B Questions regarding expansion, the vacuum in space, and black holes

[Mburris87]

TL;DR Summary

Expansion of matter in the visible universe, total volume of space outside the visible universe, black hole mechanics, and general questions from an uneducated but extremely interested evolved monkey.

Summary: Expansion of matter in the visible universe, total volume of space outside the visible universe, black hole mechanics, and general questions from an uneducated but extremely interested evolved monkey.

Hello everyone! I do not know the rules of this forum, or any forum for that matter. This is kind of a first for me. I expect that this is probably the incorrect way to gain information, but I have to try. Several things bug me on a daily basis, and having some solid answers (if possible) would be nice. I figured this was easier than stalking an astrophysicist. Please correct me if my assumptions below are incorrect.

Cosmic expansion.
The total volume of our universe increases every second. I watched The Age of Hubble, and they stated that if the visible universe was the size of an atom, the actual volume of the un-observable universe, the space beyond the stars and galaxies, would comparably be the size of the visible universe. If that is true, then the amount of absolutely empty space outside of the visible universe is unfathomably large. This presents raises several questions for me.

1. If the boundaries of the universe are expanding, then some force must be driving it. Regardless of what is causing it, the side effect of the force causing the boundaries to expand would also cause the vacuum in space to grow deeper. Do we know if there is a limit to how deep of a vacuum can exist? I am assuming that a mile cubed section of space somewhere between Earth and the moon, will have a higher pressure (less of a vacuum) than the same volume of space a 1000 Billion light years outside of the visible universe due to there still being particles spread about in space near us.
2. If the total volume of space outside the visible universe is a trillion trillion trillion trillion trillion trillion trillion times the volume of the visible universe, would the vacuum created in the empty void exert a force on the matter near in the "center" of the universe bubble causing all of the matter in the universe to be sucked in every direction? Would this not explain why far away galaxies are red shifting? If not how do we know?

I have more, but let's see what happens with this.

Thank you for your time.

 

[phinds]

There IS NO "outside" of the universe, there are no "boundaries". I recommend the link in my signature.

Also, the consensus (but not a proven fact) is that the universe is and always has been infinite in extent but whether it is or not has no bearing on whether it has a center (it doesn't) or an "edge" (it doesn't) or a "boundary" (it doesn't)

 

[Mburris87]

Wow, super interesting. This is going to take some time to fully digest. Do you mind if I reply back with any questions? I do not personally know anyone else to ask.

When they say there is no center, they are just speaking in reference to expansion, correct? Is there not still a point at which the singularity first started expanding? Would that not be the center, or does that point not really matter anymore?

I thought I knew some stuff. Turns out I know nothing.

 

[Bandersnatch]

When they say there is no center, they are just speaking in reference to expansion, correct? Is there not still a point at which the singularity first started expanding?

No, because it doesn't make sense to think of the cosmological singularity as a point, unless one means specifically a point in time.
If we take the universe now, and imagine rolling back the time, the singularity is the (likely unphysical) state of infinite density and temperature the entire universe approaches as one rolls the time sufficiently far back. If, for example, the universe is spatially infinite now, then the entire infinite expanse of it becomes singular in the past - the density and temperature everywhere in the entire universe become infinite at some particular moment in time.
It's - emphatically - not that the entire matter in the universe coalesces into a point, leaving empty space behind.

 

[phinds]

Is there not still a point at which the singularity first started expanding?

Absolutely not. I recommend the link in my signature

 

[PeterDonis]

The total volume of our universe increases every second.

More precisely, the total volume of our observable universe is increasing. The universe as a whole might be spatially infinite, in which case it makes no sense to talk about its total volume.

If the boundaries of the universe are expanding, then some force must be driving it.

No, there is no force driving the expansion. It's just inertia. The universe is expanding now because it was expanding in the past. It started out expanding very rapidly.

Currently our best explanation for why our universe started out expanding very rapidly is that the Big Bang--the hot, dense, rapidly expanding state that is the earliest for which we have good evidence--was preceded by inflation, where the universe was in a "false vacuum" state that expanded rapidly because of the particular properties of the "inflaton" field, a scalar field. Then, when inflation ended, all the energy stored in the "false vacuum" state was transferred to the Standard Model fields we know--quarks, leptons, photons, etc.--and created the hot, dense, rapidly expanding Big Bang state. Ever since, everything in the universe has been expanding by inertia.

the vacuum created in the empty void

What vacuum created in what empty void? The universe outside our observable universe is not vacuum; it's just more of the same sort of stuff that we see. There is no physical boundary between the observable universe and the rest; the observable universe is just the part from which light has had time to reach us since the Big Bang.

 

[PeterDonis]

When they say there is no center, they are just speaking in reference to expansion, correct?

No. They are speaking quite literally of the spatial geometry of the universe, which does not have a center.

There are basically two possible cases: either the universe is spatially infinite, or it is not. If it is spatially infinite, then it obviously has no center (how would you pick out the "center" point from all the others since there is no edge?).

If the universe is not spatially infinite, then its spatial geometry is a 3-sphere, which has no center for the same reason that a 2-sphere like the surface of the Earth has no center. The difference is that the Earth's surface is embedded in a 3-dimensional space that we can observe, so it's easy to get confused and think that, well, the Earth does have a center, it just isn't on the surface. But geometrically, a 2-sphere like the Earth's surface has no center--there is no point on the 2-sphere itself that is different from any of the others (since the 2-sphere itself has no edge). And if our universe is spatially a 3-sphere, it's the same, plus our universe is not embedded in any higher-dimensional space, so there isn't even a "center" somewhere outside the 3-sphere. There is just the 3-sphere itself, in which every point is the same and there is no center.