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arc, in electricity

(Encyclopedia)arc, in electricity, highly luminous and intensely hot discharge of electricity between two electrodes. The arc was discovered early in the 19th cent. by the English scientist Sir Humphry Davy, who so...

PET scan

(Encyclopedia)PET scan pŏzˈĭtrŏnˌ ĭmĭshˈən təmŏgˈrəfē [key], a medical imaging technique that monitors metabolic, or biochemical, activity in the brain and other organs by tracking the movement and co...

Weinberg, Steven

(Encyclopedia)Weinberg, Steven, 1933–, American nuclear physicist, b. New York City, Ph.D. Princeton, 1957. Since 1982 he has been a professor at the Univ. of Texas at Austin, having previously been on the facult...

motion

(Encyclopedia)motion, the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; ...

Love Canal

(Encyclopedia)Love Canal, section of Niagara Falls, N.Y., that formerly contained a canal that was used as chemical disposal site. In the 1940s and 50s the empty canal was used by a chemical and plastics company to...

Maxwell, James Clerk

(Encyclopedia)Maxwell, James Clerk klärk [key], 1831–79, great Scottish physicist. After a brilliant career at Edinburgh and Cambridge, where he won early recognition with mathematical papers, he was a professor...

Durkheim, Émile

(Encyclopedia)Durkheim, Émile dûrkˈhīm, Fr. āmēlˈ dürkĕmˈ [key], 1858–1917, French sociologist. Along with Max Weber he is considered one of the chief founders of modern sociology. Educated in France an...

harmony

(Encyclopedia)harmony, in music, simultaneous sounding of two or more tones and, especially, the study of chords and their relations. Harmony was the last in the development of what may be considered the basic elem...

physics

(Encyclopedia)physics, branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this na...

astatine

(Encyclopedia)astatine ăsˈtətēn, –tĭn [key] [Gr.,=unstable], semimetallic radioactive chemical element; symbol At; at. no. 85; at. wt. of most stable isotope 210; m.p. 302℃ (estimated); b.p. 337℃ (estima...