eli5 If the photons in light have no mass, why are they refracted by high gravity around stars and black holes in vaccuum, or mediums like water, glass and air?

Question

eli5 If the photons in light have no mass, why are they refracted by high gravity around stars and black holes in vaccuum, or mediums like water, glass and air?

In: 0

Answer 1

for gravity, light follows spacetime and it’s curvature.

For mediums like glass and water, the speed of light becomes smaller. This is in fact due to light acquiring mass in those media.