system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why is light affected by gravity if photons are massless?
gpt
Gravity doesn't pull on mass. Gravity is a distortion in spacetime. Inertial matter (matter with no force acting on it), including matter in a gravity well, will follow straight lines through spacetime. However, a straight line through spacetime will 'curve' towards the massive object. Light is an extreme of this, moving at c, but it follows the curve just as well.