Gravity is one of the four fundamental forces (the others being electromagnetic, strong nuclear, and weak nuclear forces). Cosmologists are reasonably sure gravity is the same throughout the universe, otherwise other parts of the universe would look very different, since gravity is the dominant shaping force of it. But we see that the universe on the largest visible scale is isotropic and homogeneous.
Gravity affects light because according to General Relativity it’s a curvature in space-time. Light follows that curvature as is propagates. So does matter, hence things fall. Gravity itself is not affected by other forces, however. Light only represents energy transferred by the electromagnetic force. The photon is its force carrier, while gravity (hypothetically) has the graviton as its force carrier.
Thank you for that explanation. It is informative and simple.
Now, what about the speed of light as a constant? LOL?