Re: CMBR's motion wrt the Earth

On Sep 8, 6:02 am, mluttgens <mluttg...@xxxxxxxxx> wrote:
On 8 sep, 01:32, "Inertial" <relativ...@xxxxxxxx> wrote:



"mluttgens" <mluttg...@xxxxxxxxx> wrote in message

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On 7 sep, 14:22, "Inertial" <relativ...@xxxxxxxx> wrote:
"mluttgens" <mluttg...@xxxxxxxxx> wrote in message

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On 7 sep, 01:59, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:
mluttgens wrote:
Can somebody explain how, physically, an electromagnetic
radiation filling the universe can move relative to the Earth?

Your descriptions are insufficiently precise. There is no such thing
as
"The CMBR" -- the cosmic microwave background radiation is comprised
of
myriads of photons moving in all directions. This is not a "thing" in
any normal sense, it is a vast collection of photons.

        [For the purposes of this thread I'll ignore the quantum
         aspects of photons.]

What you are missing is the fact that measurement of "the earth's
motion
with respect to the CMBR" is really a measurement of the earth's speed
relative to THE FRAME IN WHICH THE CMBR DIPOLE MOMENT IS ZERO [#]..
This
is not in any sense a "rest frame of the CMBR", because the CMBR is
myriads of photons NONE of which are at rest in any frame. This is
purely a statistical property of the collection of all the photons
comprising the CMBR.

        [#] Careful authors phrase it this way, not in the careless
        way you did. I have been phrasing it as "the CMBR dipole=0
        frame" in this newsgroup for many years.

It is rather remarkable that there is such radiation apparently
filling
the universe (it has been observed interacting with distant stars and
galaxies). This is quite strong evidence in support of the big bang
cosmologies, and the synthesis known as the standard model of
cosmology.
There remain details still unknown, and some downright puzzles (dark
matter, dark energy, ...).

Tom Roberts

Thank you.

I would have assumed it was taken from the context of talking about
frames,
and absolute frames in particular, that 'the CMBR' was referring to what
is
sometimes called the CMBR rest frame (as described above by Tom).

Do you consider that claiming (like Paul Draper and others)
that the CMBR moves wrt an object, makes sense?

It makes as much sense as an object moving wrt the CMBR.

No, read what Tom Roberts said:

I did .. read what I said

"The measurement of "the earth's motion with respect to the CMBR"
is really a measurement of the earth's speed relative to THE FRAME
IN WHICH THE CMBR DIPOLE MOMENT IS ZERO."

That's right

He didn't say that the Earth has no motion wrt the CMBR,

Neither did I

Then explain how the "radiation apparently filling the universe"
can move wrt the Earth.

You have some really strange ideas, Marcel.
First, it sounds like you imagine the universe as being a giant ball
with a boundary, where the radiation filling the universe is like some
fluid filling a ball and so stationary with respect to the boundary of
the ball. The universe has no boundary, no center.
Second, you still seem to have a problem understanding relative
motion. If a boat and the ocean are in relative motion, then the boat
is in motion relative to the ocean AND the ocean is in motion relative
to the boat. It is NOT the case that only one of these should be
considered to be in motion.


Marcel Luttgens



he only
gave his interpretation of such motion.

No .. he gave a more specific terminology for what we had simply been
calling 'the CMBR' in this thread as a frame of reference .. he said that
what one should technically be saying it "the frame where the CMBR dipole
moment is zero".  but that's pretty words, so i think its ok to continue
using 'the CMBR' as a shorthand, as long as we all know what we mean



.

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