rational number Any number that can be represented as the quotient of two integers (i.e., the denominator cannot equal zero). The set of ratio¬ nal numbers includes all integers as well as all fractions. In decimal form, rational numbers are either terminating or repeating decimals.
rational psychology Metaphysical discipline that attempted to deter¬ mine the nature of the human soul by a priori reasoning. In Christian Wolff’s division of metaphysics, rational psychology was one of three disciplines included under the heading of “special metaphysics” (the others being rational cosmology and rational theology). Immanuel Kant, in his Critique of Pure Reason , criticized the pretensions of rational psychology.
rationalism Philosophical view that regards reason as the chief source and test of knowledge. Rationalism has long been the rival of empiricism, the doctrine that all knowledge of matters of fact ultimately derives from, and must be tested by, sense experience. As against this doctrine, ratio¬ nalism holds reason to be a faculty that can lay hold of truths beyond the reach of sense perception, both in certainty and in generality. In stressing the existence of a “natural light,” rationalism also has been the rival of systems claiming esoteric knowledge, whether from mystical experience, revelation, or intuition, and has been opposed to various irrationalisms that tend to stress the biological, the emotional or volitional, the uncon¬ scious, or the existential at the expense of the rational.
rationing Government allocation of scarce resources and consumer goods, usually adopted during wars, famines, or other national emergen¬ cies. Rationing according to use prohibits the less important uses of a com¬ modity (e.g., the use of gasoline for pleasure trips as opposed to work- related travel). Rationing by quantity limits the amounts of a commodity available to each claimant (e.g., a pound of butter per month). Rationing by value limits the amount of money consumers can spend on commodities that are difficult to standardize (e.g., clothing). Point rationing assigns a point value to each commodity and allocates a certain number of points to each consumer. These can be tracked through coupons, which are issued to consumers and must be exchanged for the approved amounts of rationed goods. Consumers in a rationed economy are usually encouraged to save their money or invest in government bonds so that unspent money will not be used for unrationed items or purchases on the black market.
ratite \'ra-,tlt\ Any bird species that cannot fly because its smooth, or raftlike, sternum (breastbone) lacks a keel to which flight muscles can be anchored. The group includes some of the largest birds of all time. Two extinct types, the slow-moving, heavy-bodied elephant bird of Madagas¬ car and the moas of New Zealand, grew to 10 ft (3 m) tall. Extant ratites include the cassowary, emu, kiwi, ostrich, and rhea.
Rattigan, Sir Terence (Mervyn) (b. June 10, 1911, London, Eng.—d. Nov. 30, 1977, Hamilton, Bermuda) British playwright. After writing two comedies, he won acclaim for the drama The Winslow Boy (1946; film, 1948). His best-known work, Separate Tables (1955; film, 1958), explores the isolation created by rigidly imposed social conven¬ tions. His other plays include The Browning Version (1948), Ross (1960), and A Bequest to the Nation (1970). He wrote screenplays for the film adaptations of his plays and for The Yellow Rolls-Royce (1965) and Good¬ bye Mr. Chips (1969).
rattlesnake Any of about 30 spe¬ cies in two genera of New World pit vipers having a tail rattle that pro¬ duces a buzzing sound when vibrated. The rattle is composed of horny, loosely connected segments added one at a time with each molt.
Sistrurus species have large scales on the top of the head. Crotalus spe¬ cies have mostly small scales on the head. Species range from 1 to 8 ft (30 to 250 cm) long. Most eat small ani¬ mals, primarily rodents, birds, and lizards. All bear live young. In hot
Norway rat (Rattus norvegicus).
JOHN H. GERARD
Aesculapian snake (Elaphe longis- sima).
ANTON THAU-BAVARIA VERLAG
© 2006 Encyclopaedia Britannica, Inc.
Ratzenhofer ► ray I 1593
areas rattlesnakes become nocturnal; in cold areas they hibernate in groups. Heat-sensitive organs on the sides of the head help them locate and strike their prey. A rattlesnake bite is painful and can be fatal if not treated. See also sidewinder.
Ratzenhofer, Gustav (b. July 4, 1842, Vienna—d. Oct. 8, 1904, at sea) Austrian general, philosopher, and sociologist. After a successful military career in which he attained the rank of field marshal, he devel¬ oped an interest in the social sciences, particularly social Darwinism. He believed human interaction was characterized by “absolute hostility” between ethnic groups but that the species could evolve higher forms of association through sociology. His works included The Essence and Objective of Politics, 3 vol. (1893), and Sociological Perception (1898).
Rauschenberg Vrau-shsn-.bergV Robert orig. Milton Rauschen¬ berg (b. Oct. 22, 1925, Port Arthur, Texas, U.S.) U.S. painter and graphic artist. He studied under Josef Albers. His “combine” paintings of the 1950s, incorporating objects such as soda bottles, traffic barricades, and stuffed birds, anticipated the Pop art movement. In later work, he used silkscreen and other techniques to transfer images from commercial print media and his own photographs to canvas, reinforcing the images and unifying them compositionally with bold strokes of paint. His work has roots in Dada and the ready-mades of Marcel Duchamp.
Ravana Vra-vo-noV In Hinduism, king of the demons. Ravana is depicted with 10 heads and 20 hands and flying a magic chariot. He ruled in the kingdom of Lanka, from which he had expelled his brother Kubera. His abduction of Sita and defeat by her husband, Rama, are the central events of the epic Ramayana.
The demon king is also remembered for shaking Mount Kailasa until Shiva intervened and imprisoned him beneath it for 1,000 years. The popu¬ lar annual Ram Lila festival cli¬ maxes with the defeat of Ravana and the burning of huge effigies of demons.
Ravel \ra-'vel\, (Joseph-) Mau¬ rice (b. March 7, 1875, Ciboure,
France—d. Dec. 28, 1937, Paris)
French composer. At age 14 he was admitted to the Paris Conservatoire.
Completing his piano studies, he returned to study composition with Gabriel Faure, writing the important 1901) and a string quartet. In the next decade he produced some of his best-known music, including Pavane pour une infante defunte (1899), the String Quartet (1903), and the Sonatine for piano (1905). His great bal¬ let Daphnis et Chloe (1912) was commissioned by the impresario Sergey Diaghilev. Other works include the opera L ’Enfant et les sortileges (1925), the suite Le Tombeau de Couperin (1917), and the orchestral works La Valse (1920) and Bolero (1928). Careful and precise. Ravel possessed great gifts as an orchestrator, and his works are universally admired for their superb craftsmanship; he has remained the most widely popular of all French composers.
raven Any of several species (genus Corvus, crow family Corvidae) of heavy-billed, usually solitary, songbirds, once abundant throughout the Northern Hemisphere but now restricted to undisturbed areas. The com¬ mon raven (C. corax), the biggest passerine, grows to 26 in. (66 cm) long and has a wingspan of more than 4 ft (1.3 m). The dark, iridescent plum¬ age is shaggy, especially around the throat. Ravens eat rodents, insects, grain, birds’ eggs, and, in winter, carrion and refuse. Captive nestlings may learn to mimic a few words. The large nest, a crude structure of sticks, is built high on a cliff or treetop.
Ravenna Nro-'ve-noN City (pop., 2001 prelim.: 138,204), northeastern Italy. It is located inland from the Adriatic Sea, with which it is connected by a canal. It was the capital of the Western Roman Empire in the 5th century ad and of the Ostrogothic kingdom and Byzantine Italy in the 6th-8th centuries. Ravenna’s art and architecture reflect a fusion of Roman forms with Byzantine mosaics and other decoration; sites include the 6th-century basilica of Sant’Apollinare Nuovo and the octagonal