> It has been suggested that we can use the measureed anisotropy of the
> microwave background radiation to determine the privileged reference frame:
> "At any given place in teh universe, there is only one reference frame in
> which the universe expands isotropically. This privileged reference frame
> defines a privileged time scale (the time as told by a clock at rest in
> that frame)" (P.C.W. Davies, "Space-Time Singularities in Cosmology and
> Black Hole Evaporations," in Fraser, Lawrence and Park, eds, _The Study of
> Time III_, p. 76). Davies goes on to note that "Happily, the earth is
> moving very slowly [approx. 360 km/sec is the figure I have seen-GD]
> relative to the local privileged reference frame in our vicinity of the
> universe, so that Earth time is a fairly accurate measure of cosmic time."
The MW background provides a very convenient reference frame
set of reference frames (still, of course, with freedom of spatial
rotations & translatioons), but it isn't preferred in the sense that the
laws of physics must refer to it. An observer moving wrt to the
background can still justifiably say "My time is as good as yours". &
we tacitly agree to the extent that we would probably say that the
proper lifetime of an unstable cosmic ray particle moving with v ~ c is
a better measure of the particle's properties than is the much longer
period we see it live because of time dilation.
George Murphy