On Saturday, September 14, 2019 at 7:18:40 AM UTC-6, John Clark wrote: > > On Fri, Sep 13, 2019 at 11:22 PM Alan Grayson <[email protected] > <javascript:>> wrote: > > *> What I think you're missing (and Tegmark) is the possibility of >> UNcountable universes. In such case, one could imagine new universes coming >> into existence forever and ever, without any repeats. Think of the number >> of points between 0 and 1 on the real line, each point associated with a >> different universe. AG* >> > > There is no reason to think physics needs all the real numbers and > considerable evidence to think it does not. To my mind the strongest > evidence is that a physical Turing Machine is incapable of even > approximating most real numbers, I happened to have posted a proof of this > yesterday on the "Observation versus assumption" thread. > > Actually, physics might not even need all the rational numbers as there is > probably a grainy structure to both space and time. Distances can't get > smaller than the Planck Length and time shorter than the Planck Time. Maybe. > > >> >> true regardless of if the Many Worlds Interpretation of Quantum >>> Mechanics is correct or not, it only depends on the universe being >>> spatially infinite. >>> >> >> *> But our universe is NOT spatially infinite if its been expanding for >> finite time,* >> > > Sure it can, space could have started out infinitely large 13.8 billion > years ago and still be expanding today, it could even be accelerating. The > radius of the observable universe is 45.5 billion light years ( the light > from the most distant galaxies took 13.8 billion years to reach us but > during that time the galaxies have been accelerating away from us) but that > doesn't mean there aren't galaxies much more distant than 45.5 billion > light years. > > John K Clark >
If the universe was infinite in spatial extent at the time of, or immediately after the BB, the various parts wouldn't have been causally connected and we wouldn't need inflation to preserve (a non existent) homogeneity. It's because it was small at the time of, or just after the BB, that inflation was imagined to preserve the original homogeneity. FWIW, I'm convinced our bubble is a finite hypersphere, almost but not flat, due to its huge size. AG -- 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/c5066f75-404a-4438-8e0e-51eb503c1031%40googlegroups.com.
