On 1/30/2020 5:29 PM, Alan Grayson wrote:
On Thursday, January 30, 2020 at 5:09:56 PM UTC-7, Brent wrote:
On 1/30/2020 12:45 PM, Alan Grayson wrote:
That's not it. I think the two observers, one in a galaxy far
removed and one here, would read the same CMBR "time", regardless
of the distant galaxy's speed of recession. But relativity says
otherwise. This is what puzzles me. AG
Ask yourself /*when*/ do they read the same time.
Brent
I don't know if this helps. Since the temperature of the CMBR is the
same everywhere, at any time t,
You're missing the point. "At any time t" is /defined/ as when the CMB
has a certain temperature. It's the same everywhere at time t, because
that's how we defined t. Our model (FLRW) says the expansion is
uniform, so that's the same proper time from the Big Bang. But it's not
the time that photons we're seeing now left the distant galaxy; the
photons we would use to read a distant clock and see that it runs slow.
we can in principle determine if the two measurements are simultaneous
or not. AG
In relativity, simultaneity is not an objective property. It's motion
and coordinate dependent. So think of t as just one of four numbers, (t
x y z) used to label a spacetime event. Then we choose our labeling
system to make our equations look simple. But the labels don't have
physical significance.
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]
<mailto:[email protected]>.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/4fc556c2-5ebe-4a52-98a4-44b59b07744a%40googlegroups.com
<https://groups.google.com/d/msgid/everything-list/4fc556c2-5ebe-4a52-98a4-44b59b07744a%40googlegroups.com?utm_medium=email&utm_source=footer>.
--
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 on the web visit
https://groups.google.com/d/msgid/everything-list/8cf9af61-eed4-e01d-4e67-855a34cbf230%40verizon.net.
