'Ali ibn 'Isa al-Asturlabi

ʿAlī ibn ʿĪsā al-Asṭurlābī (Arabic: علي بن عيسى‎) was an Arab^[1] astronomer and geographer of the 9th century. He wrote a treatise on the astrolabe and was an opponent of astrology. During the reign of al-Ma'mun, and together with Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī, he participated in an expion to the Plain of Sinjar to measure the length of a degree, or the circumference of the Earth.^[2] He measured the Earth's circumference, getting a result of 40,248 km (or, according to other sources, 41,436 km).^{[citation needed]}

See also[]

• List of Arab scientists and scholars

Notes[]

References[]

• Bolt, Marvin (2007). "ʿAlī ibn ʿĪsā al‐Asṭurlābī". In Thomas Hockey; et al. (eds.). The Biographical Encyclopedia of Astronomers. New York: Springer. p. 34. ISBN 978-0-387-31022-0. (PDF version)