Einstein's theory of general relativity states that gravity is not a force, but rather a curvature of spacetime. This curvature is caused by the presence of mass and energy. The more mass and energy an object has, the greater its gravitational pull.

Light is a form of energy, so it is also affected by gravity. When light passes through a gravitational field, it is deflected towards the source of the gravity. This effect is called gravitational lensing.

The amount of deflection depends on the strength of the gravitational field. The stronger the gravitational field, the greater the deflection.

Gravitational lensing has been observed around black holes, stars, and galaxies. It is one of the ways that astronomers can study the distribution of mass and energy in the universe.

So, does gravity affect the speed of light? The answer is yes, but the effect is very small. For example, the gravitational field of the Earth deflects light by only about 0.0000001 degrees.