Where Is The Center Of The Big Bang Universe?

[MattusMaximus]

As for the oxymoron, you cannot have infinity plus one because all 'ones' would be included in the infinite number.

Not true. There was an entire area of mathematics developed dealing specifically with sticky questions such as infinity and infinity+1, etc. For example, take a look at Hilbert's paradox of the Grand Hotel as an example of what I'm talking about.

The real problem is the usual conceptualization of the center and edge of the Universe is based on an expanding Universe where light years keep expanding but staying relative to the observer. If you freeze time, space time has a center and an edge. But we try to conceptualize it without freezing time.

Imagine stopping the Earth from turning, so time is frozen. But you have the hyper-dimensional capability to walk the Earth in this state. If you walk out your front door and head due east, and never stop walking, you will eventually end up back in front of your door because the Earth is a sphere. So tell me, where's the "edge" in this example?

How do you account for everything in 3D on a scale where time is essentially irrelevant (say the distance from here to the end of the block) having a center and an edge to having those elements just stop existing in the Universe itself? If you freeze the time dimension, you get an edge.

Again, see my example of the "frozen" Earth above. Where is the "edge" in that case?

We can't freeze the time dimension, and we can't outpace light and the expansion, so we cannot see or detect the edge. For all intents and purposes you could say there isn't one. But if expansion stopped and time stopped, and you went in a straight line, you would either return to the place you left, or reach an edge. I think reaching an edge fits the data better than returning to the place you left.

If you think there is such an "edge" please point it out. Of course, such a claim is meaningless without also pointing out a "center" to the universe, which, as we've seen from the earlier posts in this thread, isn't possible to define according to our current knowledge of cosmology.

It is as you said... for all intents and purposes, the universe has neither an "edge" nor a "center".

 

[Skeptic Ginger]

I know I have a woo position here. I don't expect to convince anyone the emperor has no clothes. But I feel justified. In my Universe contemplating, I have thought this one through. I understand the no center no edge idea. I understand the Universe is all and is not expanding into anything. I understand the 2D model used to show no center/no edge.

But, we don't live in a 2D world, and no one really has a model of the same thing using 3D. In every direction looking out from the Earth we see back in time, we don't see across. But why then assume across does not exist? Actually, we assume it does exist. We assume the stuff we see is out there but the light we see came from it in the past.

If you stopped expansion and time, you would have a center and an edge.

Oh, and the infinity plus one is different in theoretical math than in the physical world so that isn't what I was referring to with the oxymoron. If the Universe were infinite, then I agree, no center, no middle. I don't think you can have one size one second after the BB and another size 14 billion years later and say both are infinite. In theoretical math, sure, but in the physical Universe, no. The time it takes light to travel across the singularity is irrelevant because I am talking about stopping expansion and time when one then gets the edge and center.

The 'frozen Earth' with no edge is a 2D model.

As for where is the edge, I said, we cannot see across the Universe, only back in time so we have no way of seeing it. We can't see what's inside a black hole either, that doesn't mean it does not exist.

And because it took 14 billion years or so for evolution, it isn't likely we would be on a planet near enough to the edge of the Universe to be able to see the void. Expansion would have overtaken our galaxy even if the material that makes up the Galaxy had ever been near the edge. In other words, the material in the Universe which is close to the edge could have different properties. In any case, expansion has resulted in no light from the edge reaching us. All the light that reaches us is from the past.

It may take a little more Universe contemplating for me to sort that out in more detail, but it could explain why we don't see the edge or evidence of a center.

 

[sol invictus]

But, we don't live in a 2D world, and no one really has a model of the same thing using 3D.

Sure we do. I could show it to you, but I don't know if it would mean much to you. So take my word for it - it's just as well understood as the 2d version (just a little harder to visualize).

In every direction looking out from the Earth we see back in time, we don't see across. But why then assume across does not exist?

We can't prove there's no edge, you're right. What we do know is that we see something very homogeneous and very isotropic. So there are basically three options:

Standard cosmo is correct, which means the universe is homogeneous and isotropic about every point, and there are no edges.

We live at the precise center of an inhomogeneous but isotropic (around us) universe. Back to Ptolemy.

Standard cosmo is almost right, but only describes a region of the universe a little bigger than what we can currently see. Somewhere past our horizon something crazy (like an edge) happens. The paper you mentioned put one kind of bound on that kind of thing - the edge would have to be quite far away. Possible, but more complicated and unsupported by data.

EDIT - on second thought, I'm not sure option 2 is really an option. There might be clever ways to rule out such a Milky Way-centric cosmology, just as there were ways to rule out the geocentric solar system without leaving earth. I'd have to think about that.

 

[MattusMaximus]

The 'frozen Earth' with no edge is a 2D model.

No it isn't, as the Earth is a 3D object in "frozen" time. If you don't believe me, just get a shovel and start digging

The point is that, lacking a shovel, you are confined to walk the surface of the Earth, which locally appears to be a 2D surface but in the larger space is actually 3D. It is a question of perception.

So, again, I ask you to think about it: in this case, where is the "edge"?

 

[~enigma~]

No it isn't, as the Earth is a 3D object in "frozen" time. If you don't believe me, just get a shovel and start digging

The point is that, lacking a shovel, you are confined to walk the surface of the Earth, which locally appears to be a 2D surface but in the larger space is actually 3D. It is a question of perception.

So, again, I ask you to think about it: in this case, where is the "edge"?

Edge? He is one of the fake wrestlers on Friday Night Smackdown

 

[Skeptic Ginger]

No it isn't, as the Earth is a 3D object in "frozen" time. If you don't believe me, just get a shovel and start digging

The point is that, lacking a shovel, you are confined to walk the surface of the Earth, which locally appears to be a 2D surface but in the larger space is actually 3D. It is a question of perception.

So, again, I ask you to think about it: in this case, where is the "edge"?

But you actually support my point. Because we cannot see 'across' the Universe in 3D space, we can only see back in 4D space time, we are lacking the "shovel". But that doesn't mean the things we cannot see don't exist.

We don't have a lot of evidence in how to interpret the time dimension. We don't know if the past or future exist. Just thought I'd throw that meaningless twist in there.

 

[MattusMaximus]

But you actually support my point. Because we cannot see 'across' the Universe in 3D space, we can only see back in 4D space time, we are lacking the "shovel". But that doesn't mean the things we cannot see don't exist.

I fail to see how I've supported your point. Explain how my example defines an "edge" and you might be on to something. The difference is that in my example, there is a definite 3D space which is observable, whereas you are making up a hypothetical extra dimension which no one has ever observed in your case (that is, the dimension through which you'd be "shoveling"). If you simply leave your arguments at "in a hypothetical 4D+? space there could be an edge, despite us having no way to observe it" then you are simply making an argument from ignorance.

I ask you, what is the difference between a completely unobservable edge and no edge at all?

 

[MattusMaximus]

We don't have a lot of evidence in how to interpret the time dimension. We don't know if the past or future exist. Just thought I'd throw that meaningless twist in there.

I wouldn't call this a meaningless twist, but I'm not sure how much of a scientific question this is as opposed to a philosophical one. I'm pretty certain the past exists, if my credit card billings are any measure

 

[~enigma~]

But that doesn't mean the things we cannot see don't exist.

Absence of evidence does not mean evidence of absence. It does however mean there is an ABSENCE OF EVIDENCE. Or do you have reason to believe contrary to science?

 

[Dan O.]

While you are contemplating the infinite universe, try contemplating this: By extrapolating back in time we hypothesize that the universe started from a dense mass that for some reason underwent inflation which created the visible universe we see surrounded by an event horizon beyond which we cannot see. We also have this hypothesis about the creation of black holes when a massive body is large enough and dense enough that it collapses behind an event horizon beyond which we cannot see. Why in the first case does the mass expand into a universe and in the second cast the mass collapses into a singularity? My question is, could these be two views of the same type of event?

Nobody has seen what goes on inside a black hole. The concept of the singularity inside the black hole is just an extension of the equations of relativity. Relativity is just a concept to reconcile that the speed of light is always the same for any reference frame. Relativity has worked well just as Newtonian mechanics works well for non relativistic events. But what if relativity is slightly wrong in extreme cases such as the conditions inside of a black hole. What kind of correction to the equations for relativity would be required so that a black hole expands into a universe instead of collapsing into a singularity?

 

[sol invictus]

While you are contemplating the infinite universe, try contemplating this: By extrapolating back in time we hypothesize that the universe started from a dense mass that for some reason underwent inflation which created the visible universe we see surrounded by an event horizon beyond which we cannot see. We also have this hypothesis about the creation of black holes when a massive body is large enough and dense enough that it collapses behind an event horizon beyond which we cannot see. Why in the first case does the mass expand into a universe and in the second cast the mass collapses into a singularity? My question is, could these be two views of the same type of event?

Nobody has seen what goes on inside a black hole. The concept of the singularity inside the black hole is just an extension of the equations of relativity. Relativity is just a concept to reconcile that the speed of light is always the same for any reference frame. Relativity has worked well just as Newtonian mechanics works well for non relativistic events. But what if relativity is slightly wrong in extreme cases such as the conditions inside of a black hole. What kind of correction to the equations for relativity would be required so that a black hole expands into a universe instead of collapsing into a singularity?

That's an excellent question. The connection between black hole singularities and cosmological singularities is very interesting. There are certain aspects which make them quite similar. In a precise sense, one can regard the big bang as what's called a "white hole" - a black hole, but in our past. We are inside the horizon, but since the singularity is in our past we are moving away from it in time. If you can imagine the time-reverse of someone falling into a horizon and hitting a singularity, that's more or less it.

Now it's true that general relativity breaks down at and near the singularity. So one very interesting question is what those corrections do in the early universe. That's a fascinating and active area of research - if we can measure something about those corrections, we've learned something about quantum gravity - and such opportunities are extremely rare. Unfortunately it turns out that long periods of inflation tend to wipe away such effects (inflation shields us from what would otherwise be very large effects from the singularity). That makes it harder, but there are still many ways in which we might be able to learn something.

Another relevant fact is the following: suppose we were in a flat, eternal, non-expanding universe for a moment (so just empty space). Now suppose someone created a spherical shell of matter surrounding us. As you probably know, the gravitational field inside such a shell is not affected by it (so it remains flat). But when the shell crosses its own Schwarzschild radius, a black hole has formed, and anyone and anything inside is doomed to eventually hit a singularity. But if the shell is massive enough, that radius can be enormous - bigger than the observable universe, even - and those inside won't know their fate for a very long time. It is quite possible that we live inside such a black hole - we'd have no way of knowing, and there's a class of theories which predict that as the generic condition.

Good question.

 

[MattusMaximus]

That's an excellent question. The connection between black hole singularities and cosmological singularities is very interesting.

Sol, is this where the Holographic principle would come into play? I've read about it but not much more.

 

[~enigma~]

Umm...since we are on the topic of singularities I have a question. Einstein had a problem with the existence of singularities because as the radius decreases the internal pressure raises. At the Schwarzschild radius the pressure becomes infinite. We now know that NOTHING resists gravity below the Schwarzchild radius and it is the degeneracy pressure that exists. My question is since degeneracy pressure exists even at absolute zero, is a singularity hot or cold?

 

[~enigma~]

Umm...since we are on the topic of singularities I have a question. Einstein had a problem with the existence of singularities because as the radius decreases the internal pressure raises. At the Schwarzschild radius the pressure becomes infinite. We now know that NOTHING resists gravity below the Schwarzchild radius and it is the degeneracy pressure that exists. My question is since degeneracy pressure exists even at absolute zero, is a singularity hot or cold?

As a follow up, if (as claimed) ALL motion ceases at absolute zero then why is pressure from electron degeneracy allowed?

 

[sol invictus]

Sol, is this where the Holographic principle would come into play? I've read about it but not much more.

It is certainly relevant, and a useful tool for trying to understand these issues. Still, so far no one has succeeded in building a model which can resolve either a black hole singularity or a cosmological one. Holographic models do a good job describing the outsides of black holes, but not the insides.

My question is since degeneracy pressure exists even at absolute zero, is a singularity hot or cold?

Hot, I guess. It's not a very well-defined question since there cannot possibly be any notion of equilibrium, but as you approach the singularity things get torn apart - so their kinetic energy must increase.

As a follow up, if (as claimed) ALL motion ceases at absolute zero then why is pressure from electron degeneracy allowed?

It's not true that all motion ceases. There is always zero-point energy.

 

[~enigma~]

Hot, I guess. It's not a very well-defined question since there cannot possibly be any notion of equilibrium, but as you approach the singularity things get torn apart - so their kinetic energy must increase.



It's not true that all motion ceases. There is always zero-point energy.

Ahh...now if kinetic energy increases and degeneracy pressure is due to shrinking the area the electron can be in...absolute zero has the same "heat" as the singularity in a black hole. Am I looking at this correctly?

ETA - Along the same lines. According to the Einstein field equations, gravity (or rather a warpage of spacetime) is caused by mass AND pressure. Is the singularity really mass or just an extreme degeneracy?

 

[sol invictus]

Ahh...now if kinetic energy increases and degeneracy pressure is due to shrinking the area the electron can be in...absolute zero has the same "heat" as the singularity in a black hole. Am I looking at this correctly?

I'm not sure. I don't see a clean way to define the temperature of a singularity. Strictly speaking temperature is defined by putting two systems in contact and letting them equilibrate. Clearly that doesn't work here. You could try to define it by the average kinetic energy, but then the singularity will be very hot, as I said.

Certainly if you go back in time towards the early universe, as you approach the big bang singularity (which, as we've been discussing, is closely analogous to a BH singularity) the temperature increases to infinity.

ETA - Along the same lines. According to the Einstein field equations, gravity (or rather a warpage of spacetime) is caused by mass AND pressure. Is the singularity really mass or just an extreme degeneracy?

The stress-energy tensor is strictly zero everywhere in the BH solution (because it's a vacuum solution) except right at the singularity, where only one component is non-zero (and infinite). I suppose you could actually consider that a pressure, because the "time" coordinate becomes spacelike inside the hole. Viewed from outside, though, the field is identical to the field of any other spherically symmetric configuration of the same total energy. For the field outside it doesn't matter whether that energy is mass or pressure.

 

[~enigma~]

I'm not sure. I don't see a clean way to define the temperature of a singularity. Strictly speaking temperature is defined by putting two systems in contact and letting them equilibrate. Clearly that doesn't work here. You could try to define it by the average kinetic energy, but then the singularity will be very hot, as I said.

Certainly if you go back in time towards the early universe, as you approach the big bang singularity (which, as we've been discussing, is closely analogous to a BH singularity) the temperature increases to infinity.

Maybe my concept of temperature is skewed. Isn't an infinite temperature essentially the same as absolute zero (same result either way)?

 

[sol invictus]

Maybe my concept of temperature is skewed. Isn't an infinite temperature essentially the same as absolute zero (same result either way)?

Eh? Same result for what?

You might be thinking of the fact that temperature can sometimes be negative, which happens in some finite systems when it first goes to infinity and then "wraps around" to minus infinity?

 

[~enigma~]

Eh? Same result for what?

You might be thinking of the fact that temperature can sometimes be negative, which happens in some finite systems when it first goes to infinity and then "wraps around" to minus infinity?

Same result was just my way of saying absolute zero or infinite temperature will both kill so there isn't much qualitative difference.