Jabir ibn Aflah
| Jābir ibn Aflaḥ | |
|---|---|
| Born | 1100 CE Seville, al-Andalus |
| Died | 1150 CE |
| Residence | Caliphate |
| Academic work | |
| Era | Islamic Golden Age |
| Main interests | Astronomy, Mathematics |
| Notable works | Iṣlāḥ al-Majisṭi (Correction of the Almagest) |
| Notable ideas | |
| Influenced | Averroes, Nur ad-Din al-Betrugi |
Abū Muḥammad Jābir ibn Aflaḥ (Arabic: أبو محمد جابر بن أفلح, Latin: Geber/Gebir; 1100–1150) was a Muslim astronomer and mathematician from Seville, who was active in 12th century al-Andalus. His work Iṣlāḥ al-Majisṭi (Correction of the Almagest) influenced Islamic, Jewish and Christian astronomers.
This work is a commentary and reworking of Ptolemy's Almagest and is the first criticism of it in the Islamic West. He particularly criticized the mathematical basis of the work. For example he replaced the use of Menelaus' theorem with ones based on spherical trigonometry, in what seems to be an attempt to increase the mathematical precision of the work. These theorems had been developed by a group of 10th century Islamic mathematicians who included Abū al-Wafā' Būzjānī and then also by Abu Abd Allah Muhammad ibn Muadh Al-Jayyani who worked in Andalusia during the 11th century. Jābir does not credit any of these authors and does not refer to a single Islamic author in this work.
One substantial change Jābir made to Ptolemy's account is that he placed the orbits of Venus and Mercury, the minor planets, outside that of the Sun, rather than between the Moon and the Sun as had been the case in the original work.
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