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Massless particles ?

  1. Nov 25, 2009 #1
    Do all massless particles travel away from you at the speed of light regardless of you speed . i know light does , does this include gravitons .
  2. jcsd
  3. Nov 25, 2009 #2
    Massless particles cannot exist otherwise. If they would have a mass, they would never reach this speed. Without a mass, with the slightest energy, they reach the speed of light.

  4. Nov 25, 2009 #3
    They could travel toward you too!
  5. Nov 25, 2009 #4


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    Yes. For a proof, see subsection 3.2.2 of this link: http://www.lightandmatter.com/html_books/genrel/ch03/ch03.html#Section3.2 [Broken]

    Gravitons are sort of a special case, because they have never been directly detected. In classical theories of gravity, we can ask whether gravitational effects propagate at c. If GR is the classical theory you have in mind, then it is true in the low-amplitude limit that they propagate at c. There is no direct experimental evidence yet on this point. Experiments on this issue are difficult to design and interpret, because nobody has a viable candidate theory of classical gravity in which gravitational effects do *not* propagate at c. Here is a more detailed discussion: http://www.lightandmatter.com/html_books/genrel/ch07/ch07.html#Section7.1 [Broken]
    Last edited by a moderator: May 4, 2017
  6. Nov 26, 2009 #5
    thanks for the answers
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