Endless Universe: Beyond the Big Bang

227 Pages·2007·1.88 MB·English

by  Paul J. Steinhardt

contents
title page
dedication
acknowledgments
preface
chapter one: 2001
chapter two: Act Two
chapter three: Two Tales of One Universe
chapter four: From Particles to the Cosmos
chapter five: Inflation and the Tale of Two Cosmologists
chapter six: From Strings to Ekpyrosis
chapter seven: A Cyclic Model of the Universe
chapter eight: The Last Question
chapter nine: Seeing Is Believing
chapter ten: Inflationary Multiverse or Cyclic Universe
chapter eleven: Back to the Future
glossary
suggestions for further reading
about the authors
copyright
To Nancy and Corinne
acknowledgments
Endless Universe was, in part, a family affair. The book could never have been
completed without the love, patience, and support of Nancy and Corinne.
Working on each side of the Atlantic, they were our most dedicated readers, our
most exacting editors, our harshest critics, and our best morale boosters. Paul’s
sisters, Alice and Nancy Steinhardt, and brother-in-law Bob Sorensen, and Neil’s
parents, Ben and Mary, read early versions and gave vital guidance. Paul’s sister-
in-law Chana Shapiro meticulously reviewed the manuscript and helped us to
resolve numerous structural issues, especially how to design a story told with
two voices. Our children, Charlie, Joe, Will, and Cindy Steinhardt, and Ruby
Turok-Squire, all helped to shape the text and the illustrations.
We also are extremely grateful to the numerous colleagues who took time to
read all or parts of the manuscript and to give us their valuable advice, including
Andreas Albrecht, Brian Greene, Stephen Hawking, Burt Ovrut, Roger Penrose,
Martin Rees, Michael Turner, and Edward Witten. Daniel Baumann, Jean-Luc
Lehners, and Paul McFadden carefully reviewed the physics presentation
throughout the manuscript. Michael Olenick contributed many useful comments.
Peter Galison, Gerald Holton, Peter Schaefer, and Jeffrey Tigay provided
guidance on the historical issues discussed in Chapter 8. We thank Carl Feinberg
for suggesting that we consider the relationship between the cyclic model and
Asimov’s short story The Last Question.
Many have contributed to our scientific and personal lives, as well as to the
ideas described herein. The imprint of our mentors, Richard Feynman, Sidney
Coleman, David Olive, and Tom Kibble, can be found throughout this book. For
Paul, Alan Guth was profoundly important in drawing him into the field of
cosmology (see Chapter 5). He, Michael Turner, and Andreas Albrecht were
influencial early in Paul’s career and have been longstanding friends ever since.
Many at Cambridge and Princeton have provided invaluable guidance, including
John and Neta Bahcall, Gary Gibbons, David Gross, Stephen Hawking, Jerry
Ostriker, Lyman Page, Jim Peebles, Malcolm Perry, Martin Rees, Nathan
Seiberg, David Spergel, Scott Tremaine, David Wilkinson, and Edward Witten.
In developing the cyclic model, we have been fortunate to have a cadre of
outstanding collaborators. Burt Ovrut, a longtime collaborator and friend of
Paul’s, started us down the path toward the cyclic model with his fateful talk in
Cambridge in August 1999 (see Chapters 1 and 6) and has been extraordinarily
important in exploring its relation to string theory. A remarkable graduate
student, Justin Khoury, was the first to join the team and played a pivotal role in
developing the physical principles underlying the first colliding brane models.
Nathan Seiberg collaborated on one of the early papers and has been a constant
source of advice. A series of talented and creative students and postdoctoral
fellows followed—Latham Boyle, Joel Erickson, Steven Gratton, Jean-Luc
Lehners, Paul McFadden, Gustavo Niz, Andrew Tolley, and Daniel Wesley—all
have made major contributions to unveiling new physical principles and
transforming the conceptual framework into a concrete, mathematical model.
Many other theorists have contributed to the cyclic model through ideas,
criticisms, and insights, including Lawrence Abbott, James Bardeeen, Thorsten
Battefeld, Martin Bojowald, Robert Brandenberger, Sean Carroll, Ben Craps,
Paolo Creminelli, Anne Davis, Ruth Durrer, Pyotr Horava, Gary Horowitz,
Renata Kallosh, Lev Kofman, James Lidsey, Andrei Linde, Roy Maartens, V.
(Slava) Mukhanov, Subhod Patil, Fernando Quevedo, Lisa Randall, Alexander
Vilenkin, David Wands, and Matias Zaldarriaga. We also thank the United States
Department of Energy and the Particle Physics and Astronomy Research Council
in the United Kingdom for supporting our research described in this book.
Pier Gustafson, our outstanding illustrator, worked tirelessly to turn our crude
ideas into illustrations that help to give the book the relaxed feel we were
seeking. We were also lucky to recruit Stewart Dickson to work with us in
developing the idea of a double-Klein bottle into a cover image that represents
symbolically an endless cyclic universe. We also thank Laura van Dam and Chad
Boutin for their professional editorial advice on early versions of the manuscript.
We are most grateful to Charlie Conrad, our editor at Broadway Books, and
his assistant, Jenna Thompson, for their patience, advice, and support throughout
the project. We appreciate the care that copyeditor Bonnie Thompson gave to the
manuscript, and we thank Angela Glenn for painstakingly incorporating the edits
into the final draft. Finally, we thank Katinka Matson and John Brockman for
their help throughout, beginning with a sketchy concept, helping us formulate it
into a book proposal, finding Charlie Conrad and Broadway Books to work with
us, and providing many opportunities to bring the book and its ideas to the
attention of the public.
preface
There is a theory which states that
if ever anyone discovers exactly
what the Universe is for and why it
is here, it will instantly disappear
and be replaced by something even
more bizarre and inexplicable.
There is another theory which states
that this has already happened.
—Douglas Adams, The
Restaurant at the End of
the Universe
Theories of the universe have abounded throughout human history, but the last
forty years have been exceptional. A single theory, the hot big bang picture, has
dominated scientific and public discourse and has even become part of the
standard curriculum for schoolchildren. Its central tenet, the idea that the
universe emerged from a very hot, dense state 14 billion years ago and has been
expanding and cooling ever since, has been firmly established through many
independent measurements. But nearly every other feature of the theory has had
to be modified. One ingredient after another—“dark matter,” “inflation,” “dark
energy”—has been added and separately adjusted to fit the observations, and
each of these adjustments has critically altered our conception of the history of
the universe. Even so, the picture remains far from complete. The big bang is
conjectured to be the beginning of time and space, but there is no clue as to how
or why the big bang occurred. Nor is there a firm prediction about the future of
the universe. Most cosmologists do not consider these flaws to be worrisome.
They think that the theory will ultimately be simplified and made more
complete. And perhaps they are right, Douglas Adams’s joke notwithstanding.
This book concerns the emergence of a new theory of the universe, according
to which our cosmic history consists of repeating cycles of evolution. Each cycle
begins with a bang, but the bang is not the beginning of space or time. Rather, it
is an event with a “before” and an “after” that can be described by the laws of
physics. Each cycle influences the next. The events that occurred before the last
bang shaped the large-scale structure of the universe observed today, and the
events that are occurring today will determine the structure of the universe in the
cycle to come. Perhaps space and time sprang into being many cycles ago, but it
is also possible that they are literally “endless.”
In this new, more integrated picture, the components that had to be added one
by one to the conventional picture are either jettisoned, as in the case of
inflation, or become essential, interwoven elements of the machinery that keeps
the universe cycling. Most remarkably, this new theory of a cyclic universe is
able to match all current astronomical observations with the same accuracy as
the modified big bang picture, and it may explain some aspects of the universe
that the big bang picture cannot.
To be sure, the concept of an endless universe is still in its infancy. Most
cosmologists continue to accept the conventional theory, and some of them
might even question the wisdom of writing a book on such a new and unproved
idea. But, in our opinion, the issues that have been raised by this theory may so
strongly affect the way one views the universe and humanity’s place in it that
they deserve to be aired even as the debate is ongoing. Furthermore, writing an
account now makes it possible to offer a behind-the-scenes look at how science
really works. Most books on science are written after the outcome is certain and
only one theory has survived. Here there is a story within the story: a rare
opportunity to capture science at an uncertain but pivotal moment, when a
nascent idea has just burst on the scene to challenge an established view and the
outcome is not yet known.
In a similar vein, this book provides a personal perspective: how we, the
authors, were drawn to cosmology, how we were influenced by existing ideas,
and how we became involved in both establishing the currently favored big bang
picture and, later, creating a radical alternative.