5. Sanad Ibn Ali
(Died after 250H/864AD)

Sanad Ibn Ali, alias Abu Tayeb was a contemporary of the Abassid Caliph al-Ma'mun. Reportedly, he was born around 850AD. According to Sarton, he died after year the 864AD. He was a Muslim astronomer and mathematician(27). It is said that Sanad was Jewish and embraced Islam, guided by the Caliph al-Ma'mun, who appointed him in his panel of astrologists and head of all observational matters.

Scientific Contributions

All the credit goes to Sanad for the setting up of Baghdad observatory. He also developed ephemeredes, he called "Azyaj al-Ma'mun", that were used by astrologists of his time and subsequently. He was renowned for the manufacturing of astronomic detection equipment and the astrolabe. He also corrected the positions of some planets and took part in the endeavor of measurement of the Earth and planet surfaces, ordered by al-Ma'mun.

Major Works

In addition of his interests in meteorology, Sanad Ibn Ali was versed in mathematics. He wrote several books in these subjects, including :

- Kitab al-Hissab al-Hindi (book on Indian Numerals);

- Kitab al-Jama' wa Tafriq (book on addition and division);

- Kitab al-Jabr wa al-Mufaraqa;

- Kitab al-Munfasilat wa al-Mutawassitat, dealing with stars and arithmetic;

Besides, Sanad explained nine essays from Euclid's treatise on geometry "Elements".