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Superposition question

  1. Jan 1, 2009 #1
    So here has been a nagging question in the back of my mind since freshman electromagnetism. I haven't taken a 400 level Electrodynamics course yet so I think I have more to learn. But I'll ask the question anyway.

    At the end of my E&M course, my professor derived a wave equation from Maxwell's equations in Integral form which shows that light is an oscillation in Electric and Magnetic fields. And from basic Quantum Mechanics I know that light comes in quantized packets called Photons.

    My question is, doesn't this mean that everywhere there is light, there HAS to be an Electric and Magnetic field? Does this mean that EVERYWHERE in the observable universe there is an Electric and Magnetic field that can serve as the medium for EM Radiation? What happens out there in the intergalactic voids where you only have about 1 particle per cubic meter? The fact that EM Radiation permeates every location in the observable universe (i think) besides a black hole says that there has to be an EM Field everywhere? There has to be some kind of charge/moving charge everywhere to create these fields out in the void?

    Any explanation would be helpful. Thanks and Happy New Year!
  2. jcsd
  3. Jan 1, 2009 #2


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    Staff: Mentor

  4. Jan 1, 2009 #3


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    With EM radiation, the moving charges that produce the radiation can be millions of light years away. They don't have to be in the vicinity of the radiation fields.
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