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Speed of light in a medium

  1. Nov 24, 2007 #1
    The speed of light in a vacuum is c in all inertial frames. What about in a medium? Light in a superfluid can be slowed to a few miles per hour, so if this speed was the same for all inertial observers, relativistic effects would be very noticeable on an everyday speed-scale. This doesnt happen, so the speed of light must be frame dependent in a medium. Is there a relation that describes this, or some explanation of why this is the case?
    Another thing that is confusing me is this: the Lorentz transformation for time is
    t' = gamma(v)[t-vx/c^2], rearranging gives
    t = t'/gamma(v)+vx/c^2
    which is not what i get from the lorentz transform in reverse
    t = gamma(-v)[t'+vx/c^2], where gamma(v) = gamma(-v)
    Hopefully someone can point out my mistake. Thanks.
  2. jcsd
  3. Nov 24, 2007 #2


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    Hint1: That "speed of light" that is being measured is the group velocity.

    Hint2: You may want to read one of the entries in the FAQ sticky located in the General Physics forum.

  4. Nov 26, 2007 #3


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    should be
    t = gamma(-v)[t'+vx'/c^2]
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