'''Silvestru al II-lea''', pe numele laic ''Gerbert d'Aurillac'', (n. ca. 945, Auvergne - d.12 mai 1003, Roma) a fost papă al Romei timp de patru ani, între 2 aprilie 999 şi 12 mai 1003. 
thumb|Silvestru al II-lea

==Viaţa==
Primul francez care a devenit Papă s-a ştiut ca era în relaţii strânse cu Imperiorul roman, dar şi cu Otto III. Pentru o reformă în ceea ce priveşte abuzurile în biserici. În Februarie, 1001, cetaţenii Romei s-au revoltat împotriva dominaţiei străine (puteri străine), Germanii i-au forţat pe amandoi să părăsească oraşul. Otto al III-lea a murit în următorul an, nu putea reînfiinţa controlul asupra Romei Silvester al II-lea a primit permisiunea să se întoarcă, sub o subraveghiere strictă de Imperiul Roman, numai în activitatea religioasă, spirituală.

În anul 1001 papa Silvestru al II-lea a fost cel care a trimis în Ungaria o coroană pentru regele Ştefan I al Ungariei, alta decât cea cunsocută ulterior drept Coroana Sfântă a Ungariei ( după o teorie aceasta din urmă a fost confecţionată într-un atelier din Bizanţ).

==Legături externe==
*[http://www.documentacatholicaomnia.eu/01_01_0999-1003-_Silvester_II.html Scrieri]

{{Infobox Pope|
English name=Sylvester II|
image=150px|
birth_name=Gerbert d'Aurillac|
term_start=April 2, 999|
term_end=May 12, 1003|
predecessor=Gregory V|
successor=John XVII|
birth_date=''ca.'' 950|
birthplace=Auvergne, France|
dead=dead|death_date=|
deathplace=Rome, Italy|
other=Sylvester}}

'''Pope Sylvester II''', or '''Silvester II''' (c. 946&ndash;Arabic knowledge of arithmetic, mathematics, and astronomy to French Pope (see list), reigning from sorcerer in league with the devil. There is also speculation that he had Sephardic-Jewish ancestry.

==Life==

Gerbert was born about 946 in the town of Aurillac, Auvergne region, St. Gerald of Aurillac. In Borrell II of Barcelona (947&ndash;992), visited the monastery, and the abbot asked the Count to take Gerbert with him so that the lad could study Atto, Bishop of Vich, some 60 km north of Barcelona, and probably also at the nearby Monastery of Santa Maria de Ripoll.<ref>[http://mathdl.maa.org/convergence/1/?pa=content&sa=viewDocument&nodeId=1187&bodyId=1323  Betty Mayfield, "Gerbert d'Aurillac and the March of Spain: A Convergence of Cultures"]</ref>

Borrell II of Barcelona was facing major defeat from the Andalusian power so he sent a delegation to Córdoba to request a cease fire. Part of the delegation was Atto who met with Islamic universities. This sparked Gerbert's veneration for the Arabs and his passion for mathematics and astronomy. Gerbert learned from the Arab teachers in Spain subjects that no one in Europe had even heard of, the most important being the Arabic numbers. It used to be rumored that he would sneak out from the monastery at night to study under the Arabs.    

In Otto I, surnamed the Great (936&ndash;973). The Pope persuaded Otto I to employ Gerbert as tutor for his young son, the future Emperor Otto II (973&ndash;983). 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 Holy Roman Emperor in 973 (he was co-emperor with Otto I from 967), 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 Lorraine from Emperor Otto III (983&ndash;1002) by supporting Hugh Capet (987&ndash;996).  Capet became King of France, ending the Carolingian line of Kings in 987. 

thumb|right|200px|Statue of Pope Sylvester II in Aurillac, Auvergne, France.
Adalbero died on Lothair instead. Arnulf was deposed in 991 for alleged treason against the King, 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&ndash;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 now became the teacher of Otto III, and Pope Gregory V (996&ndash;999), Otto III's cousin, appointed him Archbishop of Ravenna in 998. With the Emperor's support, he was elected to succeed Gregory V as Pope in 999. Gerbert took the name of Sylvester II, alluding to Pope Sylvester I (314&ndash;335), the advisor to Emperor Constantine I (324&ndash;337). Soon after he was elected Pope, Sylvester II confirmed the position of his former rival Arnulf as archbishop of Rheims. As Pope, he took energetic measures against the widespread practices of simony and concubinage among the clergy, maintaining that only capable men of spotless lives should be allowed to become bishops. 

In 1001, the Roman populace revolted against the Emperor, forcing Otto III and Sylvester II to flee to Ravenna.  Otto III led two unsuccessful expeditions to regain control of the city, and died on a third expedition in 1002.  Sylvester II returned to Rome soon after the Emperor's death, although the rebellious nobility remained in power, and died a little later. Sylvester is buried in St. John Lateran.

== Works and teaching ==
Gerbert, as a scientist, was said to be far ahead of his time. Gerbert wrote a series of works dealing with matters of the trivium (grammar, logic, and rhetoric). Walid Amine Salhab asserts that Gerbert's reintroduction of the emphasis on these liberal arts in Europe was inspired by the educational institution of Cordoba in Islamic Spain.<ref name="salhab 51">Salhab, 51.</ref>  In Rheims, he constructed a hydraulic-powered organ with brass pipes that excelled all previously known instruments,<ref name="darlington 473">Darlington, 473.</ref> where the air had to be pumped manually. In a letter of 984, Gerbert asks Lupitus of Barcelona for a book on astrology and astronomy, two terms which historian S. Jim Tester states were used synonymously by Gerbert.<ref name="tester 132">Tester, 132.</ref> Gerbert may have been the author of a description of the astrolabe that was edited by Hermannus Contractus some 50 years later. Besides these, as Sylvester II he wrote a dogmatic treatise, ''De corpore et sanguine Domini''.

===Abacus and Hindu-Arabic numerals===
right|thumb|200px|Reconstructed [[Ancient Rome|Ancient Roman Abacus.]] 
Gerbert learned of Hindu-Arabic digits and applied this knowledge to the animal horn by a shieldmaker of Rheims.<ref name="tester 131 132">Tester, 131&ndash;132.</ref><ref name="darlington 472">Darlington, 472.</ref><ref name="buddhue 266">Buddhue, 266.</ref> 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 in using only Roman numerals.<ref name="darlington 472"/> Due to Gerbert's reintroduction, the abacus became widely used in Europe once again during the 11th century.<ref name="buddhue 266"/>

===Armillary sphere and sighting tube===

Although lost to Europe since the terminus of the Trèves, 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.<ref>Darlington, 464, 467&ndash;472.</ref> Richer stated that Gerbert discovered that stars coursed in an oblique direction across the night sky.<ref name="darlington 467"/> Richer described Gerbert's use of the armillary sphere as a visual aid for teaching mathematics and astronomy in the classroom, as well as how Gerbert organized the rings and markings on his device:

thumb|right|200px|An [[armillary sphere in a painting by Sandro Botticelli, c. 1480.]]
<blockquote>
First [Gerbert] demonstrated the form of the world by a plain wooden sphere...thus expressing a very big thing by a little model. Slanting this sphere by its two poles on the horizon, he showed the northern constellations toward the upper pole and the southern toward the lower pole. He kept this position straight by means of a circle by which the Greeks call ''horizon'', the Latins ''limitans'', because it divides the stars which are visible from those which are not visible. On this horizon line, placed so as to demonstrate practically and plausibly...the rising and setting of the stars, he traced natural outlines to give a greater appearance of reality to the constellations. . .He divided a sphere in half, letting the tube represent the diameter, the one end representing the north pole, the other the south pole. Then he divided the semicircle from one pole to the other into thirty parts. Six lines drawn from the pole he drew a heavy ring to represent the arctic polar circle. Five divisions below this he placed another line to represent the tropic of Cancer. Four parts lower he drew a line which set forth the rotundity of the equinoctial circle [the equator]. The remaining distance to the south pole is divided by the same dimensions.<ref name="darlington 467">Darlington, 467.</ref>
</blockquote>

Given this account, 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.<ref name="darlington 468">Darlington, 468.</ref> By this account, the polar circle on Gerbert's sphere was located at 26 degrees, just several degrees off from the actual 23° 28'.<ref name="darlington 468"/> Furthermore, this account illustrates that his positioning of the Tropic of Cancer was nearly exact, while his positioning of the equator was exactly correct.<ref name="darlington 468"/> Richer also revealed how Gerbert made the planets more easily observable in his armillary sphere:

<blockquote>
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 which 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.<ref>Gerbert, 468&ndash;469.</ref>
</blockquote>