I am currently studying electrodynamics with all the fields and the like. Now, as I understand it, in a more modern viewpoint there is a duality between electromagnetic fields and photons, with photons being the particles that are exchanged in the process of interaction.

My question is, what is the current explanation to what an electromagnetic field is? For example, consider a point charge $q_1$. In order for another charge $q_2$ to 'feel' $q_1$, there is an electromagnetic field generated by $q_1$ that allows interaction. However, using the photon picture of view, a charge should then constantly radiate photons in all possible directions to let other charges know that it's here and should be interacted with. This leads to a problem in energy conservation, as each photon carries an energy $h\nu$, and thus even if a charge is at rest it would radiate off its energy and subsequently be gone.

How can this be resolved? What is the real connection between an electromagnetic field and photons?

  • $\begingroup$ possible duplicate of Virtual photon description of B and E fields $\endgroup$ – John Rennie Jul 4 '14 at 6:54
  • $\begingroup$ I don't think so, there they already assume the answer to this question known, refering to virtual photons. I'm asking how this really works! $\endgroup$ – Pascal Engeler Jul 4 '14 at 6:59
  • $\begingroup$ How mathematically classical electromagnetic fields emerge from a large number of photons is explained in this blog entry, motls.blogspot.com/2011/11/… $\endgroup$ – anna v Jul 4 '14 at 14:12

This is where virtual particles come into play.


Essentially you can think of these virtual particles as temporary photons as carriers that dont exactly behave ver well with conservation of energy. The field is full of these non-conservative carriers for a very brief instant as a function of the mass of the carrier (called a gauge boson). As (rest) massless particles photons can extend out ad infinium until they finally interact with another particle.

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  • $\begingroup$ if you really want some more details and in particular a better understanding of perturbation theory (from which this interpretation arises) try this link: math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html $\endgroup$ – Skyler Jul 4 '14 at 8:38
  • $\begingroup$ Virtual particles like a shower is a really bad explanation, unless you know the underlying mathemathics. $\endgroup$ – jinawee Jul 4 '14 at 8:44
  • $\begingroup$ I'm going to learn about the standard model and quantum mechanics next year, the supplied youtube channel is a nice precursor. Thanks! $\endgroup$ – Pascal Engeler Jul 4 '14 at 8:49
  • $\begingroup$ jinawee, are you talking about functionals and calc of variations? $\endgroup$ – Skyler Jul 4 '14 at 18:31
  • $\begingroup$ my pleasure pascal, i remember watching this video and it blowing my mind freshman year of highschool, and it was part of the reason I decided on physics as a major back then. It took me like 20 minutes to find it again (after watching like 20 minutes of their other videos, much to my pleasure) and I'd recommend their entire channel as a good primer, along with several videos from veritasium. $\endgroup$ – Skyler Jul 5 '14 at 4:26

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