Ali Ben Isa
Encyclopedia
ʿAlī ibn ʿĪsā al-Asṭurlābī was an Afro-Arab 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 expedition to the Plain of Sinjar
to measure the length of a degree, or the circumference of the Earth. He measured the Earth
's circumference, getting a result of 40,248 km (or, according to other sources, 41,436 km).
Islamic geography
Geography and cartography in medieval Islam refers to the advancement of geography, cartography and the earth sciences in the medieval Islamic civilization....
of the 9th century. He wrote a treatise on the astrolabe
Astrolabe
An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...
and was an opponent of astrology
Astrology
Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...
. During the reign of al-Ma'mun
Al-Ma'mun
Abū Jaʿfar Abdullāh al-Māʾmūn ibn Harūn was an Abbasid caliph who reigned from 813 until his death in 833...
, and together with Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī, he participated in an expedition to the Plain of Sinjar
Sinjar
Sinjar is the name of a town and district in northwestern Iraq's Ninawa Governorate near the Syrian border. Its population at the time of the 2006 census was 39,875....
to measure the length of a degree, or the circumference of the Earth. He measured the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's circumference, getting a result of 40,248 km (or, according to other sources, 41,436 km).