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Profile Jord
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Message 5009 - Posted: 27 Feb 2008, 1:52:57 UTC

No, not of the project... :-)

I saw this article posted in a thread over on Einstein\'s Science forum. It\'s probably better in its place here.

The End of Cosmology?

An accelerating universe wipes out traces of its own origins.

Key Concepts

* A decade ago astronomers made the revolutionary discovery that the expansion of the universe is speeding up. They are still working out is implications.

* The quickening expansion will eventually pull galaxies apart faster than light, causing them to drop out of view. This process eliminates reference points for measuring expansion and dilutes the distinctive products of the big bang to nothingness. In short, it erases all the signs that a big bang ever occurred.

* To our distant descendants, the universe will look like a small puddle of stars in an endless, changeless void.

* What knowledge has the universe already erased?


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Message 5010 - Posted: 27 Feb 2008, 7:09:14 UTC - in response to Message 5009.  
Last modified: 27 Feb 2008, 7:23:10 UTC

Another consequence derived from c constant ?

Like energy, and if already not, I suppose that the next great step will be the discovery that the space itself is quantized too.

Then, the interaction between \"quantic spaces\" will be better investigated and maybe other forms of interactions than we know now can arise...
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Message 5018 - Posted: 1 Mar 2008, 15:58:55 UTC

The mathematics of Cosmology appears to be that the number of questions is multiplied exponentially by each new discovery we make about our universe. When we ponder the universe we become like children at that age where they repeatedly ask questions like, \"Momma, why is the sky blue? Da, why is the grass green?\" For many of us, it is part of our nature and I doubt that we will ever stop asking questions, finding answers, and asked more questions. It seems to me that Cosmology will only end with the human race and it\'s possible that some other species will continue their search.

My question to all of the experts is whether there is any evidence which suggests or supports the \"inconceivable\" concept that the Universe is infinite?

Contra, what is the evidence that suggests or supports the concept that the Universe is finite?

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Profile Scott
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Message 5019 - Posted: 2 Mar 2008, 5:49:42 UTC - in response to Message 5018.  

My question to all of the experts is whether there is any evidence which suggests or supports the \"inconceivable\" concept that the Universe is infinite?

Contra, what is the evidence that suggests or supports the concept that the Universe is finite?


The extent of the universe is determined by the geometry of space, which in turn is determined by its curvature.

1) Hyperspherical (closed, positive curvature)
2) Flat (open, zero curvature)
3) Hyperbolic (open, negative curvature)

In the first case, the universe is finite but without boundaries. This is easy to see if you think about the surface of a sphere: there is only so much surface area, but there isn\'t any edge where the surface stops.

In the second case, the universe is like a 2D plane: it extends infinitely in all directions and has no boundary.

In the last case, the universe is curved similar to a saddle: like the flat universe, it is also infinite in extent and has no edge.

From data gleaned from the CMB, it\'s been determined that the universe is almost exactly flat. This means that the universe is almost definitely infinite in extent.
Scott Kruger
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Kenneth Larsen
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Message 5020 - Posted: 2 Mar 2008, 12:23:23 UTC - in response to Message 5019.  

From data gleaned from the CMB, it\'s been determined that the universe is almost exactly flat. This means that the universe is almost definitely infinite in extent.


But if the universe is expanding, doesn´t this mean that it is hyperbolic? I admit I am just an interested non-scientist and not an expert, but I thought that the cosmologic constant had to be exactly 1 for a flat universe, any infinitely small variation would make it either expanding or deccelerating (hyperbolic or spherical).
Have I misunderstood something here (if yes, don´t bother with a long explanation, perhaps I should go back and read the books I have ;-) )?
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Profile Scott
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Message 5024 - Posted: 3 Mar 2008, 23:24:47 UTC - in response to Message 5020.  

But if the universe is expanding, doesn´t this mean that it is hyperbolic? I admit I am just an interested non-scientist and not an expert, but I thought that the cosmologic constant had to be exactly 1 for a flat universe, any infinitely small variation would make it either expanding or deccelerating (hyperbolic or spherical).
Have I misunderstood something here (if yes, don´t bother with a long explanation, perhaps I should go back and read the books I have ;-) )?


You\'re mostly right. The local geometry of space is related to the energy density of the universe. If p is the current energy density and p0 is the critical density, then p/p0 must be 1 in order for the universe to be flat, and this is what we in fact observe (to within a few percent).

For a while, cosmologists were confused about how the universe could possibly be flat, since, like you said, any small departure from flatness should grow. However, the theory of inflation solves this and other cosmological coincidences by proposing that the universe expanded exponentially early on, so much that the universe appears flat locally, even though it might not be so globally. This is similar to how we perceive the Earth to be flat, even though it is actually approximately spherical.

Don\'t get discouraged; you had mostly the right answer!
Scott Kruger
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Message 5026 - Posted: 4 Mar 2008, 15:02:24 UTC

Thanks for the explanation, Scott! :-)
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