On 1/13/2020 10:51 AM, Alan Grayson wrote:
On Monday, January 13, 2020 at 11:12:36 AM UTC-7, Brent wrote:
On 1/13/2020 2:10 AM, Alan Grayson wrote:
The model says that a subset of the universe
starts small and gets bigger. This is not
inconsistent with the whole universe starting and
remaining infinite in spatial extent.
--
Stathis Papaioannou
*I thought I made that clear; what I am calling "the
universe" is precisely the SUBSET you refer to, which
starts small and gets bigger. It is THAT SUBSET which
cosmologists claim has infinite spatial extent, based
on measurements. *
First, a proper subset of an infinite set can also be infinite (in
fact that's one definition of "infinite").
*True. AG*
Second, nobody measures an infinite portion of the universe.
*I never made that claim. AG*
We can only measure the curvature of the part we can see.
*I never claimed otherwise. How could we measure what we can't (in
some sense) see? Impossible! AG*
Third, it is not clear what is THAT SUBSET to which you refer.
*I'm referring to the observable and non-observable regions. When
cosmologists claim the universe is flat, they're referring to these
regions and nothing else. It does NOT include the underlying entity
from which our bubble emerged. Thus, a subset of a possibly larger
totality. AG *
Cosmologists are aware that only an initially infinite subset of
space can be infinite after a finite expansion.
*So, at the instant of the BB, that is"initially", there's a process
which creates an infinity of space having zero time duration? *
No. If space is infinite then it was infinite at the start. Or it
might be finite and simply so inflated that our measure of curvature
can't distinguish it from flat(=infinite). Although there are ways
space can be infinite on one slice but infinite on another slice
(assuming time is future infinite).
Brent
*How is this different from a singularity? This is where I have a
problem. There is no process that can create anything, let alone a
spatial infinity, with no time passing. AG*
They refer to a part of the universe that is beyond observation
as being within the "particle horizon" because it consists of the
evolved locations of things which are seen now as they were 14
billion years ago. Those things are now 49 billion light years
away due to the expansion...which is sometimes referred to as the
present diameter of the observable
universe.https://en.wikipedia.org/wiki/Particle_horizon
<https://en.wikipedia.org/wiki/Particle_horizon>
Brent
*What you're calling "the whole universe" includes
the underlying entity on which the BB started, and on
which measurements CANNOT be made. It could be
infinite in spatial extent, or is possibly an entity
for which the concept of spatial extent might not
exist. AG*
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