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ephemeris time

(Encyclopedia)ephemeris time (ET), astronomical time defined by the orbital motions of the earth, moon, and planets. The earth does not rotate with uniform speed, so the solar day is an imprecise unit of time. Ephe...

Wen Jiabao

(Encyclopedia)Wen Jiabao wĕnˈ jyäˈbouˈ [key], 1942–, Chinese political leader, b. Tianjin. Originally a geologist, he worked for the Gansu provincial geological bureau (1968–82), where he was the head of i...

aureole, in physics

(Encyclopedia)aureole ôrˈēōlˌ [key], in physics, luminous circle seen when the sun or other bright light is observed through a diffuse medium, i.e., smoke, thin cloud, fog, haze, or mist. It sometimes occurs a...

dating

(Encyclopedia)dating, the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute. In relative dating, the tempor...

Tharp, Marie

(Encyclopedia)Tharp, Marie, 1920–2006, American oceanographer and cartographer, grad. Univ. of Michigan (M.A. 1944). A geologist with experience in mapping, she came to Columbia Univ. as a geology research assist...

Russell, Henry Norris

(Encyclopedia)Russell, Henry Norris, 1877–1957, American astronomer, b. Oyster Bay, N.Y., grad. Princeton, 1897. In 1902 he went to Cambridge, England, to study. He returned to Princeton in 1905, was professor of...

Hoyle, Sir Fred

(Encyclopedia)Hoyle, Sir Fred hoil [key], 1915–2001, British astrophysicist and mathematician, b. Bingley, Yorkshire. During the years of World War II, Hoyle primarily worked on technical problems related to rada...

Deucalion

(Encyclopedia)Deucalion dyo͞okāˈlēən [key], in Greek mythology, son of Prometheus and father of Hellen. When Zeus, angered by humanity's irreverence, flooded the earth, Deucalion, warned by Prometheus, survive...

paleomagnetism

(Encyclopedia)paleomagnetism, study of the intensity and orientation of the earth's magnetic field as preserved in the magnetic orientation of certain minerals found in rocks formed throughout geologic time. Paleom...

Manning, Patrick Augustus Mervyn

(Encyclopedia)Manning, Patrick Augustus Mervyn, 1946–2016, Trinidadian political leader, prime minister of Trinidad and Tobago (1991–95, 2001–10). He entered politics in the 1960s while studying geology at th...