17. Abu Sahl Al-Quhi(98)
(Died in 405H/ 1014AD)

Al-Quhi was one of the famous Muslim Scholars who excelled in astronomy and mathematics during the 4th century H./ 10th century AD. His name was Abu Sahl Wijen Ibn Rustum al-Quhi. The date of his birth is unknown, while his death occurred in 405 H./1014 AD. He hailed from Kuh in Tabaristan mountains and lived in Baghdad. When Sharafu Dawla al-Bouaihi acceded to power, he favored him and appointed him in 378 H./988 AD at the head of the observatory he set up in Baghdad. He requested him to provide him with a study on his observation of the seven planets, their orbits and motions within their zodiac(99).

Scientific Contributions

Al-Quhi was among the prominent astronomers in the 4th century H/ 10th century AD. He made a number of observations on which scholars of his time used to rely and criticized some of the Greek astronomers' hypotheses. His renown came also from his skills in the manufacturing of observation instruments.

In mathematics, "al-Quhi was concerned by Archimedes' and Appolonius  problems that lead to equations higher than the second degree equations. He was able to solve some them and discussed the requirements of such an operation. His studies can be considered as the best that has ever been written on geometry in the Muslim world"(100). 

Al-Quhi also contributed to the study of weights, a field in which he had precedence. He used geometric evidence to solve many problems that require the determination of weight. Moreover, he left valuable researches in the founding principles of cranes/lifts(101).

Major Works

Dr. Abdullah ad-Difa' and az-Zarkali(102) mentioned several of al-Quhi's works in astronomy and mathematics, namely the following :

- "Kitab Marakiz al-Akr";

- "Kitab al-Ussul ala Tahrikat Euclides"

- "Kitab San'at al-Usturlab bi al-Barahin"

- "Kitab Aziyadat ala Archimedes fi al-Maqala Tania"

- "Ikhraj al-Khatayn min Nuqta ala Zaouiya Maaluma"

- "Tatlit azzaouiya wa 'amal al-Musaba' al-Mutassaoui al-Adla' fi Da'era"

Dr. Abdullah ad-Difa' says in his book" Exact Sciences in Arab Islamic Civilization" : "However, most of al-Quhi's works were lost and only few references to them were found in Latin works(103).