If the Universe is indeed finite(in volume)


by Zelyucha
Tags: finitein, universe, volume
Zelyucha
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#1
Dec10-12, 03:54 PM
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What pray tell, is the definitive proof? I ask this question upon reading a recent article regarding data from the WMAP probe suggesting that the Cosmos is flat. Now it did not specify whether this implies that the Cosmos is locally Euclidean or has a Euclidean spacial metric and zero mean curvature. If the latter is such, then this would most likely imply the shape of the Universe is best described by a non-compact manifold which implies that it is indeed infinite in size.

If there is enough evidence to demonstrate that the Universe has finite size, I'd like to see some of it if you wouldn't mind.
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Drakkith
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Dec10-12, 04:25 PM
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There is no concrete evidence that the Universe is finite at this time. I remember reading about a result saying the Universe was finite, but it was only about a 1.6 or 1.3 sigma result, meaning it isn't definitive at all. It could still go either way.
phinds
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Dec10-12, 04:39 PM
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Quote Quote by Zelyucha View Post
What pray tell, is the definitive proof?
Science doesn't much go in for "definitive proof" these days. Back in the day, everyone concluded that Newton's Law of Gravity was definitively proven and thus could be called a "Law", but it is now know to be quite incorrect even though it gives good results at local scales.

These days' Einsteins Theory of General Relatively has been shown to be correct to umpteen decimal places (more than Newton's was) BUT it is known to be "wrong" at least in the sense of being incomplete (no good at the quantum level), and thus is NOT called a "law".

bapowell
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Dec11-12, 09:56 AM
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If the Universe is indeed finite(in volume)


Quote Quote by Zelyucha View Post
If the latter is such, then this would most likely imply the shape of the Universe is best described by a non-compact manifold which implies that it is indeed infinite in size.
As others have mentioned, the data from WMAP pertain to the observable universe, and constrain this geometry only. However, it's also probably worth pointing out that there are compact manifolds with flat metrics -- the torus, for example.
Zelyucha
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Dec11-12, 04:34 PM
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Quote Quote by Drakkith View Post
There is no concrete evidence that the Universe is finite at this time. I remember reading about a result saying the Universe was finite, but it was only about a 1.6 or 1.3 sigma result, meaning it isn't definitive at all. It could still go either way.


IF the Universe is indeed shown to be infinite to say, 4σ at the very least, then I daresay that in itself will strike a fatal blow to the Big Bang Theory. For a Universe of finite size to reach infinite size in any finite amount of time would be topologically impossible. Not-to-mention a gross violation of the 1st law of thermodynamics to which AFAIK there is ZERO experimental or observational evidence which is in violation to it.
phinds
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Dec11-12, 04:38 PM
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Quote Quote by Zelyucha View Post
IF the Universe is indeed shown to be infinite to say, 4σ at the very least, then I daresay that in itself will strike a fatal blow to the Big Bang Theory. For a Universe of finite size to reach infinite size in any finite amount of time would be topologically impossible. Not-to-mention a gross violation of the 1st law of thermodynamics to which AFAIK there is ZERO experimental or observational evidence which is in violation to it.
And what evidence do you have that the universe was not infinite to begin with? Please provide references. The big bang theory does not require it and I have never heard anyone (other than morons on TV) say that it was definitively finite to begin with.
Zelyucha
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Dec11-12, 04:46 PM
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Quote Quote by phinds View Post
And what evidence do you have that the universe was not infinite to begin with? Please provide references.
I have none. As a matter of fact I certainly do not disregard the possibility that the Universe was infinite to begin with.



The big bang theory does not require it and I have never heard anyone (other than morons on TV) say that it was definitively finite to begin with.
Um, WUT? Are you suggesting that the Big Bang may have resulted in a Universe of Infinite size(and total combined mass) in a finite period of time???

By what known physical mechanism would this be possible? I wager that if the Cosmos is infinite space it is also infinite in time and has no end....and no beginning.
Drakkith
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Dec11-12, 05:06 PM
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Quote Quote by Zelyucha View Post
Um, WUT? Are you suggesting that the Big Bang may have resulted in a Universe of Infinite size(and total combined mass) in a finite period of time???
Of course. The possibility exists.

By what known physical mechanism would this be possible? I wager that if the Cosmos is infinite space it is also infinite in time and has no end....and no beginning.
That would not be the way current Cosmology sees it. The Universe can be finite in age and infinite in extent.
bapowell
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Dec11-12, 05:45 PM
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Quote Quote by Zelyucha View Post
Um, WUT? Are you suggesting that the Big Bang may have resulted in a Universe of Infinite size(and total combined mass) in a finite period of time???

By what known physical mechanism would this be possible? I wager that if the Cosmos is infinite space it is also infinite in time and has no end....and no beginning.
Well, again, there is this distinction between the observable universe and the universe. When cosmologists refer to the Big Bang model, they are not generally speaking of the moment of cosmogenesis of the universe, but rather the model of an expanding homogeneous spacetime. After all, all our data refers to our observable universe -- there could well be more out there, and as others have pointed out, an infinite amount of universe. The finite time since the "Big Bang" would then refer to the finite time since the universe began its expansion (or, more correctly, since processes tied to observational evidence occurred, like nucleosynthesis and the creation of the CMB.)


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