On 12/24/2018 1:04 PM, [email protected] wrote:
On Monday, December 24, 2018 at 8:25:11 PM UTC, [email protected]
wrote:
On Monday, December 24, 2018 at 6:40:03 AM UTC, Brent wrote:
On 12/23/2018 8:22 PM, [email protected] wrote:
On Monday, December 24, 2018 at 3:50:33 AM UTC, Brent wrote:
On 12/23/2018 4:47 PM, [email protected] wrote:
*If by "flat", you mean mathematically flat, like a
plane extending infinitely in all directions, as opposed
to asymptotically flat like a huge and expanding
sphere, you have to reconcile an infinitesimally tiny
universe at the time of the BB, and simultaneously an
infinitely large universe extending infinitely in all
directions. AG*
All that's "infinitesimally tiny" is the visible
universe. You must know that the Friedmann equation just
defines the dynamics of a scale factor, not a size.
*Are you claiming the visible universe at the BB was
infinitesimally tiny, but the non visible part was infinitely
large (mathematically flat), or huge (asymptotically flat)? AG *
Right. Although we can't be sure whether it is actually flat
or just very big.
Brent
*OK. Agreed. We seemed to disagree on this in the past, but maybe
we miscommunicated. AG*
Here's what Ned Wright wrote.
Is the Universe really infinite or just really big?
We have observations that say that the radius of curvature of the
Universe is bigger than 70 billion light years. But the observations
allow for either a positive or negative curvature, and this range
includes the flat Universe with infinite radius of curvature. The
negatively curved space is also infinite in volume even though it is
curved. So we know empirically that the volume of the Universe is more
than 20 times bigger than volume of the observable Universe. Since we
can only look at small piece of an object that has a large radius of
curvature, it looks flat. The simplest mathematical model for
computing the observed properties of the Universe is then flat
Euclidean space. This model is infinite, but what we know about the
Universe is that it isreally big
<http://www.astro.ucla.edu/~wright/HGTTG.html>.
<http://www.astro.ucla.edu/~wright/cosmology_faq.html#top>
*
*
*It is misleading. He's referring to the VISIBLE universe and
concludes it might be infinite in spatial extent. Impossible due to
its finite age. I wrote him about this, but never received a reply. AG*
Why don't you look at his web tutorial. He does not conclude the
/*visible*/ universe might be infinite.
Brent
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