Qadi Zada al-Rumi
Mathematician and astronomer, Ulugh Beg's teacher
A mathematician and astronomer from Bursa who became Ulugh Beg's teacher, the leading professor of his madrasa and one of the directors of the Samarkand observatory.
© Bgag, CC0
From Bursa to Samarkand
His full name was Salah al-Din Musa ibn Muhammad ibn Mahmud. Qadi Zada means 'the judge's son' — his father was a judge in Bursa — while al-Rumi marks him as a man from 'Rum', that is, Anatolia. Born around 1364, he studied in Bursa under the celebrated Molla Fenari, then, drawn by the fame of the scholars of Transoxiana and Khorasan, headed east and reached Samarkand early in the 15th century.
He taught the young Ulugh Beg astronomy and mathematics and gave him a lifelong passion for both. In the early 1410s he wrote, for Ulugh Beg, a commentary on Mahmud al-Jaghmini's astronomical handbook; equally famous is his commentary on Ashkal al-Ta'sis, a geometry treatise by the Samarkand mathematician Shams al-Din al-Samarqandi. Both remained madrasa textbooks for centuries.
Madrasa and observatory
When Ulugh Beg's madrasa on the Registan opened in 1420, Qadi Zada became its most eminent teacher. With Jamshid al-Kashi he directed the building of the observatory and the making of its instruments, and after al-Kashi's death in 1429 he led its scientific work. He contributed to the Zij-i Sultani and wrote a treatise on al-Kashi's method for calculating the sine of one degree — a method known to us mainly through his account.
His pupils included Ali Qushji and Fathullah Shirvani, who later taught in Anatolia; his grandson Mirim Chelebi became a noted Ottoman astronomer.
Death, and the riddle of his 'tomb'
Qadi Zada died in Samarkand sometime after 1436, before the observations were complete; the exact year is unknown. An elegant double-domed mausoleum of 1434–1435 at Shah-i-Zinda long bore his name, but when its crypt was examined in 1977 it proved to hold the burial of a woman. The attribution has been dropped, and the scholar's grave remains unknown.
