One of the world's leading theoreticians on cosmic evolution, black holes and galaxies, Sir Martin Rees believes the world is ready for a new Copernican shake-up. Copernicus said the sun and not the Earth was the center of the solar system. Rees goes much further, arguing in his new book, "Before the Beginning," that our universe is but one among an infinite number.
Q. Most people have enough problems dealing with the everyday world. What is cosmology and why should people care?
A. People clearly are interested in seeing themselves in a broader context. In the 19th century, Charles Darwin's theory of evolution was of great public interest, even though it had no practical relevance.
What cosmologists are doing is setting our Earth and solar system in a broad cosmic context, tracing their evolution back to the formation of the Milky Way galaxy, right back even to the Big Bang.
Q. Is that kind of cosmic genealogical search telling us where we came from and the origins of atoms that make up the Earth and its species?
A. We've realized over the last 20 years or so that the elements of the periodic table weren't there from the beginning. They were made inside stars.
All the carbon and oxygen that we are made of was synthesized inside an early generation of stars that exploded as supernovae 5 billion years ago or more.
The solar system then condensed from the interstellar cloud already contaminated by the debris of earlier explosions.
If you're romantic, you can say we are the ashes of long dead stars and stardust. If you're less romantic, you can say we're the nuclear waste from old stars.
Q. Does progress in understanding the history of the universe lead to even deeper questions?
A. The most remarkable progress in cosmology is that we can describe the outlines of cosmic history from when the universe was a second old to the present time with a great deal of confidence.
What we want to understand better is what happened before the first second was over, in the first microsecond, back even to the 10-to-the-minus-44th second.
Q. What is the stumbling block to understanding what happened at the very beginning?
A. The trouble is that as we extrapolate back very early on, the conditions get more extreme. Densities get higher and higher. Energies get higher and higher. We lose our foothold on the physics we can test in the laboratory.
But that's where there's a lot of theoretical excitement, trying to understand the physical laws and infer what the conditions were like and then looking for things we can observe.
Q. Are we closer to figuring out the future of the universe? Will the universe go on expanding forever or will it eventually collapse?
A. The answer to that question depends on the total amount of gravitating material in the universe. Everything has a gravitational pull on everything else.
If the average density of stuff in the universe amounts to more than about five atoms for each cubic meter, then the expansion will stop eventually. If it's below that value, then it will never stop.
If you take everything we see, all the stars, interstellar gas and galaxies, and spread that thinly throughout the universe, you get only a tenth of an atom per cubic meter. That's like one snowflake in the volume of the Earth. That suggests that the universe is going to expand forever.
But the embarrassing thing we've realized in the last 10 years is that there's a lot more material in the universe than we can see. It's the famous dark matter, which probably is made up of particles left over from the Big Bang. They are hard to detect, but they are the dominating stuff of the universe.
We have fairly good evidence that there's a lot of this dark matter out there, 10 times as much as the matter that we see, because of the gravitational effect on the motion of galaxies and light.
I'm confident that within a few years we will know what the dark matter is. Then we also will know the answer to the long-range forecast of whether our universe is infinite.
Q. You are championing the theory that our universe is but one of an infinite number of universes. What makes you think so?
A. It helps us answer a lot of questions, like a missing piece of a puzzle that allows you to suddenly see the whole picture. It gives us a better handle on how our universe could have come into existence.
Q. Copernicus shocked our egos when he said the Earth was not the center of the universe. How is the notion of multiple universes going to affect our psyche?
A. Our psyches have had a lot of knocks. After Copernicus, we realized that our Earth was just a tiny speck in this huge cosmos. Now, the dark matter is a blow because we're not even made of the dominant stuff of the universe. The ordinary atoms of which we and the Earth and all the stars are made are just an afterthought, a kind of sediment in a universe whose large-scale dynamics are dominated by something quite different.