Nasir al-Din al-Tusi

NASIR AL-DIN AL-TUSI ( 1201 - 1274 A.D.) Abu Jafar Muhammad Ibn Muhammad Ibn al-Hasan Nasir al-Din al-Tusi was born in Tus, Khurasan, (now Iran) in 1201 A.D. Al-Tusi was appointed astrologer for the State by Isma'ili governor Nasir ad-Din 'Abd ar-Rahim. He learnt sciences and philosophy from Kamal al-Din Ibn Yunus, Shaikh al-Mufid, and the two brothers, members of Ahl al-bait and both outstanding scholars, al-Sharif al-Murtada and al-Sharif al-Radi. He was instrumental in the establishment an observatory at Maragha. t became operational in 1262 and housed many scientific instruments used for astronomy, designed by al-Tusi. Al-Tusi wrote many books, some of which are improved translations of Euclid, Ptolemy, Theodosius and Apollonius. However in his Memorandum on Astronomy he criticises Ptolemy's theories. He also made important original contributions to astronomy and mathematics. One of his most important mathematical contributions was the creation of trigonometry as a mathematical discipline in its own right rather than as just a tool for astronomical applications. Another mathematical contribution was his teaching about Pascal's triangle relating binomial coefficients, long before the time of Pascal. Al-Tusi put his observatory to good use, making a very accurate table of planetary movements. He published Ilkhanic Tables after making observations for 12 years. These contain tables for computing the positions of the planets. They also contain a star catalogue. Al-Tusi calculated the value of 51' for the precession of the equinoxes. He also wrote works on instruments, for example on constructing and using an astrolabe. He had a number of pupils, one of the better known being Nizam al-a'Raj who wrote a commentary on the Almagest. Another of his pupils Qutb ad-Din ash-Shirazi gave the first satisfactory mathematical explanation of the rainbow. Nasir al-Din was one of the greatest scientists, philosophers, mathematicians, astronomers, theologians and physicians of the time and was a prolific writer. He made significant contributions to a large number of subjects, and it is indeed difficult to present his work in a few words. He wrote one or several treatises on different sciences and subjects including those on geometry, algebra, arithmetic, trigonometry, medicine, metaphysics, logic, ethics and theology. In addition he wrote poetry in Persian. In mathematics, his major contribution would seem to be in trigonometry, which was compiled by him as a new subject in its own right for the first time. Also he developed the subject of spherical trigonometry, including six fundamental formulas for the solution of spherical right-angled triangles. As the chief scientist at the observatory established under his supervision at Maragha, he made significant contributions to astronomy. The observatory was equipped with the best possible instruments, including those collected by the Mongol armies from Baghdad and other Islamic centers. The instruments included astrolabes, representations of constellations, epicycles, shapes of spheres, etc. He himself invented an instrument 'turquet' that contained two planes. After the devoted work of 12 years at the observatory and with the assistance of his group, he produced new astronomical tables called 'Al-Zij-Ilkhani' dedicated to Ilkhan (Halagu Khan). Although Tusi had contemplated completing the tables in 30 years, the time required for the completion of planetary cycles, but he had to complete them in 12 years on orders from Halagu Khan. The tables were largely based on original observations, but also drew upon the then existing knowledge on the subject. The 'Zij Ilkhani' became the most popular tables among astronomers and remained so till the 15th century. Nasir al-Din pointed out several serious shortcomings in Ptolemy's astronomy and foreshadowed the later dissatisfaction with the system that culminated in the Copernican reforms. In philosophy, apart from his contribution in logic and metaphysics , his work on ethics entitled Akhlaq-i-Nasri became the most important book on the subject, and remained popular for centuries. His book Tajrid-al-'Aqaid was a major work on al-Kalam (Islamic Scholastic Philosophy) and enjoyed widespread popularity. Several commentaries were written on this book and even a number of supercommentaries on the major commentaries, Sharh Qadim and Sharh Jadid. The list of his known treatises is exhaustive; Brockelmann lists 56 and Sarton 64. About one-fourth of these concern mathematics, another fourth astronomy, another fourth philosophy and religion, and the remainder other subjects. The books, though originally written in Arabic and Persian, were translated into Latin and other European languages in the Middle Ages and several of these have been printed. Tusi's influence has been significant in the development of science, notably in mathematics and astronomy. His books were widely consulted for centuries and he has been held in high repute for his rich contributions.