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Does electromagnetic radiation occupy space ? How much?

  1. Sep 10, 2011 #1
    Anything that occupies space creates a 'distortion' to a certain degree in the space time fabric and hence will experience gravitational force.And we know radiation does experience gravitation , this would directly imply that it occupies 'space' or 'volume' . The question now is .. how much volume ?
  2. jcsd
  3. Sep 10, 2011 #2
    Hi, Atryant.

    Your question of 'How much volume' would be readdressed as 'How much energy per volume'. Because energy(-momentum) is source of gravity or distortion of space-time. Then part of the answer for energy is energy density of electromagnetic field, i.e. (ED + BH)/2 for every point of space.

  4. Sep 10, 2011 #3


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    All of it. The entire universe is filled with electromagnetic radiation.
  5. Sep 10, 2011 #4
    Does this mean that entire space-time gets, at least, infinitesimally distorted off an on at various points in time and space (by the radiation)?
  6. Sep 10, 2011 #5
    In principle, sure. But the coupling to gravity is so weak that it is negligible in most if not all cases.
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