Biography:Yaʿqūb ibn Ṭāriq

Yaʿqūb ibn Ṭāriq (يعقوب بن طارق; died c. 796 AD) was an 8th-century Persian astronomer and mathematician who lived in Baghdad.

Works

Works ascribed to Yaʿqūb ibn Ṭāriq include:

• Zīj maḥlūl fī al‐Sindhind li‐daraja daraja (زيج محلول في السندهند لدرجة درجة, "Astronomical tables in the Sindhind resolved for each degree"),
• Tarkīb al‐aflāk (تركیب الأفلاك, "Arrangement of the orbs"),
• Kitāb al‐ʿilal (كتاب العلل, "Rationales"),
• Taqṭīʿ kardajāt al‐jayb (تقطيع كردجات الجيب, "Distribution of the kardajas of the sine"), and
• Mā irtafaʿa min qaws niṣf al‐nahār (ما إرتفع من قوس نصف النهار, "Elevation along the arc of the meridian").

An astrological work called Al‐maqālāt (المقالات, "The Chapters") is also ascribed to him by an unreliable source.

The Zīj, written around 770, was based on a Sanskrit work, thought to be similar to the Brāhmasphuṭasiddhānta. This work was brought to the court of al-Mansūr from Sindh, reportedly by a Sindhi astronomer named Kankah.

The Tarkīb al‐aflāk dealt with cosmography, that is, the placement and sizes of the heavenly bodies. Its estimates of the sizes and distances of the heavenly bodies were tabulated in al-Bīrūnī's work on India; according to him, Yaʿqūb ibn Ṭāriq gave the radius of the Earth as 1,050 farsakhs, the diameter of the Moon and Mercury as 5,000 farsakhs (4.8 Earth radii), and the diameter of the other heavenly bodies (Venus, the Sun, Mars, Jupiter, and Saturn) as 20,000 farsakhs (19.0 Earth radii.)

Further reading

• Hogendijk, Jan P. (1988). "New Light on the Lunar Crescent Visibility Table of Yaʿqūb ibn Ṭāriq". Journal of Near Eastern Studies 47 (2): 95–104. doi:10.1086/373260. 
• Kennedy, E. S. (1956). "A Survey of Islamic Astronomical Tables". Transactions of the American Philosophical Society. New Series 46 (2): 123–177. doi:10.2307/1005726. 
• Kennedy, E. S. (1968). "The Lunar Visibility Theory of Yaʿqūb Ibn Ṭāriq". Journal of Near Eastern Studies 27 (2): 126–132. doi:10.1086/371945. 
• Pingree, David (1968). "The Fragments of the Works of Yaʿqūb Ibn Ṭāriq". Journal of Near Eastern Studies 27 (2): 97–125. doi:10.1086/371944. 
• Pingree, David (1976). "Yaʿqūb ibn Ṭāriq". in Gillispie, Charles Coulston. Dictionary of Scientific Biography. 14. New York: Charles Scribner's Sons. pp. 546. ISBN 978-0-684-16962-0. http://www.encyclopedia.com/doc/1G2-2830904745.html. 
• Plofker, Kim (2007). "Yaʿqūb ibn Ṭāriq". in Thomas Hockey. The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 1250–1. ISBN 978-0-387-31022-0. http://islamsci.mcgill.ca/RASI/BEA/Yaqub_ibn_Tariq_BEA.htm.  (PDF version)
• Sezgin, Fuat (1978). Geschichte des arabischen Schrifttums. Vol. 6, Astronomie, pp. 124–127. Leiden: E. J. Brill.
• Steinschneider, Moritz (1870). "Zur Geschichte der Uebersetzungen aus dem Indischen in's Arabische und ihres Einflusses aus die arabische Literatur". Zeitschrift der Deutschen Morgenländischen Gesellschaft 24: 332. http://menadoc.bibliothek.uni-halle.de/dmg/periodical/titleinfo/21506. 
• Suter, Heinrich (1900). Die Mathematiker und Astronomer der Araber. p. 4.