Question about the "information" carried by photons

[gib65]

Hello SFN,

 

I had a question about photons and the information they carry. We call photons "messenger particles" and they carry the electromagnetic force. When an electron emits a photon and it gets absorbed by a proton, the proton is attracted to the electron. We say, in a sort of metaphorical manner of speaking, that the photon carried a message that said "Hey! Look here! I'm an electron. You better be attracted to me."

 

Even though this is just a metaphor, it still leaves me with a question (which I think still needs to be asked even when taken literally): How does the proton know it was an electron that emitted the photon? I mean, in the metaphor, I guess we're supposed to assume the message carries this information. If it were another proton that emitted the photon, the first proton would be repelled, not attracted. This means the information would have to be different. It would tell the first proton that the other particle was another proton, not an electron.

 

But how should this difference in information be interpreted literally? I mean, what is there in the photon that's different if it were emitted by one kind of particle rather than another? Aren't all photons the same (aside from how much energy they carry)? How should the event of the first proton absorbing the photon be understood differently whether it received that photon from an electron or another proton? Is there any physical difference?

[Gilded]

First of all, they are virtual photons so it's not as simple as that. But it's a good question. Perhaps the photons differ in polarization?

[swansont]

It's not really a situation you can interpret classically. The attraction or repulsion are both possible in the quantum treatment.

 

http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html

[Tom Vose]

First of all, they are virtual photons so it's not as simple as that. But it's a good question. Perhaps the photons differ in polarization?

 

Even when people say this, it often leaves the non-scientist to believe they are practically ghosts with no real qualities whatsoever. Whilst this is partially true, i want to note that virtual photons still have real effects in the world, such as the stability of the hydrogen atom.