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Speed of light question

  1. Apr 3, 2008 #1
    simple question - Can light or anything else, travel faster than 3x10^5 km/sec?
    If not, why is there a limit on max speed particles/photos can travel at?
     
  2. jcsd
  3. Apr 3, 2008 #2
    From wikipedia on Special Relativity:

     
  4. Apr 4, 2008 #3
    A good way to think about it that I recently came across is that everything is moving at a constant speed. That is, every object has a 4-velocity and a 4-speed of c (speed of light). A 4-velocity is a 4-dimensional vector where the first index is time and the last three are space.

    Examples:
    Object at rest: v = (c,0,0,0)
    Photon: v=(0,c,0,0) *or any vector where the length of the spatial part is c and time is 0

    So the question isn't "why is there a maximum speed?", its really "why is everything moving through space-time at a constant speed?".
     
  5. Apr 4, 2008 #4

    robphy

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    For a photon, its tangent vector has the form
    Photon: v=(c,c,0,0), for example, so that [tex] c^2-(c^2+0^2+0^2)=0^2 [/tex].

    Here's my comment on the "speed through spacetime" idea:
    https://www.physicsforums.com/showthread.php?p=565681#post565681
     
    Last edited: Apr 4, 2008
  6. Apr 4, 2008 #5
    my bad, I forgot that detail: mass-less particles have 4-speed of 0 while massive particles have 4-speed of c.
     
  7. Apr 4, 2008 #6
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