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seeing

(Encyclopedia)seeing, in astronomy, the clarity with which stars and other celestial objects can be observed. It is primarily determined by the atmosphere of the earth. The most obvious phenomenon is twinkling, whe...

Airy, Sir George Biddell

(Encyclopedia)Airy, Sir George Biddell, 1801–92, English astronomer. The son of a poor farmer, he distinguished himself as Senior Wrangler at Cambridge, where he was elected fellow of Trinity College (1824) and a...

Schuster, Sir Arthur

(Encyclopedia)Schuster, Sir Arthur, 1851–1934, English physicist, b. Germany. At Owens College, Manchester Univ., he was professor of applied mathematics (1881–88) and professor of physics (1888–1907). He is ...

Zeeman, Pieter

(Encyclopedia)Zeeman, Pieter pēˈtər zāˈmän [key], 1865–1943, Dutch physicist. He was professor of physics at the Univ. of Amsterdam from 1900 and director of the Physical Institute, Amsterdam, from 1908. In...

cable

(Encyclopedia)cable, originally wire cordage of great strength or heavy metal chain used for hauling, towing, supporting the roadway of a suspension bridge, or securing a large ship to its anchor or mooring. Today ...

Gullstrand, Allvar

(Encyclopedia)Gullstrand, Allvar älˈvär gŭlˈstränd [key], 1862–1930, Swedish ophthalmologist. He was professor (1894–1927) successively of eye therapy and of optics at the Univ. of Uppsala. He applied the...

focus

(Encyclopedia)focus, in optics, the point at which rays converge after reflection by a concave mirror or refraction by a convex lens, also known as a real focus. The point from which rays appear to diverge after re...

Vavilov, Sergei Ivanovich

(Encyclopedia)Vavilov, Sergei Ivanovich vəvēˈləf [key], 1891–1951, Russian physicist. In 1932 he became director of the P. N. Lebedev Physical Institute, which he organized around the laboratory of the Sovie...

synthetic textile fibers

(Encyclopedia)synthetic textile fibers have revolutionized the textile industry. Such artificial fibers are usually long-chain polymers, produced industrially by the condensation of many small units. Orlon is the t...

acrylic

(Encyclopedia)acrylic, artificial fiber made from a special group of vinyl compounds, primarily acrylonitrile. Acrylic fibers are thermoplastic (i.e., soften when heated, reharden upon cooling), have low moisture r...