Friday, November 12, 2021

Index N

 Tusi, Nasir al-Din Abu Ja‘far al-

Tusi, Nasir al-Din Abu Ja‘far al- (Nasir al-Din Abu Ja‘far al-Tusi) (Abu Jafar Muhammad ibn Muhammad ibn al-Hasan Nasir al-Din al-Tusi)  (Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī) (b. February 18, 1201, Ṭūs, Khorasan – d. June 26, 1274, al-Kāżimiyyah, Baghdad).  Astronomer and Shi‘a politician.  In 1256, he lured the Assassin leader Rukn al-Din Khurshah into the hands of the Il-Khan Hulegu, accompanied the latter to Baghdad and founded the observatory of Maragha.  He had a strong sympathy with the Twelver Shi‘a, to whom a certain degree of mercy was shown during the Mongol holocaust and whose sanctuaries were spared.  He wrote on dogmatics, logic and philosophy, law and belles-lettres, and above all on the sciences, in particular on astronomy.

Al-Tusi was one of the greatest scientists, mathematicians, astronomers, philosophers, theologians and physicians of his time.  He was a prolific writer.  He wrote many treatises on such varied subjects as algebra, arithmetic, trigonometry, geometry, logic, metaphysics, medicine, ethics, and theology. 

Abu Jafar Muhammad ibn Muhammad ibn al-Hasan Nasir al-Din al-Tusi was born in Tus, Khurasan (present day Iran) in 1201.  He studied sciences and philosophy under the tutelage of Kamal al-Din ibn Yunus.  Al-Tusi was kidnapped by the Isma‘ili Hasan ibn Sabah’s agents and sent to Alamut where he remained until its capture by the Mongol Hulegu Khan in 1256.

Impressed by al-Tusi’s exceptional abilities and astrological competency, Il-Khanid Hulegu Khan appointed him as one of his ministers.  Later, he served as an administrator of Auqaf.  In 1262, he built an observatory at Meragha and directed its activity.  It was equipped with the best instruments from Baghdad and other Islamic centers of learning.  It contained a twelve foot wall quadrant made from copper and an azimuth quadrant and turquet invented by al-Tusi.  Other instruments included astrolabes, representations of constellation, epicycles and shapes of spheres.  Al-Tusi designed several other instruments for the observatory.

Al-Tusi produced a very accurate table of planetary movements and a star catalogue, and he published it under the title al-Zij Ilkhani which was dedicated to the Ilkhan, Hulegu Khan.  The tables were developed from observations over a twelve year period and were primarily based on original observations.  Al-Tusi calculated the value of 51 feet for the precession of equinoxes.  Al-Tusi was among the first of several Muslim astronomers who pointed out several serious shortcomings in Ptolemy’s models based on mechanical principles and modified it.  His critique on the Ptolemy’s theories convinced future astronomers of the need to develop an alternative model ending in Copernicus’ famous work.  The al-Zij Ilkhani was the most popular book among astronomers until fifteenth century.  His memoir on astronomy entitled Tadhkira fi Ilm al-Hayy, includes his ingenious device for generating rectilinear motion along the diameter of the outer circle from two circular motions.  At the end of his long outstanding career, he moved to Baghdad and died within a year in 1274 in Kadhimain (near Baghdad, in present day Iraq).

Al-Tusi pioneered spherical trigonometry which includes six fundamental formulas for the solution of spherical right angled triangles.  One of his most important mathematical contributions was the treatment of trigonometry as a new mathematical discipline.  He wrote on binomial coefficients which Pascal later introduced.

Al-Tusi revived the philosophy of Ibn Sina.  His book Akhlaq-i-Nasri (Nasirean Ethics) was regarded as the most important book on ethics and was popular for centuries.  Al-Tusi’s Tajrid-al-‘Aqaid was an excellent work on Islamic scholastic philosophy.  He also composed a few verses of poetry.

Al-Tusi was a prolific writer.  He wrote his works in Arabic and Persian.  Sixty-four treatises are known to have survived.  Al-Tusi’s works were translated into Latin and other European languages in the Middle Ages.  Al-Tusi’s book Shaq al-Qatta was translated into Latin by the title Figura Cata.  Among al-Tusi’s well-known students are Nizam al-Araj, who wrote a commentary on the Almagest, and Qutb ad-Din ash-Shirazi, who gave the first satisfactory mathematical explanation of the rainbow.


Nasir al-Din Abu Ja'far al-Tusi see Tusi, Nasir al-Din Abu Ja‘far al-
Abu Jafar Muhammad ibn Muhammad ibn al-Hasan Nasir al-Din al-Tusi see Tusi, Nasir al-Din Abu Ja‘far al-
Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī see Tusi, Nasir al-Din Abu Ja‘far al-

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