Al-Sabi Thabit ibn Qurra al-Harrani (836 –901) was an astronomer and mathematician born in present day Turkey, best known for translating classic Greek works on astronomy, and discovered an equation for determining the amicable numbers. He was a Mandean physician, who was known as Thebit in Latin.
Thabit was a member of the Sabian religious sect. His heritage was sharp in traditions of Hellenistic culture and pagan veneration of the stars. This background, and in particular his knowledge of Greek and Arabic, made him an attractive prospect for enclosure in one particular community of scholars, the Banu Musa and their circle in Baghdad. Thabit seems to have been asked to join this circle by a family member, the mathematician Muhammad ibn Musa ibn Shakir, who recognized his talents and potential.
Thabit subsequently came to fame after traveling to Baghdad when he was invited by Muhammad bin Musa bin Shakir, one of the Banu Musa brothers. He worked in Baghdad and he occupied himself with mathematics, astronomy, mechanics, medicine and philosophy.
Contributions and Achievements:
Thabit is credited with dozens of treatises, covering a wide range of fields and topics. While some were written in his native Syriac, most were composed in Arabic. Thabit was trilingual, a skill that enabled him to play a key role in the translation movement of 9th century Baghdad. He translated works from both Syriac and Greek into Arabic, creating Arabic versions of important Hellenistic and Greek writings. Several of Thabit’s Arabic translations are the only extant versions of important ancient works.
The medieval astronomical theory of the trepidation of the equinoxes is often attributed to Thabit. He developed a theory about the trepidation and oscillation of the equinoctial points, of which many scholars debated in the Middle Ages.
According to Copernicus Thabit determined the length of the sidereal year as 365 days, 6 hours, 9 minutes and 12 seconds (an error of 2 seconds). Copernicus based his claim on the Latin text attributed to Thabit. Thabit published his observations of the Sun. In the fields of mechanics and physics he may be recognized as the founder of statics. He observed conditions of equilibrium of bodies, beams and levers. Thabit also wrote on philosophical and cosmological topics, questioning some of the fundamentals of the Aristotelian cosmos.
He rejected Aristotle’s concept of the essence as immobile, a position Rosenfeld and Gregorian suggest is in keeping with his anti Aristotelian stance of allowing the use of motion in mathematics. Thabit also wrote important treatises related to Archimedean problems in statics and mechanics. Besides all these contributions he also founded a school of translation and supervised the translation of a further large number of books from Greek to Arabic.
Among Thabit’s writings a large number have survived, while several are not present. Most of the books are on mathematics, followed by astronomy and medicine. The books have been written in Arabic but some are in Syriac. In the Middle Ages, some of his books were translated into Latin by Gherard of Cremona. In recent centuries, a number of his books have been translated into European languages and published. Thabit’s efforts provided a foundation for continuing work in the investigation and reformation of Ptolemaic astronomy. His life is illustrative of the fact that individuals from a wide range of backgrounds and religions contributed to the flourishing of sciences like astronomy in Islamic culture.
Thabit died in Baghdad in the year 901. Thabit’s son was a distinguished physician and his grandson Ibrahim ibn Sinan studied the curves which are needed for the making of sundials.