I Is there any way in the future to determine the Universe's size?

[PeterDonis]

For the universe to be perfectly flat, it would need to be perfectly homogeneous

All of the observations described in this thread are of the average spatial curvature of the universe. Obviously its spatial curvature cannot be the same everywhere since the matter and energy in it is clumped.

 

[Ibix]

“Many independent observations indicate that the universe is in fact flat”

I suspect Siegel is over-reaching here, as well as what has been said above. I think the correct statement is that many independent observations are consistent with flatness and none are significantly inconsistent with it, but all are also consistent with a very large radius of curvature.

 

[Jaime Rudas]

All of the observations described in this thread are of the average spatial curvature of the universe.

I agree. That's why I mentioned that the probability of the universe being perfectly flat is practically zero.

 

[PeterDonis]

That's why I mentioned that the probability of the universe being perfectly flat is practically zero.

We are not talking about the probability of the entire universe being perfectly spatially flat. We are talking about the probability of the average curvature of the universe being zero, i.e., flat. That's not the same thing.

Also, since a universe which is on average positively curved is spatially closed, it has a different spatial topology from either the flat or open cases, so it is not just a question of a continuous variation in the curvature parameter; there is discontinuous choice of spatial topology involved. So just looking at things from the standpoint of a continuous probability measure is not correct.

 

[Drakkith]

Why do we insist to push the idea of nearly flat & curvature to our flat universe?
Is it just because there is no valid theory for that infinite flat universe?

A model of a flat universe works just fine with current theory (general relativity is the underlying theory).
A model of a curved universe works just fine with current theory.
A model with a 'center' or with 'edges' does not work fine with current theory.

 

[davLev]

You confirm that there is a possibility for the universe to be infinite flat.
You also confirm that the current theory can cover this infinite flat universe.
Do we have any real observation that clearly proves that the universe has a curvature?
As we consider a possibility for positive and negative curvature, why can’t we also consider one more possibility for the universe to be an infinite flat without any curvature?

 

[PeterDonis]

You confirm that there is a possibility for the universe to be infinite flat.
You also confirm that the current theory can cover this infinite flat universe.
Do we have any real observation that clearly proves that the universe has a curvature?
As we consider a possibility for positive and negative curvature, why can’t we also consider one more possibility for the universe to be an infinite flat without any curvature?

Your questions have already been answered. Since you apparently have nothing further of substance to contribute, you have now been banned from further posting in this thread.

 

[Ibix]

why can’t we also consider one more possibility for the universe to be an infinite flat without any curvature?

There's either an echo or a closed timelike curve in here...

 

[Cerenkov]

Please stop repeating yourself, Ibix.