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Does light travel for ever?

  1. Feb 10, 2012 #1
    So from an electromagnetic source, will the photons travel "forever" or will some of them "collapse" after a while ?
  2. jcsd
  3. Feb 10, 2012 #2
    Are you talking about an electric/magnetic field (ie a magnet) or light (ie a flashlight)?
  4. Feb 10, 2012 #3
    I'm gonna assume you mean a flashlight.
    In that case the photons will travel forever untill they get absorbed.

    They will also lose energy over extremely long periods of time due to the expansion of the universe, but will never 'dissapear'.
  5. Feb 10, 2012 #4
    Sorry i ment Electromagnetic radiation (Radio and Light). By loosing energy do you mean that the wavelength will be longer?
  6. Feb 10, 2012 #5

    (adding text because my post was too short)
  7. Feb 10, 2012 #6
    But remember that takes billions of years :)
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