Most of what we know, or believe we know, about the early moments of the universe is thanks to an idea called inflation theory first propounded in 1979 by a junior particle physicist, then at Stanford, now at MIT, named Alan Guth. He was thirty-two years old and, by his own admission, had never done anything much before. He would probably never have had his great theory except that he happened to attend a lecture on the Big Bang given by none other than Robert Dicke. The lecture inspired Guth to take an interest in cosmology, and in particular in the birth of the universe.
The eventual result was the inflation theory, which holds that a fraction of a moment after the dawn of creation, the universe underwent a sudden dramatic expansion. It inflated-in effect ran away with itself, doubling in size every 10-34 seconds. The whole episode may have lasted no more than 10-30 seconds-thats one million million million million millionths of a second-but it changed the universe from something you could hold in your hand to something at least 10,000,000,000,000,000,000,000,000 times bigger. Inflation theory explains the ripples and eddies that make our universe possible. Without it, there would be no clumps of matter and thus no stars, just drifting gas and everlasting darkness.
According to Guths theory, at one ten-millionth of a trillionth of a trillionth of a trillionth of a second, gravity emerged. After another ludicrously brief interval it was joined by electromagnetism and the strong and weak nuclear forces-the stuff of physics. These were joined an instant later by swarms of elementary particles-the stuff of stuff. From nothing at all, suddenly there were swarms of photons, protons, electrons, neutrons, and much else-between 1079 and 1089 of each, according to the standard Big Bang theory.
Such quantities are of course ungraspable. It is enough to know that in a single cracking instant we were endowed with a universe that was vast-at least a hundred billion light-years across, according to the theory, but possibly any size up to infinite-and perfectly arrayed for the creation of stars, galaxies, and other complex systems.
What is extraordinary from our point of view is how well it turned out for us. If the universe had formed just a tiny bit differently-if gravity were fractionally stronger or weaker, if the expansion had proceeded just a little more slowly or swiftly-then there might never have been stable elements to make you and me and the ground we stand on. Had gravity been a trifle stronger, the universe itself might have collapsed like a badly erected tent, without precisely the right values to give it the right dimensions and density and component parts. Had it been weaker, however, nothing would have coalesced. The universe would have remained forever a dull, scattered void.
This is one reason that some experts believe there may have been many other big bangs, perhaps trillions and trillions of them, spread through the mighty span of eternity, and that the reason we exist in this particular one is that this is one we could exist in. As Edward P. Tryon of Columbia University once put it: In answer to the question of why it happened, I offer the modest proposal that our Universe is simply one of those things which happen from time to time. To which adds Guth: Although the creation of a universe might be very unlikely, Tryon emphasized that no one had counted the failed attempts.
Martin Rees, Britains astronomer royal, believes that there are many universes, possibly an infinite number, each with different attributes, in different combinations, and that we simply live in one that combines things in the way that allows us to exist. He makes an analogy with a very large clothing store: If there is a large stock of clothing, youre not surprised to find a suit that fits. If there are