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C = 299 792 458 m/s and uncertainty

  1. Feb 4, 2007 #1
    c is 299 792 458 m/s without uncertainty? doesn't work the Heisenberg uncertainty principle for fotons?
  2. jcsd
  3. Feb 4, 2007 #2
    The distances typically involved in measuring c are sufficently big that quantum fluctuations are ignored.

    Also, the length of 1m is defined by the distance light travels in a certain amount of time. Because of this definition, we're effectively defining light's speed, not measuring it, so it is exact.
  4. Feb 5, 2007 #3
    we define 1m, but we must still measure in how much time light crosses 1m; we measured c but it can be less or more, right?
  5. Feb 5, 2007 #4


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