Table Of ContentFROM PARADOX TO REALITY
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OUR BASIC CONCEPTS OF THE PHYSICAL WORLD
FRITZ ROHRLIC
Syracuse University
Published by the Press Syndicate of the University of Cambridge
The Pitt Building, Trumpington Street, Cambridge CB2 l RP
40 West 20th Street, New York, NY l 0011-4211, USA
10 Stamford Road, Oakleigh, Victoria 3166, Australia
©Cambridge Press 1987
First published 1987
First paperback edition 1989
Reprinted 1990, 1992
Printed in Great Britain at the University Press, Cambridge
A catalogue record for this book is available from the British Library
Library of Congress cataloguing in publication data
Rohrlich, Fritz
From paradox to reality.
Bibliography
Includes indexes.
1. Relativity (Physics) 2. Quantum theory.
3. Science - Philosophy. I. Title.
QC173.55.R64 1987 530.l'l 86-26845
ISBN 0 521 30749 X hardback
ISBN 0 521 37605 X paperback
PN
Contents
Preface
Vll
Part A: At the root of the endeavor 1
1 Human limitations 3
a. Limits by principle 3
b. Bounds of human nature 5
c. Restrictions by complexity 6
2 Theory and the role of mathematics 9
a. What is a scientific theory? 9
b. What does mathematics have to do with nature? 11
3 Scientific objectivity 15
a. The evolution ofa scientific theory 15
b. Acceptability criteria 17
c. Invariance: the irrelevance of the specific observer 19
4 The aim of scientific theory 23
a. Explanation and prediction 23
b. Un i.fication 27
Part B: The world of relativity 33
5 Space and time: from absolute to relative 35
a. Galileo, the pioneer 35
b. Newton, the first great architect ofm athematical theory 37
c. The relativity ofN ewtonian mechanics 42
6 Imposed consistency: special relativity 49
a. Maxwell and the ether hypothesis 49
b. The paradox of the speed of light 52
c. Einstein'sfiat 55
d. Simultaneity 62
e. F1:tst'mo'iiih'icl1itks and meter sticks 65
f. ·.The con~irsion ofm atter into· energy 72
g. Space-time geometry 75
h. Poincare invariance 86
Vl Contents
7 Gravitation as geometry: general relativity 89
a. Newton's universal gravitation 89
b. Einstein searched for a new gravitation 91
c The 93
97
e. General 102
f Gravitational radiation and black holes 106
8 Revolutions without revolutions 111
a. Established theories 111
b. Scientific revolutions 114
Part C: The quantum world 119
9 The limits of the classical world 121
a. The classical world begins to fail 121
b. The discovery ofq uantization 125
10 Concepts of the quantum world 134
a. Waves and particles 135
b. Quantum particles 141
c. Indeterminacy 144
d. Uncertainty 147
e. . Complementarity 151
f The essential link 153
11 From apparent paradox to a new reality 158
a. Quantum systems 159
b. Observables and measurements 161
c. Schroedinger's cat 166
d. Einstein's reality 169
e. Quantum reality 175
f Quantum logic 180
g. Macroscopic quantum phenomena 184
12 The present state of the art 189
a. The marriage between quantum mechanics and special relativity 189
b. The onion ofm atter 194
c. Elementary particles 196
Epilogue 202
Notes 205
Glossary of technical terms 219
Name index 223
Subject index 225
Preface
Come, join me on an adventure of the mind. The going will be a little
demanding at times but there will be rich rewards. The new vistas are
spectacular. Come with me, I am an experienced guide!
I am offering the reader a guided tour to the two new fundamental
conceptual structures of twentieth-century physical science: relativity and
quantum mechanics. This is not a physics text; nor is it an account of the latest
discoveries intended to dazzle the public. It is a basis for discussion of
surprising new concepts and of the necessities that led to them.
This book developed from my lecture notes for a one-semester course that
I have been offering to undergraduates at Syracuse University for a number
of years. The course is entitled 'Concepts in Contemporary Physics'. While I
have taught almost every branch of theoretical physics, I find this course to
be by far the most demanding. One reason is that the course is intended for
non-science majors; a serious interest in the subject matter is the only
prerequisite. Consequently, the students have widely varying backgrounds
and range from freshmen to seniors. Another reason is the lack of a suitable
text. A reading list pulling together bits and pieces from a variety of sources
does not replace an integrated text. The present book is expected to fill this
need.
However, the book is not restricted to use by college students. It is
intended to attract a much wider audience: the intellectually interested and
more sophisticated of the general public. And I hope it will serve another
goal: to correct widespread misrepresentations of science. While there exist
many excellent popular presentations of various fields of science, the public
has in recent years also been exposed to a large number of books on various
pseudo-sciences, Since these range widely from
there also resulted a great deal of confusion and concern-
ing the basic physical sciences. The present book, limitedinitsscope,
is expected to help dispel misunderstandings at least two frequently
misunderstood topics: relativity and quantum mechanics.
viii Preface
The book consists of three parts: Part A brings together some basic notions
from the philosophy of science that provide the background and prepare the
reader for the two main parts; Part B deals with the
space and time brought the two theories the theory
very (special relativity) theory of gravitation (general
relativity); Part C presents the greatest conceptual revolution of all, the
discovery of the quantum world and the resulting new world view.
Most of the sections can be read without recalling one's high school
mathematics. In a few of them, however, a little elementary algebra or a few
basic geometric notions will be helpful. But those sections can be skipped
with little ill effect for the understanding of later material. The two parts on
the world of relativity (Part B) and on the quantum world (Part C) are largely
independent and either of them can be read first.
Human desires for solutions to problems and for certainty in a world of
uncertainty often make people reach out for easy answers. But science does
not have easy answers and often has no answers yet. It requires patience and
sometimes a long wait for further scientific progress. But where scientific
answers are still lacking, the door is open to wild speculations; people then
often fall prey to freak ideas. One of these is the introduction of Eastern
philosophy into the foundations of quantum mechanics. Both are respected
accomplishments of human thought; but they have nothing to do with one
another. The present book is in part intended to provide sufficient under
standing of this field of science to avoid such fallacies.
The conceptual structure of science raises not only intellectual curiosity
but also philosophical issues that are often of much greater interest to the
non-scientist than the subject matter itself. Correspondingly, this book is not
a popularization of the subject matter of twentieth-century fundamental
physics. It does not attempt to teach relativity or quantum mechanics or even
to present its subject matter in popularized form. There already exist a large
number of books for this purpose, many of them authoritative and excellent.
My present endeavor is rather to present in non-technical language the
conceptual revolutions that the scientific community had to undergo in order
to be able to accept 'modern physics'. And this is done less from a historical
point of view than from the perspective of a person confronted with new,
strange, and often paradoxical experimental evidence. The general public as
well as the college student hears little of that unless he or she pursues a
scientific career. But it is exactly this type of intellectual adventure that shows
scientific research at its best. It teaches what science is all about and it permits
one to develop a world view based on scientific evidence.
If there is just one thing the reader should learn from the following pages,
I hope it will be this. Our common sense, acquired from our everyday
Preface ix
experience, is not a reliable guide to the world far beyond our reach in daily
life. Nature is found to be much more subtle, varied, and sophisticated than
we tend to imagine. Our prejudices about how nature should behave are
usually wrong. It is this experience that gives scientists their humility; more
than the non-scientist, they are often.painfully aware of how much we do not
know and how difficult it is to acquire reliable knowledge. This is why they
treasure so highly the relatively small amount of reliable knowledge which we
did manage to acquire.
The nature and purpose of this work require me to deal not with science
only; some philosophy of science will play a necessary role. For example, we
shall encounter philosophical issues in connection with the interpretation of
quantum mechanics. Two philosophical points of view, instrumentalism and
realism, will provide the minimum background for this discussion. My own
view, that of a critical scientific realist, will unavoidably enter the picture.
But I suspect this view to be close to what the majority of scientists today
actually believe.
Side remarks that would interrupt the flow of thought are relegated to /
Notes at the end of the text; they are indicated by square brackets. The
technical terms are collected in a Glossary for easy reference. Finally, lists of
further readings are provided at the end of Part A and after each of the
subsequent chapters. They are in the form of alphabetical annotated biblio
graphies and are generally limited to non-mathematical material. Of course,
they reflect my own taste and preference. Instructors may want to add their
own favorite references.
As is the case in any introductory text, some simplifications were necessary.
While every effort has been made to avoid oversimplifications in either
science, philosophy, or history, the expert will find small liberties that I had
to take in order to avoid devoting excessive space to very minor points. In
some instances the. Notes provide elaborations for the sake of precision.
Similarly, matters that are fascinating but had to be·excluded because of
limitations in length are indicated in the Notes. There is of course a large
amount of personal judgment involved in the choice of subject matter. Items
that others may have liked to include had to be omitted entirely in order to
keep the book to its present size. It is already considerably larger than had
been intended originally.
I owe a great debt to the many authors whose works I have read over the
years and who have influenced me greatly. They are too many to list here. But
I must express my special indebtedness to Abner Shimony, Professor of
Philosophy and Physics, Boston University, for the many things I have
learned from him. My great indebtedness goes to two people who have
provided valuable constructive criticism: Clyde L. Hardin, Professor of
