On Friday, July 18, 2025 at 7:27:31 PM UTC-6 Brent Meeker wrote:
On 7/18/2025 5:18 PM, Alan Grayson wrote: On Friday, July 18, 2025 at 5:04:35 PM UTC-6 Brent Meeker wrote: On 7/18/2025 4:10 AM, John Clark wrote: On Thu, Jul 17, 2025 at 9:59 PM Alan Grayson <[email protected]> wrote: *> It seems to me that a red shift will be produced if an object is moving away from us, regardless of the cause of its motion; that is, regardless of whether space is expanding, or the object is moving away from us through space. That's the red shift we observe,* *Yes.* * >and everyone seems to agree that is represents ancient history,* *Yes.* *>what the relative motion was billions of years in the past. * *No, although astronomer sometimes speak imprecisely and people infer that the only way a redshift could be produced is by a thing moving through space away from us. I may have been guilty of such sloppy language myself from time to time.* *> So, even though the galaxies were much closer in spatial distance billions of years ago, how can we NOT conclude that those galaxies were receding from each other, AT THAT TIME, AT A HUGE RATE. represented by the measured red shift? TY, AG* *A galaxy moving through space away from us is one way to produce a redshift, another way would be for the space between galaxys to be expanding, we can determine which one is actually causing the redshift through observation. Except for the Andromeda and Triangulum galaxies and about a dozen dwarf galaxies in our local group, every galaxy in the universe is displaying a redshift to us, and the more distant it is the larger it's redshift. If that redshift is caused by them moving through space away from us then the Earth is it a very special position, the center of the universe. However the idea that the universe contains anything as mundane as a center is problematic, and the Earth just happening to occupy that center is even more so.* *But if the redshift is caused buy the expansion of space itself then every observer in every galaxy would see the same thing that we do, except for a few very nearby ones, every galaxy in the universe would be displaying a redshift to them, and the more distant it is the larger it's redshift.* Good, except there is also a small component due to the higher mass density in the universe in the distant past which also adds to the redshift relative to us. And while "the more distant it is the larger it's redshift" is true, the relation is not linear as encoded in a Hubble constant. That's where talk of accelerated expansion comes from. Brent Generally speaking I still don't get it. What I do get is that since the Earth isn't the center of the universe, the red shift observed cannot be due to relative motion in space, but to the expansion of the universe. It's all relative motion in space. But only the part due to the expansion of the universe is significant; so forget the local proper motion. HOWEVER, Clark (and you?) agrees that the observations correspond to behavior in the distant past, I don't know what that means. Galaxies are observed at all different distances and corresponding different times in the past. Then it is a curve fitting problem to say what universe model best fits the data. *You don't know what I mean? It's simple; at any distance for a particular galaxy, we're seeing it in the past, depending on how far away it is. And the farther away it is, the greater is its red shift and recessional velocity. So the recessional velocity seems to be DECREASING with time as the universe expands. But if this is true, how could galaxies at the furthest distance from us, be separating from us and each other at a slow rate as Clark (and you?) claims? Maybe much slower than during Inflation, but still presumably very rapid. AG* and the further back in time we go via Hubble, the red shift increases, implying increasing recessional velocity. Yes, things further away have a higher redshift. We have a higher recessional velocity relative to them. If that's the case, why does Clark (and you?) claim that in the very early universe, the galaxies were receding from each other slowly, presumably much slowly than today? AG Look at the curves I posted. Most of them, but not all, show a lower Hubble parameter, less slope, earlier. 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 visit https://groups.google.com/d/msgid/everything-list/a768a423-2ac3-40a1-8dbe-f0ef408cfef6n%40googlegroups.com.
