Acknowledgments
In preparing this book I have been fortunate in havingfriends and colleagues who can offer open criticism or who
have made suggestions that found their way into the text. I
have benefited from comments by Jeremy Bernstein, John
Brockman, Malcolm Diamond, John Faulkner, Randall
Furlong, George Greenstein, Alan Guth, Edward Harrison,
Joseph H. Hazen, Nicolas Herbert, James McCarthy, Richard
Ogust, Jim Peebles, Anthony Tyler and Anthony Zee. I am
especially grateful for the detailed criticism of George Field
and Engelbert Schucking in the sections of the book dealing
with astrophysics and cosmology. Alice Mayhew and
Catherine Shaw did the major editorial work on the text and
helped turn my English into English. Matthew Zimet's
inventive illustrations delight the eye and do much to
enhance the text. Finally, I want to thank the Board of
Governors of The New York Academy of Sciences for their
sympathetic appreciation of my interest in science writing.
Contents
ONE HERSCHEL'S GARDEN 1
1 Herschel's Garden 3
2 The Birth and Life of Stars 11
3 The Death of Stars: Astronecroscopy 38
4 The Discovery of Galaxies 69
5 Radio Galaxies and Quasars 101
6 Why Is the Universe Lumpy? 117
7 Classical Cosmology 132
TWO THE EARLY UNIVERSE 155
1 The Early Universe 157
2 Fields, Quanta and Symmetry 169
3 The Standard Model 208
4 Thermodynamics and Cosmology 234
5 The Big Bang 244
THREE WILD IDEAS 269
1 Unified-Field Theories 271
2 Magnetic Monopoles 296
3 Unifying Gravity 313
4 Before the Big Bang: The Inflationary Universe 331
5 Before Inflation: The Origin of the Universe 353
FOUR REFLECTIONS 369
1 The Cosmic Computer 371
2 First-Person Science 380
BIBLIOGRAPHY 392
INDEX 399
Foreword
The children's books that were my first contact with theuniverse opened my imagination to thoughts of voyages to
the moon, planets and stars. When I was older, however, I
visited the Fels Planetarium in Philadelphia and the Hayden
Planetarium in New York, and that simple, self-centered
perception was shattered. The drama and power of the
dynamic universe overwhelmed me. 1 learned that single
galaxies contain more stars than all the human beings who
have ever lived, and I saw projections of clusters of such
galaxies moving in the void of space like schools of fish
swimming in the sea. The reality of the immensity and
duration of the universe caused a kind of "existential shock"
that shook the foundations of my being. Everything 1 had
experienced or known seemed insignificant placed in that
vast ocean of existence.
While my sense of awe at the size and splendor of the
universe is a feeling that has never quite left me, reflecting
back on my childhood experience I see that the universe
provided a screen upon which I could project my feelings
about the immensity of existence; that external ocean
mirrored the one within me. Later, as I pursued the study of
theoretical physics at Princeton and Stanford Universities,
my attitude toward the universe altered. The universe
became less a screen for the projection of my feelings and
more a puzzle challenging me as a scientist, a puzzle which
left scattered, complex clues to its solution. The universe, in
spite of its size, is a physical entity governed by the laws of
space, time and matter. Someday (and that day is not yet here) physicists may know the laws that describe the
creation of the universe and its subsequent evolution. The
logical account of the foundations of physical existence will
then be complete.
As we embark on the study of the universe, it is worth
reminding ourselves that not so long ago, at the beginning of
this century, physicists were puzzled by the properties of
atoms. Atoms were so small (a few eminent scientists even
doubted their existence) and behaved in such sporadic,
uncontrollable ways that some people thought they lay
beyond the power of scientific comprehension. Yet after
major experimental and theoretical discoveries, physicists in
the 1920s invented the quantum theory which explicated the
weird world of the atom. New and unfamiliar physical
concepts were incorporated into the quantum theory,
concepts that have survived to the present day.
Similarly, as physicists attempt to comprehend the origin
and evolution of the universe, they will certainly need to
invent new and unfamiliar concepts. Scientists do not yet
understand the fundamental laws that describe the very
origin of the universe, at least not as well as they understand
the laws describing atoms. But many scientists today are
excited because such an understanding is currently in the
making, a result of the intellectual synthesis of two scientific
disciplines: quantum theory, which specifies the laws of the
smallest things—the quantum particles—and cosmology,
which specifies the laws that govern the largest thing—the
entire universe.
A major reason for the growing intimacy between quantum
physics and cosmology is the success of the "big bang"
theory of the early universe. According to this theory, if we
imagine going backward in time then we would see the
universe contract, the galaxies move closer together until
they meld into a hot, uniform gas of all the constituents of
matter—the quantum particles—interacting at enormous
energy. Elucidating the properties of such a gas of hot,
interacting quantum particles is the purview of modern
quantum theory. Physicists estimate that the high
temperatures and high energies among the quantum
particles eventually encountered in the early universe are
physically unique—they become so high that they cannot be
reproduced in laboratories here on earth. Hence the only
possible "laboratory" that can test theories of quantumparticle interactions at ultrahigh energies is the universe
itself.
Another reason for the growing intimacy between quantum
theory and astronomy is that astronomers are now observing
exotic objects like neutron stars, consisting of matter
compressed to enormous densities, and possibly black holes,
in which the very fabric of space and time undergoes
unusual distortions. Like the early universe, these strange
objects present extreme physical conditions that cannot be
reproduced here on earth. Since it is the properties of space,
time and matter, especially under extreme conditions, that
physicists endeavor to understand, these new objects
provide yet additional extraterrestrial laboratories for
testing physical laws.
Were I to summarize the optimistic theme of this book in a
single sentence, that sentence would be "From microcosm to
macrocosm, from its origin to its end, the universe is
described by physical laws comprehensible to the human
mind."
I believe that physicists will someday soon understand the
basic laws of the quantum creation of the universe (most
probably out of nothing whatsoever) as well as
astrophysicists now understand the interiors of stars. The
universe, whose very mention invokes a sense of
transcendence, will be comprehended as subject to natural
laws like all other material things. In spite of its immensity
and age, the universe will never seem the same.
Such a fulfillment of the program of the natural sciences will
have a profound impact on human thinking. As knowledge
of our universe matures, that ancient awestruck feeling of
wonder at its size and duration seems inappropriate, a
sensibility left over from an earlier age. Thousands of years
ago, many people perceived the sun as a divine presence;
today many people perceive the universe as essentially
beyond human comprehension. But just as the sun is now
understood in terms of astrophvsical processes, so too will
the universe be similarly understood. In the past, myths and
the religious creation stories shaped the values of people
who believed in them; likewise the emergent scientific
cosmology will shape the values of those who accept it.
Through the agency of scientific discovery the external
order of the universe influences our consciousness and
values This book is divided into four parts. The first part,
"Herschel's Garden," gives the reader an overview of the
dynamic universe discovered by astronomers—the stars,
white dwarfs, neutron stars, black holes, interstellar gas and
dust, quasars, galaxies, their distribution in space as clusters
and superclusters of galaxies, and the cosmos as a whole.
From this part of the book the reader should derive a sense
not only of the size of the universe and our knowledge of its
inhabitants but also of the puzzles confronting modern
astronomy such as how stars are born and galaxies are
evolving. I discuss some suggested solutions to these and
other astronomical puzzles to which we can hope to achieve
a final resolution as new observational data are acquired.
Today, the search into the universe continues with
instruments like satellites and radio telescopes, a search
manifesting, in the words of the American astronomer
Edwin Hubble, an "urge... older than history."
While the first part of the book describes the universe
observed in space, the following two parts of the book
describe a conceptual exploration of the universe in time.
The second part, "The Early Universe," describes the
remarkable picture of the universe when it was only seconds
and minutes old—the "hot big bang," a theory that came
about by the application of the laws of quantum-particle
physics to the entire universe. Without using complicated
mathematics I describe the basic framework for thinking
about the quantum particles—die discipline known as
"relativistic quantum-field theory"—and how it applies to
the study of the early universe. Amazingly, physicists
understand the universe better when it was seconds and
minutes old than for either earlier or later times because
when it was seconds old the universe was a uniform, rather
simple, gas of quantum particles, whose properties are
known. The early universe is better understood than the
weather is today.
But the very success of the hot-big-bang theory gives
physicists the confidence to press onward and conceptually
explore the universe before the first nanosecond (onebillionth
of a second) to the very origin of the universe. The
third part of the book, "Wild Ideas," leaves the secure
territory explored by astronomical observation and by highenergy
laboratory experiments and speculates about the
nature of that universe before the first nanosecond. I discuss "wild ideas" in the conceptual repertoire of
theoretical physicists that might explicate the dynamics of
the very early universe, ideas such as GUTs—grand unified
theories—magnetic monopoles, supersymmetry and the
world of many extra dimensions. If these ideas are correct—
and many physicists think they are—then an amazing
picture of the very early universe results.
The universe begins in a very hot state of utmost simplicity
and symmetry and as it expands and cools its perfect
symmetry is broken, giving rise to the complexity we see
today. Our universe today is the frozen, asymmetric remnant
of its earliest hot state, much as complex crystals of water
are frozen out of a uniform gas of water vapor. I describe the
inflationary universe—a conjectured pre—big-bang epoch of
the universe, which may explain some puzzling features of
the contemporary universe, such as its uniformity and age,
as well as provide an explanation for the origin of the
galaxies. The penultimate chapter of this third part of the
book—as far as speculation is concerned— describes some
recent mathematical models for the very origin of the
universe—how the fabric of space, time and matter can be
created out of absolutely nothing. What could have more
perfect symmetry than absolute nothingness? For the first
time in history, scientists have constructed mathematical
models that account for the very creation of the universe out
of nothing.
There is a short fourth part, "Reflections," which expresses
my opinions and attitudes (not that the other parts of the
book do not contain many of my opinions or intellectual
biases as a theoretical physicist). Here the reader will find a
chapter developing the metaphor of the universe as a cosmic
computer for which the quantum particles are the
"hardware," the laws of physics the "software" and the
evolution of the universe is the execution of the program. In
a Final chapter called "First-Person Science," I explore the
thoughts and feelings that a few People have had about the
meaning of our strangely coherent universe.
New York, New York Felton, California 1984
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