Cosmic coincidences: Dark matter, mankind and anthropic cosmology

311 Pages·1989·15.981 MB·English

by  John R Gribbin, Martin Rees

COSMIC
COINCIDENCES
- - - - * - - - -
Dark Matter, Mankind,
and Anthropic Cosmology
JOHN GRIBBIN AND
MARTIN REES
BANTAM BOOKS
NEW YORK • TORONTO • LONDON • SYDNEY • AUCKLAND
COSMIC
COINCIDENCES
- - - - * - - - -
Dark Matter, Mankind,
and Anthropic Cosmology
COSMIC COINCIDENCES
A Bantam Book I September 1989
Bantam Ne1.V Age and the accompanying figure design
as well as the statement "the search for meaning, growth
of
and change" are trademarks Bantam Books, a division
of
Bantam Doubleday Dell Publishing Group, Inc.
All rights reserved.
Copyright © 1989 by John Gribbin and Martin Rees.
Cover art copyright © 1989 by Geoffrey McCormack.
Book design by Kathryn Parise
No part of this book may be reproduced or transmitted
in any form or by any means, electronic or mechanical,
including photocopying, recording, orby any information
storage and retrieval system, without pennission in
writing from the publisher.
For information address: Bantam Books.
LmRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA
Gribbin, John R.
Cosmic coincidences.
Bibliography: p.
1. Cosmology. 2. Astrophysics. I. Rees, Martin.
II. Dark matter, mankind, and anthropic cosmology.
III. Title.
QB981.G755 1989 523.1 89-7
ISBN 0-553-05730-8
ISBN 0-553-34740-3 (pbk.)
Published simultaneously in the United States and Canada
Bantam Books are published by Bantam Books, a
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CONTENTS
---------------------*--------------------
INTRODUCTION: Why Are We Here? xi
PART ONE:
Cosmic Coincidences
I
ONE: How Special Is the Universe? 3
The Anthropic Universe; A Universe Big
Enough for Life; The Primary Puzzle; The
Flat Universe; Dark Matter Does the Trick
TWO: The Geography of the Universe 30
Redshifts, Galaxies and Quasars; To the Edge
of the Universe; The Bright Stuff; A
Background of Smoothness; Blowing
Bubbles?
THREE: Two Kinds of Dark Matter 63
Sizing Up Galaxies; A Biased View; Two
Sorts of Stuff; Before the Galaxies; Another
Coincidence?; The Long-range Forecast
PARTlWO:
The Stuff of the Universe
101
FOUR: The Particle Zoo 103
Sizing Up Neutrinos; Missing Links; The
Axion; Supersymmetric Partners; Making
the Most of Monopoles; Quark Nuggets; A
Black Hole Bonanza; Do Black Holes
Explode?; Great Dark Hopes
FIVE: Halo Stuff 132
Dusky Dwarfs; Black Hole Beasts; Baryons
May Be Cool; Making Mountains Out of
Molehills; More Answers Than Questions
SIX: Core Stuff 152
A Brief History of Black Holes; The Quasar
Connection; Black Hole Powerhouses; Weighing
the Evidence; At the Heart of the Milky Way;
A Flare for Black Holes
SEVEN: Cosmic String 175
A Theory of Everything?; Breaking Up Is
Not So Hard to Do; Out of the Shadows?;
Strings and Things; Trapping the Vacuum;
Making Galaxies; Seeking Strings
EIGHT: Gravity's Telescopes 202
Making Waves; Measuring Waves;
Gravitational Lenses; Luminous Arcs;
Shedding Light on Dark Matter; Dark
Galaxies
NINE: The Lyman Forest:
Emergence and Evolution of Galaxies 223
Quasars and Lyman Alpha; Into the Forest;
Large Scale Lessons; Heavy Signs of a
Galaxy Wall; Into the Past
PART THREE:
The Bespoke Universe
239
TEN: Tailor-Made for Man? 24]
The Beryllium Bottleneck; Hoyle's Anthropic
Insight; The Stellar Pressure Cooker; The
Supernova Connection; A Cosmic Connection;
Space, Time, and the Universe; An Alternative
Universe
ELEVEN: Or Off the Peg? 270
The Quantum Realities; Inflation in a
Nutshell; Bubbles on the River of Time;
Cosmic Dragons; The Philosophy of
Cosmology; The End of Physics?
FURTHER READING 293
INTRODUCTION
---------------------*---------------------
Why Are We Here?
THERE ARE THREE MOTIVES for studying the Universe. The
first is discovery: to learn what's out there, whether in
our own Solar System or in the extragalactic realm.
This vicarious exploration-of the surface of Mars, or
the patterns of spiral galaxies-is something a wide
public can share.
For the astrophysicist, this exploration is prelimi
nary to a second goal: to understand and interpret
what we see, in terms of the laws of physics established
here on Earth, and to place our entife Solar System in
an evolutionary context that can be traced back to the
birth of the Milky Way Galaxy, and beyond-right back,
indeed, to the initial instants of the so-called Big Bang
with which our Universe began.
To the physicist, there is a third motive: The cos
mos is a "laboratory" offering more extreme condi
tions than can be simulated on Earth. Known laws
can be tested, perhaps to the breaking point, by ap
plying them, for instance, to the amazing densities
of neutron stars; and a better understanding of the
astounding temperatures and energies of the Big Bang
could reveal new laws. Essentially all that we know
about gravity-one of the four fundamental forces,
and the one that controls the motions of stars, gal-
xi
xii Introduction
axies, and the entire expanding Universe-comes from
astronomy.
Astronomy is, of course, an old pursuit-perhaps it
was the first science to become professionalised-but it
has greatly enlarged its scope during the past two de
cades. Recent progress has been largely "driven" by
experimental and observational advances. No armchair
theorist, even equipped with current physical knowl
edge, could have envisaged the extraordinary phenomena
and objects that have been discovered. This burgeoning
is due partly to technical improvements in optical as
tronomy, but even more to the new windows on the
Universe opened up by radio astronomy and by obser
vations from space. Valuable data are also obtained in
other ways-from underground neutrino detectors and
gravitational-wave experiments. There are few branches'
of terrestrial physics, indeed, that do not find applica
tion somewhere in astronomy.
In this book, we have (especially in the middle sec
tion) described those recent developments that we have
found (from our experience of lecturing and writing)
that seem to fascinate nonspecialists most. We aim to an
swer the questions that we most often are asked. Few of
these topics-quasar spectra, protogalaxies, gravitational
lenses, gravitational waves, and cosmic strings-have
yet been given due prominence in nontechnical publi
cations. On the other hand, stories such as that of black
holes are not emphasised here because such exotic ob
jects have become so familiar from the many excellent
books that already exist.
All these topics relate to a single overall conclusion
something that has as much right to be called a para
digm shift as anything in twentieth-century astronomy.
This is the realisation that the dynamics of our Uni
verse, and of all the galaxies in it, are controlled not by
what we see but by dark matter. Only 10 percent (at
most) of the Universe shines; what we see is a biased
Introduction xiii
and incomplete sample of the Universe's overall con
tents. Without the dark matter, our Universe would be
a very different place: Dark matter controls the struc
ture and eventual fate of the Universe. Discovering what
the "dark stuff" is surely rates as the number-one prob
lem confronting cosmologists today.
The search for a solution to this puzzle is a natural
development from recent discoveries in cosmology that
have been reported in earlier books. A fuller descrip
tion of Big Bang cosmology and the expanding Uni
verse can be found in In Search of the Big Bang; the
ultimate fate of the Universe, and evidence that dark
matter does indeed exist, are discussed in detail in The
Omega Point. Here, moving on from such discoveries,
we are more concerned with the exact nature of the dark
matter, the stuff of the Universe, than with the detailed
proof that there is some sort of dark matter around.
It is no exaggeration to say that we would not be
here to wonder at the Universe if the dark stuff were
not around. We can imagine ways in which the Uni
verse might have emerged from the Big Bang without
this background sea of stuff, so that stars, galaxies, and
creatures like us would never have been produced. And
yet we are here, and this relates to the second main
theme of our book.
Science deals mostly with complex manifestations of
laws that in essence are well known-the real scientific
challenge lies in understanding the rich complexity in
herent in these phenomena. Cosmology and particle
physics are, however, the two frontier areas, where
even the basic laws are still mysterious. Moreover, deep
interconnections are becoming apparent between these
two endeavours-the study of the cosmos and of the
microworld. For example, the dark matter that domi
nates the Universe is probably in the form of myriads
of tiny particles whose individual properties can be
understood only in microphysical terms.