AIRY, SIR GEORGE BIDDELL

born July 27, 1801, Alnwick, Northumberland, Eng. died Jan. 2, 1892, Greenwich, London English scientist who was astronomer royal from 1835 to 1881. Airy graduated from Trinity College, Cambridge, in 1823. He became Lucasian professor of mathematics at Cambridge in 1826 and Plumian professor of astronomy and director of the Cambridge observatory in 1828. In 1835 he was appointed the seventh astronomer royali.e., director of the Royal Greenwich Observatory, a post he would hold for more than 45 years. Airy completely reorganized the Greenwich observatory, installing new apparatus and rescuing thousands of lunar observations from oblivion. Most importantly, he modernized the observatory's system for making extremely precise observations of stellar positions. He wielded great power within the British scientific community, and he opposed government support of pure science, arguing that original research was best left to private individuals and institutions. Modern scholars absolve him of the charge that his hesitation to publicize the calculations of John C. Adams in 1845 somewhat delayed the discovery of Neptune. Airy in 1827 made the first successful attempt to correct astigmatism in the human eye (his own) by use of a cylindrical eyeglass lens. He also contributed to the study of interference fringes, and the Airy disk, the central spot of light in the diffraction pattern of a point light source, is named for him. In 1854 he measured gravity by swinging the same pendulum at the top and bottom of a deep mine and thus computed the mean density of the Earth. Airy was also the first to propose (c. 1855) the theory that mountain ranges must have root structures of lower density, proportional to their height, in order to maintain isostatic equilibrium. He was knighted in 1872.