Pardon me for my stubborn classical/semiclassical brain. But Ibet I am not the only one finding such description confusing.

If EM force is caused by the exchange of photons, does that meanonly when there are photons exchanged shall there be a force? To myknowledge, once charged particles are placed, the electromagneticforce is always there, uninterruptedly. According to such logic,there has to be a stream of infinite photons to build EM force, andthere has to be no interval between one \"exchange event\" toanother. A free light source from an EM field? The scenario isreally hard to imagine.

For nuclei the scenario becomes even odder. The stronginteraction between protons is caused by the exchange of massivepions. It sounds like the protons toss a stream of balls to oneanother to build an attractive force - and the balls should comefrom nothing.

Please correct me if I am wrong: the excitations of photons andpions all come from nothing. So there should be EM force and strongforce everywhere, no matter what type of particles out there. Say,even electrical neutral, dipole-free particles can build EM forcein-between. And I find no reason such exchanges of particles cannothappen in vacuum.

Hope there will be some decent firmware to refresh my classicalbrain with newer field language codes.