Re: CMBR's motion wrt the Earth


"Nicolaas Vroom" <nicolaas.vroom@xxxxxxxxxx> schreef in bericht
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"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> schreef in bericht
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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.

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.


There are also people in favour to call it a rest frame:
See: http://arxiv.org/PS_cache/astro-ph/pdf/9601/9601151v2.pdf

The Dipole Observed in the COBE DMR Four-Year Data
C. H. Lineweaver, L. Tenorio, G. F. Smoot, P. Keegstra,
A. J. Banday & P. Lubin

Page 1: " A measurement of this Doppler dipole thus tells us
our velocity with respect to the rest frame of the CMB."

IMO the whole issue is a statistical (average) aspect.

Nicolaas Vroom
http://users.pandora.be/nicvroom/

However I think there is more involved.
If you position an observer at the equator than you can build
a frame of reference in which the inertial observer 1 is at rest
(rest frame observer 1)
You can also consider a second observer positioned
at the other side of the earth with a frame of reference in which
observer 2 is at rest (rest frame obeserver 2)
Both rest frames are in relative motion which each other and each
with the rest frame of the CMBR.
Suppose there is also a third observer with has the speed of
370 km/sec in the direction of the constellation of virgo.
This observer 3 sees a the uniform CMBR directly undisturbed
without the necessity for dipole subtraction.
The two other observers, to see the same, have to perform
dipole subtraction.

See:
http://aether.lbl.gov/www/projects/cobe/COBE_Home/DMR_Images.html

The question is:
is observer 3 in the special situation that only he can actually claim
that based on his observations that from all directions all photons are
having
the same speed (c) ?
At the same time he claims that for the observers 1 and 2
this is not the case.

Observer 3 can even go further:
He can claim from all directions from the same distance.

I do not know the answer.

Nicolaas Vroom
http://users.pandora.be/nicvroom/



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