Quote:
douglas said:
For example:
Suppose you are on Earth trying to carry out that torch experiment. You carefully measure the distance between the torch and a mirror, you light the torch, and you time how long it takes for the reflected light to get back to you. You will calculate from this data that you (actually your measuring device) are at rest.
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There was no mirror in the original torch example. Whether or not it has travelled the same distance/taken the same time in both directions is what is at question.
In this illustration, a red bulb sends a signal to a red mirror. Time goes by, and the bulb/mirror experiment moves to position green. The pulse strikes the green mirror and heads back. More time goes by, and the bulb & mirror move to position blue. The light pulse returns to the bulb at position blue.
If it takes a different amount of time on each leg, then we can say that the experiment moved (as illustrated), and the speed of light was the same throughout. And as Narf said, it implies that the speed of light is relative to something other than the bulb&mirror. If it comes back in the same amount of time that it took to go out, then something is amiss.
Shouldn't the stars change color sleightly as the earth approaches them, and then as the earth pulls away? If earth's motion about the sun is about 29km/sec, or roughly [edit]0.001%[/edit] speed of light, then there should be a +/-1% red/blue shift in colorbands throughout the year.