The Goldilocks Enigma: Why Is the Universe Just Right for Life?

  Table of Contents

  Title Page

  Table of Contents

  Copyright

  Dedication

  Preface and Acknowledgments

  A Note on Numbers

  The Big Questions

  The Universe Explained

  How the Universe Began

  What the Universe Is Made of and How It All Holds Together

  The Lure of Complete Unification

  Dark Forces of the Cosmos

  A Universe Fit for Life

  Does a Multiverse Solve the Goldilocks Enigma?

  Intelligent and Not-So-Intelligent Design

  How Come Existence?

  Afterword: Ultimate Explanations

  Notes

  Bibliography

  Index

  About the Author

  First Mariner Books edition 2008

  Copyright © 2006 by Paul Davies

  First published in Great Britain by The Penguin Press, a member of Penguin Group (UK), in 2006

  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.hmhco.com

  The Library of Congress has cataloged the print edition as follows:

  Davies, P.C.W.

  Cosmic jackpot : why our universe is just right

  for life / Paul Davies.

  p. cm.

  Includes bibliographical references and index.

  ISBN 978-0-618-59226-5

  ISBN 978-0-547-05358-5 (pbk.)

  1. Cosmogony. 2. Cosmology. 3. Teleology. 4. God—Proof, Cosmological. 5. God—Proof, Teleological. 6. Anthropic principle. 7. Human beings. 8. Life on other planets. I. Title.

  BS651.D325 2007 523.1'2—dc22 2006023567

  eISBN 978-0-547-34846-9

  v2.1113

  TO JOHN ARCHIBALD WHEELER

  who was never afraid to tackle

  the big questions

  Preface and Acknowledgments

  WHEN I WAS A PHD STUDENT at University College London in the 1960s, my supervisor handed me a curious technical paper to read “as a bit of light relief” from my major project. The paper (which was never actually published in the form in which I read it) was based on a lecture given in the United States by the young English cosmologist and theoretical physicist Brandon Carter. The subject matter was both radical and unusual. The normal work of a theoretical physicist is to investigate an unsolved problem about a natural phenomenon by applying the laws of physics in the form of mathematical equations and then trying to solve the equations to see how well they describe the real thing. But Carter was addressing an entirely different sort of problem, having to do with the forms of the laws themselves. He asked himself the following question: “Suppose the laws had been a bit different from what they actually are, in this or that respect—what would the consequences be?” Philosophers call this type of investigation counterfactual analysis, and although fiction writers have long been fond of the device (I recently read a novel in which the Nazis defeated Britain in World War II and the UK became a German puppet state), it was groundbreaking for a scientist to consider.

  The focus of Carter’s “what if” analysis was again unusual for a theoretical physicist. It concerned the existence of life. Specifically, Carter’s calculations suggested that if the laws had differed only slightly from what we find them to be, then life would not have been possible and the universe would have gone unobserved. In effect, said Carter, our existence hinges on a certain amount of delicate “fine tuning” of the laws. Like Goldilocks’ porridge, the laws of physics seemed to Carter to be “just right” for life. It looked like a fix—a big fix. Somewhat unwisely, he named this fine-tuning “the anthropic principle,” giving the false impression that it concerned humankind specifically (which was never his intention).

  Although Carter’s paper was modest in scope and cautious in conclusion, it triggered nothing less than a revolution in scientific thinking and sparked a furious controversy that has rent the scientific community ever since. The study of counterfactual analysis in physics and cosmology was taken up in the 1970s by Martin Rees and Bernard Carr, resulting in a landmark review paper published in 1979.1 Inspired by this paper, I wrote a little book on the subject called The Accidental Universe, which was published by Cambridge University Press in 1982. A few years later, a much more systematic and thoroughgoing text appeared—The Anthropic Cosmological Principle, by John Barrow and Frank Tipler.2 It has formed the starting point for hundreds of papers over the years.

  During the early 1980s, the anthropic principle was slammed by many scientists as quasi-religious mumbo jumbo. In a scathing put-down in the New York Review of Books in 1986, the mathematician and writer Martin Gardner itemized the various proposed versions of the anthropic principle (AP): Weak (WAP), Strong (SAP), Participatory (PAP), Final (FAP), and—his favored version—the Completely Ridiculous Anthropic Principle (CRAP).3 And that was pretty much the tone of the debate for a decade or so. But developments in high-energy particle physics and cosmology, especially in the study of the hot big bang that gave birth to the universe, slowly changed sentiment. The laws of physics, once regarded as cast in tablets of stone, began to look less absolute. Evidence accumulated that some of the laws at least were not true, fundamental laws, but “effective laws,” the familiar form of which applies only at energies that are very low compared with the fierce violence of the big bang. Significantly, theoretical analysis suggested that some features of the laws might be accidental, reflecting the vagaries of the manner in which our patch of the universe cooled from the big bang. The implication was, of course, that the low-energy form of these laws could have been different, and might even be different, in some other cosmic region. What we had previously been calling “the universe” began to resemble a variegated “multiverse”—“a crazy quilt of environments with different properties and different laws of physics,” in the words of Leonard Susskind, a theoretical physicist and cosmologist at Stanford University and a leading proponent of the multiverse idea.4 It would of course be no surprise that we find ourselves living in a region fit for life, for we obviously could not be living in a place where life is impossible.

  At this stage, atheists began to take an interest. Unhappy that the fine-tuning of the laws of physics smacked of some sort of divine design, they seized on the multiverse theory as a neat explanation for the uncanny bio-friendliness of the universe. So, confusingly, the anthropic principle came to be seen, at one and the same time, as both a scientific alternative to design and a quasi-religious theory. I stepped into this muddle in 2003, persuading the John Templeton Foundation to sponsor a workshop on multiverse cosmology at Stanford University, which I co-chaired with the cosmologist Andrei Linde. The results of our deliberations were published in a volume edited by Bernard Carr.5 A follow-up workshop, with more emphasis on string theory (the currently fashionable attempt to unify physics), was held in March 2005.

  While these theoretical developments were taking place, some spectacular advances were being made in observational cosmology. These came about from increasingly painstaking surveys of the universe by the Hubble Space Telescope and various ground-based instruments, the detailed mapping of the cosmic afterglow of the big bang by a satellite named WMAP, and the unexpected discovery that the universe is accelerating under the action of some mysterious “dark energy.” As a result of this fillip, cosmology, long a scientific backwater, suddenly became a mainstream science, with a f
erment of new ideas, many of them weird and counterintuitive. It seems that we are now entering a new era that is transforming our view of the universe and the place of humankind within it.

  In this book I shall explain the ideas that underlie these dramatic developments, focusing especially on “the Goldilocks factor”—the fitness of the universe for life. In the early chapters I shall set out the basic concepts of modern physics and cosmology and then describe the multiverse theory and the arguments for and against it. Toward the end of the book I shall take a critical look at the various responses to the fine-tuning issue. I shall also ask whether scientists really are on the verge of producing a theory of everything—a complete and self-contained explanation for the entire physical universe—or whether there will always remain a mystery at the heart of existence.

  For these later chapters I have drawn inspiration from the great theoretical physicist John Archibald Wheeler, to whom I have dedicated this book. I first learned of Wheeler’s work while I was a student, and in subsequent years I came to know him quite well, on both the personal and the professional level. I visited him in Austin, Texas, and he visited me in England on a number of occasions. He graciously endorsed my first book, The Physics of Time Asymmetry, with enthusiastic praise and took a keen interest in my work over three decades. It was a privilege to assist in the organization of his ninetieth-birthday party conference in March 2002, a gathering of extremely distinguished scientists in Princeton, New Jersey, where Wheeler began and ended his career.

  In the late 1930s Wheeler worked with the legendary Niels Bohr on key aspects of nuclear fission. He went on to manage the rebirth of gravitational theory in the 1950s, taking up where Einstein left off. It was Wheeler who coined the terms black hole and wormhole. Above all, he recognized the need to reconcile the twin pillars of twentieth-century physics—the general theory of relativity and quantum mechanics—in a unified theory of quantum gravity. Many of his graduate students have enjoyed scientific careers of immense distinction; one of them was the well-known Nobel Prize winner Richard Feynman.

  Wheeler’s style was distinctive. He was the master of the “thought experiment,” taking an accepted idea and extrapolating it to the ultimate extreme, to see if and when it would break down. He loved to focus on the really big questions: whether physics could be unified; whether space and time could be derived from some more basic entity; whether causality could operate backward in time; whether the complex and abstract laws of physics could be reduced to a single, simple statement of the obvious; and how observers fitted into the scheme. Not content with simply applying the laws of quantum mechanics, he wanted to know where they came from: “How come the quantum?” he asked. Unhappy with the disjunction between the concepts of matter and information, he proposed the idea of “it from bit”—the emergence of particles from informational bits. Most ambitious of all was his question “How come existence?”—an attempt to explain everything without resorting to some fixed foundation for physical reality that had to be accepted as “given.”

  I once asked Wheeler what he considered his most important achievement, and he answered, “Mutability!” By this he meant that nothing is absolute, nothing is so fundamental that it cannot change under suitably extreme circumstances—and that includes the very laws of the universe. These concepts together led him to propose “the participatory universe,” an idea (or, as Wheeler preferred, “an idea for an idea”) that has proved to be an important part of the multiverse/anthropic discussion. In his beliefs and attitudes, Wheeler represented a large section of the scientific community: committed wholeheartedly to the scientific method of inquiry, but not afraid to tackle deep philosophical questions; not conventionally religious, but inspired by a reverence for nature and a deep sense that human beings are part of a grand scheme that we glimpse only incompletely; bold enough to follow the laws of physics wherever they lead, but not so arrogant as to think that we have all the answers.

  I have tried to keep the level of explanation in this book as nontechnical as possible by avoiding jargon and unnecessarily pedantic descriptions. Equations are kept to an absolute minimum. Here and there I have used boxes to summarize or expand some difficult topics. In some ways this book is a sequel to my earlier work The Mind of God,6 but in spite of the emphasis on the deep and meaningful, I intend it also to serve as a straightforward introduction to modern cosmology and fundamental physics. I have drawn clear distinctions between secure facts, reasonable theorizing, and wild conjecture. The primary purpose of the book is to appeal to scientific inquiry and reason in order to address the big questions of existence. I have made no attempt to consider other modes of discovery, such as mysticism, spiritual enlightenment, or revelation through religious experience.

  Many people have assisted me in this project. First and foremost was my wife, Pauline, who has an uncompromising attitude toward sloppy reasoning or unjustified assumptions, and a meticulous attention to detail. She read the text with extraordinary thoroughness, pouncing on many a non sequitur or confusing explanation and chiding me for my irrepressible tendency to lapse into starry-eyed philosophizing. (She also complained that the book stopped just when it was getting interesting.) Having such a hardheaded critic close at hand has improved the book enormously. My literary agent, John Brockman, was the driving force behind the project, having perceived that cosmology is at a crossroads and the reading public hopelessly confused about the plethora of new discoveries and theories. I have benefited greatly from the participants in the two Stanford workshops, especially Andrei Linde. I am grateful to the John Templeton Foundation for making these lively events possible. Over the years, several people have influenced my thinking, in many cases from personal contact and discussions as well as through their written work. They include Nancy Abrams, John Barrow, Bernard Carr, Brandon Carter, David Deutsch, Michael Duff, George Ellis, David Gross, John Leslie, Charles Lineweaver, Joel Primack, Martin Rees, Frank Tipler, and, of course, John Wheeler. I should also like to thank Chris Forbes for comments on part of the manuscript and John Woodruff for his meticulous care with the copyediting.

  P.C.W.D.

  A Note on Numbers

  In this book I often have to deal with very large and very small numbers. In many cases I write out these numbers in words, but where necessary I use the conventional powers-of-ten notation, as follows:

  One million 1,000,000 106

  One billion 1,000,000,000 109

  One trillion 1,000,000,000,000 1012

  One millionth 1/1,000,000 10-6

  One billionth 1/1,000,000,000 10-9

  One trillionth 1/1,000,000,000,000 10-12

  1

  The Big Questions

  Confronting the Mystery of Existence

  FOR THOUSANDS OF YEARS, human beings have contemplated the world about them and asked the great questions of existence: Why are we here? How did the universe begin? How will it end? How is the world put together? Why is it the way it is? For all of recorded human history, people have sought answers to such “ultimate” questions in religion and philosophy or declared them to be completely beyond human comprehension. Today, however, many of these big questions are part of science, and some scientists claim that they may be on the verge of providing answers.

  Two major developments have bolstered scientists’ confidence that the answers lie within their grasp. The first is the enormous progress made in cosmology—the study of the large-scale structure and evolution of the universe. Observations made using satellites, the Hubble Space Telescope, and sophisticated ground-based instruments have combined to transform our view of the universe and the place of human beings within it. The second development is the growing understanding of the microscopic world within the atom—the subject known as high-energy particle physics. It is mostly carried out with giant particle accelerator machines (what were once called “atom smashers”) of the sort found at Fermilab near Chicago and the CERN Laboratory just outside Geneva. Combining these two subjects—the science of t
he very large and the science of the very small—provides tantalizing clues that deep and previously unsuspected linkages bind the micro-world to the macro-world. Cosmologists are fond of saying that the big bang, which gave birth to the universe billions of years ago, was the greatest ever particle physics experiment. These spectacular advances hint at a much grander synthesis: nothing less than a complete and unified description of nature, a final “theory of everything” in which a flawless account of the entire physical world is encompassed within a single explanatory scheme.

  The Universe Is Bio-Friendly

  One of the most significant facts—arguably the most significant fact—about the universe is that we are part of it. I should say right at the outset that a great many scientists and philosophers fervently disagree with this statement: that is, they do not think that either life or consciousness is even remotely significant in the great cosmic scheme of things. My position, however, is that I take life and mind (that is, consciousness) seriously, for reasons I shall explain in due course. At first sight life seems to be irrelevant to the subject of cosmology. To be sure, the surface of the Earth has been modified by life, but in the grand sweep of the cosmos our planet is but an infinitesimal dot. There is an indirect sense, however, in which the existence of life in the universe is an important cosmological fact. For life to emerge, and then to evolve into conscious beings like ourselves, certain conditions have to be satisfied. Among the many prerequisites for life—at least, for life as we know it—is a good supply of the various chemical elements needed to make biomass. Carbon is the key life-giving element, but oxygen, hydrogen, nitrogen, sulfur, and phosphorus are crucial too. Liquid water is another essential ingredient. Life also requires an energy source and a stable environment, which in our case are provided by the sun. For life to evolve past the level of simple microbes, this life-encouraging setting has to remain benign for a very long time; it took billions of years for life on Earth to reach the point of intelligence.