On Saturday, January 18, 2020 at 6:40:49 PM UTC-7, Brent wrote: > > > > On 1/18/2020 4:04 PM, Alan Grayson wrote > > > On Saturday, January 18, 2020 at 2:55:16 PM UTC-7, Brent wrote: >> >> >> >> On 1/18/2020 1:29 AM, Alan Grayson wrote: >> >> *the infinite spatial extent must have occurred instantaneously, at the >> BB.* >> >> >> It doesn't have to "occur". If the universe is infinite then it didn't >> become infinite, it was always (in some timeless way) infinite. The >> equations of cosmology are just for a scale factor. We estimate the >> parameters from observation and project back to a beginning. So there's >> really no sense in projecting back to zero scale factor...there the size of >> a flat universe according the equations is infinity*zero. Hopefully a >> quantum theory of gravity will replace that oo*0 with something more >> sensible. >> >> Brent >> > > What do "infinity*zero" and "oo*0" mean? I see your point. My problem is > that we seem to have a universe with a BEGINNING, called the BB, > > That's not true and whether the universe had a beginning is a independent > of their having been a Big Bang. The “Big Bang” is used to designate the > sudden expansion of the universe which is the current best theory of the > universes evolution. >
*IMO, the BB is more than that. In say, eternal inflation, it's the moment of emergence from the Multiverse. A few Planck durations later, the sudden expansion began. AG* > It doesn’t actually refer to some beginning from nothing. > *My "nothing" doesn't imply no Multiverse. "Nothing" is what our universe was before it emerged. It's a reasonable inference, not just philosophical bias or garbage. Even with eternal inflation, it's postulated that something that previously wasn't, emerged from something we call, for lack of a better word, the Multiverse. AG* > There are theories, like Hartle and Hawking’s in which there is a t=0 > starting point, although physical time starts at t>0. > *This is what I've been assuming, a starting point! **So at t=0 there might have been infinite spatial extent? But you say not to take "infinity" seriously. I have a more reasonable theory; that the emergent bubble started out with zero volume (a real number btw), and has always been finite and closed. If you can't show that the equations demonstrate an infinite universe at time of emergence -- which they can't since infinity is not a number -- ISTM you're adding an unwarranted ad hoc hypothesis. AG* > And there are theories like eternal inflation in which our universe > condenses like a bubble out of an eternal background multiverse, and some > other theories besides. Almost all of them include a Big Bang phase because > the Big Bang is implicit in just projecting current motions back in time. > Whether there is a zero time depends on the model, but it will have to be a > model that does something different near the beginning than simply > extrapolating GR equations back because those extrapolate back to > infinity*zero which as your algebra teacher no doubt told you is > indeterminate. > * Since infinity isn't a number, one can't use it for arithmetic operations. (I didn't realize that the " * " meant multiplication.) AG* > > and I find it virtually impossible to imagine it starting with an infinite > spatial extent. > > > So it's a failure of your imagination. Work on that. > *Your condescension adds nothing. You say not to take infinity in a theory seriously, yet you assume it at t=0. AG* > How could "nothing" become > > > You keep sticking "become" and "emerge" into the story. It equations say > it STARTS OUT INFINITE! > *All the equations tell us is that matter density decreases as time increases, and that it increases as time decreases; that is, expansion and contraction of the physical universe. I don't believe you can show where the equations say the universe starts out infinite? TIA, AG* > You seem stuck with that meta-physical prejudice that nothing is a natural > state and can be assumed with no justification. > *No. I am just assuming that OUR universe, or bubble, didn't exist before it emerged from, say, the Multiverse. So there was "something" before our universe emerged. I even went so far to assert that this something might be flat with an infinite past. AG* > Remember Norm Levitt used to say, "What is there? Everything! So what > isn't there? Nothing!" > > infinite in any parameter, suddenly, or due to finite processes? What I > can imagine is it emerging from something flat and eternal, having an > infinite past. AG > > > Any physics with "infinite" or "infinitesimal" in it should be taken with > a big grain of salt. > *Isn't this precisely what you're doing when you claim flat space, and therefore spatial extent to, perish the word, infinity? AG * It just shows the mathematics has run the problem over the horizon of our > knowledge. > > Brent > -- 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/8baea187-86a9-47a5-9e0c-6bec0e6b6204%40googlegroups.com.
