Expert: Jayendra Upadhye - 5/28/2007

Question
Hi,

In a recent lecture it was stated that the observable universe is fourteen billion years old, but forty-plus- billion light years "wide."

How did it get so big in so "short" a time?

I realize that space can expand--and has expanded--faster than the speed of light. But, even if this is the case, I would think that light, which is limited to, um, the speed of light would not have had time to reach us to be observed.

Even if we think of the observable universe as a sphere, so that it would be twenty-eight-billion light years "wide", this would still not give light from forty-billion-plus light years away to reach us.

As you can see, there's clearly something I'm missing.

Any help greatly appreciated.

Steve
nighttrain@nyc.rr.com

Answer
Hi,
Thoughtful of you to include your emailid!!
Steve, i think i am on thin ice here.
I have not really been reading things up lately and so you may find my answer "obsolete"!

The reason why this happens (universe wider than distance light could travel in the lifetime of the iniverse, is the theory of inflation.

It is believed that the universe happened simultaneously over a very wide area a little time after the actual bang.

It is this "head start" that the far flung regions had, that has caused this apparent paradox to happen.

The simultaneity spread over a reasonable great distance (only in the initial stages of the bang, and for a very short duration, has resulted in the fact that many outlying regions are still "unseen", and the farther you are, the faster you recede!!

That compounds the problem.

Hope that suffices.
Jayen