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Speed of light measurements using different light source.

  1. Oct 31, 2011 #1
    As far as I know all light speed measurements done using light sources that utilized electrons. The nominal light speed measurement used laser which is actually exited electrons. The speed of X-ray radiation from synchrotron used accelerated electrons. The speed of gamma radiation also involved with inhalation of electron and positron. The speed of RF is also involved with electrons modulation in coils and capacitors.

    Are there any speed measurements of electromagnetic radiation coming say from oscillated or accelerated protons?
  2. jcsd
  3. Oct 31, 2011 #2


    Staff: Mentor

  4. Oct 31, 2011 #3
    Thanks DaleSpam
  5. Nov 1, 2011 #4
    Following the list provided by DaleSpam , the relativistic pion decay to 2 gamma photons as an electromagnetic source radiation in light speed measuring experiment. Is the only one of this type (namely light source that no electrons involve). Am I correct?
    May be it is not the proper thread but how come a neutral (pion decay into 2 gammas) elementary entity generates electromagnetic radiation? As far as we learned, electromagnetic radiation generates only when charge entity changes its velocity (accelerates or decelerates, see oscillators)
  6. Nov 1, 2011 #5


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    Back up a bit.

    What makes you think that there is a difference in the type of EM radiation due to these different sources. Do you think EM radiation generated by accelerating protons, ions, etc. is different than those generated by electrons? What is the physics for this difference?

  7. Nov 1, 2011 #6


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    A pion is not elementary, it's a quark-antiquark bound state. The Higgs boson is usually assumed to be elementary, but it can also decay into a quark-antiquark pair and from that into 2 gammas. A photon certainly does not 'remember' what type of particle emitted it.
  8. Nov 1, 2011 #7


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    A neutral pion is its own anti-particle, so it always exists as a superposition of the particle and anti-particle. This allows it to annhilate itself and decay into two photons, as happens with other particle-anti-particle annhilations.

    Maybe classically you can justify that statement, but in the quantum world photons are produced in order to conserve energy and momentum in a wide variety of decays.
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