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Re: [Phys-L] Big Bang

I am certainly not up to speed here, but if the mass of the universe was infinite wouldn't the mass density still be infinite? Isn't the fact that the current observed (local) density is not infinite preclude infinite mass. Infinite density at the time of the Bing Bang is still possible with zero volume, but I would think not infinite mass??


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----- Jeffrey Schnick <JSchnick@Anselm.Edu> wrote:
This is a side issue, but I think that in arriving at the size of the universe at the time of the big bang, based on the essentially infinite density of the universe at that time, one assumes that the universe is currently a sphere of diameter 14 billion light years with us at the center. I think that the size that they are actually talking about is the size of that portion of the universe which is visible to us and that they should refer to it as such.

I think that in arriving at the size of the universe one assumes that there is a finite amount of mass in the universe in which case infinite density implies infinitesimal diameter. I don't think we have evidence that the mass of the universe is finite. I don't think we can rule out infinite density and infinite diameter at the time of the big bang.

-----Original Message-----
From: Phys-l [] On Behalf Of Anthony
Sent: Thursday, March 14, 2013 9:38 AM
Subject: [Phys-L] Big Bang

I'll be teaching cosmology next month in my (high school) astronomy class.
The book I use discusses inflation and that the volume of the universe during
the Big Bang was less than the size of a proton! How can this be? I realize the
universe had a "hot" and "dense" beginning, but isn't there a limit to how
closely matter (made up of particles) can be packed together?
Particles take up space, so how could an object -- let alone the entire
universe -- have essentially "infinite" density (zero volume)?

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