Citing back to Owen: Gil is right. The universe could be infinite, and it is at the least big enough that we have no positive evidence so far that it isn’t infinite.
If it were infinitely large, but only finitely old, then at any given place, the only photons that could yet have sped past us would be those from a distance away that is less than the age divided by c. But there would always be someplace enough further out that you are only now seeing it. Cue lyrics to “The way we were”, of course.... There is a thing I never learned to understand about cosmological models, which is how they reconcile finite age with infinite size. Presumably infinity is infinity, and if your solution is always infinitely extended (flat or negative spatial curvature), then even if you go back to a Big Bang of infinite density in the finite past, that infinite density is still infinitely extended. If there were positive spatial curvature and the universe were closed, one could just work in the finite-but-large. (btw, of course, inflation doesn’t solve this; it just changes rates of various expansions in various eras.) I guess cosmologists don’t worry about this, because they know there are enough phase transitions going on in the vacuum going back toward the beginning, that even if you appear to be negatively curved and open now, the current story may not extend all the way back. Another thing that is fun to think about but that I don’t feel comfortable as having really internalized, is that old parts of the universe are like old cowboys: they never seem to be traveling away from you at faster than c; they just fade away in redshift to black. So things can be totally unreachable at some finite time, yet never seem to have exceeded a finite speed limit to do it. Eric > On Dec 28, 2022, at 10:56 AM, Gillian Densmore <[email protected]> wrote: > > (using a bad analogy) and those photons record what's going on like a on > going WEBB stream? so we now have essentially the ability to see old streams > (as it were) from photons any anything else that can get a snippet of that. > and basically light does take time to show up. it's not exactly instant on > the galatic scale (see also: Relativity). and so by the time WEBB or any > other other telescopes s mirrors cameras and blah blah blah send that to our > eyes those photons are now old reeely old. And the grand expansion is fast > enough to go faster then light? or is it because the universe is stupendously > big. so it takes a while to get to where we can snag some photons? > > On Wed, Dec 28, 2022 at 10:49 AM Frank Wimberly <[email protected] > <mailto:[email protected]>> wrote: > My guess: stars, including the Sun, are constantly producing and emitting > new photons. This happens as a result of fusion and other processes. > > --- > Frank C. Wimberly > 140 Calle Ojo Feliz, > Santa Fe, NM 87505 > > 505 670-9918 > Santa Fe, NM > > On Wed, Dec 28, 2022, 9:21 AM Owen Densmore <[email protected] > <mailto:[email protected]>> wrote: > In aj NYTimes article: > https://www.nytimes.com/2022/12/27/science/astronomy-webb-telescope.html > <https://www.nytimes.com/2022/12/27/science/astronomy-webb-telescope.html> > ..there is the usual discussion on "seeing back to the first several > millennia". > > But, and be kind, why haven't these photons already sped past us? I suppose > it is because the exanssion is uniformly everywhere, we just kept ahead of > them? 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