Speeds in Outer Space
Name: helen f roberts
Date: 1993 - 1999
What is the reference point for an object's speed
Up until the 1940's this was a very deep philosophical question.
Then the cosmic "microwave background" was discovered, and
that sort of settled everything. This microwave background in
space comes from the most distant points in space and time.
It should look isotropic (the same in all directions) - but
ONLY if you are at rest with respect to the average of those
distant points. From the earth there's a clear difference between
the background in one direction and in the reverse direction
(one is "redshifted", the other "blueshifted") which tells us
our true velocity relative to the background. From all this it
was discovered in the last decade or so that the local cluster
of galaxies which we are part of is moving at quite high speed
in the direction of a much bigger concentration of galaxies.
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Update: June 2012