an English astronomer who discovered the aberration of light in 1729 (also referred to as astronomical aberration or stellar aberration). By observing a single star- Gamma Draconis - through his telescope for a period of time, Bradley observed its elliptic annual orbits, according to the latitude of the star; consequently at any moment the star appears to be displaced from its true position. Bradley reasoned that the apparent motion is due to the finite speed of light relative to the velocity of an observer on the Earth. In 1742, Bradley was appointed to succeed the famed Edmund Halley as Astronomer Royal, director of the Royal Greenwich Observatory in England.