Ibn Qurrah: Greatest Arab polymath of 9th century

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Ibn Qurrah

The world today is unimaginable without reference to that branch of mechanics which is known as statics. Yet very few today would know that one of the pioneers in this particular field of study was an Arab polymath of the 9th century. Al-Sabi Thabit Ibn-Qurrah al-Harrani was of course just not a mathematician, he was a polymath with seminal contributions in the fields of astronomy, medical sciences, and philosophy. He was also a great translator of Greek mathematical texts into Arabic.

Ibn Qurrah in Baghdad

Ibn Qurrah, as he has been widely referred to in history, was born in 826 (according to some sources 1836) in Harran. Then a part of the Abbasid Caliphate. It is said he began his carrier as a humble money-changer in the Harran market. But soon moved to Baghdad, then the nerve-center of Islamic intellectual pursuits. And Qurrah’s foray into the intellectual world began after being employed by three wealthy brothers. Known as Banu Musa. He was hired for translating Greek mathematical treatises into Arabic.

Among others, he translated major works of Euclid, Archimedes, and Ptolemy. Besides, Qurrah did extremely important summaries from renowned European works, such as those from the works of important physicians like Galen of Pergamum and Hippocrates as well as the philosophy of Aristotle. Shortly Qurrah started penning original works on geometry, statics, the theory of numbers, music, astronomy, medicine, and philosophy. It has been claimed that the medieval theory of the trepidation of the equinoxes was developed by Qurrah.

His breakthrough in amicable numbers

Copernicus has mentioned that Ibn Qurrah calculated the length of the sidereal year to be of 6 hours, 9 minutes, and 12 seconds. Which is just two seconds different from modern calculations. Thabit also penned a book, in a manner summarizing the major events of the 9th century in terms of Astronomy, titled De Anno Solis. In mathematics, there is a term called ‘amicable numbers’. When two different numbers are related in such a way that the sum of the proper divisors of each is equal to the other number, they are known as ‘amicable numbers’.

Ibn Qurrah was the first mathematician to formulate an equation for determining amicable numbers. Again, in the field of recreational mathematics, there are certain ‘problems’ known as ‘chessboard problems’. Qurrah devised a solution to a chessboard problem.

Books by Ibn Qurrah

Qurrah’s contributions to physics are no less important. His book Liber Karatonis offered proof of the law of the lever. A study that he conducted combining Aristotelian and Archimedean ideas of dynamics and mechanics. Another of Qurrah’s large number of books is Kitab fi sifat alqazn. This oeuvre discusses concepts of equal-armed balance. It is also said that Qurra was one of the first to develop the concept of equal-armed balance.

Late in his life, this great Arab polymath became the court astronomer of the Abbasid Caliph al-Mu’tadid. By the end of his life, Qurrah had authored as many a 150 books. Sadly only about a dozen of those have survived to the modern period. He passed away in 901 in Baghdad. His son Sinan ibn Thabit and grandson Ibrahim Ibrahim ibn Sinan continued his good work forward.


(Written by Author and Translator Nilanjan Hajra)

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