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51 [84] GERBERT
ALHAZEN [85] Arabs, but little more. The only ad vances, minor ones, were made by Alba- tegnius, the son of a builder of astro nomical instruments and the greatest of Islamic astronomers. Albategnius went over Ptolemy’s cal culations carefully and inserted a few improvements. He noticed, for instance, that the point at which the sun was smallest in apparent size (a point now called the aphelion) was no longer lo cated where Ptolemy said it was. From this he deduced that the position moved slowly and obtained a fairly correct value for that motion. He used better instruments than the Greeks did (the advantage of being the son of his father) and so got more accu rate results for the length of the year. (This value was used in the Gregorian reform of the Julian calendar seven cen turies later.) He also determined the time of equinox to within an hour or two and got an excellent value for the angle at which the earth’s axis was tipped to its plane of revolution. He introduced new types of mathe matical computations in astronomy, being the first to make use of a table of sines for the purpose. The greatest con tribution of Arabic astronomy was the perfecting of spherical trigonometry. In medieval Europe he was to be the most respected of the Arabian astrono mers.
[84] GERBERT (zhare-bare') French scholar Bom: Aurillac, Auvergne, about 945
Died: Rome, Italy, May 12, 1003 As a scholar, Gerbert tutored the son of Hugh Capet, king of France, and gained the admiration of the Holy Roman emperor, Otto II. As a churchman he reached the pinna cle, becoming archbishop and finally pope (the first French one), in 999, under the name of Sylvester II. (It was a ticklish time to be pope, for there was strong feeling in Europe that the world was coming to an end in 1000.) Gerbert was for his time a famous scholar, fa mous enough to be suspected of wiz ardry, despite his eminence in the church. He reintroduced the use of the abacus in mathematical calculation and may have picked up the use of Arabic numerals (without the zero) from al- Khwarizmi [79]. He built clocks, organs, and astronomical instruments out of his consultation of Arabic works, which he procured in translation. The rebirth of European learning may be dated from Gerbert. [85] ALHAZEN (aPha-zen); Arabic name, ABU-‘ALI AL-HASAN IBN AL-HAYTHAM Arabian physicist
now Iraq), about 965 Died: Cairo, Egypt, 1039 Alhazen, in an attempt to obtain a si necure for himself, put forth the claim that he could devise a machine that would regulate the flooding of the Nile. As he hoped, this attracted the atten tion of the Egyptian caliph, who hired him to do the job. Unfortunately for Alhazen, the Egyptian caliph was al- Hakim, the most dangerous crowned madman between the times of Caligula and Ivan the Terrible. It dawned on Alhazen that al-Hakim was not joking about his request that the machine should be built at once and that he would see that Alhazen was put to death in some complicated fashion if the ma chine was not built. There was nothing for Alhazen to do but pretend to have gone mad. He had to keep it up for years, until al-Hakim died in 1021. At the times when Alhazen could afford to be sane, he proved himself the most important physicist of the Middle Ages. His field of particular interest was optics. This science had been fumblingly begun by Hero [60] and by Ptolemy [64], who felt that men saw by means of rays of light issuing from the eye and reflecting from the objects seen. Alhazen held the correct view that light issued from the sun or from some other lumi
[8 6 ] AVICENNA
OMAR KHAYYAM [87] nous source and was reflected from the object seen into the eye. He also explained, correctly, how a lens worked, attributing its magnifying effect to the curvature of the surface and not to any inherent property of the sub stance making it up. He was interested in the reflection and refraction of light, discussed the rain bow, studied the focusing of light through lenses and constructed a pinhole camera. He also constructed parabolic mirrors, a type now used in telescopes. Like Ptolemy he assumed the atmo sphere had a finite depth, and estimated that depth to be about ten miles. His work was published in Latin trans lation in the sixteenth century and ex erted an important influence on such men as Kepler [169]. It was not until Kepler, six centuries later, in fact, that work on optics progressed beyond the point to which Alhazen had brought it. [86] AVICENNA (av-ih-sen'uh); Ara bic name, ABU-ALI AL-HUSAIN IBN ABDULLAH IBN SINA Persian physician Born: Kharmaithen, near Bukhara (in what is now the Uzbek SSR of the Soviet Union), 980
Died: Hamadan (in what is now northwest Iran), June 1037 Avicenna, the son of a tax collector, was an infant prodigy able to recite the entire Koran at the age of ten. He re ceived all the education the cultivated Arab world of the time could offer. Un fortunately the once-great Arabian em pire, although still highly cultured, had fallen apart into warring pieces and there was no safe place even for the greatest physician of medieval times, which Avi cenna was. Avicenna was in the employ of several Muslim rulers but political in stability was such that although this brought him fame, money, and a chance to do research, it also placed his life in danger more than once. In Hamadan, he served as vizier for a while and for his pains was nearly put to death during a military coup. He re mained in hiding until a medical emer gency on the part of the shah made his presence necessary and his person safe. When Hamadan fell to a neighboring ruler, Avicenna was one of the spoils of war and served a new master. In the end he died on the march with the army of that new master when it was heading for another attack on Hamadan. Avicenna apparently had a tendency to work hard at his pleasures as well as his studies, for it was of indigestion (or colic) that he died. More than two hundred and fifty books are attributed to Avicenna (many are probably really his) and of these the most important are his works on medi cine. His theories were based on those of Hippocrates [22] and Galen [65], and once his books were translated into Latin in the twelfth century, they became Europe’s most important medical text books, remaining so until the time of Harvey [174], Avicenna also dealt with alchemy, and he was unusual in being one of the few who intuitively felt that transmutation was impossible. In his philosophical works he helped preserve the views of Aristotle [29] for western Europe, but his importance in this respect is less than that of Averroës [91]. [87] OMAR KHAYYAM (oh'mar ky- ahm')
Persian astronomer Born: Nishapur (in what is now Iran), May 15, 1048 Died: Nishapur, December 4, 1131
The two things known about Omar Khayyam to the average well-educated modern are that he was a tentmaker, which is what “Khayyam” means, and that he wrote clever quatrains. His fa ther was a tentmaker, and he himself was a tentmaker in early life, it is true, but he was recognized as a gifted scholar and spent most of his life pensioned by, first, the vizier of the Seljuk sultan, Alp Arslan, and then by the sultan’s succes sor, Malik Shah. (Under these two rul ers, the Seljuk Turkish Empire reached
[ 8 8 ] ABELARD
ADELARD OF BATH [89] its height.) Omar’s poetry came into prominence in English only in 1859 when Edward FitzGerald produced his translation of the Rubaiydt. However, the lines we admire are far more the work of FitzGerald than of Omar. Omar Khayyam wrote a book on alge bra that was the best of its time, and he also prepared improved astronomical tables. His most spectacular feat was that of reforming the Muslim calendar in 1074 and producing one that would bet ter fit the astronomical facts of life. This was comparable with the Gregorian re form in Europe five centuries later. He could handle quadratic equations neatly but was stumped by cubic equations. He suspected that a general solution for the cubic equation did not exist, but Car dano [137] was to publish one four and a half centuries later. After the death of Malik Shah and the assassination of his vizier, Omar Khay yam fell into disfavor in 1092, partly be cause of his free-thinking attitudes (which show up in his quatrains). How ever, he was allowed to live out his life in peace. [88] ABELARD, Peter (ab'uh-lahrd, or a-bay-lahr in French) French scholar, French name, PIERRE ABÉLARD
tany, 1079 Died: near Chalon-sur-Saône, April 21, 1142 Abelard was the son of a landowner, and it would have been natural for him to train for a military career; but he en tered the field of scholarship and theol ogy, although his attitude toward it was that of a fighter and polemicist. He studied with competing masters and developed contempt, to a greater or lesser degree, for all, since they taught on the basis of what authorities had said and did not use reason—or, rather, they distrusted it as leading to pitfall and error. It was Abelard’s service to the cause of science that he fought hard for the use of reason and praised the ancient pa gans for it. What is more, in his most fa mous book, Sic et Non (“Yes and No”) he carefully quoted the most respected authorities on a variety of important theological questions and showed them, in every case, to be hopelessly at odds with each other. It needed no comment from Abelard to show the bankruptcy of appeals to authority. Naturally, Abelard, who was a magnificent and popular lecturer, (and is usually considered the founder of the University of Paris) incurred the wrath of less intelligent, but more orthodox, scholars (particularly the wrathful Ber nard of Clairvaux, an abbot more power ful than the pope) and he was in con stant danger of condemnation for heresy. Indeed, when he died he was preparing his defense against such a charge. The best-known aspect of Abelard’s life, however, is his affair with his beau tiful and intelligent student Heloise. It was apparently a case of deep love on both sides. They were secretly married (It had to be secret or Abelard’s career in the church would have come to an end.) and a son was born to them. Heloise’s uncle, Fulbert, the powerful canon of Notre Dame, was furious at all this, and hired thugs to castrate Abelard in 1121. That prevented any advance ment in the church just as surely as mar riage would, since no eunuch could be a priest. He continued his studies and his writings, however. [89] ADELARD OF BATH English scholar Born: Bath, about 1090 Died: about 1150 Adelard was a tutor of the English prince who later became Henry II. He is supposed to have traveled widely during his youth through the lands of ancient learning, Greece, Asia Minor, northern Africa. He learned Arabic and upon his return to England translated Euclid [40] from Arabic into Latin. This was the first time Euclid became available to Europe. He also translated al-Khwarizmi [79], and made use of “Arabic nu merals,” something that Fibonacci [95]
[90] GERARD OF CREMONA MAIMONIDES
was to establish firmly a century later. For popular consumption Adelard also wrote a book called Natural Questions which contained a summary of all he had learned of Arabic science. [90] GERARD OF CREMONA (jer- ard')
Italian scholar Born: Cremona, about 1114 Died: Toledo, Spain, 1187 The twelfth century is unique in the history of science as being the time when it was possible for translation to be the most important scientific work. The books of the Arabic scholars, who for centuries had preserved the works of the Greek philosophers by translation and commentary, began to be rendered into Latin. One of the earliest men to encour age the task was Gerbert [84], an impor tant churchman. Over the space of three centuries, however, the most important translator was Gerard of Cremona. He spent much of his life in Toledo, Spain, working under church auspices. Toledo had been a center of Muslim learning and had been reconquered by the Spaniards in 1085. It was a good place to find learned Arabic works, and learned Arabs too, who could help with the translation and with clearing up uncertain points. Gerard translated (or supervised the translation of) ninety-two Arabic works, some extremely long. These included portions of Aristotle [29] and all of the
works of Hippocrates [22], Euclid [40] and Galen [65], [91] AVERROËS (uh-ver'oh-eez); Ara bic name: ABU-AL-WALID MUHAMMAD IBN AHMAD IBN RUSHD Arabian philosopher Born: Cordoba, Spain, 1126 Died: Marrakesh, Morocco, De cember 10, 1198 Averroës, the son of a judge in Cordoba, had, like Avicenna [86] and Alhazen [85], both the benefit and the difficulties involved in being patronized by powerful Muhammadan rulers. The rulers of those portions of Spain still under Muhammadan control set him up as a judge, first in Seville and then, like his father, in Cordoba. He was sent on diplomatic missions. Because (ap parently) he was suspected of being a scholar, he was imprisoned for a while in 1195. Finally he retired to Morocco for his own safety. Averroës’ importance is not due to any original work, but to his lengthy and thoughtful commentaries on the work of Aristotle [29], In this only his younger contemporary Maimonides [92] is to be compared to him. Averroës was at once the peak and the end of Arabic philosophy, for the gather ing woes of Muslim disunity were com ing to a head. After Averroës’ time, the Muhammadans were to feel the blows of the Christians in Spain and the Mongols and Turks in the east. The Muslim world entered a Dark Age, where scientific in quiry was lost, just as the Christian world was emerging from one. It followed, then, that Averroës’ im portance was not felt by the Muslims as much as by the Christians of Europe, who read his work in Latin translation and who built on it, this reaching a cli max with Thomas Aquinas [102]. In fact, some of Averroës’ books are lost in their Arabic original and exist only in their Latin translations. [92] MAIMONIDES (my-mon'ih-deez); Hebrew name, MOSES BEN MAIMON
Jewish philosopher Born: Cordoba, Spain, March 30, 1135
Died: Cairo, Egypt, December 13, 1204
As a child, Maimonides left Spain with his family. Cordoba had been taken by a new and barbaric line of rulers from North Africa and Maimonides’ family no longer felt comfortable there. He traveled eastward and finally settled in Egypt in 1165. There he served as physi
[93] NECKAM
FIBONACCI [95] cian to Saladin himself, the famous ruler who opposed Richard the Lion- Heart during the third Crusade. Indeed, Richard invited Maimonides to come to England but the philosopher preferred to remain in Egypt, then by far the more civilized of the two nations. Maimonides in his book Guide for the
oncile the teachings of Aristotle [29] with the teachings of the Old Testament. He has been the most influential of all Jewish philosophers. [93] NECKAM, Alexander (nek'am) English scholar
September 8, 1157 Died: Kempsey, Worcestershire, early 1217 Neckam was bom, according to leg end, on the same night as the prince who later became Richard I, the Lion-Heart. Neckam’s mother was wet nurse for the prince as well, but if Neckam lacked the stature, gallantry, and derring-do of the prince, he far surpassed him in intelli gence.
Neckam traveled to Paris, and studied and later lectured at its renowned uni versity. In 1186 he returned to England and in 1213 became abbot of Circen- cester. In Paris, Neckam had learned of the mariner’s compass, which the Chi nese had been using for at least two cen turies. In a book he wrote about 1180 was the first reference to the compass as being in use among Europeans. He must have had his enemies though (as most scholars did in the ferociously polemical philosophical battles of the Middle Ages) for he was often deliber ately misreferred to as “Nequam,” which is Latin for “useless.” [94] GROSSETESTE, Robert (grohs'- test)
English scholar Born: Stradbroke, Suffolk, about 1168
Died: Buckden, Huntingdonshire, October 9, 1253 Grosseteste’s primary fame is that of a theologian and prelate. Of a poor family, he was nevertheless educated at Oxford and rose steadily in the church, becom ing bishop of Lincoln in 1235. He did not fear controversy, standing firmly on principle against all authorities. He fought for the inclusion of more science in the university curriculum, defended the Jews against King Henry III and at tacked church abuses even against Pope Innocent IV. He was also pre-eminent in scholarship and was one of the earliest to introduce Aristotle [29] to Europe. In an age when the translation of the Arabic works of science was of crowning importance, he went even further back. Feeling that third-hand Latin translations from Ara bic translations of Greek originals were inevitably corrupt, he brought scholars from the remains of the Byzantine Em pire (sections of which were under the temporary control of the West at the time) to translate from the original Greek.
Grosseteste was particularly interested in optics, using Alhazen [85] as his guide. He experimented with mirrors and with lenses and advanced an explanation for the rainbow. Indeed, he thought the primal substance of the universe was not any form of matter, but light itself. If, for light, we substitute the more general term of “energy,” Grosseteste, like Heraclitus [10] would seem curiously close to the modem conception. And yet his greatest claim to fame lies not in his own deeds, but in the fact that he was the teacher of Roger Bacon [99], [95] FIBONACCI, Leonardo (fee-boh- naht'chee); also called LEO NARDO DA PISA Italian mathematician Born: Pisa, about 1170 Died: about 1240 Fibonacci, the first great Western mathematician after the end of Greek science, lived in Pisa at a time when it was one of the great mercantile centers
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