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Herzberg, Gerhard

(Encyclopedia)Herzberg, Gerhard gĕrˈhärt hûrtsˈbûrg [key], 1904–99, Canadian physicist, b. Hamburg, Germany. He studied at Darmstadt, Göttingen, and Bristol, England, receiving a doctorate in engineering p...

transmission

(Encyclopedia)transmission, in automobiles, system of parts connecting the engine to the wheels. Suitable torque, or turning force, is generated by the engine only within a narrow range of engine speeds, i.e., rate...

Prometheus, in astronomy

(Encyclopedia)Prometheus prōmēˈthēəs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XVI (or S16), Prometheus is an irregularly shaped (nonspherical) body me...

Lewis, C. S.

(Encyclopedia)Lewis, C. S. (Clive Staples Lewis), 1898–1963, English author, b. Belfast, Ireland. A fellow and tutor of English at Magdalen College, Oxford, from 1925 to 1954, C. S. Lewis was noted equally for hi...

altitude

(Encyclopedia)altitude, vertical distance of an object above some datum plane, such as mean sea level or a reference point on the earth's surface. It is usually measured by the reduction in atmospheric pressure wit...

Sagan, Carl Edward

(Encyclopedia)Sagan, Carl Edward sāˈgən [key], 1934–96, American astronomer and popularizer of science, b. New York City. Early in his career he investigated radio emissions from Venus and concluded that the c...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...

Roche limit

(Encyclopedia)Roche limit, the closest distance that a celestial body held together only by its own gravity can come to a planet without being pulled apart by the planet's tidal (gravitational) force. This distance...

Tombaugh, Clyde William

(Encyclopedia)Tombaugh, Clyde William tŏmˈbô [key], 1906–97, American astronomer, b. Streator, Ill. Although lacking formal training or a college degree, he was hired in 1929 as an assistant by the Lowell Obse...

numeration

(Encyclopedia)numeration, in mathematics, process of designating numbers according to any particular system; the number designations are in turn called numerals. In any place value system of numeration, a base numb...