Below is the only meaningful post in a thread I started a few days ago
with the same title and I have gotten no further response from the
rather thin skinned Tom Roberts.
I think the problem with him, and probably a few more of you is that

you don't believe anything can exceed light speed. If this is the case
you are unaware of the observational evidence provided by IaSNe. This
is a type of supernova that is the greatest standard candle ever
discovered. They all explode in the same fashion and in a non red
shifted environment they continue to brighten, (rise time of the light
curve) from the instant of explosion, for 21 days. At a red shift of z
= .5 it takes 10.5 days longer = 31.5 days. At z = 1, it takes twice as

long = 42 days and at the superluminal speed of z = 1.2 it takes 46.2
days, then they all start to get dimmer. Understand, they all take 21
Earth days to reach peak brightness in their host galaxies but because
of their speeds of recession away from us, the rise time appears to
increase, PROVING conclusively that red shift is a near perfect
speedometer.
My website: http://hometown.aol.com/dwhig265/myhomepage/index.html
I invite your response, Dwain W. Higginbotham

15 From: - view profile
Date: Mon, Aug 21 2006 12:32 pm



Tom Roberts wrote:
wrote:
xxein: What is the red-shift velocity of quasars? We see them, but
can they see us? (just a hint for you to think about).
Right now, they cannot see us as we appear to ourselves right now. But
they could, in principle, observe "us" as we were at an appropriate time
in the past (billions of years ago).


DWH says: Assuming the quasar in xxein's post was superluminal when the


radiation we are now observing left the quasar, they were already
outrunning our radiation and could not have been observing us at that
time.


In a universe with no absolute reference frame, galaxies moving
apart in excess of light speed would not be able to see each other.



Hmmm. In GR it is indeed possible for two distant galaxies to be moving
apart with a "speed" c, but this depends on the definition of "speed".
The limit of c is applicable only to _local_ measurements using standard
clocks and rulers at rest in a locally-inertial frame. Cosmological
models including distant galaxies do not have a suitable locally
inertial frame for that to hold for such pairs.
But it is indeed possible for two galaxies that are CURRENTLY moving c
apart to see each other IN THE DISTANT PAST. In particular, separation
speed (however defined) need not be constant over cosmological time.


DWH says: Perhaps I should have said in my statement 2 paragraphs above


" In a universe with no absolute reference frame, galaxies that were
moving apart in excess of light speed when their radiation was emitted,



would never be able to see each other in the future."



Since we
see the quasar, there is an absolute reference frame.
Your lack of logic makes your pronouncements useless.


DWH says: I won't retort in kind until I see if you respond further.
Thus far it has been double entendre gobblydegook. I stand by the
"pronouncements" above and below your comment and will provide further
explanations on the heel if you require.


any observer
that sees a superluminal galaxy can be sure observers in that galaxy
cannot see him.
See him as he is TODAY, sure. As he was in the past, no, if one goes far
enough into the past.
Please say you know why we can see superluminal galaxies.
In SR and GR, a distant object moving near light speed (but c) almost
in the direction of the observer will appear to be moving faster than
the speed of light to a naive observer. This is mere appearance due to
the optical situation.


DWH says: I take this to mean that you don't believe superluminal
speeds are possible. Please correct me if this is not the case.


In FRW cosmological models one can define "speed" such that distant
galaxies can be moving apart c by simply using
constant-time-distance/cosmological-time (the most obvious way to define
such a separation speed in this class of manifolds). What an observer in
one of them sees TODAY is the distant galaxy in the distant past, but
that speed c is measured TODAY, not in the distant past.
Since we see
superluminal galaxies in all directions
Not really. We see galaxies with finite redshifts, and by this measure
their relative speed is c.


DWH says: If they were moving superluminally when the radiation we are
currently receiving was emitted it is reasonable to assume they still
are. This applies to your previous paragraph (FRW) as well. I only use
one definition for :speed"

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Note this is NOT the same definition of
"speed" in my previous paragraph -- this one is directly measurable,
that one is not. Note also this does not mean that there are no distant
galaxies with infinite redshifts, it merely means we don't see tham (duh!).
Tom Roberts