Friday, January 23, 2009

How big is your Universe.?

It is 13.7 billion years since the big bang, so light now reaching us cannot have started its journey longer ago than that. Yet the most distant object we could conceivably see today lies further away than 13.7 billion light years. That's because throughout the life of the universe, space has been expanding. Taking this into account, cosmologists calculate that the edge of our observable universe is now approximately 45 billion light years away.

Beyond that, who knows? The inflation theory of cosmology predicts that the universe grew from a bubble. Just how big that bubble has now become depends on how long inflation lasted. If it continued for a very long time - in this context "very long" is still only a fraction of a second - then the edge of our universe might lie far beyond the 45-billion-light-year limit of our vision. That could also rule out the possibility of observing the influence of other universes on our own. As physicist Matthew Kleban of New York University puts it: "It's totally possible that we live in a multiverse and we'll never know because there's been so much inflation."

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