ensemble, the multiverse, could encompass
27, 28, 29, 2003
...Our home universe has to be special-in its contents,
and in the laws and forces governing it-for any life to evolve in it.
But we can understand it better by realizing that it is just
one island in the cosmic archipelago."
-Martin J. Rees
Before the Beginning
The concept of a multiplicity of possible or actual universes is a very ancient one. In recent years, however, advances in physics and cosmology have given the “multiverse” idea a plausible scientific basis. Its new lease on life can be traced to the theory of inflation, which in its original form, suggested by Alan Guth, held that a split second after the Big Bang the universe abruptly jumped in size by a huge factor. Most theorists agreed that inflation could explain many puzzles about the structure and evolution of the universe. In the variant introduced by Andrei Linde, inflation spawns a network of branching “bubble” universes with different laws of physics operating inside of them. It has become fashionable to invoke some species of the multiverse theory to account for the well-known examples of parameter fine-tuning associated with the emergence of life in the observable universe where Earth has its home. The possibility of many universes raises deep scientific, philosophical, and theological questions. How does the multiverse modify our understanding of the ultimate origin of the physical universe in time? Does the cosmos reproduce forever? Can the multiverse theory be made consistent with Occam’s razor? Is the theory falsifiable, and if so, how? If our universe, subtle, beautiful, and intelligible as it appears, is just, in Martin Rees’s phrase, “one island in the cosmic archipelago,” can it really be so special after all? To examine the conjectures that are so dramatically enlarging our cosmic perspective, fourteen scientists and philosophers gather in Palo, Alto, California under the aegis of the John Templeton Foundation. Their conversation takes place on the campus of Stanford University, home of one of the world's leading research laboratories, the Stanford Linear Accelerator Center, and to a highly-regarded physics department with dynamic astrophysics and particle-theory groups.
Paul Davies is the professor of natural philosophy in the Australian Centre for Astrobiology at Macquarie University. After earning a Ph.D. in physics at University College, London in 1970, he held academic appointments in astronomy, physics, and mathematics at the universities of Cambridge, London, Newcastle upon Tyne, and Adelaide. His research has spanned the fields of cosmology, gravitation, and quantum field theory, with particular emphasis on black holes and the origin of the universe. Dr. Davies is also widely known as an author. He has written over twenty-five books, both popular and specialist works, including The Physics of Time Asymmetry, Quantum Fields in Curved Space (co-authored with Nicholas Birrell), The Mind of God, About Time, How to Build a Time Machine, and, most recently, The Origin of Life, which was published by Penguin in January. He also has extensive experience in television and radio, including the presentation of two Australian television series entitled The Big Questions. His work in astrobiology was the subject of a BBC television documentary, “The Cradle of Life,” earlier this year. He has won numerous awards for his scientific and media work, most notably the 1995 Templeton Prize. He received the 2001 Kelvin Medal presented by the UK Institute of Physics and the 2002 Michael Faraday Prize of the Royal Society for his contributions to promoting science to the public. In April 1999 the asteroid 1992 OG was officially named (6870) “Pauldavies” in his honor.
Nick Bostrom is a philosopher of science. A native of Sweden, he received his undergraduate degree from the University of Gothenburg and went to earn a master’s degree in philosophy and physics at the University of Stockholm and another master’s degree in computational neuroscience at King’s College, London. He was awarded a Ph.D. in philosophy from the London School of Economics in 2000. The late Robert Nozick, the Harvard philosopher, selected his dissertation as one of the best dissertations in philosophy in its year of its presentation. Dr. Bostrom began his teaching career as a lecturer at Yale University and last year won a prestigious junior research fellowship from the British Academy to work at Oxford University. He is the recipient of a John Templeton Foundation research award. The former editor of the Journal of Evolution and Technology, he is the author of some thirty articles published in scholarly journals and chapters in volumes of collected works. Routledge published his first book, Anthropic Bias: Observation Selection Effects in Science and Philosophy, in 2000.
A professor of physics emeritus at Stanford University, James D. Bjorken is one of the outstanding theoretical physicists of his generation. He formulated the scaling law for so-called “deep inelastic electron-proton scattering,” which led to the identification of point-like quark constituents within the proton, and has made many other seminal contributions to particle physics and quantum field theory. With Sheldon Glashow, he presented arguments for the existence of a fourth kind of quark, which they dubbed “charmed” to denote its special charge or flavor. Dr. Bjorken also participated in experiments that searched for hypothetical particles called “axions,” as well as in an experiment that searched for a novel state of matter called “disoriented chiral condensate.” He contributed to a widely used theory of the growth of circulating beams of protons in storage rings and constructed a hydrodynamic model of central particle production in ion-ion collisions. A graduate of the Massachusetts Institute of Technology, he earned his Ph.D. in physics at Stanford in 1959, the year he began his teaching career there as an assistant professor. He joined the faculty of Stanford Linear Accelerator Center (SLAC) in 1962, and in 1979, he became the associate director for physics of the Fermi National Accelerator Laboratory in Batavia, Illinois. Dr. Bjorken returned to SLAC ten years later and retired in 1998. A member of the National Academy of Sciences, the American Academy of Arts and Sciences, and a foreign member of the Swedish Academy of Sciences, he has delivered the Morris Loeb Lectures at Harvard University and held the George Eastman Visiting Professorship at Oxford. Dr. Bjorken is the recipient of honorary degrees from the University of Torino and the University of Notre Dame. His many other honors include the Daniel Heinemann Prize in Mathematical Physics awarded by the American Physical Society and the Ernest Orlando Lawrence Medal in Physics presented by the U.S. Department of Energy. In addition to numerous and often cited research papers, he wrote, with Sidney Drell, a pair of books, Relativistic Quantum Mechanics (1964) and Relativistic Quantum Fields (1965), that served as standard graduate texts for more than twenty years.
Bernard J. Carr is professor of mathematics and astronomy at Queen Mary College, University of London, where he is a member of the astronomy unit and head of the cosmology research group. His special interests are the early universe, primordial black holes, dark matter, Population III stars, and the anthropic principle. Dr. Carr took first class honors in mathematics at Trinity College, Cambridge, and went on to do doctoral research in relativity and cosmology under Stephen Hawking at the Institute of Astronomy in Cambridge and the California Institute of Technology. After completing his Ph.D. in 1976, he became a research fellow at Trinity College and an advanced SERC fellow at the Institute of Astronomy. In 1979 he was awarded a Lindemann Fellowship for post-doctoral research at several American universities. He joined the Queen Mary College faculty in 1985. Dr. Carr has held visiting professorships at Kyoto University, the University of California in Santa Barbara, and the Fermi National Accelerator Laboratory. He is the author of more than a hundred scientific papers and his monograph, “Cosmological Gravitational Waves,” won the 1985 Adams Essay Prize.
A philosopher whose research interests focus on the relationship of physics and religion, Robin Collins teaches at Messiah College in Grantham, Pennsylvania where he is an associate professor of philosophy. He received a baccalaureate degree from Washington State University, whose faculty named him the outstanding student in physics in his junior and senior years, and went on to do graduate work in theoretical physics at the University of Texas in Austin. He earned a doctorate in philosophy at the University of Notre Dame in 1993 and received Notre Dame’s Graduate Student Award in the Humanities that year for outstanding research, teaching, and publication. After post-doctoral research in the philosophy of science at Northwestern University, Dr. Collins joined the Messiah faculty in 1994. In more than a dozen scholarly articles and essays in volumes of collected works, he has examined the findings of twentieth-century science and concluded that such concepts as the fine-tuning of the cosmos suggest a broader and deeper conception of a “designer” than older, mechanistic models of the universe. He has written that theories positing the existence of multiple universes support the idea of a creator of infinite creativity. Dr, Collins is the recipient of a John Templeton Foundation Science and Religion Course Award and a Pew Fellowship, as well as a fellowship from the Center for Philosophy of Religion at Notre Dame, to support work on a book he is preparing for publication. It is tentatively entitled “The Well-Tempered Universe: God, Cosmic Fine-Tuning, and the Laws of Nature.” He is also completing an introductory textbook entitled “The Big Questions: A Philosophical Inquiry into the Meaning of Life and Related Issues.”
Savas Dimopoulos is a theoretical physicist widely known for proposing (with Howard Georgi) the supersymmetric extension of the standard model of particle physics, the self- contained picture of fundamental particles and their interactions. His theories about the supersymmetric unification of the strong and electroweak forces, first published in 1981, were subsequently confirmed by experiments at the Stanford Linear Accelerator Center and CERN. Dr. Dimopoulos's and Dr. Georgi's prediction of the presence of "superpartners" of each of the fundamental particles will be tested at CERN's Large Hadron Collider beginning in 2007. More recently Dr. Dimopoulos (with Nima Arkani-Hamed and Gia Dvali) made the startling suggestion that the extreme weakness of gravity can be attributed to the existence of large extra dimensions of space, perhaps as big as a millimeter, where the scale at which gravity becomes comparable to other forces is lowered to the electroweak scale. Among the implications of his thinking is the notion that our universe is a three-dimensional island floating inside a fourth dimension—a membrane called a D-brane— and but one of innumerable parallel universes. A native of Athens, Dr. Dimopoulos was graduated from the University of Houston and received his Ph.D. in physics from the University of Chicago in 1978. He did post-doctoral work at Columbia University and joined the Stanford faculty in 1979. He also has taught at Harvard and served as a visiting professor at the University of California, Santa Barbara and Boston University. From 1994 to 1997, he was a staff member at CERN. The recipient of an Alfred P. Sloan Foundation Fellowship and a Distinguished Alumnus Award of the University of Houston, Dr. Dimopoulos is a fellow of the Japanese Society for the Promotion of Science. He is the author of some 115 scientific papers.
Working on the leading edge of high-energy theoretical particle physics for more than thirty years, Renata Kallosh has been a professor of physics at Stanford University since 1990. She has done much of the important research in the still-evolving field of supersymmetry and black holes. In particular, she was the first to perform quantization of supergravity. Using string theory, the leading candidate for a unified quantum theory of elementary particles and their interactions including gravity, in her investigations of puzzling questions about quantum gravity, Dr. Kallosh has provided a formula for the macroscopic entropy of a sub-class of extreme black holes and shown it to be universal. Her current studies also involve looking at the possible role of M-theory, a candidate theory of everything that is proving useful in linking supergravity with string theory and various string theories with each other, in cosmology. With her husband, Andrei Linde, she examined some of the assumptions in recent cosmic models, which were built on the discovery that the expansion of the universe appears to be speeding up, and found that dark energy, the mysterious component of space thought to drive acceleration, may eventually become negative, which may lead to a collapse of the universe. Dr. Kallosh is a native of Russia and earned her baccalaureate degree at Moscow State University. After taking her Ph.D. in physics at Moscow's Lebedev Physical Institute in 1968, she remained there as a junior fellow and was named a professor in 1981. Nine years later, she became a scientific associate at CERN for a year before immigrating to the United States and joining the Stanford faculty. Dr. Kallosh has published 158 papers in scientific journals.
Theoretical cosmologist Andrei Linde is the author of theories of the origin of the universe that have revolutionized cosmology. He helped lay the foundation for the concept of inflation -the idea that the universe began not with a hot big bang but with an extraordinarily rapid expansion of space in a vacuum-like state- while working at the Lebedev Physical Institute in his native Russia. A graduate of Moscow State University, Dr. Linde took his Ph.D. in physics at Lebedev in 1975 and became a professor there in 1985. He was the Morris Loeb Lecturer at Harvard in 1987, joined the staff of CERN in 1989, and came to Stanford in 1990. After his initial contribution to inflationary cosmology, Dr. Linde went on to propose other promising versions of this theory, such as "chaotic inflation." Published in 1986, his theory of a chaotic self-reproducing inflationary universe suggests that our universe is one of many inflationary universes that sprout from an eternal cosmic tree. His current research also involves phase transitions in the early universe, large-scale structure formation, and cosmological constraints on the properties of elementary particles. In three papers published last year with his wife, Renata Kallosh, Dr. Linde proposed that the dark energy, the haunting theoretical phenomenon reminiscent of Einstein's "cosmological constant," which is presently stretching spacetime at an ever increasing rate, may eventually become negative. As a result, the universe may begin collapsing in 10 to 100 billion years and end in a "big crunch." Our universe, in their model, is middle-aged, not, as once thought, at the beginning of its life cycle. But according to Dr. Linde's inflationary theory, while our "bubble" may die, the multiverse of bubbles will go on forever. The winner of the Lomonosov Award of the Academy of Sciences of the USSR, Dr. Linde received the Oskar Klein Medal in physics in 2001 and last year shared the Dirac Medal awarded by the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy on the centenary of Nobel laureate Paul Dirac's birth. He is the author of two books on inflationary theory and 194 scientific papers.
Viatcheslav Mukhanov is a professor of astroparticle physics and cosmology at Ludwig-Maximillians-Universität in Munich. Born in Russia, he was graduated from the Physical-Technical Institute in Moscow and took a Ph.D. in theoretical physics there in 1982. He began his career as a research scientist at Moscow’s Institute for Nuclear Research and became the senior scientist in 1991 after spending a year as a visiting professor at Brown University and at Tufts University. In 1992, he joined the faculty of the ETH (Swiss Federal Institute of Technology) in Zurich where he remained until accepting his present position in 1997. Dr. Mukhanov was the first scientist in his native country to recognize the power of the “many worlds” interpretation of quantum mechanics and published several important early papers on the approach, which envisages the entire universe as a quantum system. He was also the first author of the theory of density perturbations in inflationary cosmology. In 1981, he predicted that a remnant spectrum of the perturbations may have seeded large-scale structure formations in the universe and may have left an imprint on the cosmic microwave background anisotropy. His work was recognized in 1988 by a Gold Medal of the Academy of Sciences of the USSR. Dr. Mukhanov went on to explore novel models of inflation and introduced the concept of “k-essence” as a dynamic solution for explaining naturally why the universe has entered an epoch of accelerated expansion at a late stage of its evolution. He is the author of some 80 research papers in his field.
A professor of physics at the University of Alberta, Don N. Page does research mainly on theoretical gravitational physics, especially black hole thermodynamics and quantum cosmology. He has recently worked on the entropy of near-extreme charged black holes and black holes surrounded by reflecting shells and on finding logarithmic correction terms to the Bekenstein-Hawking formula for the entropy of a black hole. In cosmology, his investigations focus on what a quantum mechanical analysis of gravity can tell us about the size, shape, and arrow of time of the universe. He also has looked at the consequences on a new framework he developed for the laws of psycho-physical parallelism to connect quantum physics with consciousness. Dr. Page received his baccalaureate degree summa cum laude from William Jewell College and earned a Ph.D. in physics at California Institute of Technology in 1976. He was awarded a NATO post-doctoral fellowship to study at Cambridge University where he was a research assistant to Stephen Hawking. Joining the faculty of Pennsylvania State University in 1979, he became a professor of physics in 1986 and four years later accepted his present position at Alberta. Dr. Page has been a member of the visiting research faculty of the University of Texas at Austin, Caltech, and the University of California at Santa Barbara as well as a member of the Institute for Advanced Study in Princeton. He was a fellow of the Canadian Institute for Advanced Research from 1991 to 2002. He is currently a member of the Collaborative Research Group of the Pacific Institute for Mathematical Sciences and an affiliate member of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario. The recipient of research fellowships awarded by Darwin College, the Alfred P. Sloan Foundation, and the John Simon Guggenheim Foundation, he is the author of more than 120 scientific papers.
Martin J. Rees, England’s Astronomer Royal, is one of the world’s leading theoretical astrophysicists. He was for many years the director of Cambridge University’s famed Institute of Astronomy. Since 1992 he has been the Royal Society Research Professor at Cambridge and an official fellow at King’s College, Cambridge. Dr. Rees’s contributions to our understanding of the origin and nature of the universe have been exceptionally broad-based. Two decades ago, he showed how the anthropic principle could be used to determine most of the fundamental constants of physics. He has added to our knowledge about the birth of stars and galaxies, demonstrated how deep-space quasars, the highly energetic cores of active galaxies seen through the Hubble Space Telescope, might be powered by massive black holes, and expounded theories that explain the mysterious explosions known as gamma-ray “bursters.” A graduate of Trinity College, Cambridge, he took an undergraduate degree in mathematics and earned a Ph.D. in theoretical astronomy in 1967. He was a fellow of Jesus College, Cambridge, a research fellow at California Institute of Technology, and a staff member of Cambridge University’s Institute of Theoretical Astronomy before becoming a professor of astronomy at the University of Sussex in 1972. He returned to Cambridge the next year as Plumian Professor of Astronomy and Experimental Philosophy, a position from which he resigned in 1991 to devote more time to research and writing. Dr. Rees has lectured around the world and been a visiting professor at Caltech, Harvard, and the Institute for Advanced Study in Princeton, as well as a Regents Visiting Fellow at the Smithsonian Institution. He has served as president of the International Astronomical Union’s Commission on High Energy Physics, the Royal Astronomical Society, and the British Association for the Advancement of Science and as a trustee of the British Museum. He is currently a trustee of the John F. Kennedy Memorial Trust and the Institute of Public Policy Research. A Fellow of the Royal Society, a Fellow of the Institute of Physics, and a Fellow of the Institute of Mathematics and Its Applications, he is a foreign honorary member of the American Academy of Arts and Sciences, a foreign associate of the U.S. National Academy of Sciences, an officer in the French Ordre des Arts et des Lettres, a foreign member of the American Philosophical Society, the Royal Swedish Academy of Sciences, and the Italian Accademia Nazionale dei Lincei, an honorary fellow of the Indian Academy of Sciences and of Jesus College and Trinity College, Cambridge, an honorary member of the Russian Academy of Sciences and the Norwegian Academy of Science and Letters, and a member of the Accademia Europaea and the Pontifical Academy of Sciences. Dr. Rees was knighted by Queen Elizabeth II in 1992. He has won a dozen major scientific prizes, including, most recently, the Bower Prize of Philadelphia’s Franklin Institute and the Peter Gruber Foundation Cosmology Prize. He holds honorary degrees from ten universities. A member of the editorial boards of a number of leading scientific journals, he has published nearly 500 research papers and three technical books. His first volume for a lay audience, Before the Beginning (1997), was both an overview of and meditation on what is known and what is merely conjectured about our universe in which he suggested that the universe we observe may be part of a multiverse. His latest books are Just Six Numbers: The Deep Forces That Shape the Universe (2000), Our Cosmic Habitat (2001), and Our Final Hour, which was published this year by Basic Books.
The Felix Bloch Professor in Physics at Stanford University, Leonard Susskind has made pioneering contributions to some of the most important areas in contemporary theoretical physics. Thirty-five years ago, he developed the light cone frame as a tool for the study of relativistic quantum mechanics. In 1969, with Yoichira Nambu, he proposed a revolutionary, still mysterious idea called “string theory,” which holds that the building blocks of the universe are not point like particles, the familiar electrons and quarks, but unimaginably small, vibrating strings of some unknown component. Dr. Susskind has continued to refine his string hypothesis, now generally accepted as the only viable candidate to reconcile the differences between gravity and quantum mechanics despite its challenges to traditional understanding of space and time as well as energy and matter. Building on the idea that the universe can be compared to a hologram, in which information for a three-dimensional image can be stored on a flat surface, he discovered a matrix model as a more basic starting point for string theory. But he has also questioned string theory’s applicability to cosmology if recent observations of an accelerating universe prove true. Last summer he suggested that an evermore rapidly expanding universe is destined to repeat itself, but that the chances it would generate a world like ours are infinitesimal. The deep paradox he suggested is that either space is not accelerating for the reasons that scientist expect or we have yet to discover some other law of nature that is responsible for cosmic evolution. A graduate of City College of New York, Dr. Susskind earned his Ph.D. in physics at Cornell University in 1965. He held a National Science Foundation post-doctoral fellowship there the next year and in 1966 joined the faculty of Belfer Graduate School of Science at Yeshiva University. Named a professor in 1970, he spent a year as a visiting professor at the University of Tel Aviv and went to Stanford in 1979. Dr. Susskind has been a Loeb Lecturer at Harvard University and a Welch Lecturer at the University of Toronto. The recipient of Pregel Award of the New York Academy of Sciences and the J. J. Sakurai Prize in Theoretical Physics, he also won a Science Writing Award given by the American Institute of Physics. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. Dr. Susskind has published some 200 papers in scientific journals.
Max Tegmark is an assistant professor of physics and astronomy at the University of Pennsylvania whose principal research is focused on cosmological theory and connecting theory to observation. He uses data from analyses of galaxy clustering and the cosmic microwave background radiation to place sharp constraints on cosmological models, that is, to try to ground them in what can be measured in experiments. A native of Sweden with baccalaureate degrees both from the Stockholm School of Economics and the Swedish Royal Institute of Technology, he studied theoretical cosmology with astronomer Joseph Silk at the University of California, Berkeley and received his Ph.D. in physics in 1994. After two years as a research associate at the Max-Planck Institute for Physics in Munich, he spent more than three years doing post-doctoral research at the Institute for Advanced Study in Princeton before joining the Penn faculty in 1999. He has held a Hubble Fellowship awarded by the Space Telescope Institute and currently holds a David and Lucille Packard Foundation Fellowship. For contributions to research and teaching, the Research Corporation recently named him a Cottrell Scholar. Dr. Tegmark’s first work involved predicting the size of the earliest galaxies based on molecular physics. He has developed widely-used statistical techniques for analyzing cosmic microwave background and galaxy maps to measure cosmological parameters such as the amounts of ordinary matter and dark matter in the universe, the curvature of space, and the amplitudes of various types of density fluctuations that emerged in the first split second after the Big Bang. Many of Dr. Tegmark’s more than 100 scientific papers present ideas and data relevant to parallel universes, including evidence for infinite space and cosmological inflation, as well as for the possibility that the microwave background fluctuation level, the dimensionality of spacetime, and fundamental laws of physics can vary throughout a multiverse.
The application of quantum theory to cosmology has defined the research of Alexander Vilenkin for more than twenty years. His pursuit of questions about the origin and the destiny of the universe became possible, however, only after he left his native Russia. A Jew, born in the Ukraine, he was graduated from Kharkov State University with a degree in physics, but could neither gain admission to a doctoral program nor find work in his field. Emigrating in 1976, he was temporarily resident in Italy when he applied and was accepted at the State University of New York in Buffalo. Awarded a Ph.D. in physics the next year, he accepted a post-doctoral position at Case Western Reserve University in the physics of metals even as he conducted research in an area he found far more intriguing—black holes. In 1978, Dr. Vilenkin joined the faculty of Tufts University where he was named a professor of physics in 1987 and appointed director of the Tufts Institute of Cosmology two years later. His first major paper on inflation and quantum cosmology, published in 1982, explained how the universe could have been created ex nihilo through quantum energy spacetime fluctuations. In another paper, the following year, he made the then astonishing suggestion that almost all inflationary models are eternal—once the process starts it continues without end like a chain reaction, stopping in one region of space only to start in another, ultimately spawning an infinite number of “pocket universes.” His variant account for the universe’s birth “by quantum tunneling from nothing,” involved a leap from no size at all—zero radius—to a radius large enough for inflation to take over. Continuing to explore the implications of this idea, he and Arvinde Borde showed mathematically that a universe eternally inflating toward the future cannot be geodesically complete in the past, so that there must have existed in the indefinite past an initial “singularity,” an ultimate boundary, or beginning. Dr. Vilenkin is also a leading developer of the concept of cosmic strings—dense, linear “defects” in the fabric of space formed in the hot early universe, which he once thought might have a role in transforming matter and energy into galaxies. With Jaume Garriga, he has recently argued that there are an infinite number of regions of space the same size as our observable universe, but that their “histories”—or things that could possible happen within these realms, including the evolution of intelligent life— are finite, so that every possible version of history will have occurred elsewhere. They call their work a “metaphysical exercise” and name their concept “many worlds in one.” A fellow of the American Physical Society, Dr. Vilenkin has been the recipient of a National Science Foundation Presidential Young Investigator Award and a research grant from the John Templeton Foundation. He is the author of more than 160 scientific papers and (with E. Paul Shellard) the book, Cosmic Strings and Other Topological Defects (Cambridge University Press, 1994 and 2000).
hypothesis is that biology does not actually select a
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