>In fact, photons don't interact with each other at all. They can. It's a non-classical concequence of Quantum Electrodynamics. If you are interested in the c

>In fact, photons don't interact with each other at all. They can. It's a non-classical concequence of Quantum Electrodynamics. If you are interested in the cross-sections, check out Berestetskii et al., 1982.