On 1/30/2020 10:33 AM, Alan Grayson wrote:
On Thursday, January 30, 2020 at 10:40:26 AM UTC-7, Lawrence Crowell
wrote:
On Thursday, January 30, 2020 at 11:21:25 AM UTC-6, Alan Grayson
wrote:
On Thursday, January 30, 2020 at 10:16:48 AM UTC-7, Lawrence
Crowell wrote:
On Wednesday, January 29, 2020 at 2:57:25 AM UTC-6, Alan
Grayson wrote:
Considering the distant galaxies, they're receding at
near light speed. So according to SR, their clocks
should be ticking at a much slower rates than, say, a
local clock in our galaxy. OTOH, there's a physical
clock for the entire universe; namely, the temperature
of the CMBR. If we tell time by this clock, all clock
readings of all galaxies are identical. So which is
it? Are clocks in distant galaxies running slower than
a local clock in our galaxy, or are both clocks
running at the same rate? TIA, AG
The physics with distant galaxies is general relativistic,
not special relativity.
*I know. Now, if you can, please answer my question. AG*
I did below
LC
The redshift factor v = Hd, in the near linear form, has
the redshift factor v/c = z = Hd/c. In the FLRW metric
this is a bit more general with z = e^{Ht} - 1, where for
small HT << 1 then t = d/c and z =~ Ht. The reshift factor
for the CMB is z = 1100, which means that anIR photon with
wavelength 1000nm is expanded to 1100 microns, or a
millimeter. The peak of the CMB blackbody radiation is 160
GHz and this was produced by radiation peaked at
17.6x10^{4}GHz. This is in the IR region with a wavelength
of 5,87x10^{-5}cm, in the IR, The z multiplicative factor
is the same as a time dilation, where we can think of
these red shifted photons are representing the slowdown of
clocks (clocks being the quantum oscillations of atoms
etc) in this surface of last opaque scatter.
LC
Maybe I was making the wrong assumption; namely, that the CMBR "clock"
reads the same "time" for the far galaxy as compared to its reading in
our galaxy.
"Reads the same time" /*when?*/, is the relevant question...and there's
no absolute answer. If you take the CMB as your clock, you are defining
what "simultaneous at distant points" means. Simultaneity is a relative
attribute. It's relative to state of motion in special relativity and
it's relative to motion through curved spacetime in general
relativity...so you can define it in different ways.
Brent
But this is probably wrong since CMBR as viewed from the far galaxy is
from a much earlier epoch, so the reading cannot be identical. Do you
agree? AG
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