all reflect my experience as a theoretical physicist. Like the essays in my earlier Harvard Press collection, Facing Up, they express a viewpoint that is rationalist, reductionist, realist, and devoutly secular.

Nine of the essays presented here appeared originally in the New York Review of Books. Of the other essays, most were published in periodicals or books intended for the general reader. But a book review and two other articles appeared in a journal, Physics Today, published monthly for physicists by the American Institute of Physics. Physics Today aims to keep the whole physics community up to date on anything related to physics, so its articles avoid the technical language of specialized research articles. Even so, on rereading these articles I saw that in them I had sometimes casually used words that would be generally familiar to physicists, but not to other readers. Where this was the case, I have added explanations of these terms, or found other language.

One other article, Living in the Multiverse, was written for theoretical physicists, and I have deleted the mathematical parts. The remaining essays in this collection are presented here pretty much as they originally appeared, with just a little rewriting where clarification or correction seemed necessary or where I wanted to avoid repeating myself. Where I have had afterthoughts about the topics discussed, I have generally included them as footnotes, labeled Added note. As in Facing Up, I have added a new introduction to each essay, explaining how it came to be written. For some essays I have also added an afterword to bring the subject of the essay up to date.

In a few of these articles I need to refer to numbers that are very large or very small, and for that purpose I use a notation that will probably be familiar to most but perhaps not to all readers, writing these numbers as powers of 10 or 1/10. For instance, 10 is the product of fifty-six tens, or a one followed by fifty-six zeroes, and 10 is the product of thirty-three factors of 1/10, or a decimal point followed by thirty-two zeroes and a one.

I am grateful again to Michael Fisher of Harvard University Press for suggesting the publication of the original collection of my articles, Facing Up, and for his help now in publishing this second collection. Thanks are due to Terry Riley and Jan Duffy for finding many books and articles and old files. I gratefully acknowledge the help of numerous colleagues at the University of Texas who provided information about special topics. For suggestions that I think have greatly improved these articles I owe thanks to many friends and editors, especially Robert Silvers of the New York Review of Books.

The end of the twentieth century prompted magazines and newspapers to indulge in a good deal of guesswork about the future. As part of this prophetic effort, Time magazine asked me to assess how far we yet have to go in understanding the fundamental laws of nature. My answer: pretty far. This brief essay was published by Time in April 2000.

The twentieth century was quite a time for physicists. By the mid-1970s we had in hand the so-called Standard Model, a theory that accurately describes the forces and particles we observe in our laboratories and that provides a basis for understanding virtually everything else in physical science.

No, we dont actually understand everythingthere are many things, from the turbulence of ocean currents to the folding of protein molecules, which cannot be understood without new insights and radical improvements in our methods of calculation. They will provide plenty of interesting continued employment for theorists and experimenters for the foreseeable future. But no new freestanding scientific principles will be needed to understand these phenomena. The Standard Model provides all the fundamental principles we need for this.

There is one force, though, that is not covered by the Standard Model: the force of gravity. Einsteins General Theory of Relativity gives a good account of gravitation at ordinary distances, and if we like, we can tack it onto the Standard Model. But serious mathematical inconsistencies turn up when we try to apply it to particles separated by tiny distancesdistances about 10 million billion times smaller than those probed in the most powerful particle accelerators.

Even apart from its problems in describing gravitation, however, the Standard Model in its present form has too many arbitrary features. Its equations contain too many constants of naturesuch as the masses of the elementary particles and the strength of the fundamental unit of electric chargethat are given specific numerical values for no other reason than that these values seem to work. In writing these equations, physicists simply plugged in whatever values made the predictions of the theory agree with experimental results.

There are reasons to believe that these two problems are really the same problem. That is, we think that when we learn how to make a mathematically consistent theory that governs both gravitation and the forces already described by the Standard Model, all those seemingly arbitrary properties will turn out to be what they are because this is the only way that the theory can be mathematically consistent.

One clue that this should be true is a calculation showing that, although the strengths of the various forces seem very different when measured in our laboratories, they would all be equal if they could be measured at tiny distancesdistances close to those at which the above-mentioned inconsistencies begin to show up.

Theorists have even identified a candidate for a consistent unified theory of gravitation and all the other forces: superstring theory. In some versions, it proposes that what appear to us as particles are stringy loops or lines that exist in a space-time with ten dimensions. But we dont yet understand all the principles of this theory, and even if we did, we would not know how to use the theory to make predictions that we can test in the laboratory.