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Does anything travel at speed c in the atmosphere.

  1. Oct 3, 2013 #1
    I understand the electromagnetic spectrum travels below speed c in Earth’s atmosphere. Is there any part of the spectrum which remains at speed c, or indeed anything which travels at speed c in the atmosphere?

  2. jcsd
  3. Oct 3, 2013 #2
    The atmospheric effect on the speed of electromagnetic radiation becomes more and more negligible the higher the energy of the incoming photon. gamma rays will travel very close to c through the atmosphere.
  4. Oct 4, 2013 #3

    Claude Bile

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    Science Advisor

    Most portions of the EM spectrum have a phase velocity in excess of c.

    Some portions I suspect have a group velocity in excess of c, but are highly absorbing at these wavelengths - so you ultimately cannot trasmit information faster than c.

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