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Name: helen f roberts
Status: N/A
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Date: 1993 - 1999


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'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.

A Smith



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