Sind ibn Ali

Sind ibn Ali-Musa
Died	after 864 AD
Residence	Mansura, Sindh
Occupation	Sindhi Muslim Astronomer, Translator, Mathematician, Engineer
Notable work	Zij al-Sindhind, Decimal mark
Parent(s)	Ali-Musa (father)

Sind ibn Ali-Musa, Sind ibn ʿAlī (died after 864 AD), was a renowned Sindhi Muslim astronomer, translator, mathematician and engineer. His father Ali-Musa was a convert to Islam and an aristocrat who lived in Mansura, Sindh. Sind ibn ʿAlī traveled to Baghdad and received the best education available.

He is known to have translated and modified the Zij al-Sindhind. The Zij al-Sindhind was the first astronomical table ever introduced in the Muslim World. As a mathematician Sind ibn ʿAlī was a colleague of al-Khwarizmi and worked closely with Yaqūb ibn Tāriq together they calculated the diameter of the Earth and other astronomical bodies. He also wrote a commentary on Kitāb al-ğabr wa-l-muqābala and helped prove the works of al-Khwarizmi. The decimal point notation to the Arabic numerals was introduced by Sind ibn Ali.

According to Ibn Abi Usaibia: the Banū Mūsā brothers out of professional jealousy kept him away from Abbasid Caliph al-Mutawakkil at his new capital Samarra and had caused Sind ibn ʿAlī to be sent away to Baghdad. Both Ja'far Muhammad ibn Mūsā ibn Shākir and Ahmad ibn Mūsā ibn Shākir delegated the work of digging a great canal instead to Al-Farghani and thus ignoring Sind ibn ʿAlī, the better engineer. Al-Farghani committed a great error, making the beginning of the canal deeper than the rest and water never reached the new garrison of Al-Ja'fariya. News of this greatly angered al-Mutawakkil and the two Banū Mūsā brothers were saved from severe punishment only by the gracious willingness of Sind ibn ʿAlī, to vouch the corrections of Al-Farghani's calculations thus risking his own welfare and possibly his life.