Unsatisfied in the case of uniform distribution everywhere. The level of compression has nothing to do with it. The current density of the universe (about 6 protons per cubic meter) is enough to prevent expansion if it was that mass expanding into empty space. None of the material would have sufficient recession speed to exceed the escape velocity of the bounded mass that comprised the occupied part of the universe. — noAxioms

Good thought. Add to that, if you would; What does the vision of "multiple" contractions and expansions do if we focus on the velocity of (light in space) during these periods. Then the question of; how far does the universe contract before it starts to expand. Lots and lots of questions about the model.

I am curious as to how the current density would have any influence on either the physical possibility of expansion, or the degree to which it occurs. In what way then are these two factors correlated, in particular? — Vessuvius

It goes a bit beyond my expertise, but density affects overall gravitational effect to the extent that sufficient density suffices to overcome the effects of dark energy. The gravitational epoch epoch ended some billions of years ago and the expansion reached a minimum. The average density is now low enough that dark energy has the greater effect. The Hubble 'constant' will eventually settle on an actual constant of about 57 km/sec/mpc which corresponds to exponential expansion as opposed to the nearly linear expansion of the last several billion years.

Good thought. Add to that, if you would; What does the vision of "multiple" contractions and expansions do if we focus on the velocity of (light in space) during these periods. — Don Wade

You mean a cyclic model? I'm not familiar with any such model that matches empirical evidence at the level of the accepted FLRW tunings. So I think you can make up any rules you want about what properties are preserved from one bang to the next.

Then the question of; how far does the universe contract before it starts to expand. Lots and lots of questions about the model.

I've never heard of a model that posits contraction that doesn't accelerate to some kind of crunch singularity. Doesn't mean such a model doesn't exist, but I've never heard of it.

I've never heard of a model that posits contraction that doesn't accelerate to some kind of crunch singularity. Doesn't mean such a model doesn't exist, but I've never heard of it. — noAxioms

The big bang and the big crunch kind of go hand-in-hand in some models. https://en.wikipedia.org/wiki/Big_Crunch . However, the jury is still out as to which models are more acceptable. Trying to get a grasp on the fundamentals of the different models is what makes cosmology a fun science - and is especially great for philosophy.

Just a small note on the topic of the OP and a few replies I’ve seen here: no evidence directly indicates that the universe as a whole was any smaller than it is now, only that it was much denser, so the part we see now fit in a much smaller space... but for all we can tel there could have been a lot more stuff that at that time fit into the presently observable volume.

As far as we can measure, space is indistinguishable in size from an infinite size. If it is infinite, then it was still infinite in the past, and even at the beginning, if there really was a beginning. Imagine a grid on your screen where each square is 1 inch. Now zoom out from the infinite grid so that each square is just 1 pixel. Imagine you could keep zooming out until each square was much much smaller than a pixel. But the grid still fills your whole screen. There’s no edge to it to push out into anything else else: it’s just a very compact infinity of squares that expands into a much looser infinity of squares, but at any time it’s still the same size: infinitely large.

I am familiar with, albeit in a rather vague sense of how the so-called Cosmological Constant, with this latter term being interpreted in more modern treatments as encompassing the effects of 'Dark-Energy', has a great influence on the rate of universal expansion when possessed of a non-zero value and with a countervailing effect being accounted for by the forces of gravitational interaction instead; expectedly, it thus follows that their relationship to each other is one of competitive inhibition. I am familiar also with how the rate of expansion has since accelerated by virtue of gravitational forces exerting less of an influence than before, as the relative density of matter itself continues to decline, and that the associated factor, known as Hubble's Constant, will eventually reach its true value once the expansion becomes exponential. With the exception of what this particular value is, such as you communicated to me, all the information which has been proffered for my sake, I know of already. Certainly, this isn't to say I wish to sound disparaging, nor to overlook how much of a delight I found our exchange to be, just that I had hoped for a more thorough analysis of that relevance which current density has, as opposed to any other form of density, when modelling universal expansion.

In any case, that my role in society is of being a literal dropout, and with few prospects as it regards professional advancement, every one of those ideas which has been given mention for lies beyond my field of expertise. For this reason, I am sure you are still in a position to claim the advantage of that betterment of human-understanding which can be conferred only through a higher-institution, with respect to my own circumstances at least.