While some constants seem as if they will be fixed, others have the scope to be other than they are, and some seem completely untouched by everything else about the Universe. Do their values fall out at random? Could they really be different? How different could they be if life is to be possible in the Universe?

Back in 1981, my first book, The Anthropic Cosmological Principle, explored all the then-known ways in which life in the universe was sensitive to the values of the constants of Nature. Universes with slightly altered constants would be still-born, devoid of the potential to evolve and sustain the sort of organised complexity that we call life. Since that time, cosmologists have found more and more ways in which the Universe could exhibit variations in its defining constants; more and more ways in which life could have failed to emerge in the Universe. They have also begun to take seriously the possibility and actuality of other universes in which the constants of Nature do take different values. Inevitably, we find ourselves in a world where things fell out right. But what was the chance of that happening? Here we shall look at many of these possibilities, connecting them to the curious history of our attempts to understand the values of our constants of Nature.

Recently, one big story about the constants of Nature has produced a focus for media attention and detailed scientific research. It raises the most basic question of all: are the constants of Nature really constant after all? A new method of scrutinizing the constants of Nature over the last 11 billion years of the Universe's history has been devised by a group of us. By looking at the atomic patterns barcoded into the light that reaches us from distant quasars we can look and see what atoms were like when the light began its journey billions of years ago. So, were the constants of Nature always the same? The answer, unexpected and shocking, raises new possibilities for the Universe and the laws that govern it. This book will tell you about them.

I would like to thank Bernard Carr, Rob Crittenden, Paul Davies, Michael Drinkwater, Chris Churchill, Freeman Dyson, Vladimir Dzuba, Victor Flambaum, Yasunori Fujii, Gary Gibbons, J. Richard Gott, Jörg Hensgen, Janna Levin, João Magueijo, Carlos Martins, David Mota, Michael Murphy, Jason Prochaska, Martin Rees, Håvard Sandvik, Wallace Sargent, Ilya Shlyakhter, Will Sulkin, Max Tegmark, Virginia Trimble, Neil Turok, John Webb, and Art Wolfe for discussions and contributions of ideas, results, and images.

I would also like to thank Elizabeth, for surviving at one stage the thought that the book might need to be retitled A River Runs Through It, and our three children David, Roger and Louise who were always worried that pocket-money might be a constant of Nature.

J.D.B

Cambridge, April 2002

chapter one
Before the Beginning

‘What happens first is not necessarily the beginning.’

Henning Mankell1

SAMELINESS

‘There is nothing that God hath established in a constant cause of nature, and which therefore is done everyday, but would seem a miracle, and exercise our admiration, if it were done but once.’

John Donne2

Change is a challenge. We live in the fastest moving period of human history. The world around us is driven by forces that make our lives increasingly sensitive to small changes and sudden responses. The elaboration of the Internet and the tentacles of the Worldwide Web have put us in instantaneous contact with computers and their owners all round the world. The threats from unchecked industrial progress have brought about ecological damage and environmental change that appears to be happening faster than even the gloomiest prophets of doom had predicted. Children seem to grow up faster. Political systems realign in new and unexpected ways more quickly and more often than ever before. Even human beings and the information they embody are facing editorial intervention by more ambitious spare-part surgery or the reprogramming of parts of our genetic code. Most forms of progress are accelerating and more and more parts of our experience have become entwined in the surge to explore all that is possible.

In the world of scientific exploration the recognition of the impact of change is not so new. By the end of the nineteenth century it had been appreciated that once upon a time the Earth and our solar system had not existed; that the human species must have changed in appearance and average mental capability over huge spans of time; and that in some broad and general way the Universe should be winding down, becoming a less hospitable and ordered place. During the twentieth century we have fleshed out this skeletal picture of a changing Universe. The climate and topography of our planet is continually changing and so are the species that live upon it. Most dramatically of all, we have discovered that the entire universe of stars and galaxies is in a state of dynamic change, with great clusters of galaxies flying away from one another into a future that will be very different from the present. We have begun to appreciate that we are living on borrowed time. Cataclysmic astronomical events are common; worlds collide. Planet Earth has been hit in the past by comets and asteroids. One day its luck will run out, the shield provided so fortuitously by the vast planet Jupiter, guarding the outer reaches of our solar system, will not be able to save us. Eventually, even our Sun will die. Our Milky Way galaxy will be drawn into a vast black hole deep in its centre.