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How do things of opposite charge attract?

  1. Dec 3, 2003 #1
    I've racked my brain over this one since I was 15 and I really can't figure it out. I can see how two electrons would bounce away from each other with the exchange of a virtual photon, since one pushes off on the photon and the other absorbs it(even if I don't understand how the electron knows when to shoot out the photon, in which direction and where it goes when it's absorbed). But how a positron and an electron can attract with the same kind of exchange is completely beyond me. Is this just the kinda weirdness that goes on at those levels?
  2. jcsd
  3. Dec 3, 2003 #2


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    In all honesty, this kind of question is really more in the realm of philosophy or the "theory development" thread, than in general physics.

    Physics doesn't really describe the mechanisms of the forces as much as it describes their behavior. Even if you go to the unified field theories, or whatnot, there really isn't a good qualitative description of how the forces work.
  4. Dec 3, 2003 #3
    Thanks, Nate. You put years of wonder to rest with the answer "no one knows." And in a weird way that satisfies me somehow. Now I can get some rest while I wait for them to build bigger particle accelerators. :smile:
  5. Dec 3, 2003 #4
  6. Dec 3, 2003 #5
    It's not quite true that this is not understood. We don't know why attractive forces exist in the first place, but we understand how virtual particle exchange can result in attraction. There is even a FAQ on this, but IMHO it's not too clearly written for the layman:

  7. Dec 3, 2003 #6
    Re: Re: How do things of opposite charge attract?

    What an irony! We both posted the same link and almost at the same time!
  8. Dec 4, 2003 #7
    Would it not lie in the theme of balanace? Everthing in the universe should/'wants to be balanced therefore an electron will attract a positron?
  9. Dec 5, 2003 #8


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    Re: Re: How do things of opposite charge attract?

    I'm not trying to denigrate the theory of virtual particles, but this doesn't really answer the question that was asked.
    Unfortunately this theory does little but replace one set of behavioral descriptions with another. Instead of an electromagnetic field, there is now a quantum field or virtual particle. AFAIK this model makes better predictions than Maxwell's, but it still doesn't explain the atraction.

    That notion is, as I predicted, philosophic in nature. Moreover, it does not apply to other forces, such as gravity (which is universally attractive).
  10. Dec 5, 2003 #9
    Re: Re: Re: How do things of opposite charge attract?

    Yes, it does. The original poster said that he was fine with virtual particles causing a repulsion, since he could see a particle pushing another particle away, but he didn't understand how the same virtual particles could cause an attraction. The FAQ was written to address that question in the context that it was asked here: how virtual exchange can result in both attraction and repulsion, as opposed to only repulsion.
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