Silvester II

Pope Sylvester II ( – 12 May 1003), originally known as Gerbert of Aurillac, was a French-born scholar and teacher who served as the bishop of Rome and ruled the Papal States from 999 to his death. He endorsed and promoted study of Arab and Greco-Roman arithmetic, mathematics and astronomy, reintroducing to Europe the abacus and armillary sphere, which had been lost to Latin Europe since the end of the Greco-Roman era. He is said to be the first in Europe to introduce the decimal numeral system using the Hindu-Arabic numeral system. He is credited with the invention of the first mechanical clock in 996.

Early life

Gerbert was born about 946 in the town of Belliac, near the present-day commune of Saint-Simon, Cantal, France. Around 963, he entered the Monastery of St. Gerald of Aurillac. In 967, Count Borrell II of Barcelona (947–992) visited the monastery, and the abbot asked the count to take Gerbert with him so that the lad could study mathematics in Catalonia and acquire there some knowledge of Arabic learning.

Scholarly work

Gerbert studied under the direction of Bishop Atto of Vich, some 60 km north of Barcelona, and probably also at the nearby Monastery of Santa Maria de Ripoll. Like all Catalan monasteries, it contained manuscripts from Muslim Spain and especially from Cordoba, one of the intellectual centres of Europe at that time: the library of al-Hakam II, for example, had thousands of books (from science to Greek philosophy). This is where Gerbert was introduced to mathematics and astronomy. Borrell II was facing major defeat from the Andalusian powers so he sent a delegation to Córdoba to request a truce. Bishop Atto was part of the delegation that met with al-Ḥakam II, who received him with honour. Gerbert was fascinated by the stories of the Mozarab Christian bishops and judges who dressed and talked like the Arabs, well-versed in mathematics and natural sciences like the great teachers of the Islamic madrasahs. This sparked Gerbert's veneration for the Arabs and his passion for mathematics and astronomy.

Abacus and numerals

Gerbert learned of Hindu–Arabic digits and applied this knowledge to the abacus, but probably without the numeral zero. According to the 12th-century historian William of Malmesbury, Gerbert got the idea of the computing device of the abacus from a Moorish scholar. The abacus that Gerbert reintroduced into Europe had its length divided into 27 parts with 9 number symbols (this would exclude zero, which was represented by an empty column) and 1,000 characters in all, crafted out of animal horn by a shieldmaker of Rheims.. According to his pupil Richer, Gerbert could perform speedy calculations with his abacus that were extremely difficult for people in his day to think through using only Roman numerals. Due to Gerbert's reintroduction, the abacus became widely used in Europe once again during the 11th century.

Armillary sphere and sighting tube

Although lost to Europe since the terminus of the Greco-Roman era, Gerbert reintroduced the astronomical armillary sphere to Latin Europe via the Islamic civilization of Al-Andalus, which was at that time at the "cutting edge" of civilization. The details of Gerbert's armillary sphere are revealed in letters from Gerbert to his former student and monk Remi of Trèves and to his colleague Constantine, the abbot of Micy, as well as the accounts of his former student and French nobleman Richer, who served as a monk in Rheims. Richer stated that Gerbert discovered that stars coursed in an oblique direction across the night sky.. Richer described Gerbert's use of the armillary sphere as a visual aid for teaching mathematics and astronomy in the classroom.

Historian Oscar G. Darlington asserts that Gerbert's division by 60 degrees instead of 360 allowed the lateral lines of his sphere to equal to six degrees.. By this account, the polar circle on Gerbert's sphere was located at 54 degrees, several degrees off from the actual 66° 33'. His positioning of the Tropic of Cancer at 24 degree was nearly exact, while his positioning of the equator was correct by definition. Richer also revealed how Gerbert made the planets more easily observable in his armillary sphere:

He succeeded equally in showing the paths of the planets when they come near or withdraw from the earth. He fashioned first an armillary sphere. He joined the two circles called by the Greeks ''coluri'' and by the Latins ''incidentes'' because they fell upon each other, and at their extremities he placed the poles. He drew with great art and accuracy, across the ''colures'', five other circles called parallels, which, from one pole to the other, divided the half of the sphere into thirty parts. He put six of these thirty parts of the half-sphere between the pole and the first circle; five between the first and the second; from the second to the third, four; from the third to the fourth, four again; five from the fourth to the fifth; and from the fifth to the pole, six. On these five circles he placed obliquely the circles that the Greeks call ''loxos'' or ''zoe'', the Latins ''obliques'' or ''vitalis'' (the zodiac) because it contained the figures of the animals ascribed to the planets. On the inside of this oblique circle he figured with an extraordinary art the orbits traversed by the planets, whose paths and heights he demonstrated perfectly to his pupils, as well as their respective distances.

Richer wrote about another of Gerbert's last armillary spheres, which had sighting tubes fixed on the axis of the hollow sphere that could observe the constellations, the forms of which he hung on iron and copper wires.. This armillary sphere was also described by Gerbert in a letter to his colleague Constantine.. Gerbert instructed Constantine that, if doubtful of the position of the pole star, he should fix the sighting tube of the armillary sphere into position to view the star he suspected was it, and if the star did not move out of sight, it was thus the pole star.. Furthermore, Gerbert instructed Constantine that the north pole could be measured with the upper and lower sighting tubes, the Arctic Circle through another tube, the Tropic of Cancer through another tube, the equator through another tube, and the Tropic of Capricorn through another tube.

Ecclesiastical career

In 969, Borrell II made a pilgrimage to Rome, taking Gerbert with him. There Gerbert met Pope John XIII and Emperor Otto I. The pope persuaded Otto I to employ Gerbert as a tutor for his young son, Otto II. Some years later, Otto I gave Gerbert leave to study at the cathedral school of Rheims where he was soon appointed a teacher by Archbishop Adalberon. When Otto II became sole emperor in 973, he appointed Gerbert the abbot of the monastery of Bobbio and also appointed him as count of the district, but the abbey had been ruined by previous abbots, and Gerbert soon returned to Rheims. After the death of Otto II in 983, Gerbert became involved in the politics of his time. In 985, with the support of his archbishop, he opposed King Lothair of France's attempt to take Lorraine from Emperor Otto III by supporting Hugh Capet. Hugh became king of France, ending the Carolingian line of kings in 987.

Adalberon died on 23 January 989.. Gerbert was a natural candidate for his succession, but King Hugh appointed Arnulf, an illegitimate son of King Lothair, instead. Arnulf was deposed in 991 for alleged treason against Hugh, and Gerbert was elected his successor. There was so much opposition to Gerbert's elevation to the See of Rheims, however, that Pope John XV (985–996) sent a legate to France who temporarily suspended Gerbert from his episcopal office. Gerbert sought to show that this decree was unlawful, but a further synod in 995 declared Arnulf's deposition invalid. Gerbert then became the teacher of Otto III, and Pope Gregory V (996–999), Otto III's cousin, appointed him archbishop of Ravenna

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