The English geophysicist Sydney Chapman (1888-1970) made fundamental contributions to gas theory, to analysis of geomagnetic variations and atmospheric tides, and to theories of magnetic storms, auroras, and ionospheric layers.

Sydney Chapman was born at Eccles near Manchester on Jan. 29, 1888. Winning university scholarships, he first took an engineering degree at Manchester (1907), then mathematics degrees at Manchester (1908) and Cambridge (1911).

Chapman began work on gas theory during his third year at Cambridge, and he continued this work when he returned to Cambridge in 1914, producing two trailblazing papers. He shared with David Enskog the credit for a new method of investigating transport phenomena in gases and the discovery of gaseous thermal diffusion. Gas theory provided the background for much of his later work.

Chapman's years at the Greenwich Observatory, where he became a chief assistant under Frank Dyson (astronomer royal) in 1911, largely determined his future bent. He began by supervising the...