Orpheus Greek legendary hero who sang and played the lyre so beauti¬ fully that animals, trees, and rocks danced around him. When his wife, Eurydice, was killed by a snake, he went to the underworld in search of her, and his music and grief so moved Hades that he agreed to let Orpheus take Eurydice back to the land of the living on the condition that neither of them look back as they left. On seeing the Sun, Orpheus turned to share his delight with Eurydice, and she disappeared. Orpheus was later torn to pieces by maenads, and his head, still singing, floated to Lesbos, where an oracle of Orpheus was established. By the 5th century bc, a Hellenistic mys¬ tery religion (the Orphic mysteries), based on Orpheus’s songs and teach¬ ings, had arisen. His story became the subject of some of the earliest operas.
Orphic mysteries See mystery religions
Orphism Trend in Cubism that gave priority to colour. Its name, bestowed in 1912 by Guillaume Apollinaire, recalls not only the legendary Orpheus but the Symbolist painters’ description of Paul Gauguin’s use of colour as “Orphic art.” Among the painters who worked in this style were Robert Delaunay, Fernand Leger, Francis Picabia, and Marcel Duchamp. The best-known example is Delaunay’s abstract Simultaneous Composition: Sun Disks (1912-13), in which superimposed circles of colour have their own rhythm and movement.
Orr, Bobby in full Robert Gordon Orr (b. March 20, 1948, Parry Sound, Ont., Can.) Canadian-born U.S. ice-hockey player. He was signed to a junior amateur contract by Boston Bruins scouts when he was 12. He joined the Bruins in 1966 and played with them for 10 seasons, helping them to the playoffs in eight consecutive seasons and to two Stan¬ ley Cup victories (1970, 1972). The first defenseman to lead the National Hockey League in scoring (1970,
1975), he is the only player ever rec¬ ognized as the most valuable defen¬ seman eight years in a row (1967-68 to 1974-75).
Orsted Voer-stodV Hans Christian (b. Aug. 14, 1777, Rudkpbing, Den.—d. March 9, 1851, Copenhagen) Danish physicist and chemist. In
1820 he discovered that electric current in a wire can deflect a magne¬ tized compass needle, a phenomenon that inspired the development of electromagnetic theory. His 1820 discovery of piperine, one of the pun¬ gent components of pepper, was an important contribution to chemistry, as was his preparation of metallic aluminum in 1825. In 1824 he founded a society devoted to the spread of scientific knowledge among the gen¬ eral public. In 1932 the oersted was adopted as the physical unit of mag¬ netic field strength.
Ortega \or-'ta-go\ (Saavedra), (Jose) Daniel (b. Nov. 11, 1945, La Libertad, Nic.) President of Nicaragua (1984-90). In 1963 he became a member of the Sandinista National Liberation Front and organized urban resistance to the corrupt dictatorship of the Somoza family. Jailed and later exiled, he returned secretly to Nicaragua and helped unite opposition to Somoza. After the Sandinistas prevailed in 1979, he coordinated the rul¬ ing junta; in 1984 he was elected Nicaragua’s president. U.S. efforts to destabilize his government led to economic hardship and a protracted war, and Ortega lost his bid for reelection in 1990, 1996, and again in 2001. See also Violeta Chamorro; contras.
Ortega y Gasset Vor-'ta-ga-e-ga-'setX, Jose (b. May 9, 1883, Madrid, Spain—d. Oct. 18, 1955, Madrid) Spanish philosopher. He taught at the University of Madrid from 1911 and lived abroad from 1931 to 1946. Though influenced by Neo- Kantianism, he diverged from it in works such as Adam in Paradise (1910), Quixote’s Meditations (1914), and Modern Theme (1923). He saw individual life as the fundamental reality; for abso¬ lute reason he substituted reason as a function of life; for absolute truth he substituted the perspective of each individual. Sharing his generation’s preoccupation with Spain’s problems, he founded the periodicals Espaha (1915), El sol (1917), and Revista de Occidente (1923). Of his other works, the best known are Invertebrate Spain (1922) and The Revolt of the Masses (1929), which foreshadowed the Spanish Civil War. He greatly influenced Spain’s 20th-century cultural and literary renaissance.
orthoclase V6r-th3-,klas\ Common alkali feldspar mineral, potassium aluminosilicate (KAlSi 3 O g ), that usually occurs as variously coloured grains in granite. Orthoclase is used in the manufacture of glass and ceramics; occasionally, transparent crystals are cut as gems. It is prima¬ rily important as a rock-forming mineral, however, and is abundant in IGNEOUS ROCKS, PEGMATITES, and GNEisses. The feldspar minerals con¬ sist of sodium, potassium, and cal¬ cium aluminosilicates, and any feldspar may be chemically classed by the percentage of each of these three pure compounds, called end- members. Orthoclase is the potassium-bearing end-member of the sys¬ tem. Microcune is a lower temperature structural form of the same chemical composition as orthoclase.
Orthodox Catholic Church See Eastern Orthodoxy
Orthodox Judaism Religion of Jews who adhere strictly to tradi¬ tional beliefs and practices; the official form of Judaism in Israel. Ortho¬ dox Jews hold that both the written law (Torah) and the oral law (codified in the Mishna and interpreted in the Talmud) are immutably fixed and remain the sole norm of religious observance. Orthodox Judaism has held fast to such practices as daily worship, dietary laws, intensive study of the Torah, and separation of men and women in the synagogue. It also enjoins strict observance of the Sabbath and does not permit instrumental music during communal services. A leading center of Orthodoxy in the U.S. is New York’s Yeshiva Univ.
orthogonal polynomials A system of polynomials that are mutually orthogonal (orthogonality is the higher-dimensional analog of perpen¬ dicularity), useful in solving differential equations arising in physics and engineering. The study of such systems began with Adrien-Marie Le¬ gendre (1752-1833), who employed a system now known as Legendre polynomials in the solution of problems in celestial mechanics. Other famous examples are the sets of Hermite and Chebyshev polynomials.
orthogonality Xor-.tha-go-'na-lo-teV In mathematics, a property syn¬ onymous with perpendicularity when applied to vectors but applicable
Orr (number 4), 1968
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Orthoclase from Serra de Peneda, Portugal
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1420 I orthopedics ► Osceola
more generally to functions. Two elements of an inner product space are orthogonal when their inner product—for vectors, the dot product (see vector operations); for functions, the definite integral of their product—is zero. A set of orthogonal vectors or functions can serve as the basis of an inner product space, meaning that any element of the space can be formed from a linear combination (see linear transformation) of the elements of such a set.
orthopedics \,6r-th3-'pe-diks\ or orthopedic surgery Medical specialty concerned with the skeleton and its associated structures. Ortho¬ pedists treat fractures, strained muscles, torn ligaments and tendons, and other injuries and deal with acquired and congenital skeletal deformities and the effects of degenerative diseases such as osteoarthritis. Originally dependent on heavy braces and splints, orthopedics now uses bone grafts, hip and other joint replacements, prostheses (see prosthesis), special foot¬ wear, and braces to enhance mobility. Orthopedics uses the techniques of PHYSICAL MEDICINE AND REHABILITATION and OCCUPATIONAL THERAPY in addition tO those of traditional medicine and surgery.