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On ether

  1. May 30, 2005 #1
    When Einstein conducted thought experiments, he imagined himself moving at the speed of light with a mirror in front. He was later forced to discard the idea of ether and he concluded that light must travel at the speed of light regardless of wherever and whatever speed an observer is moving.

    My question is: How does discarding the idea of ether make him conclude the constancy of the speed of light?
  2. jcsd
  3. May 30, 2005 #2
    He believed Maxwell's electromagnetic theory, and without an ether, that theory says c is constant.
  4. May 30, 2005 #3
    If you were to detect a change in the speed of light, you would be detecting the ether. Think about this for a few moments. Imagine waves rippling on the surface of a pond, if you start moving then the speed of the waves will change relative to you. The idea is the same.
  5. May 30, 2005 #4


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    The ether theory predicted that Maxwell's laws would only work exactly in a single inertial reference frame, the rest frame of the ether. In other frames the equations governing electromagnetism would look different, according to the ether theory. Einstein discarded this idea, and tried to see how things would have to work in order for Maxwell's laws to work exactly in every inertial reference frame.
  6. May 30, 2005 #5


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    It was the other way. Assuming that the speed of light is constant, together with the fact that in Maxwell´s equations any movement relative to an ether does´t have any observable consequences, he concluded that the concept of an ether was no longer needed.
  7. Jun 1, 2005 #6
    Quite right Ich - no longer needed - but not necessarily obviated
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