Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Graviton source

  1. May 29, 2017 #1
    If gravitational force is caused by a particle (tensor boson) which is massless and so travels at c, why doesn't matter ever exhaust, or even seem to reduce, its supply of these particles?
     
  2. jcsd
  3. May 29, 2017 #2

    Drakkith

    User Avatar

    Staff: Mentor

    Force carrier particles aren't literal particles that go streaming out from an object to exert a force. It's very difficult to explain, but the simplest answer I can give you is that these carrier particles are closer to a convenient way of looking at the math than actual particles.
     
  4. May 29, 2017 #3

    jtbell

    User Avatar

    Staff: Mentor

    If the electrostatic force is caused by a particle (photon) which is massless and so travels at c, why doesn't a charged object ever exhaust, or even seem to reduce its supply of these particles?

    I expect the answer to the gravitational case is the same (or very similar) to the electrostatic case, which is that the "force-carrying particles" are "virtual" ones, i.e. artifacts of a certain procedure (the "perturbation expansion") for calculating the effects of those forces. In the electrostatic case, there are other ways of doing the calculation (at least in principle) besides using virtual photons, so the virtual photons aren't "necessary." I expect the situation is similar with the gravitational case.
     
  5. May 30, 2017 #4
    I think it's also clear that you can't treat gravitons as regular particles by the sheer fact that even though they move with c *away* from the heavy object, their effect is to *pull* at whatever they meet.
     
  6. May 30, 2017 #5

    Drakkith

    User Avatar

    Staff: Mentor

    They don't even *move*, as they're virtual particle in this context, not real particles.
     
  7. May 30, 2017 #6
    True, but any change will propagate with c away from the source. That could be conceived to be a particle-like property, i.e. an indication that there is a constant "stream" (not that it is, just saying).

    Honestly, I myself am still uncomfortably vague about the nature of particles. I understand they are excitations of a field, but whenever I think I'm getting a good mental handle on them, there's an aspect to it that confuses me again. Like for example virtual particles.
     
  8. May 30, 2017 #7

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    That's fair, but maybe your shouldn't attempt to explain them to others until you are comfortable and no longer confused.
     
  9. May 30, 2017 #8

    Drakkith

    User Avatar

    Staff: Mentor

    If so, then you could ask, "What rate are they being emitted?" But that concept makes no sense when it comes to virtual, force carrying particles. The electromagnetic and gravitational interactions are continual processes that display no particle-like behavior outside of E&M waves.
     
  10. May 30, 2017 #9
    Thank you all very much for your clarifications and musings. (Actually, Vanadium, hearing from the similarly "confused" is helpful, or at least interesting.)

    I like your explanation, Drakkith. Almost seems to say the math is defining more than describing reality. It jives with what I've read since posting my admittedly unenlightened question: that virtual particles aren't particles at all, but disturbances in fields. As Matt Strassler puts it: "A particle is a nice, regular ripple in a field, one that can travel smoothly and effortlessly through space, like a clear tone of a bell moving through the air. A 'virtual particle', generally, is a disturbance in a field that will never be found on its own, but instead is something that is caused by the presence of other particles, often of other fields." Note that in his simile he likens them to compression waves.

    Intrigued by your rhetorical parody of my question, rumborak. Coulumb force/interaction is the attraction or repulsion (not emission) of particles. I guess your analogy is lost on me a little.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Graviton source
  1. The Graviton (Replies: 3)

  2. Gravity and gravitons (Replies: 1)

  3. What are Gravitons (Replies: 1)

  4. What is graviton ? (Replies: 2)

Loading...