Jeffreys, Sir Harold
Geophysicist, astronomer, and mathematician, born in Fatfield, Tyne and Wear, NE England, UK. He studied at Cambridge, where he became reader in geophysics (1931--46) and professor of astronomy (1945--58). In a wide-ranging scientific career, he investigated the effect of radioactivity on the cooling of the Earth, and postulated that the Earth's core is liquid. He studied earthquakes and monsoons, made a fresh estimate of the age of the Solar System, and re-calculated the surface temperatures of the outer planets. In mathematics he made contributions to probability theory and operational calculus.