Ebu Sehl El-kûhî

Scholar of mathematics and astronomy. (B. ?, Kûh / Iran – D. 990-1000? ). His full name is Ebû Sehl Veycen (Vîcen) b. Rüstem el-Kûhî. He was born in the village of Kûh which is located at the mountainous Mazenderan region of Iran. There is no further information on his life and education. He completed his scientific researches under the protection of Büveyhi rulers Adudüddevle and his son Şerefüddevle between the years 969-989 in Shiraz and Baghdad. Kûhi who in the same time invented astronomic observation tools observed the solar declination in 971 in Shiraz using his own tools. Thus he determined the seasonal variations; winter after the 16^th of December (today 22 December) and summer after the 17^th of June (today 21 June). He was appointed Head of the Observatory in Baghdad by Şerefüddevle. Ten scholars consisting of the prominent judges, astronomers and mathematicians of his age signed a report he prepared about his observations by the end of June 988. Kûhî’s findings prove that his tools were more sensitive and accurate than tools used until that day. According to Birûnî, Kuhi’s observations ceased after the death of Şerefüddevle (989).

According to Ömer Hayyâm, Kuhi was a perfect mathematician. He proved his success rather in the field of geometry and therefore was regarded as one of the followers of Euclid, Apollonios of Perge and Archimedes. In his works, which came until the present, it is seen that he solved problems which led to higher than 2^nd level equations. Kûhî’s works were appreciated by Ebû Saîd Ahmed b. Muhammed es-Siczî, İbnü’l-Heysem, Birûnî, Ömer Hayyâm, Nasîrüddîn-i Tûsî and Ebû Nasr İbn Irak, besides Nasîrüddîn-i Tûsî added to Archimedes’ book “Sphere and Cylinder” the spherical sector problem he solved.

Kûhî stated that works of Greek scientists about the calculation of pressure and gravity centers were ridiculously simple and far from being scientific. He proved his original methods and discoveries with very firm evidences. Theories he presented on this issue were unknown until that date. He was the first scholar to use and apply the terms of analysis and synthesis in mathematics. Thus Kûhî was the founder of mathematical analysis method. In natural sciences, in other words in empirical sciences, he believed that the final result could be achieved using mathematical methods. His longsighted understanding was adopted after centuries by Newton and other scientists.

Kuhi who was a hardworking and productive scholar was in the same time one of the major promoters of science. His works and efforts encouraged two famous Muslim astronomers Ebü’l-Vefâ Buzcânî and Ebû Hâmid Sağanî and led them to scientific works. Thus Kûhî caused the establishment of academic studies in an extraordinarily high scientific level at that time.

Ebû Sehl’s studies on pressure and gravity centers were discussed only centuries after him, in the 19^th century by A. F. Mâbius. All this proves that Islamic scholars created numerous works of high scientific value, centuries ago. Researches on the works of Kûhi, who is regarded as the master of geometry at his time, are still on progress.  

WORKS:

Es-Sâire fil-Emtâr alâ Temâd-il E’sâr, Kitâbu Merâkiz-il-Ekr, Kitâb-ul-Usûl alâ Tahrikât-ı Oklîdes, Kitâb-ül-Berkân-it-Tâm, Kitâbu Merâkiz-ud-Devâir alel Hutût min Tarîk-it-Tahlîl Dûn-et-Terkîb, Kitâbu San’at-il-Usturlâb bil-Berâhîn, Kitâbu Ihrâc-il-Hatteyn alâ Nisbetin, Kitâb-ud-Devâir-il-Mütemâsse min Tarîk-it-Tahlîl, Kitâb-uz-Ziyâdât alâ Arşimedes fil-Makâlet-is-Sâniye, Kitâbu İstihrâcı Dil-il-Misbâ’ fid-Dâire, Kitâb-ül-Murâselât Beynel Kûhî ves-Sâbî, Risâletün fî Amel-i Muhammesin.

REFERENCE: Aydın Sayılı / The Observatory in İslam (s. 104-107, 112-117, I960), Rüstem Kaya / Analitik Geometri (s. 150-151, Eskişehir 1992), Mehmet Emin Bozhüyük / “Kûhî” (Türkiye Diyanet Vakfı İslam Ansiklopedisi, c. 26, s. 346-347, 2002), İhsan Işık / Ünlü Bilim Adamları (Türkiye Ünlüleri Ansiklopedisi, C. 2, 2013) - Encyclopedia of Turkey’s Famous People (2013).