Harold Jeffreys
Jeffreys, Harold (1891-1989), a British geophysicist, was a leading authority on the structure of the earth. In his book The Earth: Its Origin, History, and Physical Constitution, published in 1924, he provided the theory for the modern method of exploring the inside of the earth by means of seismic (earthquake) waves from explosions near the surface.
Jeffreys was born on April 22, 1891, in Fatfield, in Durham County, England. He was educated at Armstrong College, which became Newcastle University, and Cambridge University, from which he earned a doctoral degree in 1917. From 1917 to 1922, Jeffreys worked in the Meteorological Office. He spent the rest of his career at Cambridge, serving as lecturer in mathematics (1922–1931), reader in geophysics (1931–1946), and Plumian Professor of Astronomy and Experimental Philosophy (1946–1958).
Jeffreys had many scientific achievements. In 1923, he used mathematical calculations to show that the surface temperatures of outer planets in our solar system are extremely cold, not red-hot, as scientists had previously believed. In 1926, he was the first scientist to claim that the center of the earth is a dense mass of molten rock. In 1940, Jeffreys and his research partner Keith Bullen published the Jeffreys-Bullen tables, in which they calculated travel times of seismic waves and the location and distance from the observer of an earthquake's epicenter.
Jeffreys married Bertha Swirles, a mathematician, in 1940. Together they wrote the book Meth ods of Mathematical Physics (1946). They had no children. Jeffreys was knighted in 1953. He died on March 18, 1989, in Cambridge.