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retrograde motion

(Encyclopedia)retrograde motion, in astronomy, real or apparent movement of a planet, dwarf planet, moon, asteroid, or comet from east to west relative to the fixed stars. The most common direction of motion in the...

geophysics

(Encyclopedia)geophysics, study of the structure, composition, and dynamic changes of the earth, its atmosphere, hydrosphere and magnetosphere, based on the principles of physics. The term was probably first used i...

Hutton, James

(Encyclopedia)Hutton, James, 1726–97, Scottish geologist, chemist, and naturalist. He was initially attracted to chemistry; he entered the legal profession at the Univ. of Edinburgh; turned to medicine, as it clo...

Clarke, Arthur C.

(Encyclopedia)Clarke, Arthur C. (Sir Arthur Charles Clarke), 1917–2008, British science fiction writer. During World War II he served as a radar instructor and aviator in the Royal Air Force. After the war he obt...

phase, in astronomy

(Encyclopedia)CE5 Phases of the moon phase, in astronomy, the measure of how much of the illuminated surface of a planet or satellite can be seen from a point at a distance from that body; the term is most ofte...

geochemistry

(Encyclopedia)geochemistry, study of the chemical changes on the earth. More specifically, it is the study of the absolute and relative abundances of chemical elements in the minerals, soils, ores, rocks, water, an...

San Andreas fault

(Encyclopedia)San Andreas fault, great fracture (see fault) of the earth's crust in California. It is the principal fault of an intricate network of faults extending more than 600 mi (965 km) from NW California to ...

trade winds

(Encyclopedia)trade winds, movement of air toward the equator, from the NE in the Northern Hemisphere and from the SE in the Southern Hemisphere. The trade winds originate on the equatorial sides of the horse latit...

celestial sphere

(Encyclopedia)celestial sphere, imaginary sphere of infinite radius with the earth at its center. It is used for describing the positions and motions of stars and other objects. For these purposes, any astronomical...

planet

(Encyclopedia)planet [Gr.,=wanderer], a large nonluminous body of rock, gas, or ice that orbits the sun or another star, has a rounded shape due to gravity, and has cleared its orbit of smaller objects. The term, o...