Saturday, February 19, 2011

Brian Greene

Brian Greene's new book is The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos.

From his interview by David Gelernter at the Wall Street Journal:

Mr. Gelernter: Your book is about the idea of a "multiverse"—that is, multiple universes. But that sounds impossible. If "universe" means "all there is," how can there be more than one?

Mr. Greene: Right, so how can you have multiple "everythings"? It sounds meaningless, like asking whether the number 9 is blue. But lots of recent research in physics has made the canvas of reality look much wider than we ever imagined. Our most refined cosmological theories indicate, for instance, that the big bang, which created our own universe, may not have been a unique event. There may have been (and may still be) various big bangs at far-flung locations, each one creating its own universe. Our "everything" may be just one enormous expanding bubble in a gigantic cosmic bubble bath of universes.

In one of the theories that you describe, there are universes not only apart from ours but identical to it, moment-by-moment. This staggering idea is the result of an amazingly simple argument. Would you explain?

In any finite region of space, matter can only arrange itself in a finite number of configurations, just as a deck of cards can be arranged in only finitely many different orders. If you shuffle the deck infinitely many times, the card orderings must necessarily repeat. Similarly, in an infinite expanse of space, particle arrangements must repeat too—there just aren't enough different particle configurations to go around. And if the particles in a given region of space the size of ours are arranged identically to how they are arranged here, then reality in that region will be...[read on]
--Marshal Zeringue