Name: Helen F Roberts
Status: Other
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Date: N/A
Question:
What is the reference point for an object's speed in outer-space?
Replies:
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 is a clear difference between
the background in one direction and in the reverse direction (one is "red
shifted", the other "blue shifted") 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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