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Can the universe contract at speed faster than speed of light?

Answers:1   |   LastAnswerAt:2011.04  

Asked at 2011.04.20 01:57:55
If universe were to slow down, stop, and start contracting, can it contract faster than the speed of light. If so, how much of a blue shift will we see from the photons? Would it blue shift into the gamma range?
answer Orac  Answered at 2011.04.20 01:57:55
Well... sort of.

It doesn't expand faster than light in actual terms.
It's just a quirk of all space expanding that gives us a light speed event horizon on the universe.
The expansion should perhaps be thought of as a marathon runner, running along a moving walkway or travellator working against him. To him it feels like he is moving at a normal speed but his destination at the end of the travellator seems to take much longer than expected to reach. If he has been running since the beginning of the universe -13.8 billion years ago, he should expect to reach the other end of the universe 13.8 billion years later - but he doesn't. He only gets about half way because the travellator is forever moving him backwards.

The contraction of universal space would be the opposite effect with the travellator switched to head the same direction as the runner. So he runs 13.8 billion miles but actually covers nearly twice as much. Space is forever scrunching up, and yes we would see a strong blue shift as light gets bunched up on it's way to us. Anything consequently moving towards us at the speed of light - those objects would disappear to our view. This is just like galaxies now which are invisible to us which are moving away faster than light.

It looks very unlikely at present that the universe will ever contract. endless expansion looks far more likely unless physics is introduced to some new concepts.
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