Natural Order and Science

[little_monkey]

Maybe I misunderstand you. Can you briefly clarify what you mean is a matter of definition, and how does that relate to the question whether virtual particles really exist?

Basic definition: two electrons interact, they exchange a photon. That photon is "virtual". It's not going to be a photon that any of my detectors  - eyes, voltmeters, or whatever apparatus I have at hand - will register. The photon goes from one electron to the other. Period. It's virtual.

Now, should a photon be emitted by an electron and not absorbed - for whatever reason, then that photon can be detected (by my eyes or any other detector). That photon is observable, so it's not a virtual photon. The reason you can see is that there are gazillions of those photons floating around, bouncing everywhere and then.

Now if you understand that basic definition, then we can talk about interactions, what are they, how are they calculated, what role does the Heisenberg Principle play, what are Feynman diagrams, what's their use, what's their limitations, what's renormalization, what's gauge theory, what role does symmetry play in QFT, what's the advantages of going through the Hamiltonian as opposed to the Lagrangian formulation, what about the Feynman path integral, what's the core idea behind QFT, and why do we need QFT instead of QM, and a dozen other topics. But if you have trouble of understanding basic definition, we're not going to get anywhere.