Do We Live in a Multiverse?
Interview with Paul Davies
Paul Davies has spent his professional life wearing two hats: one, as a widely respected physicist, and two, as someone who spends a good part of his time explaining complicated science in terms accessible to the layperson. As the author of over 25 books, including The Mind of God, How to Build a Time Machine, and most recently, The Goldilocks Enigma: Why is the universe just right for life? we asked him to talk about the multiverse, why it's important, and what his peers in the scientific community make of the concept.
JTF: The concept of a multiverse is a very ancient one. Why is it coming to the public's attention again?
PD: Advances in fundamental physics and cosmology lead to a definite prediction that the universe should have a domain structure in which the laws of physics vary from one domain to another. The currently fashionable attempt to unify all of physics, called string theory, suggests that there are an almost limitless number of alternative possible low-energy worlds, called "the landscape". When this is combined with the favored model for the origin of the universe – eternal inflation – then a mechanism exists for populating the landscape with really-existing universes, each universe being a "bubble" of expanding space with its own distinctive set of laws dictated by where on the landscape of possibilities it emerges.
JTF: What do scientists make of the "multiverse" concept?
PD: The concept of a multiverse has split the scientific community more sharply than any cosmological controversy since the big bang challenged the steady state theory. Passions are running high. The consequences are profound, because the ramifications include whether the universe is designed for life, or is life-encouraging merely as a result of a fluke, or is seen by us to be life-friendly only as a result of a selection effect. For string theorists, a major issue is whether their theory will yield a unique description of the universe, or permit a vast array of possibilities. The latter conclusion is seen as dangerously undermining of the whole enterprise.
JTF: What should people understand, that they don't, about what the multiverse concept demands of science, and us?
PD: The multiverse demands different criteria of scientific test, because the other universes may never be directly observable. But there could be indirect support, for example, from statistical analyses. The "leap of faith" needed to accept the existence of a multiverse is greater than that normally expected of scientists, which is to assume the unexplained existence of the laws of physics, although it is perhaps less than that required for belief in a cosmic designer who made a universe fit for life.
Bibliography
Davies, Paul. About Time: Einstein's Unfinished Revolution. New York: Touchstone, 1996.
Davies, Paul. How to Build A Time Machine. New York: Penguin Press, 2003.
Davies, Paul. The Mind of God: The Scientific Basis for a Rational World. New York: Touchstone, 1993.
Davies, Paul. The Origin of Life. New York: Penguin Press, 2003.
Davies, Paul. The Physics of Time Asymmetry. Berkeley: University of California Press, 1989.
Davies, Paul & Nicholas Birrell. Quantum Fields in Curbed Space. New York: Cambridge University Press, 1984.
Paul Davies, theoretical physicist and cosmologist, holds the post of College Professor at Arizona State University. He previously held academic appointments at the Universities of Cambridge, London, Newcastle upon Tyne and Adelaide, before helping establish the Australian Centre for Astrobiology at Macquarie University in Sydney. His research has been in the fields of quantum gravity, black holes and early-universe cosmology. More recently, he has worked in astrobiology on problems concerning the origin of life and the transfer of micro-organisms between planets. He is the author of over 25 books, the latest of which is The Goldilocks Enigma: Why is the universe just right for life? Previous well-known titles include The Mind of God, About Time, The Fifth Miracle and How to Build a Time Machine. In 1995 Dr. Davies received the Templeton Prize.