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
awaysince 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.
*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>*
3//
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