luvluv

I guess you're right Shadowy Man. Perhaps I should have said that everything we know SUGGESTS that the universe began about 15 billion years ago, or that most cosmologists believe the universe began to exist 15 billion years ago.

eh, I suppose that is correct. I know string theory, for instance, imposes a minimum size on the universe even from the momment before the big bang. Nevertheless, it would seem to be stretching things, IMHO, to assert that this incredibly small bundle of all energy in the known universe existed in this state eternally until the big bang. I guess this is the impasse where all these discussion go, when everyone insists that we must "wait for a full interpretation of quantum gravity" before we can compose any arguments. I suppose that is true, but for me an Intelligence is the best explanation for both the big bang and the anthropic coincidences, and I've never heard a coherent naturalistic theory based on any emprical evidence (as opposed to the multiverse conjecture) which could succesfully explain both.

For the record I never intended to defend the cosmological argument, only to clarify it. I don't think any of the arguments for the existence of God amount to "proofs", but I think taken altogether they amount to more than enough argumentative evidence for the existence of God to make belief in Him reasonable, if not intellectually compulsive.

eh

It does get infinitely dense, and the size is infinitely small (zero).

Shadowy Man

I guess I wonder whether this is really true. Most of the astronomers that I work with are actually not cosmologists, but I can ask around to see if they really believe that there was a T=0 moment.

My current understanding is more of a phase change kind of thing, where before the "current", i.e. post-inflation, era things were just different and that there is not necessarily a finite boundary of time in the pre-inflationary era.

But then again, this is mostly based on going to a few talks by cosmologists, including Guth. I should read up some more.

Shadowy Man

But, see here is where I have problems. Say the universe is open, i.e. spatially infinite, then you have a problem going from an infinite universe to a finite universe. A zero size universe is finite, an open universe is not. So if the universe is open, when was it finite in size? When did the tranition occur. I prefer to think of just extrapolating the density backward - you still have a mathematical singularity (density --> infinity).

I'll need to review the GR equations for open universes as T-->0. It's been a while since I opened my gravitational physics text.

eh

This is not what is being claimed. We've gone through many threads on how time can have a finite length in the past, yet be eternal, and I don't think we need to do it again. Let's just focus on the point that space is not literally created from some prior state.

Nah, we can discuss it without a final theory. Energy is conserved, so there is no reason to think the universe could fail to exist. The anthropic discussions are really the only place we need such a theory, since we have already defined the planck scale to be the absolute beginning.

Fair enough. But I find it interesting that you opt to believe the universe can be explained as being designed from some intelligence - when they very intelligence would be unexplained. Personally, I find the idea of some complex intelligence just existing to be brutally arbitrary. A non contingent universe is a much simpler explaination, and in complete absence of any evidence for a divine creator, I think it's the more rational viewpoint. In short, "God" explains absolutely nothing.

eh

I'm no expert on cosmology, but this discussion comes up often at other forums. Apparently, only closed, finite universe shrink down to zero size. Open infinite universe are infinite in size from the very beginning. In the case of a singularity for an infinite volume of space, each point reaches infinite density, but the universe as a whole remains the same size forever.

I believe that's just what you get when dealing with the math of infinity.

luvluv

eh:

I don't think I was a part of any of those threads. Are you referring to the Hawking-Hortle model?


He would explain the anthropic coincidences, for one. Perhaps this is easier for me to believe since the concepts you are applying to the universe seem to fit the concept of God better than they fit the concept of matter. From a philosophical standpoint, a non-contingent contingency is a contradiction. If the universe does not have to exist, it is a contingent entity, and thus cannot be uncaused. If the universe has to exist, then it should have always existed.

luvluv

And I should also add that I have numerous independant reasons for believing in God. I have not been convinced of His existence on the basis of the cosmological argument or the teleological argument. But at the same time I have not found my beliefs to have been refuted by any of the innovations in science which correspond to these arguments.

So, I believed in God before I had ever heard of or understood the cosmological argument, and I am encouraged to the extent that many recent advances in astronomy and cosmology confirm, rather than deny, my faith. However it is not the case that I believe in God BECAUSE OF the cosmological argument.

If I were like you, eh, and perhaps had no independant reason for believing in God beyond the cosmological evidence, I might take your view. Or at any rate, I would remain undecided on the question.

Shadowy Man

It's more that astronomy and cosmology don't contradict your faith than that they confirm.

luvluv

Same difference, wouldn't you say?

I'd disagree at any rate.