George Biddell Airy, English astronomer and geophysicist, c 1870.

UNITED KINGDOM - MAY 21: Lithograph showing the English astronomer and geophysicist, Sir George Biddell Airy (1801-1892), who was Astronomer Royal and director of the Royal Greenwich Observatory from 1835 to 1881. Airy initiated the efficient and accurate observation of stellar positions, published works on celestial mechanics and made discoveries in theoretical and practical optics. He reorganised the Greenwich Observatory and discovered errors in planetary theory in relation to the motion of the Earth and Venus. A telescope designed by Airy was used to measure Greenwich Mean Time, which became Britain's legal time in 1880. (Photo by SSPL/Getty Images)