Since photons are bosons and do not follow the pauli exclusion principle, does this mean that two photons can be at the same place at the same time? Is it meaningful to talk about a photon 'colliding' with another photon? I mean, suppose we send two photons of the same color towards each other at an angle of 60 degrees between them, and they meet. Is that a 'collision'? Do the photon's directions change and just add up vectorially? I'm thinking that since the photon speeds can't add up, and must stay the same, since they already travel at the speed of light, how can momentum be conserved? Does one absorb the other? How about energy conservation?