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- Posted: Wed, 03 Oct 2012 23:10:53 +0000
Um...the idea of the empty void that we call "outer space" could "tear"...does not in any way conform to the laws of physics. Also, it is my understanding that the universe itself does not expand nor contract. It's just....empty void. It's nothingness.
The idea of space-time "tearing" is absurd, but it is the universe itself which is expanding. It is incorrect to picture everything drifting off into a void after some event flung it all outwards as such an event is incapable of explaining the observations and would require unobserved inhomogeneities and anisotropies. What this means is that we should, by observation, be able to very easily tell where the edge of universe is because the density there must be radically different than the density not at the edge. We do not observe any such differences at the boundaries of the observable universe. So, why is everything moving away from everything else? They are drifting apart because space is carrying them away from each other. It explains the largely isotropic and homogeneous universe we see and eliminates problems of requiring some spatially identifiable center for everything. It also helps explain why some red shifts are associated with velocities in excess of the speed of light.
As for what the fate of the universe is which appears to have spawned the debate, it is going to expand forever. Dark energy is causing an acceleration in the expansion which is strongly counteracting gravity and the universe is observed to be flat anyways [it has a density such that it will expand forever even without dark energy]. Penrose, I think it was, has this idea of cosmological conformal remapping, where after a certain period of expansion, the universe essentially restarts, but the idea is not very popular nor is it well supported despite Penrose's claims otherwise [he claims to have found patterns in the WMAP data, but no one else agrees with his analysis and believe he did some rather heavy cherry picking to get it to agree with his theory].
For what is probably the more pertinent question, where did the universe come from, we don't know. All modern theory simply tells us what happens once it is there for things to happen too. There have been various scientifically minded ideas which would give rise to a universe which looks like ours, but they are rather unspecific and very, very far from being precise or scientifically well founded. This does not mean that they are bad ideas, just that this line of inquiry is rather young and currently underdeveloped [cosmology has only held that the universe has a finite age for around of 60-70 years and the lack of ideas as to how to get observational evidence is a rather large roadblock to advancement].
Except the universe won't expand forever because A) eventually every star that has ever existed or will exist will blink out of existence.
B) Time isn't infinite.
C) Space-time has an elastic property which allows it to stretch and there are thousands of physicists and a lot of renowned physicists who liken the fabric of space to a rubber band.
D) The universe is not infinite in size or density and cannot expand forever.
string theory, wave theory, and general relativity all support the idea of a universe which will collapse on itself