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cosmology

(Encyclopedia)cosmology, area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. The earliest pre-Ptolemaic theories assumed that the earth was the cent...

radioactivity

(Encyclopedia)CE5 Effects of a magnetic field on the products of radioactivity CE5 Disintegration series: Radioactive decay of radium-226 into lead-206 radioactivity, spontaneous disintegration or decay of t...

Mississippi, river, United States

(Encyclopedia)Mississippi, river, principal river of the United States, c.2,350 mi (3,780 km) long, exceeded in length only by the Missouri, the chief of its numerous tributaries. The combined Missouri-Mississippi ...

comet

(Encyclopedia)CE5 Comet: Whatever the direction of a comet's flight, its “tail” always points away from the sun. The tail disappears when the comet is far from the sun. comet [Gr.,=longhaired], a small cele...

cold war

(Encyclopedia)cold war, term used to describe the shifting struggle for power and prestige between the Western powers and the Communist bloc from the end of World War II until 1989. Of worldwide proportions, the co...

radio

(Encyclopedia)CE5 A. AM transmitter B. AM receiver radio, transmission or reception of electromagnetic radiation in the radio frequency range. The term is commonly applied also to the equipment used, especially...

Rousseau, Jean Jacques

(Encyclopedia)Rousseau, Jean Jacques ro͞osōˈ [key], 1712–78, Swiss-French philosopher, author, political theorist, and composer. Rousseau's influence on posterity has been equaled by only a few, and it is...

space exploration

(Encyclopedia)CE5 Moon mission assembly CE5 Stages in a moon mission shown counterclockwise from launching on the first day to splashdown on the ninth day. space exploration, the investigation of physical co...

nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

theater

(Encyclopedia)CE5 Plan of Greek amphitheater CE5 Proscenium theater CE5 Theater-in-the-round theater, building, structure, or space in which dramatic performances take place. In its broadest sense theater...