In the end, how did Bradley explain the strange shift in the position of Polaris and other stars?
–The aberration of starlight allows us to deduce that the Earth is indeed moving. Doesn’t that contradict an earlier claim that absolute motion is undetectable? The claim was that absolute motion with constant velocity in a straight line was undetectable. The motion of the Earth discussed here is around a circular orbit. [Optional further discussion by the teacher: Suppose Earth and the whole solar system did move with constant velocity u along a straight line. The positions of stars would then be shifted, too, but the shift would not change as time went on. Astronomers would see the positions of the stars fixed and not suspect their real direction was different. Actually, a systematic shift does exist, and from it we know that the solar system is moving at about 20 km/s towards a point known as the solar apex, near the star Vega. But in principle, it could also be that we are at rest and all those stars are moving in our direction, away from the solar apex. The physical effects would
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