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Photons from the past

  1. Dec 11, 2011 #1
    Relativity states that as anything approaches the speed of light, time slows down. At the speed of light, time stops. If this is true then photons from 1 billions light years away would not exist in the present unless they stopped and remained stationary for 1 billion years after reaching earth. What am I missing?
  2. jcsd
  3. Dec 11, 2011 #2


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    Time does not slow down to a stop at the speed of light, in spite of what you may have heard or read. Time does not apply to light or photons. Einstein said that time is what a clock measures and since no clock can travel at the speed of light, there is no meaning to the concept that a clock stops and thus time stops at the speed of light. Photons don't experience time.
  4. Dec 11, 2011 #3
    Photons experience time as all inanimate objects do. They change over time. If there is a spacetime, which I doubt, anything moving through space would experience time. If we destroy all the clocks, will time stop?
    If time slowed down at all, my point is made. It does not have to stop.
    Last edited: Dec 11, 2011
  5. Dec 11, 2011 #4
    Maxwell showed that photons are time-variant electric fields giving rise to time-variant magnetic fields and vice versa right? So how is this if photons don't experience time? I have not been able to understand this one.
  6. Dec 11, 2011 #5


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