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Feb28-12, 05:03 AM
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Quote Quote by cepheid View Post
The contradiction would seem to be that the scale factor goes to 0 as t → 0. That seems to suggest that as you go back in time, everything collapses down to a singular point......It just means that what happens as t → 0 is undefined.
Quote Quote by marcus View Post
I don't think there is any scientific evidence that our universe had a beginning.
Quote Quote by zbe View Post
I say **** infinity since it has nothing to do in physics.
Hi,
I hope the extracts above and the highlighted words from previous posts do not misrepresent the original context, as they seem to capture some key issues, which I would like to raise. In the first quote, the key word appears to be whether ‘everything’ in the totality of the universe expanded from some conceptual singularity? In my own personal review of the various cosmology models, there seems to be plenty of scope to, at least, speculate that the expansion of what we often describe as the universe is only part of some larger process/universe.

I agreed that what happens as t->0 is ‘undefined’ in terms of current science, i.e. both GR & QFT, although we might be allowed to speculate that our ‘universe’ could have been triggered by some sort of quantum process within some larger definition of the universe.

In this respect, the speculative larger universe might not have any obvious ‘beginning’, although it might still be correct to say that our ‘local’ universe came into existence some 13.7 billion years ago.

However, there still appears to be the troublesome issue of infinities, which I am not sure that physics or the maths can ultimately avoid. If the common description is taken at face value, then you have to explain a universe, which is 13.7 billion years old, created from a singularity of near ‘infinite’ density that would conceptually occupy a near infinitely small volume, outside of which ‘absolute’ nothing exists or has ever existed. In this context, the issue of ‘creation’ from absolute nothing always seemed a bit metaphysical for my taste. Of course, the speculative model suggested cannot really avoid infinities, as the idea of an extended universe suggests a possibly infinite size and infinite age. Maybe Marcus, as a mathematician, and Cephid, as an astrophysicists, might like to comment further on such issue. Thanks