James Bradley (1693-1762), English astronomer. After his education at Oxford University, he became vicar of Bridstow, but resigned in 1721 to hold an astronomy chair at Oxford. He succeeded Edmond Halley as Astronomer Royal in 1742. His observations led him to discover the aberration of light. Bradley attributed this phenomenon, which causes apparent motions of astronomical bodies, to the finite speed of light and the motion of the Earth. Later, he also detected nutation, or tiny irregular motions of bodies due to tidal forces. His reputation allowed him to procure a range of valuable astronomical instruments for the Royal Observatory in Greenwich, London, which contributed to the accuracy and calibre of the science performed there.