Stationary Centre of Universe Defined?

[ynot]

If the Universe uniformly expanded from a very small singularity doesn't that mean that the original position of the singularity defines a centre point of the Universe that is absolutely/Universally stationary?

 

[edd]

No. There is no original position - everywhere is a position that maps back to it.

 

[ynot]

No. There is no original position - everywhere is a position that maps back to it.

What is "it"?

Are you saying that the entire Universe is the same position?

 

[edd]

No. That'd be crazy. I'm saying the Big Bang happened everywhere.

 

[JoeTheJuggler]

If the Universe uniformly expanded from a very small singularity doesn't that mean that the original position of the singularity defines a centre point of the Universe that is absolutely/Universally stationary?

No, because it didn't expand into pre-existing space.

Every part of space is where that singularity was.

ETA:

Are you saying that the entire Universe is the same position?

In a way, yes. Remember, the universe is space. So every position within the universe is the space that expanded from the singularity. (I think edd worded it better.)

 

[ynot]

Is it correct to say that the singularity was a single thing that contained no space? Then with the Big Bang the singularity was broken up into many things that uniformly move apart by continuously expanding space?

 

[ynot]

No, because it didn't expand into pre-existing space.

Then what did it expand into?

Every part of space is where that singularity was.

So the location of space separating two planets 1,100,000 lightyears away is the same location as the space that separates the Earth from Mars?

ETA:
In a way, yes. Remember, the universe is space. So every position within the universe is the space that expanded from the singularity. (I think edd worded it better.)

The Universe is also things. Expanding space continuously moves these things to different relative positions.

 

[alexi_drago]

I don't know if this question will make much sense but say there's 3 objects sitting on a line, two are at the edges of what the middle one can see but in opposite directions. What in the singularity decided that one object should be on one side and the other object on the opposite side? (I suppose this should/could? probably be in reference to space rather than objects)

 

[JoeTheJuggler]

Then what did it expand into?

It didn't expand into anything. It is the expansion of space itself.

So the location of space separating two planets 1,100,000 lightyears away is the same location as the space that separates the Earth from Mars?

As edd said it, both locations map back to the center of the Big Bang. If you were asking where is the center of the universe today, both locations would be as valid an answer.

The Universe is also things.

When we talk about the expansion of the universe it is the expansion of space itself (more space between the galaxies or larger structures) and not the expansion of the things in the universe.

 

[sol invictus]

Is it correct to say that the singularity was a single thing that contained no space? Then with the Big Bang the singularity was broken up into many things that uniformly move apart by continuously expanding space?

No. It's a singularity; nothing much can be said about it.

Then what did it expand into?

The entire 3-dimensional space expands uniformly with time. If you insist you can think of it expanding into a 4th spatial direction (so there are 4 spatial dimensions and one time). If you do think of it that way there is a center, but it's not part of the universe (think of the surface of the earth - there's a center to the earth, but it's not part of the surface).

I don't know if this question will make much sense but say there's 3 objects sitting on a line, two are at the edges of what the middle one can see but in opposite directions. What in the singularity decided that one object should be on one side and the other object on the opposite side? (I suppose this should/could? probably be in reference to space rather than objects)

At every moment of time after the big bang they've been arranged like that (at least assuming they aren't moving relative to each other apart from the expansion of space). If you're asking why they started off like that, the answer is that no one knows. We don't understand what physics, if any, set up the "initial" conditions at the big bang (or even if it was truly the beginning).

 

[JoeTheJuggler]

I don't know if this question will make much sense but say there's 3 objects sitting on a line, two are at the edges of what the middle one can see but in opposite directions. What in the singularity decided that one object should be on one side and the other object on the opposite side? (I suppose this should/could? probably be in reference to space rather than objects)

The pathetic fallacy aside (nothing "decided" this), that sort of thing was determined later by gravity. (Someone who knows better might be able to give you a more accurate answer than I can.) My understanding is that by the time there were discrete "things" there were already distortions in space (gravity) that account for their motions and positions.

 

[JoeTheJuggler]

Is it correct to say that the singularity was a single thing that contained no space? Then with the Big Bang the singularity was broken up into many things that uniformly move apart by continuously expanding space?

I don't think so. It sounds like you still imagine the singularity sitting in pre-existing space and spreading out into pre-existing space. That's not so.

 

[Foster Zygote]

The best way to think about it is to visualize the surface of a sphere. If the three dimensional sphere expands, its two dimensional surface also expands. But there is no stationary center on the sphere's surface. Our space/time is like the surface of that sphere.

 

[JoeTheJuggler]

At every moment of time after the big bang they've been arranged like that (at least assuming they aren't moving relative to each other apart from the expansion of space). If you're asking why they started off like that, the answer is that no one knows. We don't understand what physics, if any, set up the "initial" conditions at the big bang (or even if it was truly the beginning).

I'm not the most knowledgeable person on this subject, but I don't think this is accurate. Without getting into an epistemological debate about whether we "know" anything, we do think that the earliest universe was homogenous.

According to the Wiki article (my bolding on this point and the bit that I think answers alexi's question):

The earliest phases of the Big Bang are subject to much speculation. In the most common models, the Universe was filled homogeneously and isotropically with an incredibly high energy density, huge temperatures and pressures, and was very rapidly expanding and cooling. Approximately 10−37 seconds into the expansion, a phase transition caused a cosmic inflation, during which the Universe grew exponentially.[30] After inflation stopped, the Universe consisted of a quark–gluon plasma, as well as all other elementary particles.[31] Temperatures were so high that the random motions of particles were at relativistic speeds, and particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions. At some point an unknown reaction called baryogenesis violated the conservation of baryon number, leading to a very small excess of quarks and leptons over antiquarks and antileptons—of the order of 1 part in 30 million. This resulted in the predominance of matter over antimatter in the present Universe.[32]

 

[alexi_drago]

If you're asking why they started off like that,

Yep.

the answer is that no one knows.

ok.

 

[JoeTheJuggler]

ok.

Again, the random motion of the high-energy homogenous stuff resulted in non-homogeneity. By the time we get to normal matter, it's already in discrete lumps, bits of it in different places relative to other bits.

 

[alexi_drago]

I'm not the most knowledgeable person on this subject, but I don't think this is accurate. Without getting into an epistemological debate about whether we "know" anything, we do think that the earliest universe was homogenous.

According to the Wiki article (my bolding on this point and the bit that I think answers alexi's question):

I was meaning the point where there was nothing more than the singularity.

 

[JoeTheJuggler]

I was meaning the point where there was nothing more than the singularity.

At that point all was homogenous (no information--no bits with position relative to each other). Nothing about that determined the position of things later.

 

[ynot]

Can we at least explain the singularity as being all things of the Universe being in pretty much the same place at the same time (together)? And that the expanded Universe is essentially the expanded singularity where all things of the Universe are in different places at the same time (apart)? Forgetting space, if all things were once together and they are now all apart as the result of a uniform expansion (regardless what causes it), then the very point that the things expanded from (where they were together) must be the stationary centre of the expansion.

I cannot accept an analogy of the Universe as a 2D surface of a sphere and I think it‘s ludicrous woo to do so. The Universe is always spatially 3D. Nothing more, nothing less.

 

[JoeTheJuggler]

Can we at least explain the singularity as being all things of the Universe being in pretty much the same place at the same time (together)? And that the expanded Universe is essentially the expanded singularity where all things of the Universe are in different places at the same time (apart)?

I suppose so, as long as you can similarly think of a chicken as merely an expanded egg.

Forgetting space, if all things were once together and they are now all apart as the result of a uniform expansion

No. "All things" didn't always exist. The singularity and some time after expansion started, the universe was homogenous, and there were no things.

I cannot accept an analogy of the Universe as a 2D surface of a sphere and I think it‘s ludicrous woo to do so.

It's a legitimate analogy, but I understand your frustration with it. For those of us that don't have the mathematical ability to understand these things for real, that's about the best visualization we can get.

I prefer just to cling to the idea that the Big Bang happened everywhere in our universe. The universe doesn't expand into pre-existing space. Expansion is essentially new space coming into being between the galaxies.

If you can, try to imagine St. Louis and Kansas City getting farther apart by the coming into being of more mid-Missouri and NOT by St. Louis moving east into Illinois or K.C. moving west into Kansas. Again, it's only an analogy and not without major flaws.