crashfrog writes:
Well, we know the duration of the universe isn't infinite in the past.
Actually I think it would be more correct to say that it appears spacetime is
bounded in the past, but boundaries on a continuum do not make it finite in every sense of the word -- especially in the case of a thing as relativistically plastic as spacetime. IOW, there may be a maximum spacetime interval from the past to the present, however unless spacetime is discrete (which our latest observations seem to refute), there may still be an infinite
number of intervals in the past.
Also it is important to note that the Big Bang singularity is really only a feature of our mathematical model, and it is not necessarily a feature of reality. So it is overly presumptive to state that we "know" the universe has a finite history. Several of the latest models actually challenge that notion.
crashfrog writes:
If it were, the night sky would be infinitely bright from the light of an infinite number of stars, which would have had an infinite amount of time to suffuse the universe. Or so it's been explained to me
I don't think that is a realistic expectation since stars do not shine forever, and additionally we would only expect a finite number of stars to be in close enough proximity to us that their photons would have had sufficient time to reach our planet. IOW, some stars would be so infintely distant from us
spatially that no amount of time would permit their photons to reach us.
I suspect there is some confusion among the various usages of the term "universe" in this thread. In general, it should be taken to mean "everything that exists," but in the context of some cosmological models like Tegmark's Multiverse it is used (actually
abused, IMHO) to represent "this patch of spacetime we presently observe" or "this bubble amongst many other bubbles." If we adhere strictly to the first definition in this paragraph, a beginning to "everything that exists" would be logically inconsistent, or at the very least claiming that we have observed such a beginning would be unsupportable.
[This message has been edited by ::, 11-10-2003]