Is Reality a Universe or a Multiverse?

Brian Greene, a professor of physics and mathematics at Columbia University, has an article in the May 21, 2012, Newsweek about whether the universe is alone or merely one of multiple universes (a "multiverse"). He writes,

"It’s a striking prospect. If correct, it would provide the capstone on a long series of cosmic reappraisals. We once thought our planet was the center of it all, only to realize that we’re one of many planets orbiting the sun, only then to learn that the sun, parked in a suburb of the Milky Way, is one of hundreds of billions of stars in our galaxy, only then to find that the Milky Way is one of hundreds of billions of galaxies inhabiting the universe. Now, inflationary cosmology was suggesting that our universe, filled with those billions of galaxies, stars, and planets, might merely be one of many occupying a vast multiverse."But the universe is expanding, as if it were being pulled apart. This may be due to a mist of dark energy that is repulsive to ordinary gravity – forcing all galaxies away from each other.

String theory suggests multiple universes (a "multiverse"). This area of theoretical physics has partisans on both sides.

"By combining inflationary cosmology and string theory, however, the stock room of universes overflows: in the hands of inflation, string theory’s enormously diverse collection of possible universes become actual universes, brought to life by one big bang after another. Our universe is then virtually guaranteed to be among them. And because of the special features necessary for our form of life, that’s the universe we inhabit."The way to prove or disprove the multiverse theory is through scientific observation. "But string theory remains hypothetical, largely because its primary distinguishing features become manifest at scales billions of times smaller than we can probe even with today’s most powerful accelerators," writes Greene.

So we are stuck for a while, knowing that we don’t know whether this is the universe or one of many multiverses.

A thorough discussion by Greene is online at:

http://www.thedailybeast.com/newsweek/2012/05/20/brian-greene-welcome-to-the-multiverse.html