On Saturday, February 8, 2025 at 5:31:25 AM UTC-7 John Clark wrote:
On Sat, Feb 8, 2025 at 3:47 AM Alan Grayson <[email protected]> wrote: *> I can't recall on which thread I made the argument, and Clark agreed, that if the universe has a finite age, it cannot be infinite in spatial extent.* *That's not quite what I agreed to. If it has a finite age then the observable universe can't be infinite in spatial extent, but no cosmologist believes that the observable universe is the entire universe, despite the fact that it's impossible even in principle to ever see it.* I deleted, and then rewrote this post because I realized you didn't "quite" agree to my conjecture. What is true is that the universe, the entire universe, cannot be infinite in spatial extend unless it started that way. This is what you agreed to. AG * > Isn't there a theorem, which might have been proven by Penrose, that the contracting universe must converge to a point or zero volume containing all matter and energy? What is the name of that theorem, assuming it exists? AG* *Some call it the Penrose Singularity Theorem, in 1965 Penrose used topology to prove that any sufficiently dense object must form a Black Hole, he won the Nobel prize because of it. It was the first time anyone had found a use for topology in physics. * If we run the clock backward in time, the universe becomes progressively denser as the average distance between galaxies decreases. So if it becomes a BH, it seems highly unlikely it started out infinite in spatial extent, which is what you and Brent conjectured. AG *John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* tiu -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/dd8a72ca-27bc-4aac-ab16-06df79c0ba88n%40googlegroups.com.
