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angstrom

(Encyclopedia)angstrom ăngˈstrəm [key], abbr. Å, unit of length equal to 10−10 meter (0.0000000001 meter); it is used to measure the wavelengths of visible light and of other forms of electromagnetic radiatio...

epoch

(Encyclopedia)epoch, unit of geologic time that is a subdivision of a period. The Pleistocene and Holocene epochs, for example, are divisions of the Quaternary period. Epoch is also used to describe a short length ...

charter

(Encyclopedia)charter, document granting certain rights, powers, or functions. It may be issued by the sovereign body of a state to a local governing body, university, or other corporation or by the constituted aut...

barn

(Encyclopedia)barn, abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleus for collisions leading to nuclear reactions; it is equal to 10−24 square centimeters. The ...

Ohm, Georg Simon

(Encyclopedia)Ohm, Georg Simon gāˈôrkh zēˈmôn ōm [key], 1787–1854, German physicist. He was professor at Munich from 1852. His study of electric current led to his formulation of the law now known as Ohm's...

South Pass

(Encyclopedia)South Pass, broad, level valley (alt. c.7,550 ft/2,301 m), SW Wyo., cutting across the Rocky Mts. It was used by trappers and explorers before Jedediah Smith inaugurated its use as a route for settler...

equivalent weight

(Encyclopedia)equivalent weight. The equivalent weight of an element or radical is equal to its atomic weight or formula weight divided by the valence it assumes in compounds. The unit of equivalent weight is the a...

syndicalism

(Encyclopedia)syndicalism sĭnˈdĭkəlĭzəm [key], political and economic doctrine that advocates control of the means and processes of production by organized bodies of workers. Like anarchists, syndicalists bel...

Columbia basin project

(Encyclopedia)Columbia basin project, central Wash., a multipurpose development of the U.S. Bureau of Reclamation providing irrigation, hydroelectric power, and flood control. Its key unit, the Grand Coulee Dam, pr...

parsec

(Encyclopedia)parsec pärˈsĕc [key] [parallax + second], in astronomy, basic unit of length for measuring interstellar and intergalactic distances, equal to 206,265 times the distance from the earth to the su...