Particles for all forces: how do they know where to go, and what to avoid?

Question

Here's an intuitive problem which I can't get around, can someone please explain it? Consider a proton P and an electron E moving through the electromagnetic field (or other particles for other forces, same argument). They exert a force upon one another. In classical mechanics this is expressed as their contributing to the field and the field exerts a force back upon them in turn. In quantum mechanics the model is the exchange of a particle. Let's say one such particle X is emitted from P and heads towards E. In the basic scenario, E absorbs it and changes its momentum accordingly. Fine. How does X know where E is going to be by the time it arrives? What's to stop E dodging it, or having some other particle intercept X en route? Are P and E emitting a constant stream of force-carrying particles towards every other non-force-carrying particle in the universe? Doesn't this imply a vast amount of radiation all over the place? I am tempted to shrug of the entire particle exchange as a mere numerical convenience; a discretization of the Maxwell equations perhaps. I am reluctant to say "virtual particle" because I suspect that term means something different to what I think it means. Or is it a kind of observer effect: E "observes" X in the act of absorbing it, all non-intercepting paths have zero probability when the waveform collapses? Or have I missed the point entirely?

Answer 1

Particles are described in quantum mechanics by wave functions that permeate throughout all of space and time. This description includes not only matter and anti-matter particles (fermions), such as electrons, but also force-carrying particles (bosons), such as photons. The interaction between the fermions and the bosons is mediated by the interaction between their respective wave functions.

Answer 2

Think for example of a laser. It is emitting photons in a straight beam and if something is on the way of it, the atoms from the target material are going to absorb this photons, but no one is telling this photons where to go to meet some E particle. They are just following the most straight line. And in fact there is a lot of radiation coming from everywhere onto you. Not only photons but also neutrinos and some other of particles are going trough you body every second, also mostly every kind of material is a little radioactive all the time. The wave function collapses when a measure is realized to the traveling photon, so this implies an interaction with some other atom, which causes that the measured value becomes the state of the particle with probability equals to one. So every other "path" (measure value) get's 0 of probability when that happens.