The speed of light in a vacuum remains constant even in the presence of gravity. However, gravity affects the path that light takes due to the curvature of spacetime, a concept described by Einstein’s General Theory of Relativity. Massive objects such as stars, galaxies, or black holes create dents or warps in spacetime. When light passes near such massive objects, its path appears to bend — this phenomenon is known as gravitational lensing.
Although the local speed of light remains unchanged, the curvature causes light to follow a longer, curved trajectory rather than a straight line. This bending effect leads to observable outcomes such as multiple images of the same astronomical object, distorted or magnified views of distant galaxies, and the formation of structures like Einstein rings.
In addition, when light travels through a strong gravitational field, it experiences what’s known as the Shapiro time delay. This means light takes slightly longer to traverse a region of space near a massive object, not because the speed of light has slowed, but because time itself runs slower in that region and the path is longer due to curvature.
So, gravity influences how light travels through space — not by changing its speed, but by altering the geometry of the space it moves through.