Russell McMahon wrote:
>>> Russell McMahon wrote:
>>> But, only about 500 years at earth's (believed**) absolute velocity.
>
>> Now that's a good one, "absolute velocity".
>> Reminds me of "jumbo shrimp" and "sales ethics".
>
> Absolutely, my dear Watson.
>
> Hence the '(believed)' and the foot note.
>
> Hubble may have something to say about it too.

There is no such thing as absolute velocity.  Velocity is always relative to
something else, usually a local inertial observer.  Here on earth we tend to
measure velocity relative to the local part of the planet's surface.  That
of course has a rather "interesting" velocity relative to the sun, which
itself has some velocity relative to the center of the galaxy, which has a
velocity relative to the local group, etc.

These is no absolute velocity because there is no point that can be defined
as the center of the universe.  And as you alluded to, Hubble showed that
the universe on a large scale is currently expanding.  Your velocity
relative to one point of the universe will therefore be rather different
relative to another distant point.  Since there is no center of the
universe, each of these velocities are equally valid.  The reference
location for many velocity measurements may be implied from context, hiding
the fact that there is one, but there is always a reference.


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