Providence (pop. 156,200), capital of Rhode Island, on the Providence River at the head of Narragansett Bay. The second-largest city in New England (after Boston), Providence is an important industrial, commercial, and education center. Its port is among the busiest in New England. Its major industries include jewelry, silverware, textiles, machinery, and metal products. Brown University is locate…
Province, region governed or administered by a country, empire, or diocese.
Provincetown See: Cape Cod; Mayflower.
Provo (pop. 263,590), a city in Utah and the seat of Utah County.
Prud'hon, Pierre Paul (1758–1823), French painter.
Prune, dried plum.
Pruning, the cutting away of a plant's branches, shoots, buds, or roots.
Prussia, state in north central Europe that became the foundation of the modern state of Germany. At the height of its strength it stretched from west of the Rhine to Poland and Russia. The Baltic territory later known as East Prussia was Germanized by the Teutonic Knights in the 1200s and later became the duchy of Prussia. In 1618 it came under the rule of the Electors of nearby Brandenburg, the …
Prussian blue, category of deep-blue pigments containing ferrocyanide.
Prussic acid (HCN), also called hydrocyanic acid, a colorless, highly toxic, aqueous solution of hydrogen cyanide.
Przewalski's horse, or Eastern wild horse, last remaining race of true wild horses.
Psalms, Book of, collection of 150 songs in the Old Testament, used as the hymn book of Judaism since the return from exile and prominent in Christian liturgy.
Psi particle, subatomic particle consisting of a charmed quark and an anticharmed quark bonded by their opposite electric charges and a strong nuclear force, or strong interaction.
Psittacosis, infectious atypical form of pneumonia caused by Chlamydia psittaci and transmitted by certain birds.
Psoriasis, skin condition characterized by patches of red, thickened, and scaling skin.
Psychedelics See: Hallucinogenic drug.
Psychiatry, field of medicine concerned with the study and treatment of mental disorders, including neurosis and psychosis.
Psychical research, field of study concerned with the evaluation of phenomena having to do with so-called extrasensory perception.
Psychoanalysis, system of psychology having as its base the theories of Sigmund Freud; also the psychotherapeutic technique based on that system. The distinct forms of psychoanalysis developed by Carl Jung and Alfred Adler are more correctly termed analytical psychology and individual psychology, respectively. Freud's initial interest was in the origins of neuroses. On developing the techni…
Psychological warfare, various propaganda methods directed at a nation's enemy.
Psychology, originally the branch of philosophy dealing with the mind, then the science of mind, and now, considered in its more general context, the science of behavior, whether human or animal, and of human thought processes. Psychology is closely connected with medicine, psychiatry, and sociology. There are a number of closely interrelated branches of human psychology. Experimental psychology e…
Psychosis, any mental disorder that, whether neurological or purely psychological in origin, renders an individual incapable of distinguishing reality from fantasy.
Psychosomatic medicine, that aspect of medical treatment that considers the emotional and mental component of physical illness.
Psychotherapy, application of the theories and discoveries of psychology to the treatment of mental illness, particularly in the form of some sort of relationship between the therapist and the patient.
Psyllium, herb belonging to the plantain family, Plantagnaceae.
PT boat, small, manueverable boat used by the U.S.
Ptarmigan, any of several birds of the grouse family that can be identified by their white wings and underparts.
Pteranodon See: Pterosaur.
Pteridophyte, class of plants that produce spores and have roots, stems, and leaves.
Pterosaur, member of a group of flying reptiles that lived 195–65 million years ago, during the Mesozoic era.
Ptolemy, or Claudius Ptolemaeus (2nd century A.D.), Alexandrian astronomer, mathematician, and geographer.
Ptolemy, name used by all 15 Egyptian kings of the Macedonian dynasty (323 B.C.–30 B.C.). Ptolemy I Soter (367 B.C.–283 B.C.) was one of Alexander the Great's generals. He secured Egypt for himself after Alexander's death and defended it in a series of wars against Alexander's other generals. He founded the library of Alexandria, which became a center of Hellenis…
Ptomaine poisoning, type of food poisoning caused by spoiled foods.
Pu Yi (1906–67), as Hsuan T'ung, the last emperor (1908–12) of China.
Puberty See: Adolescence.
Public domain, in U.S. law, ownership of a property or resource by the people.
Public health, organization and practice of preventative medicine within a community.
Public lands, land areas owned by the U.S. government, especially those it sells or leases to individuals.
Public opinion, opinions held by many people on issues of local, national, or worldwide importance.
Public opinion poll, technique for measuring the range of opinions held by the general public or by specifically limited groups of people.
Public relations (PR), general term for fostering goodwill for a person, corporation, institution, or product without actually paying for advertisements.
Public utility, business that performs a service for the public and is subject to government regulation.
Public Works Administration (PWA), or Federal Emergency Administration of Public Works, a New Deal agency set up in 1933 to stimulate employment and purchasing power.
Publishing, preparation, manufacture, and distribution of printed materials.
Puccini, Giacomo (1858–1924), Italian opera composer.
Pudding stone, kind of conglomerate rock.
Puebla (pop. 646,600), capital of Puebla, Mexico.
Puebla, state of Mexico, in central Mexico, near Mexico City.
Pueblo (pop. 123,051), city in southeastern Colorado and the seat of Pueblo County.
Pueblo, several Native American tribes living in southwestern United States (Arizona and New Mexico) in permanent villages (pueblos).
Puerto Rico, officially the Commonwealth of Puerto Rico, island in the Caribbean Sea. Puerto Rico is the smallest and easternmost island of the Greater Antilles, the other members of which are Cuba, Jamaica, and Hispaniola. It is about 950 mi (1,529 km) southeast of Miami, Florida and 550 mi (885 km) north of Caracas, Venezuela. A number of offshore islands, including Vieques, Culebra, and Mona, a…
Puff adder See: Adder.
Puffball, fungus of the family Lycoperdaceae.
Puffer, or globe fish, fish that blows up its body like a balloon.
Pufin, any of several stubby seabirds of the auk family.
Pug, breed of toy dog.
Pugachev, Emelian Ivanovich (1742–75), Cossack leader of the great Urals peasant revolt (1773–74).
Puget, Peter (1762?–1822), British naval officer and explorer.
Puget Sound, irregular inlet of the Pacific Ocean in northwestern Washington.
Pulaski, Casimir (c.1748–79), Polish soldier, hero of the anti-Russian revolt of 1768 who, exiled from Poland, fought in the American Revolutionary War.
Pulitzer, Joseph (1847–1911), Hungarian-born U.S. publisher who created the Pulitzer Prizes.
Pulitzer Prizes, awards for achievement in U.S. journalism and letters, given every May since 1917 through a foundation created by the estate of Joseph Pulitzer and administered by Columbia University.
Pulley, grooved wheel mounted on a block with a cord or belt passing over it.
Pullman, George Mortimer (1831–97), U.S. industrialist and inventor of the first modern railroad sleeping car, the Pullman (patented 1864).
Pullman Strike (May-July 1894), famous boycott of rolling stock of the Pullman Palace Car Co., Pullman, Ill., by E.V.
Pulsar, short for pulsating radio star, a celestial radio source emitting brief, extremely regular pulses of electromagnetic radiation.
Pulse, throb in the artery walls due to the beating of the heart.
Puma, cougar, panther, or mountain lion (Felis concolor), the most widespread of the big cats of the Americas, occupying an amazing variety of habitats.
Pumice, porous, frothy, volcanic glass formed by the sudden release of vapors as lava cools under low pressure.
Pump, device for taking in and forcing out a fluid, thus giving it kinetic or potential energy. The heart is a pump for circulating blood around the body. The steam engine was developed to power pumps for pumping out mines. Piston pumps—the simplest of which is the syringe—are reciprocating volume displacement pumps, as are diaphragm pumps, with a pulsating diaphragm instead of the p…
Pumpkin, plant (genus Cucurbita) of the gourd family.
Punch and Judy, leading characters in a children's handpuppet show of the same name.
Punic Wars, 3 conflicts between Carthage and Rome.
Punishment See: Capital punishment.
Punjab (Sanskrit, “five rivers”), large wheat-growing region in the northwest of the Indian subcontinent, on the upper Indus River plain.
Pupa, immature stage in the development of those insects whose larval form is completely different in structure from the adult form and in which complete metamorphosis occurs.
Pupfish, about 30 species of fish (genus Cyprinodon) belonging to the killifish family.
Pupil See: Eye.
Puppet, figure of a person or animal manipulated in dramatic presentations.
Purcell, Edward Mills (1912–97), U.S. physicist who shared the 1952 Nobel Prize for physics for his discovery of nuclear magnetic resonance (NMR) in solids.
Purcell, Henry (c.1659–95), English composer, the foremost of his time.
Pure food and drug laws, in the United States, general term for laws such as the Federal Food, Drug and Cosmetic Act (1938) prohibiting the distribution of impure foods and drugs and the false or misleading labeling of such products.
Purgatory, in Roman Catholicism, the place where Christians after death undergo purifying punishment and expiate unforgiven venial sins before admission to heaven.
Purim (Feast of Lots), Jewish festival of the 14th day of Adar (Feb.–Mar.), a celebration of the deliverance from massacre of Persian Jews through intervention by Esther and Mordecai.
Puritans, English reforming Protestants who aimed for a simpler form of worship expressly warranted by Scripture, devout personal and family life, and the abolition of clerical hierarchy. They stressed self-discipline, work as a vocation, and the Christianizing of all spheres of life. Most were strict Calvinists. The term was first used in the 1560s for those dissatisfied with the compromise of th…
Purple Heart See: Decorations, medals, and orders.
Purus River, third-longest river in South America and a major tributary of the Amazon River.
Pusan (pop. 3,798,100), second-largest city in South Korea, in the southeast.
Pushkin, Alexander (1799–1837), poet, widely recognized as the founder of modern Russian literature.
Pushtuns, ethnic group comprising about one half the population of Afghanistan and one fifth the population of Pakistan.
Pussy willow, small tree (Salix discolor) particular to North America and characterized by a silky, often drooping flower cluster called a catkin, produced in the early spring.
Putnam, Israel (1718–90), U.S. patriot and general in the Revolutionary War.
Putnam, Rufus (1738–1824), U.S. pioneer who served in the French and Indian Wars and in many of the engagements of the Revolutionary War.
PVC See: Vinyl.
Pygmalion, in Greek mythology, king of Cyprus who carved a statue of a beautiful woman and then fell in love with it.
Pygmy, term used to denote those people whose adult males are on average less than 5 ft (1.52 m) tall.
Pyle, Ernie (Ernest Taylor Pyle; 1900–45), U.S. journalist and war correspondent.
Pyle, Howard (1853–1911), U.S. writer and illustrator of children's books, such as The Merry Adventures of Robin Hood (1883) and The Story of King Arthur and His Knights (1903).
Pylos (modern Greek Pilos, formerly Navarino), ancient port in the southwestern Peloponnese, Greece, site of a Mycenaean palace of the 13th century B.C., associated with king Nestor.
Pym, John (1584–1643), English statesman.
Pynchon, Thomas (1937– ), U.S. novelist whose works, influenced by James Joyce and Vladimir Nabokov, are noted for their ingenious wordplay and complexity.
Pyongyang (pop. 2,000,000), capital and largest city of North Korea.
Pyorrhea See: Periodontitis.
Pyramid, polyhedron whose base is a polygon and whose sides are triangles having a common vertex.
Pyramids, structures built by the Egyptians and other ancient peoples as royal tombs or temples; they are composed of square bases and 4 triangular faces that meet at a common point, the apex.
Pyrenees, mountain range between France and Spain, stretching 270 mi (435 km) from the Bay of Biscay to the Mediterranean and rising to Pico de Aneto (11,168 ft/3,404 m) in the central section.
Pyrethrum, any of a group of flowers (genus Chrysanthemum) that produce insect powder.
Pyridoxine See: Vitamin.
Pyrite, or iron pyrites (FeS2, iron (II) disulfide), hard, yellow, common sulfide known as fool's gold for its resemblance to gold.
Pyromania, recurring impulse to set fire to objects or buildings.
Pyrometry, process of measuring exceedingly high temperatures through the use of a pyrometer, an instrument that can function in heat far hotter than that tolerated by ordinary thermometers.
Pyroxene, general term for a group of crystalline silicate minerals containing iron, calcium, and magnesium, prevalent in igneous, metamorphic, and lunar rocks.
Pyrrho of Elis (360–270 B.C.), Greek philosopher, the founder of skepticism.
Pyrrhus (c.318–272 B.C.), king at the age of 12 of Epirus, northwestern Greece, he served with Demetrius I of Macedonia in Asia Minor, was helped by Ptolemy I of Egypt to regain his throne, and later won and lost Macedonia.
Pythagoras (c.582–507 B.C.), Greek philosopher who founded the Pythagorean school.
Pythagorean theorem, statement that, for any right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.
Pythias See: Damon and Pythias.
Python, Old World equivalent of the New World boa, a snake bearing small spurs as the vestiges of hindlimbs.
Q, 17th letter of the alphabet, can be traced back to the letter koph in the Semitic alphabet and koppa in ancient Greek, on through the Etruscan alphabet, taking its modern form in Latin, usually followed by u.
Qadhafi, Muammar Muhammad al- (1942– ), Libyan leader.
Qandahar, or Kandahar (pop. 191,300), city in southern Afghanistan, second largest Afghan city, and major international trade center.
Qatar, oil-rich emirate in Arabia.
Qin dynasty, also Ch'in dynasty, era of totalitarian Chinese rule dating from 221 B.C.–206 B.C.
Quadhafi, Muammar Muhammad al- See: Qadhafi, Muammar Muhammad al-.
Quadrilateral, in geometry, plane 4-sided polygon.
Quadruple Alliance, alliance of 4 countries.
Quail, name for 2 distinct groups of game birds of the pheasant family.
Quaker-ladies See: Bluet.
Quakers, or Society of Friends, church known for its pacifism, humanitarianism, and emphasis on inner quiet. Founded in 17th-century England by George Fox, it was persecuted for its rejection of organized churches and any dogmatic creed. Many Quakers emigrated to America, where in spite of early persecution they were prominent among the colonizers. In 1681 William Penn established his “Holy…
Quanah, or Quanah Parker (1845–1911), North American Comanche chief and leader of a brief uprising against settlers in an effort to end their slaughter of the buffalo in Texas.
Quantico Marine Corps Development and Education Command, training center for U.S.
Quantrill, William Clarke (1837–65), Confederate guerrilla leader in the U.S.
Quantum electrodynamics, or QED, concept in theoretical physics.
Quantum mechanics, fundamental theory of small-scale physical phenomena (such as the motions of electrons within atoms). This theory was developed during the 1920s, when it became clear that the existing laws of classical mechanics and electromagnetic theory were not successfully applicable to such systems. French physicist Louis De Broglie suggested (1924) that particles have a wavelike nature, w…
Quantum theory See: Quantum mechanics.
Quapaw, North American Plains Indians of the Siouan language group.
Quarantine, period during which a person or animal must be kept under observation in isolation from the community after having been in contact with an infectious disease.
Quark, particle believed by physicists to be the basic subunit of neutrons and protons.
Quarles, Benjamin Arthur (1904– ), U.S. historian, teacher and writer of the impact of African-American culture on U.S. history.
Quarrying, excavation, from open-pit mines, of dimension stone (cut stone) or crushed stone to be used for building projects or ornamentation.
Quartering Act See: Revolutionary War in America.
Quartz, rhombohedral form of silica, usually forming hexagonal prisms, colorless when pure.
Quartzite, hard metamorphic rock composed of and cemented by recrystallized quartz grains.
Quasar, or quasi-stellar object, a starlike celestial object whose spectrum seen telescopically shows an abnormally large red shift.
Quasimodo, Salvatore (1901–68), Italian poet and translator of poetry awarded the 1959 Nobel Prize for literature.
Quaternary Period, period in geologic time, of the Cenozoic era whose beginning is marked by the advent of humans.
Quayle, Dan (James Danforth Quayle; (1947– ), U.S. vice president (1989–93) with George Bush.
Quebec, largest province in Canada, second-largest in terms of population. Its capital is Quebec City, one of the oldest cities in North America. About 80% of the people of Quebec are of French descent and speak French. Montreal, on the St. Lawrence River, is the second-largest French-speaking city in the world. The enormous land area of Quebec can be divided into 3 well-defined regions: th…
Quebec (pop. 645,500), capital of Quebec province, situated on the St.
Quebec Act, passed by the British Parliament in 1774, one of the Intolerable Acts that led to the American Revolution.
Quebec, Battle of, most important battle of the French and Indian War, whose outcome transferred control of Canada from France to Britain.
Quebec Conference (1864), conference in the city of Quebec that laid the foundations of the Canadian Confederation.
Quebec separatist movement, various French-Canadian political factions in Quebec, Canada, which demand that French be the sole language of Quebec and that Quebec separate from Canadian rule and become an independent nation.
Quebec, University of, also Université du Québec, largest Canadian university, founded 1969.
Quebracho, South American hardwood tree (genus Schinopsis) of the cashew family, with a high content of tannin, an extract used to tan leather.
Quechua, also Kechua or Quichua, linguistic family belonging to natives of South America.
Queen, female monarch or the wife of a king, with all the powers allowed by the country that she rules.
Queen Anne's lace See: Wild carrot.
Queen Anne's War See: French and Indian Wars.
Queen, Ellery, pen-name and fictional hero of American detective writers Frederic Dannay (1905–82) and Manfred B.
Queens, largest and second most populous of the 5 boroughs that make up the city of New York.
Queensberry rules, basic rules of modern boxing, drawn up in 1865 under the auspices of John Sholto Douglas, 8th Marquess of Queensberry, supplanting London prize-ring rules.
Queensland, second largest Australian state, in the northeastern region of Australia, covering 667,000 sq mi (1,727,530 sq km).
Quemoy, or Chin-men, island group on the Formosa Strait off southeastern China.
Querétaro, state in central Mexico, on the Mexican Plateau, 6,119 ft (1,865 m) above sea level.
Quesnay, François (1694–1774), French economist and a leader of the physiocrats.
Quetzal (Pharomacrus mocinno), bird in the trogon family.
Quetzalcóatl (Nahuatl, “plumed serpent”), ancient Mexican god identified with the morning and evening star.
Quevedo Villega, Francisco de (1580–1645), Spanish satirist, poet, and prose writer.
Quezon City (pop. 1,169,800), Philippine city on Luzon Island, near Manila.
Quezon y Molina, Manuel Luis (1878–1944), Filipino statesman who played a leading role in the Philippine independence movement before becoming the first president of the Philippine Commonwealth (1935).
Quicksand, sand saturated with water to form a sand-water suspension possessing the characteristics of a liquid.
Quicksilver See: Mercury (element).
Quilt, bedcover made from 2 layers of cloth with an inner padding of insulating material.
Quincy (pop. 42,554), westernmost city in Illinois, located on the Mississippi River.
Quincy (pop. 84,743), city in eastern Massachusetts, the birthplace of Presidents John Adams and John Quincy Adams and an important industrial and shipbuilding center.
Quine, Willard Van Orman (1908– ), U.S. philosopher and logician.
Quinine, alkaloid derived from cinchona bark from South America, long used in treating a variety of ailments (now rarely used).
Quinsy, acute complication of tonsillitis in which abscess formation causes spasm of the adjacent jaw muscles, fever, and severe pain.
Quintana Roo, state in southeastern Mexico on the Yucatán Peninsula, whose capital is Chetumal.
Quintilian (Marcus Fabius Quintilianus; A.D. 35?–95?), Roman rhetoric teacher, whose famous 12-volume Institutio Oratoria, covering rhetorical techniques, educational theory, literary criticism, and morality, deeply influenced Renaissance culture.
Quirinal Hill, one of the famous 7 hills of Rome.
Quirinus, in Roman mythology, god responsible for the well-being and prosperity of the community.
Quisling, Vidkun Abraham Lauritz (1887–1945), Norwegian fascist leader who assisted the German invasion of Norway (1940) during World War II and was afterward appointed premier of Norway's puppet government (1942–45) by Adolf Hitler.
Quito (pop. 1,100,800), capital and second largest city of Ecuador and oldest capital in South America.
Quixote, Don See: Don Quixote.
Qumran, village on the northwestern shore of the Dead Sea, on the West Bank of Jordan, near the caves where the Dead Sea Scrolls were found (1947).
Quoits, game similar to horseshoes in which 2 players alternately attempt to toss a ring (quoit) around a stake (hob or mott).
Quorum, minimum number of members who must be present before an organization can legally transact business.
Qur'an See: Koran.
R, 18th letter of the English alphabet, corresponding to the Semitic letter resh, meaning “head,” and represented by a sign based on an ancient Egyptian picture symbol for a human head.
Ra See: Re.
Rabat (pop. 1,472,000), capital city of Morocco, in the north, on the Atlantic Ocean.
Rabbi (Hebrew, “my master” or “my teacher”), leader of a Jewish religious congregation with the role of spiritual leader, scholar, teacher, and interpreter of Jewish law.
Rabbit, herbivorous lagomorph (gnawing) mammal (family Leporidae), usually with long ears and a white scut for a tail.
Rabbit fever See: Tularemia.
Rabelais, François (1492?–1553), French monk, doctor, and humanist author.
Rabi, Isidor Isaac (1898–1988), U.S. physicist whose discovery of new ways of measuring the magnetic properties of atoms and molecules paved the way for the development of the maser and the atomic clock.
Rabies, or hydrophobia, acute infectious disease of mammals, characterized by irritation of the central nervous system, followed by paralysis and death.
Rabin, Yitzhak (1922–95), late prime minister of Israel (1974–77, 1992–95) and Israeli military leader.
Rabinowitz, Soloman See: Sholem Aleichem.
Raccoon, stout, bearlike, nocturnal mammal (genus Procyon), with a distinctive black mask and five to eight black bands on the bushy tail.
Raceme, type of flower cluster characterized by multiple flowers with separate short stems ranging along a common stalk (or peduncle).
Racer, any of several species (family Colubridae) of swift North American snakes.
Races, human, subdivisions of the species homo sapiens. The concept of race provides distinctions that are useful in the scientific study of the human species, its dissemination and adaptation to various environments and conditions throughout the world. It can also provide useful clues and insights for historians and cultural anthropologists into a people's development. Like Darwin's…
Rachel, in the Old Testament, daughter of Laban, wife of Jacob, and mother of Joseph and Benjamin.
Rachmaninoff, Sergei Vassilievich (1873–1943), Russian composer and virtuoso pianist.
Racial segregation See: Segregation.
Racine (pop. 84,298), industrial city of southeastern Wisconsin, situated on Lake Michigan at the mouth of the Root River.
Racine, Jean (1639–99), French tragic dramatist.
Racing, contest of speed in both individual and team competition, popular throughout history.
Racism, belief that some races are inherently superior to others. Racism in the early 19th century was an offshoot of nationalism, placing emphasis on the differences among cultures. Also, the study of human types revealed some physical differences among the races. Despite the theories of Carolus Linnaeus and J.F. Blumenbach, that environment rather than heredity molded intellectual development, m…
Rack, implement of torture made of a wooden structure with rollers at two ends.
Rackham, Arthur (1867–1939), English artist best known for his fanciful, delicately colored illustrations for children's books, such as Grimm's Fairy Tales (1900), Peter Pan (1906), and A Wonder Book (1922).
Racquetball, fast-paced indoor court game played by 1–4 players with 18-in (45.7-cm) racquets and a hollow rubber ball.
Radar (radio detection and ranging), system that detects long-range objects and determines their positions by measuring the time taken for radio waves to travel to the objects, be reflected, and return. Radar is used for navigation, air control, fire control, storm detection, in radar astronomy, and for catching speeding drivers. It developed out of experiments in the 1920s that were measuring the…
Radcliffe, Ann (1764–1823), English novelist remembered for her Gothic novels, notably The Mysteries of Udolpho (1794) and The Italian (1797).
Radcliffe-Brown, A(lfred) R(eginald) (1881–1955), British anthropologist and author of studies of kinship and social organization.
Radcliffe College, private liberal arts college affiliated with Harvard University, in Cambridge, Mass.
Radian, in geometry, metric unit for measuring angles, used to simplify calculations.
Radiant energy See: Star; Sun.
Radiation, emission and propagation of energy through space or through a material medium in the form of waves.
Radiation belt See: Van Allen belts.
Radiation detector See: Geiger counter.
Radiation sickness, malaise, nausea, loss of appetite, and vomiting occurring several hours after exposure to ionizing radiation in large doses.
Radiator, device in which steam or hot water circulates and gives off heat.
Radical, atom or group of atoms having an unpaired electron.
Radical Republican See: Reconstruction.
Radicalism, political philosophy whose purpose is to root out economic, political, and social injustices.
Radio, communication of information between distant points using electromagnetic radiation (radio waves). Radio waves are often described in terms of their frequency, which is measured in hertz (Hz) and found by dividing the velocity of the waves by their wavelength. Radio communications systems link transmitting stations with receiving stations. In a transmitting station a piezoelectric oscillato…
Radio, amateur, hobby practiced throughout the world by enthusiasts (“hams”) who communicate with one another on short-wave radio, by voice “phone,” or by using international Morse code.
Radio Free Europe/Radio Liberty (RFE/RL), radio broadcasting networks based in Munich, Germany.
Radio telescope, basic instrument of radio astronomy.
Radio waves See: Electromagnetic waves; Radio.
Radioactive fallout See: Fallout.
Radioactivity, spontaneous disintegration of unstable atomic nuclei, accompanied by the emission of alpha particles (weakly penetrating helium nuclei), beta rays (more penetrating streams of electrons), or gamma rays (electromagnetic radiation capable of penetrating up to 4 in/100 mm of lead). In 1896, Antoine Becquerel noticed the spontaneous emission of energy from uranium compounds (particularl…
Radiocarbon, or Carbon 14, naturally occurring radioactive isotope of carbon. With an atomic weight of 14, it is heavier than ordinary carbon, which has an atomic weight of 12. Radiocarbon is produced when cosmic rays disturb nitrogen atoms in the upper atmosphere, causing them to gain a neutron and lose a proton. Radiocarbon, found in 1.1% of CO2 (carbon dioxide) molecules, is absorbed by …
Radiochemistry, use of radioisotopes in chemistry, especially in studies involving chemical analysis.
Radiogeology, branch of geology in which scientists measure radioactive elements in rocks, fossils, and other geological specimens to determine their age.
Radioisotope See: Isotope; Radioactivity; Radiochemistry.
Radiology, in medicine, diagnosis and treatment through the use of radioactivity, gamma rays, and X-rays.
Radiosonde, meteorological instrument package attached to a small balloon capable of reaching the earth's upper atmosphere.
Radish, herb (Raphanus sativus), relative of mustard whose edible root looks like a small white to red turnip and has a burning flavor.
Radisson, Pierre Esprit (1636?–1710), French fur trader who worked for both French and British in the exploration of parts of present-day Minnesota and Wisconsin.
Radium, chemical element, symbol Ra; for physical constants see Periodic Table.
Radon, chemical element, symbol Rn; for physical constants see Periodic Table.
Raeburn, Sir Henry (1756–1823), Scottish painter.
Raffia, Asian palm (Raphia ruffia) whose long, tough leaf fibers are used for making baskets and tying up plants.
Raffles, Sir Stamford (1781–1826), British colonial administrator who re-founded the ruined city of Singapore (1819).
Rafflesia, genus of parasitic Indonesian plants with the largest flower in the world, up to 1 yd (0.9 m) across.