The Great Design: Particles, Fields, and Creation

385 Pages·1989·21.81 MB·English

by  Robert K. Adair

THE GREAT DESIGN
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The
Great
Design
Particles, Fields,
and Creation
ROBERT K. ADAIR
OXFORD UNIVERSITY PRESS
New York • Oxford
Oxford University Press
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and associated companies in
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Copyright © 1987 by Oxford University Press, Inc.
First published in 1987 by Oxford University Press, Inc.,
198 Madison Avenue, New York, New York 10016-4314
First issued as an Oxford University Press paperback, 1989
Oxford is a registered trademark of Oxford University Press
All 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 permission of Oxford University Press, Inc.
Library of Congress Cataloging-in-Publication Data
Adair, Robert Kemp.
The great design.
Includes index.
1. Physics. 2. Particles (Nuclear physics)
3. Field theory (Physics) I. Title.
QC21.2.A28 1987 539 87-5729
ISBN 0-19-504380-4
ISBN 0-19-506069-5 (PBK.)
To the memory of my father
Robert Cleland Adair
from whom I learned about science
and to the memory of my mother
Margaret Wiegman Adair
who taught me to care for the humanities
10 9 8 7 6 5
Printed in the United States of America
Preface
About 60 B.C. one of the world's great poets, Titus Lucretius Carus, wrote a
long poem in Latin hexameters preaching the Epicurian gospel of salvation
through common sense. The atomic model of Demokritos and Leukippos,
proposed five centuries before, provided the bases of the description of the
universe attributed to this "common sense." Lucretius gave to his poem the
title, De rerum natura, which can be translated as, "On the Nature of the
Universe." Directed nominally to his friend the Roman statesman Gaius
Memmius, the poem was written for all educated laymen of the time.
Neither Epicurean nor Poet, but with the advantage of two millenia of
scientific progress, I am attempting to address the same kind of audience with
a similar exposition. Writing in a less heroic age, I apologize for foresaking
the hexameter form, Latin or English. But, prose though it be rather than
verse, I follow Lucretius in requesting the reader to "lay aside your cares and
lend undistracted ears and an attentive mind to true reason."
In this book I have tried to present those basic concepts of particles and
fields and of space and time, as illuminated by modern physics, very much
as a professional physicist understands them. I believe that these concepts are
accessible to the nonprofessional—that which I can't explain to an interested
layman, I must not understand properly myself. Which is not to say the ideas
are so trivial that they can be understood by physicist or layman without the
"attentive mind" to which Lucretius refers.
By and large, there is little controversy in physics and hence there is little
that is controversial in the book. The exceptions, largely concerned with the
interpretation of quantum mechanics, are addressed in a spirit of "naive real-
ism" and operationalism, which represent my own views and which I believe
are not very different from those held by most physicists.
The text is nonmathematical, though on occasion simple relations are
expressed in algebraic forms that should be known to anyone with a high-
school education. Some more complex relations that seem to be especially
interesting are presented in the extensive set of footnotes. Though few of
these require mathematical sophistication beyond that taught in the first few
weeks of a high-school algebra course, mathematical simplicity does not
translate into conceptual simplicity, and these presentations will often require
careful and time-consuming thought. Once written, a book has a life of its
vi The Great Design
own independent of the author's control; however, I suggest that the mathe-
matical footnotes be sampled rather than consumed. There are those who can
"read" mathematics like a light novel, but for most of us so compact an infor-
mation transfer cannot be assimilated easily and the time required to pene-
trate the arguments interrupts the narrative flow excessively.
It has been said that all expository books are simply forms of selected
plagiarism. So be it for this book. I claim originality only for the errors, and
even original errors are hard to come by. Thus, I am indebted to many col-
leagues, over many years, for most of the forms of presentation I have used.
Only rarely have the pedagogical contributions of others been so marked—
and remembered by me—that I have been able to name sources.
Perhaps one-half of the book concerns physics developed during my
professional lifetime (the first paper under my name was published in 1947).
Hence, I am often discussing work conducted by my friends and colleagues.
Physics is a human endeavor and to describe developments without using
names leads to a bloodless picture of physics. On the other hand, there is little
gained by burying the reader under a load of names of strangers. Originally,
I tried to solve the problem of selection by using only the names of Nobel
and Wolf prize winners, but this plan broke down. To those physicists I have
not mentioned when I might have, I apologize.
In 1930, with money he had earned from his book, The Bridge of San Luis
Rey, Thornton Wilder built a home in Hamden, Connecticut, for his sister
Isabel, his parents, and himself. Much of his later work was written in his fine
study on the second floor of that house. This book was written in that same
study and I like to think viewed tolerantly by a kindly ghost.
May 1987 R. K. A.
Hamden, Connecticut
Contents
1 Concepts in Physics 3
2 Invariance and Conservation Laws 14
3 Covariance, Scalars, Vectors, and Tensors 30
4 The Discrete in Nature—The Atoms of Demokritos 38
5 The Continuum in Nature—Faraday's Fields 49
6 The Nature of Space and Time—The Special Theory of
Relativity 67
7 The Equivalence Principle and the General Theory of
Relativity 103
8 The Electromagnetic Field—The First Unified Field Theory 128
9 The Problem of Change—The Second Law of
Thermodynamics 140
10 Quantum Mechanics—Determinism to Probability 149
11 The Atom—A Quantum Laboratory 194
12 Fundamental Particles and Forces—An Introduction 208
13 Symmetries and Conservation Laws—CPT 230
14 The Strong Interactions 248
15 The Weak Interactions 280
16 Cosmology—The World's Beginning and End 308
17 Gauge Invariance—The Unification of Fields 325
18 To the Ultimate Theory—Through a Glass Darkly 344
Index 370
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THE GREAT DESIGN