Re: What. A. Shock.
This quote always annoyed me.
We actually have no way of knowing if the universe is infinite or not. Since it is demonstrably expanding (red-shifts can be measured so that's not really at question), things further from us move away from us faster. Since the speed of light is also constant and known, we can't see beyond the point at which stuff is moving away from us, relatively, faster than the light from it can reach us. This imposes a "horizon" we can't see beyond, so we can't say one way or another whether the universe is infinte, from empirical observation.
Big bang theory, on the other hand, which is a perfectly reasonable extrapolation from the observable expansion of the universe, suggests that the universe expanded from a point. Since there's no way to get from a point to infinity without an infinite amount of expansion, it's a fair conclusion that the universe is not, in fact infinite, although we can't observe this to confirm it.
There are obvious problems with infinities (and indeed with getting something from nothing), and our understanding of the early universe is limited by what we can actually observe, although we can fairly accurately measure its age as 13.77 Bn years. By comparison, the age of the Earth is around a third of that at 4.5 Bn years. It always surprises me that our planet should have existed for an appreciable fraction of the lifetime of the universe, I get the feeling that the universe itself ought to be a lot, lot older.