 There are additional effects that arise from general relativity.One is gravitational redshift distortion, which arises from the net gravitational redshift, or blueshift, that is acquired when the photon climbs out of the gravitational potential well of the distant galaxy and then falls into the potential well of the Milky Way galaxy.This effect will make galaxies at a higher gravitational potential than Earth appear slightly closer, and galaxies at lower potential will appear farther away.