On Sat, Jan 25, 2020 at 10:27 PM Alan Grayson <[email protected]> wrote:
*> JC wants to know how to distinguish a finite spherical universe from an > infinite flat universe* No, JC doesn't care if the universe is spherical or flat, he just wants to know if he keeps going will he always keep getting further from his starting point, or will he start to return. or will he eventually hit some sort of wall. > *he thinks if he can't directly MEASURE non-observational regions, which > both have, he can't distinguish the cases. * Correct. > *> The difference is this: every observer in a spherical universe can > calculate its radius if he knows the rate of expansion and how long it has > persisted for,* Incorrect. He can't determine how big the universe is, from the date of the expansion and its rate of acceleration he can only calculate how far into the universe he can see. You're error is you ignored a fact that is fundamental and very important, the speed of causality is not infinite. That's why regardless of if the universe is infinite or finite I doubt there is a cosmologist alive who thinks that what we'll someday be able to see with even tomorrows planet sized telescopes is all of the universe that there is. There will always be part of the universe we will be unable to see even in principle because parts of it are moving away from us faster than the speed of causality. We have a good lower limit of how big that unobservable part is, it's larger than zero, but its upper limit is pure speculation and always will be. John K Clark -- 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 on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv26-Dk01VPvWGp5xOfY%2B3OgjyFa3A%3D0%2Bu26w7ZRbRhuyw%40mail.gmail.com.
