The Library of Congress’s African and Middle Eastern Division recently added to its treasure trove a very important 15th century Arabic manuscript on astronomy and mathematics. “Tahrir al-Majisti” (“Commentary on the Almagest”), by Nasir al-Din al-Tusi, is part of the corpus of major commentaries by Muslim scholars on Ptolemy’s “Almagest,” many of which date back to the 8th century. In his treatise, al-Tusi challenges some of Ptolemy’s theories and reformulates the Ptolemaic planetary model, producing a system in which planets move in uniform circular motion.
Although the original work was written in 1247 by al-Tusi (1201-1274), this manuscript was probably produced in 1467 in Turkestan, in Central Asia. It is illustrated with numerous diagrams and tables in red and black ink and includes astronomical theorems, information on solar eclipses, descriptions of the movement of planets, the regressions of Mars and Mercury and attempts to measure the distance between the Sun and the Earth.
So who was Nasir al-Din al-Tusi?
Al-Tusi’s full name was Nasir al-Din Muhammad ibn Muhammad al-Tusi. A philosopher, astronomer and mathematician who knew Arabic, Persian and possibly Greek, al-Tusi was born in Tus (in today’s Iran) into a family of Shi’ite jurists. While raised in a religious environment, al-Tusi followed in his uncle’s footsteps and at a young age began studying science, including physics and mathematics. This laid the foundation for his scientific accomplishments in his later years.
Al-Tusi’s scientific journey started in Tus and flourished in Maragha (in today’s Azerbaijan). During his lifetime, the Mongol empire expanded from Beijing in the east to Europe in the west, and al-Tusi’s talents did not go unnoticed by the new rulers. First he served as a scientific advisor to the Mongol administration and then was put in charge of the ministry of religious bequests. Later he directed an observatory in Maragha. This observatory was his brainchild, which the then ruler, Hülegü Khan (c. 1217-1265), fully funded because of Hülegü’s belief in astrology.
Al-Tusi’s foresight also led to the inclusion in this facility of an excellent library and a faculty of notable Islamic and Chinese scholars. The Maragha Observatory, which was considered one of the greatest astronomical observatories of its day, continued to operate for many years until it fell into disrepair due to lack of funds, war and earthquakes.
The work done there represented a new wave of scientific research in the Islamic world in early medieval times and played a key role in the development of astronomy. The Maragha Observatory would become the model for several observatories that were subsequently built in Persia and Asia Minor up to the 17th century. Today in Azerbaijan a new observatory by the same name has been erected on the location where it is believed al-Tusi’s observatory once stood.
Approximately 150 works left by al-Tusi are known today, ranging from astronomy and mathematics to philosophy and theology. One of his most important works, “Tadhkira fi ‘ilm al-Hay’a” (“Memoir on Astronomy”), written later in his life, may be viewed through the Library’s online exhibition “Rome Reborn: The Vatican Library & Renaissance Culture.” The exhibit also contains several editions of Ptolemy’s “Almagest.”
Al-Tusi also invented a device, known today as the “Tusi Couple,” for generating linear motion along the diameter of the outer circle from two circular motions. This device enabled him to correct the Ptolemaic planetary models by proposing a system in which all orbits’ movements may be accurately predicted. Some believe that al-Tusi’s new theories may have been read by Nicolaus Copernicus (1473-1543) in the development of his sun-centered cosmological theories.
In addition to this latest acquisition, the African and Middle Eastern Division also houses a rich collection of Arabic science manuscripts as part of its 1,700 manuscript collection. The subjects of these science manuscripts in this collection include agriculture, arithmetic, medicine, astronomy, physics and time measurements. Some of these manuscripts have been digitized and are available to view via the Library of Congress Online Catalog and on the World Digital Library.
Among the digitized astronomy manuscripts are “Suwar al-kawākib” (“The Book of the Constellations of the Fixed Stars”), by ʻAbd al-Raḥmān ibn ʻUmar al-Ṣūfī (903-986), a Persian astronomer; and “Qāḍīʹzādah ʻalá al-Mulakhkhaṣ fī al-hayʼah” (“Commentary on “The Compendium of Plain Astronomy”),by Mūsá ibn Muḥammad Qāḍīʹzādah, an astronomer and mathematician born in Bursa (in today’s Turkey).
“Suwar al-kawākib” depicts celestial constellations and serves as an authority on Arabic names for the stars and constellations. Persian note before beginning of the text claims that the manuscript was created in 1417, but the note probably dates from the 18th century when the book was rebound. Published/created in the 17th century, “Qāḍīʹzādah ʻalá al-Mulakhkhaṣ fī al-hayʼah” is a treatise about theoretical astronomy by Maḥmūd ibn Muḥammad Jighmīnī (d. ca. 1221), a renowned Persian mathematician and astronomer.