> I have never read anything that suggests that photon collisions would lead to annihilation. You may at least have heard that a particle antiparticle collisio

> I have never read anything that suggests that photon collisions would lead to annihilation. You may at least have heard that a particle antiparticle collision can lead to the production of two photons. Viewed in reverse this would be two photons annihilating and producing a particle antiparticle pair. Since the laws of physics work equally well in reverse two photons must therefore be able to annihilate.