'Did God Have a Choice?'

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Some of that success came in April 1992, when scientists announced that the Cosmic Background Explorer, or COBE, satellite had observed subtle temperature changes in the cosmic background radiation. In the 1980s, Primack and his colleagues, including Sandra Faber, had shown how quantum fluctuations caused galaxies to form in some parts of the universe, but not in others. Now, the COBE discovered that these fluctuations were of the amount predicted by the scientists' theory of cold dark matter, which claims most of the matter in the universe cannot be observed by its electromagnetic radiation and is made up of particles moving slowly. "It was an amazing experience. I'd wake up at night in a cold sweat," Primack says, comparing the bliss of scientific success to a religious revelation. "We had been living in an imaginary universe, but we found out the dream world is real. It gives you a sense that you're reading the mind of God."

Without the whole story, however, some cosmologists have bypassed the strange uniqueness of our universe by imagining that ours is not the only one. The idea of multiple universes, or the "multiverse," has become increasingly popular in the last two decades, in part because it explains anthropic arguments. If there is an infinity of universes-be they separate or joined, big or little, and with all kinds of values of fundamental constants and varying life cycles-then it is not altogether bizarre that a universe like ours could, and should, exist.

The theory of the multiverse "removed the mystery of the fine-tuning of our universe, which is a serious mystery that we worry about," says cosmologist Sir Martin Rees, British Astronomer Royal and a "practicing but nonbelieving Christian" who attends church on occasion, but doesn't adhere to religious dogma. Rees is uncomfortable with the argument that our universe is one of a kind. "We used to think the Earth and solar system were indeed very special, and that was a mystery; but we now realize there are zillions of planets orbiting other stars, and we wouldn't be surprised to find some that have the special properties needed for the Earth," he says. "And it may turn out that that is the case with the universe."

Because it is nearly impossible to prove alternate universes exist, it is arguable that multiverse cosmology requires a nearreligious faith on the part of its followers. "Some people say that the multiverse is appealing to an infinite number of unseen things, which makes the multiverse explanation, in some sense, infinitely complex. This is equivalent to appealing to an infinite, unseen God," says Davies, who is working on a book about multiple universes. He takes the idea seriously, but says even if there is an infinity of universes, we cannot ignore the exceptionality of the one we live in-the one with conditions so improbably perfect that we humans came to be.

There are others who admit the idea of multiple universes requires a good dose of faith, although they believe this faith will, someday, be proven by science. Believers in God, however, do not seem to agree. Proof notwithstanding, "How does the multiverse get around the design question?" asks Gingerich, a Christian who believes God designed the universe and is using the evolutionary process to achieve larger goals.

Today, there are theoretical predictions of the multiverse. The cosmological theory of inflation devised by Massachusetts Institute of Technology cosmologist Alan Guth twenty-five years ago posits that for a brief time after the big bang, the universe expanded extremely quickly. One version of this theory speculates that the material driving inflation began to decay and bits of the decaying universe, still expanding exponentially, became their own pocket universes. "Right now, very little is known," admits Guth, who does not believe there is a God who had any involvement in the process.

The inflationary theory also accounts for some of the universe's perfection. At about one second after the big bang, the rate of expansion is fine-tuned to fifteen decimal places-a value so precise it means that had the universe swollen in size even the tiniest bit faster, it would have flown apart; the smallest bit slower, and it would have collapsed.

"Inflation fixes that problem and drives expansion to just the right value," says Guth. As for the other constants, Guth isn't sure their values are all that special. "We don't know yet how to calculate whether or not life would exist, [to] make a prediction about what the parameters of physics should be for there to be life," he says. "There could be lots of other forms of life."

Cosmology is filled with speculation. Mere decades ago, few considered it a legitimate scientific field because cosmologists knew little more than the humans who first contemplated the night sky. But in the last half-century, cosmology has come of age. While there remain many interesting questions-are there other life forms?- there is much we are confident about.

We have proof that planets orbit stars, stars form galaxies, and galaxies are organized into even larger structures. We understand that the early universe was composed almost entirely of hydrogen and helium and that carbon is created in nuclear reactions in stars-stars that are the source of all the atoms in our bodies. And we know with certainty that our life form exists under the laws of physics established by our world. We just might have to live with the fact that where those laws came from, and why, may always be a source of mystery and a matter of faith.

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