Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Semaphore on 27/01/2017 21:02:42
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There's a nice article in the print edition of SciAm which indicates that the latest data does not necessarily support Cosmic Inflation, and goes on to suggest that the smoothing effect which CI provides could equally well be provided by the contraction of a previous universe followed by a 'Big Bounce', thus negating the need for the Big Bang and all the quantum effects associated with it. This is not the first time the Big Bounce theory has been advanced. What do you think?
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If you have access to New Scientist, 16.06.2008 there’s an interesting article by Anil Ananthaswamy. This is a brief extract from it.
“Abhay Ashtekar remembers his reaction the first time he saw the universe bounce. ‘I was taken aback,’ he says. He was watching a simulation of the universe rewind towards the big bang. Mostly the universe behaved as expected, becoming smaller and denser as the galaxies converged. But then, instead of reaching the big bang ‘singularity’, the universe bounced and started expanding again. What on earth was happening?
Ashtekar wanted to be sure of what he was seeing, so he asked his colleagues to sit on the result for six months before publishing it in 2006. And no wonder. The theory that the recycled universe was based on, called loop quantum cosmology (LQC), had managed to illuminate the very birth of the universe – something even Einstein’s general theory of relativity fails to do.
LQC has been tantalising physicists since 2003 with the idea that our universe could conceivably have emerged from the collapse of a previous universe. Now the theory is poised to make predictions we can actually test. If they are verified, the big bang will give way to a big bounce and we will finally know the quantum structure of space-time. Instead of a universe that emerged from a point of infinite density, we have one that recycles, possibly through an eternal series of expansions and contractions, with no beginning and no end.”
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Nice post. Of course the idea of a bounce has been around for a while. The new twist here (for me at least) was that it could make Cosmic Inflation unnecessary, together with questioning whether the most recent data supports CI specifically or only provides a reasonable fit.
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The new twist here (for me at least) was that it could make Cosmic Inflation unnecessary
Without inflation, does the bouncing universe necessarily solve the and flatness problem?
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I don't know about this particular model, but the usual problem with 'Big Bounce' universes is that there is no mechanism for reversing the entropy increase during expansion.
Without such a mechanism the entropy will increase during each bounce and eventually a low but increasing entropy universe such as we live in will be impossible. You would then need a Big Bang theory to explain the origin of the posited bouncing universe.
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The new twist here (for me at least) was that it could make Cosmic Inflation unnecessary
Without inflation, does the bouncing universe necessarily solve the and flatness problem?
That was not addressed in the article.
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I don't know about this particular model, but the usual problem with 'Big Bounce' universes is that there is no mechanism for reversing the entropy increase during expansion.
Without such a mechanism the entropy will increase during each bounce and eventually a low but increasing entropy universe such as we live in will be impossible. You would then need a Big Bang theory to explain the origin of the posited bouncing universe.
I suppose the authors were addressing the way the current universe began rather than multiple bounces.