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Photons in the derivation of relativistic equations

  1. Feb 12, 2006 #1
    Do you think that the involvement of photons in the derivation of the fundamental equations of relativistic dynamics is under the likmit of "elegance" and "simplification" imposed by Einstein?
  2. jcsd
  3. Feb 13, 2006 #2


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    Do you mean the Lorentz transformations?

    I don't think photons have anything to do with relativity.
  4. Feb 13, 2006 #3
    Photons are used because they happen to be massless particles and therefore travel at a constant velocity (c) in all reference frames. You could do the derivation with golf balls if you wanted, it just wouldn't be as simple.
  5. Feb 13, 2006 #4

    Yes. I mean the transformation for momentum and energy.
    I aggree that photons have anything to do with relativity but they start to have when we use them deriving relativistic equations.
    Thanks for your answer.
  6. Feb 13, 2006 #5


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    I don't think there is anything "inelegant" or "complex" about photons in relativity, at least if you consider them as semiclassical objects without the probabilistic aspects of quantum mechanics. They fit into the general relationship between (invariant) mass, momentum and energy. In 1905 it was already known that the energy density and momentum density carried by an electromagnetic wave are related by E = pc, the same as we now accept for the photon.

    QM as we know it, with its probabilistic aspects, didn't arise until twenty years after Einstein first published about special relativity.

    Or am I missing your point completely?
    Last edited: Feb 13, 2006
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