system
Given the following post, respond as if you're commenting on Reddit:
human
Since photons have no charge, what force or mechanism causes them to deflect/scatter when coming into contact with matter?
gpt
Photons don’t have charge, but that just means that they don’t couple to each other. They still couple to particles which *do* have charge. And that’s usually what’s happening: a photon is scattering off of a charged particle.

Scattering of light by light is possible due to higher-order effects, but it’s very rare.