[QUOTE=xilman;308569]As for the second, it is a matter of observational record that the CMB does indeed have a preferred direction and speed as measured by its differential red shift and the direction in the sky where it is hottest and coldest. [b]If[/b] you regard the CMB as being at rest with respect to the universe as a whole, and that seems to be a reasonable assumption to most people who have thought about it, we are demonstrably moving with respect to the universe as a whole.[/QUOTE]
Not the universe as a whole - in a globally expanding spacetime geometry that is impossible, as Mr. Hubble so famously established. The correction which removes the dipole moment is simply to establish the local frame which is at rest with respect to one's local point in the global scheme of things. The observed dipole moment is thus simply due to the (ill-named) "peculiar velocity" of the observation platform (our solar system) with respect to the local spacetime-geometric fabric.

In the spacetime geometry postulated by BBT, if all such peculiar velocities were magically set to zero, i.e. everyone suddenly found themselves at rest with respect to their local spacetime, everyone would still be moving with respect to everyone else due to the global expansion, but not in a way which indicates any "preferred point".

[QUOTE=ewmayer;308582]Not the universe as a whole - in a globally expanding spacetime geometry that is impossible, as Mr. Hubble so famously established. The correction which removes the dipole moment is simply to establish the local frame which is at rest with respect to one's local point in the global scheme of things. The observed dipole moment is thus simply due to the (ill-named) "peculiar velocity" of the observation platform (our solar system) with respect to the local spacetime-geometric fabric.

In the spacetime geometry postulated by BBT, if all such peculiar velocities were magically set to zero, i.e. everyone suddenly found themselves at rest with respect to their local spacetime, everyone would still be moving with respect to everyone else due to the global expansion, but not in a way which indicates any "preferred point".[/QUOTE]Sure. All I'm saying is there is a [b]local[/b] preferred inertial frame in which the vast majority of the visible universe appears to have no peculiar velocity. Further, I believe it extremely likely that such a preferred local inertial frame exists essentially everywhere in the universe.

The CMB photons out number the electrons and nucleons by a factor of a billion or so. The CMB neutrinos are far too low energy to be directly detectable but most physicists believe them to be as isotropic as the photons (i.e with some spacial structure but remarkably smooth nonetheless) and to have a black body spectrum because of scattering when the universe was of roughly nuclear density and before. Opinions are still out on the matter we can't see and who knows what dark energy is?

I'm a relativitist at heart, when thinking about large-scale cosmology at least, and don't try to extend a local coordinate patch into a globally consistent coordinate system because non-Euclidean geometry tells you that can't be done in general.

[QUOTE=davieddy;308144]To sum it up "there are no preferred reference frames".
OTOH Cosmic background radiation makes the idea of a "fixed" one plausible.

Which newly jumped-up Supermod saw fit to delete my post to this effect?

Er... LET ME GUESS[/QUOTE]

[URL="http://news.discovery.com/tech/mit-gamifies-relativity-121101.html#mkcpgn=fbdsc17"]LAB GAMIFIES EINSTEIN'S RELATIVITY[/URL]

Yeah yeah, relativity, CMB etc. Yeah yeah, uniform expansion of cake in oven. But has it actually been proven that I am not the centre of the universe because my wife wants me to double-check.
I don't know what all the fuss is about.

[OT]
 

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[QUOTE=science_man_88;316683][I]Last fiddled with by ewmayer on 01 Nov 12 at 21:59 Reason: "Gamify"? Seriously? [/I][/QUOTE]Seriously.

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