pyrometer \pl-'ra-m3-t3r\ Instrument for measuring relatively high tem¬ peratures, as in furnaces. Most pyrometers work by measuring radiation from the body whose temperature is to be measured (radiation devices have the advantage of not having to touch the material being measured). Optical pyrometers measure the temperature of glowing bodies by comparing them visually with an incandescent filament of known temperature whose tem¬ perature can be adjusted. In resistance pyrometers, a fine wire is put in con¬ tact with the object; the instrument converts the change in electrical resistance caused by heat to a reading of the temperature of the object.
pyroxene \pl-'rak-,sen\ A group of important rock-forming silicate min¬ erals of variable composition, among which calcium-, magnesium-, and iron-rich varieties predominate. Common pyroxenes belong to either the low-calcium enstatite-(ortho)ferrosilite series, (Mg,Fe)Si0 3 , or the high- calcium diopside-hedenbergite series, Ca(Mg,Fe)Si 2 0 6 . Rare pyroxenes include jadeite, aegirine, and johannsenite. See also enstatite.
pyroxenite \pi- , rak-so- l n!t\ Dark medium- to coarse-grained igneous rock that consists chiefly of pyroxene. Accessory minerals include horn¬ blende, biotite, or olivine. Pyroxenites are not abundant.
pyrrhotite Vpir-a-.ffiA Iron sulfide mineral in which the ratio of iron to sulfur atoms is somewhat variable but is always slightly less than 1. It commonly is found in association with other sulfides. The variety troilite, with a composition near that of iron sulfide (FeS), is an important con¬ stituent of some meteorites.
Pyrrhus \'pir-9s\ (b. 319— d. 272 bc, Argos, Argolis) King of Hellenis¬ tic Epirus. After being allied to Demetrius and taken hostage, he was befriended by Ptolemy I Soter and restored to his kingdom. In 281 he was asked for help against Rome by the Greek enclave of Tarentum (Taranto) and won costly victories at Heraclea and Ausculum. Crossing to Sicily, he conquered most of the Punic territory, but the Greek Sicilians revolted against his despotism. He suffered serious losses on his return to Italy (275) but defeated Antigonus II Gonatas in Macedonia (274) and became king there. He died in a skirmish in Argos trying to help Sparta. His costly victories gave rise to the term “Pyrrhic victory.”
Pythagoras \p3-'tha-g3-r3s\ (b. c. 580 bc, Samos, Ionia—d. c. 500, Metapontum, Lucania) Greek philosopher and mathematician. He estab¬
lished a community of followers in Croton who adhered to a way of life he prescribed. His school of philosophy reduced all meaning to numeri¬ cal relationships and proposed that all existing objects are fundamentally composed of form and not material substance. The principles of Pythagoreanism, including belief in the immortality and reincarnation of the soul and in the liberating power of abstinence and asceticism, influ¬ enced the thought of Plato and Aristotle and contributed to the develop¬ ment of mathematics and Western rational philosophy. The proportions of musical intervals and scales were first studied by Pythagoras, and he was the first influential Western practitioner of vegetarianism. None of his writ¬ ings survive, and it is difficult to distinguish the ideas he originated from those of his disciples. His memory is kept alive partly by the Pythagorean theorem, probably developed by his school after he died.
Pythagorean \p9-,tha-g3-'re-3n\ theorem Rule relating the lengths of the sides of a right triangle. It says that the sum of the squares of the lengths of the legs is equal to the square of the length of the hypotenuse (the side opposite the right angle). That is, a 2 + b 2 = c 2 , where c is the length of the hypotenuse. Triads of whole numbers that satisfy it (e.g., 3, 4, and 5) are called Pythagorean triples. See also law of cosines; law of sines.
Pythagoreanism Xps-.tha-gs-'re-s-.ni-zsnA Philosophical school, probably founded by Pythagoras c. 525 bc. It originated as a religious brotherhood or an association for the moral reformation of society; broth¬ ers were sworn to strict loyalty and secrecy. The brotherhood had much in common with the Orphic communities (see Orphism), which sought by rites and abstinence to purify the believer’s soul and enable it to escape from the “wheel of birth.” Pythagoreanism held that reality, at its deepest level, is mathematical, that philosophy can be used for spiritual purifica¬ tion, that the soul can rise to union with the divine, and that certain sym¬ bols have mystical significance. It was the first important Western system of thought to advocate vegetarianism. The school became extinct in the mid-4th century.
Pythian \'pi-the-an\ Games In ancient Greece, various athletic and musical competitions held in honour of Apollo, chiefly those at Delphi. The games were held from before the 5th century bc to the 4th century ad. They took place in August of the third year of each Olympiad (the four- year period between Olympic Games). Events were similar to those of the ancient Olympics.
python \'pl-,than\ Any of 28 species (family Pythonidae, sometimes a subfamily of Boidae) of sluggish, docile, nonvenomous snakes found in tropical and temperate regions. Except for one Central American species {Loxocemus bicolor ), pythons are found from western Africa to China, Australia, and the Pacific islands. Pythons feed on birds and mammals, killing them by constriction. Most are found near water; some are arbo¬ real. Unlike boas, pythons lay eggs (15-100, depending on body size). The Asian reticulated python (.Python reticulatus) may be the world’s longest snake (the anaconda is heavier); specimens over 30 ft (9 m) long have been recorded.
© 2006 Encyclopaedia Britannica, Inc.
Qadariya ► Qatar I 1571
Qadariya \,ka-d3-'re-3\ In Islam, adherents of the doctrine of free will. The name was also applied to the Mutazila. The issue of free will was a major point of controversy in Islamic theology, and the Qadariya took the most extreme stand in its defense. They based their argument on the necessity of divine justice, maintaining that without responsibility and freedom one cannot fairly be held accountable for one’s actions. See free WILL PROBLEM.
Qaddafi \k3-'da-fe\, Muammar al- or Mu'ammar al-Qadhdhafi (b. 1942, Surt, Libya) Ruler of Libya from 1969. Son of a Bedouin farmer, he was born in a tent in the desert. He graduated from the University of Libya and Libya’s military academy and was a devout Muslim and ardent nationalist. As a captain in the army, he led the 1969 coup that deposed King Idris I. He espoused his own form of Islamic socialism, and his foreign policy was anti-Western and anti-Israel. In 1970 he closed U.S. and British military bases and expelled Italians and Jews.
He banned alcoholic beverages and gambling and in 1973 nationalized the oil industry. He made unsuc¬ cessful attempts to unify Libya with other coun¬ tries. His government was repeatedly linked with terrorist incidents in Europe and elsewhere, and he supported groups trying to overthrow neighbour¬ ing governments. He narrowly escaped death in 1986 when U.S. planes bombed sites in Libya, including his own residence.
qadi \'ka-,de\ Muslim judge who renders decisions according to the Shari"ah, the canon law of Islam. The qadi hears only religious cases, such as those involving inheritance, pious bequests, marriage, and divorce, though theoretically his jurisdiction extends to civil and criminal mat¬ ters. The second caliph, "Umar ibn al-Khattab, was the first to appoint a qadi to eliminate the necessity of his personally judging every dis¬ pute that arose in the community.
Qadisiyyah N.ka-di-'se-oV Battle of (636?) Battle fought near Al-Hlrah (in present-day Iraq) between forces of the Sasanian dynasty and an invading Arab army. The Arab victory over the army of Yazdegerd (r. 632-651) marked the end of his dynasty and the beginning of Arab and Islamic rule in Persia.
Qaeda, al- also al-Qa'idah Arabic "the Base" Broad-based Islamic militant organization founded in Afghanistan by Osama bin Laden. Its members supported Muslim fighters during the Afghan war of 1979— 89; afterward the organization dispersed but continued to oppose secu¬ larized Muslim regimes and foreign (notably U.S.) presence in Islamic lands. It staged numerous terrorist attacks, including the bombing of the World Trade Center in 1993, the destruction of two U.S. embassies in Africa in 1998, and a suicide bomb attack against the U.S. warship Cole in 2000. During that time it merged with other Islamic extremist organi¬ zations and eventually reestablished its headquarters in TAUBAN-controlled Afghanistan, where it trained thousands of Muslim militants. In 2001, 19 such militants staged the September 11 attacks. The U.S. and allied forces responded by attacking Taliban and al-Qaeda forces in Afghanistan, kill¬ ing and capturing thousands and driving the remainder into hiding.