The electromagnetic force is mediated by photons , which have 0 mass. so electromagnetic forces have infinite range. the weak force is mediated by three intermediate bosons, W+, W-and Z0 particles. these all have mass, the two W particles about 80GeV and the Z is about 90GeV. the bit below is what i dont really get.... "in order to carry out the weak interaction from 1 particle to the next, the appropriate intermediate boson has to be created out of nothing at all." but why? and it says "using energy borrowed from the vacuum." what does it mean by " borrow " the energy from the vacuum. thanks ..