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Speed of light

  1. Jan 29, 2012 #1
    Special relativity states that nothing can travel faster than c. But how do we know that c is the speed of light?
  2. jcsd
  3. Jan 29, 2012 #2


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    c is a constant in Maxwell's equations of Electromagnetism.
    A simple derivation shows that this constant, c, is the speed of EM waves which describe the propagation of light.
  4. Jan 29, 2012 #3
    c is defined as the speed of light in vacuum and is exactly 299792458 m/s.
  5. Jan 30, 2012 #4
    SR asserts that there is a invariant speed. One consequences is that this is a maximal speed.

    Light happens to travel at this speed (for good reason).
  6. Jan 30, 2012 #5


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    Special relativity states that nothing can travel faster than the speed of light. Which we happen to call "c".
  7. Jan 30, 2012 #6


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    Just to chime in, we have measured the speed of light, and it is c.
  8. Feb 1, 2012 #7
  9. Feb 2, 2012 #8


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    What, then, is your understanding of the meaning of c?
  10. Feb 2, 2012 #9
  11. Feb 3, 2012 #10
    As you can see, there are different opinions as to what c officially stands for. This is because both in theory and experiment, Maxwell's electromagnetic constant equals the speed of light and this speed also equals the maximal speed.
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