On Wednesday, December 3, 2025 at 7:08:03 PM UTC-7 Brent Meeker wrote:
On 12/3/2025 11:05 AM, Alan Grayson wrote: On Wednesday, December 3, 2025 at 5:51:29 AM UTC-7 John Clark wrote: On Wed, Dec 3, 2025 at 6:08 AM Alan Grayson <[email protected]> wrote: On Sunday, August 24, 2025 at 10:03:20 PM UTC-6 Alan Grayson wrote: *I think not. It just tell us how rapidly it is expanding at different distance, but at the same time, NOW. So, there is no basis for the claim it was expanding very slowly in its very early history. AG* *> Wrong conclusion! Since galaxies far away are receding the faster than those close to us, Hubble's law also says that those close to us are receding more slowly than those farther away since in the very early universe the galaxies were closely separated, Hubble's law says they were receding from each other more slowly than today. AG * *I think you would be less confused if you forget about recessional velocity and forget about distance, strictly speaking Hubble's Law is about the relation between the amount of red shift we observe in the light spectrum of a galaxy and the amount of time it took for the light from that galaxy to reach us. **If Hubble's Law indicates that it took a particular galaxy 10 billion years to reach us it would NOT be even approximately correct to say that the galaxy is now 10 billion light years away, it would actually be much much further away than that; and it would also NOT be correct to say that when that light started its journey the Earth was 10 billion light years away, back then it was actually much less than that, or it would've been if Earth had existed 10 billion years ago, which it didn't. * *Distances to galaxies is measured using standard candles. So the attenuation in brightness compared to intrinsic brightness is a true measure of distance * A true measure at what time? *even though the universe is expanding. So there doesn't seem to be any problem with Hubble's values for distances. Or does the attenuation cease to exist due to the expansion of space? TY, AG* *You've got to remember Einstein tells us there is a fundamental difference between:* *1) Two objects moving through space away from each other. * *2) Space itself between two objects expanding. * *I am aware of these facts. The observed red shift includes both effects and the second effect is much more significant. AG * *In cosmology only the second case is important. If we ignore the era of hyperinflation that ended about 10^-32 seconds after the big bang, for about 9 billion years after the Big Bang space was expanding much faster than it is now, but the rate of expansion was decreasing. About 5 billion years ago things changed, the rate of expansion started to increase, * *During inflation, if it existed, the expansion greatly exceeded light speed, and presumably this was when the UNobservable region came into existence. But since there were no galaxies at this time, what exactly couldn't be observed if observers existed to do the observing? TY, AG* If the universe is infinite, as seems likely, most of it was always unobservable, since the observable part is necessarily finite. *I tend to think it's finite in volume, including the unobservable part which was created during the finite doublings of volume during the period of Inflation. It's also likely approximately spherical in shape since that's the usual theme of shapes of material bodies as they get large. For example, smaller material objects like asteroids can be shaped like potatoes, whereas large ones approximate spheres. Galaxies are exemptions to this rule, which of course is not a proof of anything. But one thing seems clear; that measurements can never reveal whether the universe is infinite in volume, that is, flat, since there will always be errors in any measurement, and it's impossible to tell what part of the error, if any, can be attributed to some small curvature, to negate the possibility of a flat or infinite universe. AG * *If gravity is slowing the rate of expansion, it must have been higher in the past than now. * Rate of expansion as %/time or as velocity/time? Brent *On the other hand, Hubble's law seems to claim that when galaxies are close to each other, the rate of expansion is slow. How do you resolve this contradiction, particularly in the very early universe? TY, AG* *this would make sense IF Dark Energy is an intrinsic part of space because as space expands matter, which wants to retard the expansion gets diluted but space, which wants to increase the expansion, does not. * *However that might not be true, Dark Energy might not be caused by space itself, maybe it's produced by some sort of field that can change with time. Very recently there have been indications that the rate of change of the acceleration of the universe (believe it or not called a cosmic jerk) might be decreasing, but the evidence is not yet strong enough to claim a discovery. * * John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* -- 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]. 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