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Extremely energetic photon threshold

  1. Jul 10, 2013 #1
    Does anyone have any information regarding if a photon will at some point obtain mass at huge energy amounts?

    Let's say perhaps the photon gains so much energy that it's wavelength reaches planck's length, is it possible that it would gain mass? Is there any information regarding this inquiry? Is it possible there's a threshold energy that a photon can suddenly gain mass?

    I guess its wavelength will just approach 0 as its energy approaches infinity...

  2. jcsd
  3. Jul 10, 2013 #2


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    Staff: Mentor

    Photons will never, ever ever gain mass. They are massless particles.
    I believe that above a certain threshold, photons begin to interact with each other or the interstellar medium and their energy is used to produce massive particles, but I'm not really sure on that, it's just something I think I remember reading at some point.
  4. Jul 10, 2013 #3
    High energy photons also frequently "pair-produce" electrons and positrons when they wanna get really funky, don't they?
  5. Jul 11, 2013 #4

    It makes so much more sense that they would create another particle...

    something didn't seem quite right haha
  6. Jul 11, 2013 #5
    1. What do you mean by that statement?

    2. Why would it make "so much sense?"

    3. If it makes so much sense, then you must have in mind some kind of mechanism through which this may occur. What is the mechanism you have in mind? That way we may be able to tease apart is validity.
  7. Jul 11, 2013 #6
    I'm sorry, I'm a bit too ignorant to know of a mechanism through which some particles might be created. =(

    Where my logic comes from is...

    If the planck length is the smallest quantized unit of length, then what happens when a photon gets excited enough to reach a wavelength of that length, or rather exceeds that energy?

    If the photon were to obtain mass, it wouldn't be a photon anymore, right? Isn't the particle identified by its properties? Massless being a property of a photon.

    So what happens? I thought it made more sense that another particle was created than the photon being turned into another particle... I'm not sure though how either of those could happen. I'm just wondering if there is any info on what could happen?

    EDIT: I mean, there's a limit velocity to things with mass, the speed of light. When they approach it, they gain mass to sort of "fit in" all the energy they're receiving.
    Do photons have a place to "fit in" the energy they're receiving? Or do they just approach a 0 length wavelength?
  8. Jul 11, 2013 #7
    That hasn't really been determined yet, see this thread:


    It is not known what the limit of the energy/wavelength of a photon can be. We don't know if the wavelength can come anywhere near the planck length or exceed it, so that is an open question.

    That sounds reasonable, but let's use the term "rest mass" instead of just "mass."

    I don't see the distinction here. They seem to be equivalent circumstances to me...

    My guess would be the latter, they just approach a 0 wavelength.
  9. Jul 13, 2013 #8


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    Staff: Mentor

    Also remember that a photon's wavelength is frame dependant. A gamma ray photon could easily be seen as a radio wave photon if something is moving away from its source fast enough. And the opposite is true. A gamma ray photon could be seen as having a wavelength shorter than the plank length just because something is traveling towards its source at a high velocity.
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