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The Question

(Submitted September 04, 2007)

I have read articles that cosmologists believe that the universe is expanding at an accelerated rate. Another theory states that the speed of light is constant and nothing can move faster than the speed of light. My question is if the universe is accelerating, eventually should it not reach a speed faster than the speed of light? Has anyone investigated the question as to what will happen if the expansion of the universe breaks the light speed barrier?

The Answer

Thanks for your question. It is true that nothing can go faster than the speed of light. And it is also true that our universe is expanding faster than the speed of light today. This sounds like a contradiction, but actually it is space itself that is expanding faster than the speed of light, driving objects further apart at an increasing rate. The concept of space expanding faster than the speed of light is not in contradiction with the limit for zero mass particles, ultimate speed. A nice discussion of this can also be found at: http://curious.astro.cornell.edu/question.php?number=575

Hope this helps,
Georgia & Mike
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