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Frame dragging effects on speed of light

  1. Oct 9, 2007 #1
    I had a question that I was hoping someone could answer for me.

    If light passes next to a massive rotating object such as a black hole, would the affects of frame dragging cause a blue shift or would the light essentialy travel at a speed faster than the C?
  2. jcsd
  3. Oct 22, 2007 #2
    Light cannot exceed the speed of light in a vacuum. It would be blue shifted.
  4. Oct 29, 2007 #3

    Shooting Star

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    Could you explain in detail why it would be blue shifted.
  5. Oct 29, 2007 #4
    I think that's wrong. The light lensed from one side should certainly be brighter than the other (since the source is effectively "closer" in space-time from that side).

    No, actually, that's too sloppy. There will be more light from one side, because the "closeness" will cause the source to subtend a bigger angle on that side.

    But the colour-shifts (and hence also the surface brightnesses) will not be different between each side. If light frequencies were different, then the entire image would also be evolving at different rates on either side. So although you might initially see two images of the source at approximately the same point in the image's history, if you waited long enough then you would end up seeing simultaneous images of two arbitrarily separated points in the source's history. That will lead to a contradiction.

    Note to the OP: It won't locally travel faster than c either, maybe it helps to think of there as being "less space" (and extra time) in that direction.
    Last edited: Oct 29, 2007
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