Lee Smolin - Time Reborn

The Trouble with Physics

Three Roads to Quantum Gravity

The Life of the Cosmos

PUBLISHED BY ALFRED A. KNOPF CANADA

Copyright 2013 Spin Networks, Ltd.

All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any electronic or mechanical means, including information storage and retrieval systems, without permission in writing from the publisher, except by a reviewer, who may quote brief passages in a review. Published in 2013 by Alfred A. Knopf Canada, a division of Random House of Canada Limited, Toronto, and simultaneously in the United States by Houghton Mifflin Harcourt Publishing Company, New York. Distributed in Canada by Random House of Canada Limited.

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Knopf Canada and colophon are registered trademarks.

FIGURES BY HENRY REICH , with the following exceptions: by the author.

Library and Archives Canada Cataloguing in Publication

Smolin, Lee, 1955
Time reborn : from the crisis in physics to the future of the universe / Lee Smolin.

Includes bibliographical references.

eISBN: 978-0-307-40073-4

1. Time. I. Title.

BD638.S66 2013 115 C2012-905617-0

Jacket design by Martha Kennedy
Front jacket photograph Oleg Moiseyenko/Getty Images

v3.1

For my parents, Pauline and Michael
With many thanks to Roberto Mangabeira Unger for a shared journey

All things originate from one another,

and vanish into one another

according to necessity

in conformity with the order of time.

ANAXIMANDER , On Nature

W HAT IS TIME ?

This deceptively simple question is the single most important problem facing science as we probe more deeply into the fundamentals of the universe. All of the mysteries physicists and cosmologists face from the Big Bang to the future of the universe, from the puzzles of quantum physics to the unification of the forces and particles come down to the nature of time.

The progress of science has been marked by the dismissal of illusions. Matter appears to be smooth but turns out to be made of atoms. Atoms seem indivisible but turn out to be built of protons, neutrons, and electrons, the first two of which are made of still more elementary particles called quarks. The sun appears to go around the Earth, but its the other way around and when you get right down to it, it turns out that everything moves relative to everything else.

Time is the most pervasive aspect of our everyday experience. Everything we think, feel, or do reminds us of its existence. We perceive the world as a flow of moments that make up our life. But physicists and philosophers alike have long told us (and many people think) that time is the ultimate illusion.

When I ask my nonscientific friends what they think time is, they often answer that its passage is deceptive and whatever is actually real truth, justice, the divine, scientific laws lies outside it. The idea that time is an illusion is a philosophical and religious commonplace. For millennia, people have reconciled themselves to lifes hardships and our mortality by believing in the possibility of an eventual escape to a timeless and more real world.

Some of our most illustrious thinkers assert the unreality of time. Plato, the greatest philosopher of the ancient world, and Einstein, the greatest physicist of the modern world, both taught a view of nature in which the real is timeless. They saw our experience of time as an accident of our circumstance as human beings an accident that hides the truth from us. Both believed that the illusion of time must be transcended to perceive the real and the true.

I used to believe in the essential unreality of time. Indeed, I went into physics because as an adolescent I yearned to exchange the time-bound, human world, which I saw as ugly and inhospitable, for a world of pure, timeless truth. Later in life, I discovered that it was pretty nice to be human and the need for transcendent escape faded.

More to the point, I no longer believe that time is unreal. In fact, I have swung to the opposite view: Not only is time real, but nothing we know or experience gets closer to the heart of nature than the reality of time.

My reasons for this volte-face lie in science and, in particular, in contemporary developments in physics and cosmology. Ive come to believe that time is the key to the meaning of quantum theory and its eventual unification with space, time, gravity, and cosmology. Most important, I believe that to make sense of the picture of the universe that cosmological observations are bringing to us, we must embrace the reality of time in a new way. This is what I mean by the rebirth of time.

Much of this book sets out the scientific argument for believing in the reality of time. If you are one of the many who believe that time is an illusion, I aim to change your mind. If you already believe that time is real, I hope to give you better reasons for your belief.

This is a book for everyone, because there is no one whose thinking about the world is not shaped by how they see time. Even if you have never pondered its meaning, your thinking the very language with which you express your thoughts is colored by ancient metaphysical ideas about time.

When we adopt the revolutionary view that time is real, how we think about everything else will change. In particular, we will tend to see the future in a new way, one that vividly highlights both the opportunities and the dangers confronting the human species.

A small part of the story of this book is the personal journey that led me to rediscover time. My initial motivation might best be described in the language not of science but of fatherhood, through the conversations I have had with my young son, especially when I put him to bed at the end of the day. Daddy, he asked once as I read to him, did you have my name when you were my age? Here was a child awakening to the knowledge that there was a time before him and seeking to connect the short story of his life so far to a longer epic.

Every journey has a lesson to teach, and mine has been to realize just how radical an idea is contained in the simple statement that time is real. Having begun my life in science searching for the equation beyond time, I now believe that the deepest secret of the universe is that its essence rests in how it unfolds moment by moment in time.

Theres a paradox inherent in how we think about time. We perceive ourselves as living in time, yet we often imagine that the better aspects of our world and ourselves transcend it. What makes something really true, we believe, is not that it is true now but that it always was and always will be true. What makes a principle of morality absolute is that it holds in every time and every circumstance. We seem to have an ingrained idea that if something is valuable, it exists outside time. We yearn for eternal love. We speak of truth and justice as timeless. Whatever we most admire and look up to God, the truths of mathematics, the laws of nature is endowed with an existence that transcends time. We act inside time but judge our actions by timeless standards.

As a result of this paradox, we live in a state of alienation from what we most value. This alienation affects every one of our aspirations. In science, experiments and their analysis are time-bound, as are all our observations of nature, yet we imagine that we uncover evidence for timeless natural laws. The paradox also affects our actions as individuals, family members, and citizens, because how we understand time determines how we think about the future.