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Electromagnetic force

  1. Jan 4, 2009 #1
    Suppose we take there are one electron and one proton, they attract each other by exchange of virtual photon of energy ∆E and it exists for ∆t. From where virtual photon gets energy ∆E? Is it from electron or proton?if it gets energy from electron or proton, will the energy of electron and proton also change?
    There are so many electrons and protons in this universe and every electron and proton interact with every other electron and proton so there are many virtual photons floating here and there in the universe. Is this true? if so then, there would be almost infinite energy going with these virtual photons? from where these virtual photons getting energy?
  2. jcsd
  3. Jan 4, 2009 #2


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    There are two diagrams, in one of them the electron emits the photon and proton recieves it. In the second the process is opposite. Each diagram contributes to the total process of electron - proton scattering.

    Well, yes and no. Virtual particles are tools in perturbation theory, it is hard to tell wheter they exists or not and we must raise the question on a philosophical level on what existence really means. But anyway, in the language of virtual particle exhange, an electron emits and absorbs vritual photons all the time. One feynman diagram is that the electron emits a virtual photon at time t_1 and then absorbs it at latter time t_2. And so on and so on.
  4. Jan 4, 2009 #3
    So if electron emits virtual photon,then its energy decreases and since there are so many electrons and protons in this universe,hence this electron interacts with all of them and emits many virtual photons for each interaction and so its energy will be decreasing and decreasing and it will vanish..isn't it? this is strange.
  5. Jan 4, 2009 #4


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    no in total the energy is conserved. When you construct a diagram, you impose momentum and energy conservation. Then between ingoing and outgoing states, things can happen such as mass off shell particles (the one we call virtual).

    You are mixing these things up with "spontaneous" pair creation out of the vacuum, where a pair of particles,antiparticles are excited from the vacuum to again annihilate and thus preserving energy conservation.

    Also you think that interaction MUST take place, but there is a probability for a process to occur.

    Stop worrying.
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