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The Question

(Submitted June 29, 2006)

I have trouble seeing how time came to existence from the Big Bang. If this is the case, it will mean no time will before the Big Bang they would be no time for something to cause the Singularity to explode it will be frozen in time without causing any Big Bang.

The Answer

Thanks for your excellent question. You are among some of our great scientific thinkers when it comes to wondering about the beginning of time. The truth is that, we don't yet have a definitive answer. The Big Bang certainly suggests that time began at the first instant of the Big Bang, since before then, the universe was collapsed into a singularity. The notion of time within the Big Bang scenario is discussed at length by Stephen Hawking. Everything is squeezed down to zero and such physical quantities as spacetime become infinite. The singularity is the point at which time has no meaning.

However, there are other theories about our universe that suggest that there was indeed a time before the initial "bang." Two of the most popular theories are pre-Big Bang theory (using string theory) and the Ekpyrotic scenario (using the collision of "D-branes"). In these theories, the pre-big bang universe was very sparse and weakly interacting, but did eventually give rise to a sudden transition that is similar to our "big bang." We recommend an excellent article on the subject at :

http://www.sciam.com/article.cfm?articleID=00042F0D-1A0E-1085-94F483414B7F0000

Hope this helps,
Georgia & Mike
For "Ask an Astrophysicist"

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