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ecliptic coordinate system

(Encyclopedia)ecliptic coordinate system, an astronomical coordinate system in which the principal coordinate axis is the ecliptic, the apparent path of the sun through the heavens. The ecliptic poles are the two p...

isobar

(Encyclopedia)isobar īˌsəbărˈĭk [key], line drawn on a weather map through points of equal atmospheric pressure. Isobars are used to define cyclones (low-pressure regions) and anticyclones (high-pressure regi...

non-Euclidean geometry

(Encyclopedia)non-Euclidean geometry, branch of geometry in which the fifth postulate of Euclidean geometry, which allows one and only one line parallel to a given line through a given external point, is replaced b...

Ovechkin, Alexander Mikhailovich

(Encyclopedia)Ovechkin, Alexander Mikhailovich, 1985–, Russian hockey player. He joined Dynamo Moscow, a professional team, at 16, and led Russia to a junior championship. A Washington Capitals first-round pick i...

plane

(Encyclopedia)plane, in mathematics, flat surface of infinite extent but no thickness. An example of a plane, or more exactly of a bounded portion of a plane, is the surface forming one face, or side, of a cube. A ...

Andersen, Hans Christian

(Encyclopedia)Andersen, Hans Christian, 1805–75, Danish poet, novelist, and writer of fairy tales. Born to an illiterate washerwoman and reared in poverty, he left Odense at 14 for Copenhagen, where he lived with...

Royal Danish Ballet

(Encyclopedia)Royal Danish Ballet, one of the oldest major ballet companies, established at the opening of Denmark's Royal Theater in Copenhagen in 1748. Its ballet school, which trains the group's dancers, has als...

Cleaver, Eldridge

(Encyclopedia)Cleaver, Eldridge (Leroy Eldridge Cleaver), 1935–98, African-American social activist, b. Wabbaseka, Ark. Growing up in Los Angeles, he spent much of 1954–66 in prison for various crimes including...

hafnium

(Encyclopedia)hafnium hăfˈnēəm [key], metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227℃; b.p. 4,602℃; sp. gr. 13.31 at 20℃; valence +4. Hafnium is a lustrous, ductile, si...

Böhm-Bawerk, Eugen

(Encyclopedia)Böhm-Bawerk, Eugen oigānˈ bömˈ-bäˈvĕrk [key], 1851–1914, Austrian economist. Three times minister of finance (1895, 1897, and 1900), he initiated important tax reforms and farsighted financi...