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sand dollar

(Encyclopedia)sand dollar, common name for a marine animal in the same phylum as the starfish (see sea star). The sand dollar has a rigid, flattened, disk-shaped test, or shell, made of firmly united plates lying j...

thermionic emission

(Encyclopedia)thermionic emission thûrmˌīŏnˈĭk [key], emission of electrons or ions by substances that are highly heated, the charged particles being called thermions. The number of thermions emitted increase...

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...

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...

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...

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...