Jabir ibn Aflah

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.^[1]

Iṣlāḥ al-Majisṭi (Correction of the Almagest)

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.^[1]

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.^[1]

Inventor

He invented an observational instrument known as the torquetum, a mechanical device to transform between spherical coordinate systems.^[2]

Influence

The Torquetum was invented by Jabir ibn Aflah.

Several later Islamic authors were influenced by Jābir, including Ibn Rushd (Averroes) and Nur ad-Din al-Betrugi, both of whom worked in Andalusia. The work was transmitted to Egypt in the 12th century by Maimonides and further east by the end of the 13th century.^[1]

The work was translated from the Arabic into both Hebrew and Latin, the latter by Gerard of Cremona, who Latinized his name as "Geber". Through that channel it had a wide influence on later European mathematicians and astronomers and helped to promote trigonometry in Europe.^[1]

Much of the material on spherical trigonometry in Regiomontanus' On Triangles (c.1463) was taken directly and without credit from Jābir's work, as noted in the 16th century by Gerolamo Cardano.^[3] The trigonometry that Nicholas Copernicus (1473–1543) outlined in the first part of his epochal work De revolutionibus was also apparently inspired by Jābir.^[4]

Notes

References

• Calvo, Emilia (2007). "Jābir ibn Aflaḥ: Abū Muḥammad Jābir ibn Aflaḥ". In Thomas Hockey; et al. The Biographical Encyclopedia of Astronomers. New York: Springer. pp. 581–2. ISBN 978-0-387-31022-0.  (PDF version)

External links

• Lorch, R. P. (2008) [1970-80]. "Jābir Ibn Aflah Al-Ishbīlī, Abū Muḥammad". Complete Dictionary of Scientific Biography. Encyclopedia.com. 

Mathematics in medieval Islam
Mathematicians (Works)	9th century 'Abd al-Hamīd ibn Turk Sind ibn Ali Al-Abbās ibn Said al-Jawharī Al-Ḥajjāj ibn Yūsuf ibn Maṭar Al-Kindi De Gradibus Al-Mahani Banū Mūsā Hunayn ibn Ishaq al-Khwārizmī The Compendious Book on Calculation by Completion and Balancing ibn Qurra Na'im ibn Musa Sahl ibn Bishr Habash al-Hasib al-Marwazi 10th century Abd al-Rahman al-Sufi Book of Fixed Stars al-Būzjānī Abū Ja'far al-Khāzin Abū Kāmil Shujāʿ ibn Aslam Abu'l-Hasan al-Uqlidisi Abu-Mahmud Khojandi Ahmad ibn Yusuf Al-Nayrizi Al-Saghani Brethren of Purity Ibn Sahl Ibn Yunus Ibrahim ibn Sinan Muhammad ibn Jābir al-Harrānī al-Battānī Sinan ibn Thabit Al-Isfahani Nazif ibn Yumn Abū Sahl al-Qūhī 11th century Abū Ishāq Ibrāhīm al-Zarqālī Abu Nasr Mansur Abū Rayḥān al-Bīrūnī Ibn al-Haytham / Alhazen Book of Optics Ibn Muʿādh al-Jayyānī Al-Karaji Al-Sijzi Alī ibn Ahmad al-Nasawī Avicenna The Book of Healing Ibn Tahir al-Baghdadi Kushyar ibn Labban Yusuf al-Mu'taman ibn Hud 12th century Al-Khazini Ibn Yahyā al-Maghribī al-Samaw'al Omar Khayyám Jabir ibn Aflah Abu Bakr al-Hassar 13th century Muhyi al-Dīn al-Maghribī Nasīr al-Dīn al-Tūsī Zij-i Ilkhani Shams al-Dīn al-Samarqandī Sharaf al-Dīn al-Tūsī Ibn al‐Ha'im al‐Ishbili Ibn Abi al-Shukr 14th century Yaʿīsh ibn Ibrāhīm al-Umawī Ibn al-Banna' al-Marrakushi Ibn al-Shatir Kamāl al-Dīn Fārisī Al-Khalili Qotb al-Din Shirazi Ahmad al-Qalqashandi 15th century Abū al-Ḥasan ibn ʿAlī al-Qalaṣādī Ali Qushji Jamshīd al-Kāshī Qāḍī Zāda al-Rūmī Ulugh Beg Ibn al-Majdi 16th century Al-Birjandi Muhammad Baqir Yazdi Taqi al-Din Ibn Hamza al-Maghribi Ibn Ghazi al-Miknasi
Other treatises	Almanac Encyclopedia of the Brethren of Purity Tables of Toledo Tabula Rogeriana Zij Zij-i-Sultani
Concepts	Alhazen's problem Islamic geometric patterns
Centers	Al-Azhar University Al-Mustansiriya University House of Knowledge House of Wisdom Istanbul observatory of Taqi al-Din Madrasah Maktab Maragheh observatory University of Al-Karaouine
Influences	Babylonian mathematics Greek mathematics Indian mathematics
Influenced	Byzantine mathematics European mathematics Indian mathematics