Aberration of Light, a phenomenon in which a star or other celestial body, as viewed from the earth, appears to be slightly displaced from its true position. This phenomenon, which was first explained by the English astronomer James Bradley in 1729, occurs because (1) the earth is constantly moving in its orbit around the sun and (2) light travels through space at a finite speed (about 186,000 miles per second [300,000 km/s]). If the earth were stationary, or if light traveled through space instantaneously, the aberration phenomenon would not exist.
The traces left by raindrops on the side windows of a moving automobile provide an analogy to the aberration of light. Even if the rain is coming straight down, the traces will be at an angle.