One of the most astonishing discoveries astrophysicists have made in recent decades is that if gravity were just 0.000000000001 (one-trillionth of one) percent stronger, our universe would have reversed course long ago. It would have collapsed catastrophically, ending in a big crunch, the opposite of the big bang. Likewise, if gravity were just 0.000000000001 (one-trillionth of one) percent weaker, our universe would have flown apart so rapidly that planets, stars, galaxies—all the basic constituents of the universe—would never have had a chance to coalesce. We'd all be dust in the wind.

Is it an accident that everything turned out so well? That gravity is not too strong, not too weak, but just right?

Sir Fred Hoyle, the late University of Cambridge astronomer and avowed atheist, didn't think so, not for a second. After doing innumerable computations, Hoyle discovered that the odds of our being accidents of nature are comparable to the likelihood of a tornado sweeping through a junkyard and assembling scrap metal into a fully functioning Boeing 747. "'So small as to be negligible," he said, following his calculations, "even if a tornado were to blow through enough junkyards to fill the whole universe." Hoyle said, "One arrives at the conclusion that biomaterials with their amazing measure or order must be the outcome of intelligent design."