The Edge of Physics: A Journey to Earth's Extremes to Unlock the Secrets of the Universe

333 Pages·2010·28.73 MB·English

by  Anil Ananthaswamy

Anil Ananthaswamy

THE E D G E o F
PHYSICS

A Journey to Earth's Extremes

to Unlock the Secrets of the Universe

HOUGHTON MIFFLIN HARCOURT

2010 • BOSTON • NEW YORK

Copyright © 2010 by Anil Ananthaswamy

ALL RIGHTS RESERVED

For information about permission to reproduce selections from
this book, write to Permissions, Houghton Mifflin Harcourt Publishing
Company, 215 Park Avenue South, New York, New York 10003.

www.hmhbooks.com

Library of Congress Cataloging-in-Publication Data
Ananthaswamy, Anil.
The edge of physics: a journey to Earth's extremes to unlock the
secrets of the universe / Anil Ananthaswamy.

p. cm.
Includes bibliographical references and index.

ISBN 978-0-618-88468-1

1. Physics-Popular works. I. Title.

QC24·5·A53 2010
530-dc22

Book design by Melissa Lotfy

Printed in the United States of America

Portions of the prologue and chapters 6, 8. 9. and 10 appeared in New Scientist
magazine and on NewScientist.com in slightly different form.

To my parents, Shantha and Narayana Iyer Ananthaswamy

CONTENTS

List of Illustrations • viii

Author's Note • ix

Prologue· 1

1 Monks and Astronomers • 9

2 The Experiment That Detects Nothing· 31

3 Little Neutral Ones • 56

4 The Paranal Light Quartet· 81

5 Fire, Rock, and Ice • 109

6 Three Thousand Eyes in the Karoo • 135

7 Antimatter over Antarctica • 168

8 Einstein Meets Quantum Physics at the South Pole· 194

9 The Heart of the Matter • 222

10 Whispers from Other Universes • 248

Epilogue • 273

Appendix 1: The Standard Model of Particle Physics • 283

Appendix II: From the Big Bang to Now: The Standard Model
of Cosmology • 285

Notes· 287

Bibliography • 293

Acknowledgments • 298

Index • 301

LIST OF ILLUSTRATIONS

All photographs are by the author except as noted.

A woodpecker at the New Camaldoli Hermitage in Big Sur, California.
(page 9)

Twenty-seventh level of the Soudan Mine, site of the Cryogenic Dark Matter
Search experiment in Soudan, Minnesota. (page 31)

Section of the old Trans-Siberian Railway on the shores of Lake Baikal,
Siberia. (page 56)

The Very Large Telescope, Cerro Paranal, Chile. Copyright ,© ESO/ H. H.
Heyer. (page 81)

The Keck I and II and Subaru telescopes on Mauna Kea, Hawaii. Copyright
© w. M. Keck Observatory. (page 109)

The Karoo, South Africa. (page 135)

Launch of the Balloon-borne Experiment with a Superconducting
Spectrometer (BESS), McMurdo, Antarctica, in December 2007. (page 168)

Drilling for the IceCube neutrino telescope, the South Pole, Antarctica.
(page 194)

The ATLAS detector at the Large Hadron Collider near Geneva, Switzerland.
Copyright © CERN -Maximilien Brice. (page 222)

An artist's impression of Planck separating from the rocket's upper stage.
Copyright © ESA -
D. Ducros. (page 248)

AUTHOR'S NOTE

This book is more narrative than pedagogical, so concepts in phys-
ics are introduced and explained when needed. To aid readers, and
prevent a lot of flipping back and forth, I've included two appendices
summarizing the standard model of particle physics and the stan-
dard model of cosmology (from the big bang to the universe as it is
today).
Readers will also notice that I mix up my units for physical quan-
tities, such as length, distance, weight, and volume; for instance,
sometimes the height of a mountain is given in meters and some-
times in feet. This is done purely for readability and effect. "A mile-
high mountain" just sounds better than "a 1.6-kilometer-high peak";
similarly, a 1,000-foot-high balloon is more dramatic than one 305
meters high. Sometimes the metric system wins: The 27-kilometer-
long tunnel housing the Large Hadron Collider near Geneva, Swit-
zerland, would be jarring at 16.777 miles long. The use of different
units also reflects the diversity of the places, people, and experiments
discussed in this book.

But, after all, who knows, and who can say
whence it all came, and how creation happened?
The gods themselves are later than creation,
so who knows truly whence it has arisen?

Whence all creation had its origin,
he, whether he fashioned it or whether he did not,
he, who surveys it all from highest heaven,
he knows-or maybe even he does not know.

-
FROM THE RIGVEDA 10.129. CIRCA 1500 B.C.

PROLOGUE

IT WAS THE DAY after Christmas in 2004, a bright winter's day
in Berkeley, California. I was outside a cafe at the corner of Shattuck
and Cedar, waiting for Saul Perlmutter, an astrophysicist at the Uni-
versity of California. The campus is nestled at the base of wooded
hills that rise steeply from the city's edge. About 1,000 feet up in the
hills is the Lawrence Berkeley National Laboratory (LBNL). In the
1990s, the UC campus and LBNL housed several members of two
teams of astronomers that simultaneously but independently discov-
ered something that caused ripples of astonishment, even alarm. Our
universe, it seems, is being blown apart.
Perlmutter was the leader of one of those teams. His enthusi-
astic, wide-eyed gaze, enhanced by enormous glasses, along with a
forehead made larger by a receding hairline, reminded me of Woody
Allen. But what he had found was no laughing matter. In fact, Perl-
mutter admitted that their discovery had thrown cosmology into cri-
sis. The studies of distant supernovae by the two teams had shown
that the expansion of the universe, first observed by Edwin Hub-
ble in 1929, was accelerating-not, as many had predicted, slowing
down. It was as if some mysterious energy were creating a repulsive
force to counter gravity. Unsure as to its exact nature, cosmologists
call it dark energy. More important, it seems to constitute nearly
three-quarters of the total matter and energy in the universe.
Dark energy is the latest and most daunting puzzle to confront
cosmologists, adding to another mystery that has haunted them
for decades: dark matter. Nearly 90 percent of the mass of galaxies

2
THE EDGE OF PHYSICS

seems to be made of matter that is unknown and unseen. We know
it must be there, for without its gravitational pull the galaxies would
have disintegrated. Perlmutter pointed out that cosmologists in par-
ticular, and physicists in general, are now faced with the stark real-
ity that roughly 96 percent of the universe cannot be explained with
the theories at hand. All our efforts to understand the material world
have illuminated only a tiny fraction of the cosmos.
And there are other mysteries. What is the origin of mass? What
happened to the antimatter that should have been produced along
with matter after the big bang? After almost a century of spectacu-
lar success at explaining our world using the twin pillars of modern
physics-quantum mechanics and Einstein's general theory of rela-
tivity-physicists have reached a plateau of sorts. As Perlmutter put
it, he and others are now looking to climb a steep stairway toward
a new understanding of the universe, with only a foggy idea of what
awaits them at the top.
Part of this seemingly superhuman effort will involve reconciling
quantum mechanics with general relativity into a theory of quantum
gravity. In situations where the two domains collide-where over-
whelming gravity meets microscopic volumes, such as in black holes
or in a big bang - the theories don't work well together. In fact, they
fail miserably. One of the most ambitious attempts to bring them
together is string theory, an edifice of incredible mathematical com-
plexity. Its most ardent proponents hope that it will lead us not just
to quantum gravity but to a theory of everything, allowing us to de-
scribe every aspect of the universe with a few elegant equations. But
the discovery of dark energy and recent developments in string the-
ory itself have conspired to confound. On yet another winter'S day in
the Bay Area, more than two years after meeting Perlmutter, I got a
taste of just how grave things had gotten in physics.
It was a late February afternoon in 2007. A conference room on
the ballroom level of the San Francisco Hilton was filled to capacity
for this session at the annual meeting of the American Association
for the Advancement of Science (AAAS). Three physicists were ar-
guing about dark energy and how it relates to some of the most se-

PROLOGUE
3

rious questions one can ask: Why is our universe the way it is? Is it
fine-tuned for the existence of life? Dark energy, it turns out, is not
merely mysterious; it seems to be at about the right value for the for-
mation of stars and galaxies. "The great mystery is not why there is
dark energy. The great mystery is why there is so little of it," Leon-
ard Susskind, Felix Bloch Professor of Theoretical Physics at Stan-
ford and co-inventor of string theory, told the audience at the Hilton.
He continued in a poetic vein: "The fact that we are just on the knife
edge of existence, [that] if dark energy were very much bigger we
wouldn't be here, that's the mystery."
The hope until recently had been that string theory would ex-
plain this, that dark energy's value would fall out naturally as a solu-
tion to the theory's equations-as would the answers to other puz-
zling questions. Why does the proton weigh almost two thousand
times more than the electron? Why is gravity so much weaker than
the electromagnetic force? Essentially, why do the fundamental con-
stants of nature have the values they do? The question of dark energy
is emblematic of such concerns. Nothing in the laws of physics can
explain why many aspects of our universe are what they are. They
seem to be extraordinarily fine-tuned to produce a universe capable
of supporting life-a fact that bothers physicists no end.
But string theory's hoped-for denouement is nowhere in sight.
Indeed, some physicists are slowly abandoning the notion that every-
thing about the universe can be reduced to a handful of equations. In
San Francisco, Susskind rose to address this issue. His talk was titled
"Why the Rats Are Fleeing the Ship." However, abandoning reduc-
tionism hasn't meant abandoning string theory. Quite the contrary.
For Susskind and many others, it has meant embracing the theory in
all its mathematical glory, despite its mind-boggling consequences.
One of the most outlandish implications of string theory, as it stands
today, is the existence of a multiverse. The idea is that our universe
is just one of a possible 10500 universes, if not more. And in this ex-
traordinary scenario lies an answer to the conundrum of why dark
energy and other fundamental constants have the values they do. In
a multiverse, all values of dark energy and fundamental constants

4
THE EDGE OF PHYSICS

are possible; in fact, the laws of physics can differ from universe to
universe. To explain our universe, physicists don't have to resort to
tweaking and fine-tuning. If a multiverse exists, then there is a fi-
nite probability, however small, that our universe randomly emerged
with the properties it has. The laws governing it give rise to stars and
galaxies-and, indeed, planets and intelligent life, including physi-
cists asking the question: Why is the universe the way it is?
This is the so-called anthropic principle, which, loosely stated,
says that our universe is what it is because we are here to say so,
and if it were any different we wouldn't exist to inquire. The idea
is viewed by many as a cop-out, for then physicists don't have to
work so hard to explain all things from first principles. Another
speaker, cosmologist Andrei Linde, Susskind's colleague at Stanford,
recalled his efforts to talk about the anthropic principle to physi-
cists at Fermilab, outside Chicago, nearly twenty years ago. Linde
had been warned that eggs were thrown at people who talked about
such things, so he began by discussing something else entirely and
switched topics midway, on the assumption that the Fermilabbers
wouldn't "have enough time to go to Safeway and buy eggs."
Given string theory's support for a multiverse, the anthropic prin-
ciple is gaining traction. But string theory itself is so far from being
experimentally verified that many physicists find it difficult, if not
impossible, to take its implications seriously. The third participant
that afternoon, cosmologist Lawrence Krauss, then of Case Western
Reserve University, summed up the argument for the opposition. "I
think you can imagine a theory where the multiverse would be sci-
ence. If one had a theory, a real theory, a real theory that predicted
lots of things we see about the universe, predicted lots of things we
could test, but also predicted lots of things we couldn't test, then
I think most of us would say we believe the things we cannot test
[such as the existence of a multiverse]," he said.
Susskind was staring daggers at Krauss by then. But Susskind's
somber tone at the end of the session suggested that it wasn't go-
ing to be easy to answer critics. '1\11 I can say is that we worry about
this," he said. " [String theory] is the biggest question in physics
right now. Can we make observational science out of it?"