Joe V.

So I've been watching these shows on the Science Channel and they describe how all the galaxies in the universe are sorta formed like a giant sponge cake, with galaxies as the strands and lots of open spaces inbetween them. The big question everybody asks is, what caused the universe to expand? Well, I'm thinking to myself, what causes a cake to expand when you bake it? Heat. Did the universe expand simply because it was hot? Has this been used as the reason for the universe's expansion and I just missed that part, or was there not enough heat at the beginning of the universe to account for its expansion (although I thought the universe was infinitely hot at its beginning)? Just wondering, thanks.

Oh, and Hi! This being my first post here.

- Joe

[ November 07, 2002: Message edited by: Joe V. ]</p>

Seraphim

"... although I thought the universe was infinitely hot at its beginning..."

Infinitely hot? Not very sure about that but gases attended to get hotter easily rather than solid or liquid matters, so the Mass which gave birth to the Universe through Big Bang could be consists of gases which become hotter and hotter till it blow itself outwards.

That's why I think, anyway.

Corona688

All the energy of the universe, crammed into a tiny point? Yes, I imagine it'd be VERY hot.

eh

It seems that if you were to remove all matter from the universe, it would still expand. There seems to be some kind of cosmological constant, which would mean there is some kind of field present throughout the entire universe. Since this energy is repulsive in terms of gravity, a static universe does not seem possible. So this field should cause the expansion regardless of what matter exists.

Answerer

If spacetime is proved to be quantized, then the problem of infinitely hot universe during the time of its birth will most likely be resolved.

Joe V.

Thanks for the replies everyone. So, did heat play any part in the expansion of the universe, or was it merely a result of it? Of course, maybe just looking at those models of the universe made me think of cake too much and I'm thinking how good a piece of cake would be right now...

- Joe

Oxymoron

Mmmmm.... cake

I think the baked confectionery metaphor only works so far: a cake rises because hot air causes yeast and/or baking powder to release CO2 causing the mixture to expand. Heat is commonly misunderstood. It's a form of energy that is manifested by the velocity of the particles of the constituent material. Temperature measures the amount of heat in an object. Nevertheless, in a typical interstellar gas cloud it can be extremely hot (the particles are very energetic) but you'd freeze instantaneously because the density of particles is so low.
In the early universe, the 'temperature' again measures how fast particles are moving, and the whole idea of the Big Bang is that particles start with a high (maybe infinitely high, we don't know) energy density and that it drops over time. However there's also the expansion of space to consider. What makes space expand is not understood but is connected both with the energy density of the contained matter and (maybe!) an extra source, the famous 'dark energy' which seems to be accelerating the rate of expansion.
To understand the expansion, we really need to reconcile General Relativity and Quantum Mechanics. So far, they're incompatible - GR says space is smooth and continuous, QM says space is grainy. However, two classes of superstring theories currently hold some promise: the 10-dimensional G2 string model, and the 11-dimensional membrane string model ('M-theory').

So I'm afraid there is no simple answer to your question. It's not just about heat!

Ernest Sparks

In fact, I suspect extreme heat enters the situation as a result of a hyperdense universe in an early, highly confined space.

Also, heat helps to realize another hoped for agenda item of expanding models, namely primordial unification of interactions and their sequenced separation out at just the right time to explain later universal structures and events.

Also, heat helps to provide the right conditions for yet another hoped for agenda item of expanding models, namely, generating light elements/isotopes from Deuterium to Carbon, without the need for primordial stars to do it.

eh

Even an empty universe would expand, so I would guess no.

joedad

The Universe is not only expanding, but the rate of expansion has increased. That's certainly a counterintuitive discovery.

Perhaps the universe is in the form of a bubble, where most of the mass is concentrated at the periphery. This could possibly account for the increased rate of expansion, an acceleration due simply to gravity and not the presence of an exotic form of energy.

joe