It was only fitting that the day before John Barrow was announced the 2006 Templeton Prize winner, it was International Pi Day, an annual celebration to mark the mathematical constant, 3.14. When prompted, Barrow playfully rattled off nearly a dozen numbers to the right of the decimal point in Pi, second nature for the Professor of Mathematical Sciences at the University of Cambridge. The author of 17 books, as well as one play—Infinities—Barrow’s work explores the deep reality of the universe through the lens of science. In the following Q&A, Professor Barrow explains why the multiverse has no beginning, the power of “doubling” and what roll cosmology plays as a bridge between science and religion.

Q: How did you come to know you had been chosen for the Templeton Prize? Was it a classic early morning phone call with you at the shaving mirror?

JB: Well, not quite, I was half expecting Jack Templeton to be ringing me about something else completely different. So I was completely surprised. I had no idea even at what time of year such decisions were made. It’s not like the Noble Prize where people know it’s a particular date and they all get up early in the morning to sit next to the phone.

Q: As a cosmologist and mathematician you obviously deal with physics and theoretical science, but one of the other constants you deal with is time. The universe is 13.7 billion years old. How does one even begin to think about something like that when it is so off the human time scale?

JB: It’s easier to think of distances rather than time. You have the same sort of fantastic extrapolation to deal with. So, what does it mean to say the universe is 13.7 billion years in size? In fact, if you take a piece of paper and double it in size, doubling works very, very quickly. I think you probably go from about 70 or so doublings of this piece of paper up to the whole size of this physical universe of 13.7 billion years. And if you took the piece of paper and you cut it in half, say about 120 to 130 times, then you’d be down to the smallest size of distance that physicists ever talk about, so called Planck length, where the very nature of space and time become uncertain. Just 205 doubling and halving of this piece of paper takes you from the smallest to the largest scales of physical reality. What you’re really doing is using a logarithmic scale and if you’re an astronomer, you tend to think that way.

Q: The idea that we are all made of carbon atoms from stars that exploded billions of years ago is, for some, a startling way of understanding the scale and scope of the universe. Did you have a moment when you first understood that big time scale and the circular nature of it?

JB: Not particularly, I mean, this argument is one we sort of introduced in our book The Anthropic Cosmological Principle (with Frank Tipler)] in 1986, of all the things that flow from the enormous age of the universe. So, we just said, ‘It’s the enormous age that produces all these remarkable links between us and universe as a whole.’ To make those atoms of carbon requires lots and lots of time, billions of years of time before they then get dispersed in supernova around the universe. Because the universe is expanding over that huge period of time, it necessarily becomes enormously large. So if the universe were just the size of the Milky Way galaxy, with the actual 100 billion stars in it, that universe would only be about a month old. There wouldn’t have been enough time to develop and sustain complexity of any sort. Also, because the universe is old, it’s expanded a lot and it’s become very cool. So the universe is necessarily rather cold and all the energies and radiation energy in it is degraded by the expansion and that’s why the sky is dark. There’s not enough energy in the universe to make it bright.

Q: What was our younger universe like?

JB: When the universe was much, much younger, when it was a thousand times smaller in its expansion than today, the temperature was a thousand times higher, 3,000 degrees, rather than 3 degrees. And then the whole sky was bright in the universe. But there could be no atoms then, so no observers could have seen a bright sky. The fact that we see that the universe is very big, is very old, is dark and cold; these are all necessary conditions for there to be hospitable, life-supporting conditions. We couldn’t observe the universe at different properties.

Q: Because we weren’t around to see it …

JB: We couldn’t be around. When the universe was younger, smaller, hotter, brighter, there couldn’t have been carbon atoms, no oxygen atoms, and nitrogen, it would have been too hot. You wouldn’t have complexity.

Q: Right, and we need complexity to form us . . .

JB: Yes, we are complexity.

Q: What is your opinion of the idea that our universe may be part of a multiverse?

JB: It’s an inescapable consequence of the type of theory that we have at the moment. Many physicists find it very unsatisfactory in a sense that it removes the possibility of explaining many things in a way that they would like to. You know that many different possibilities form out differently from place to place, and we do just happen to be living in one of the regions where things are now likely to develop. In the future, we want to know what’s the probability of that happening. We don’t know how to do that calculation at the moment. It turns out to be very difficult to give an answer to the question: How likely, in the multiverse, is the type of universe that we see?

The other issue here is when people say, ‘Did the universe have a beginning? Will it have an end?’ Suddenly you’ve got a more complicated situation. You can think, in a cartoon-like way, about the multiverse, rather like a great foam of bubbles expanding, and we live in one of the bubbles. When you say, ‘Did our universe have a beginning?’ There’s really two answers. It’s possible for our little bubble to have a beginning. It can pop into existence in some kind of vacuum fluctuation, and it may, or may not, have an end. The bubble may burst, or collapse. But yet the whole foam in this scenario does not have a beginning. So, it’s like an eternal process continually giving rise to the appearance of bubbles, some of which disappear, some of which persist. So, our bit of the universe, our mini-universe, has a beginning, but the whole multiverse does not.

Q: That might be unsatisfying to some people.

JB: Yes, but again it’s not possible to falsify or test, so far as we can see, this sort of multiverse scenario.

Q: Do you feel like superstring theory is physics or metaphysics at this point in time?

JB: Well I think its mathematics. There’s a mathematical structure that’s very beautiful and compelling and it’s unique for its purpose. There’s one mathematical structure that allows you to make calculations which have finite answers and within this mathematical structure you can pack in lots of the other mathematical structures that describe all physics that we know. So people explore ‘How can we extract predictions?’ ‘How can we get more physics out of this structure?’ so it’s closer to pure mathematics than the metaphysics, which means that you can do rather rigorous calculations. It’s not just the matter of opinion, or somebody’s philosophical prejudice. There is just one way to develop the mathematics, but the challenge is to extract predictions from it that relate to things we can see. People have gotten used to expecting that this is always possible, but maybe not. You know, the universe is not made for our convenience and why should it be that every true theory of nature is accessible to us, here and now, experimentally. I’ll be a bit suspicious if a fundamental Theory of Everything suddenly turned up to be . . .