View source for Biography:Jabir ibn Aflah

{{Short description|Al-Andalusi mathematician and astronomer}}
{{Infobox scholar
| image       = Jabir ibn Aflah (MUNCYT, Eulogia Merle).jpg
| image_size       = 180px
| alt        = 
| caption    = Fictional portrait by Eulogia Merle for the Fundación Española para la Ciencia y la Tecnología (2011)
| name             = Jābir ibn Aflaḥ
| fullname         = 
| birth_date       = 1100 CE
| birth_place      = Seville, al-Andalus
| death_date       = 1150 CE
| death_place      = 
| era              = Islamic Golden Age
| school_tradition = 
| main_interests   = [[Astronomy:Astronomy|Astronomy]], [[Mathematics]]
| notable_ideas    = {{Unbulleted list|[[Engineering:Torquetum|Torquetum]]|}}
| major_works      = ''Iṣlāḥ al-Majisṭi (Correction of the Almagest)''
| influences       = 
| influenced       = [[Biography:Averroes|Averroes]], Nur ad-Din al-Betrugi
}}

'''Abū Muḥammad Jābir ibn Aflaḥ''' ({{lang-ar|أبو محمد جابر بن أفلح}}, {{lang-la|Geber/Gebir}}; 1100–1150) was an Arab<ref>{{cite book|last1=Schlager|first1=Neil|last2=Lauer|first2=Josh|title=Science and Its Times: 700-1449|date=2001|publisher=Gale Group|isbn=9780787639341|url=https://books.google.com/books?id=To1FAAAAYAAJ&q=Jabir+Aflah|language=en}}</ref><ref>{{cite book|last1=Publishing|first1=Britannica Educational|title=Portugal and Spain|date=2013|publisher=Britanncia Educational Publishing|isbn=9781615309931|url=https://books.google.com/books?id=IT2dAAAAQBAJ&q=Jabir+Aflah+%22arab+mathematician%22&pg=PA218|language=en}}</ref> [[Religion:Muslim|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 [[Religion:Christians|Christian]] astronomers.{{sfn|Calvo|2007}}

==''Iṣlāḥ al-Majisṭi (Correction of the Almagest)''==

This work is a commentary and reworking of [[Biography:Ptolemy|Ptolemy]]'s ''[[Astronomy:Almagest|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|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 al-Andalus during the 11th century. Jābir does not credit any of these authors and does not refer to a single Islamic author in this work.{{sfn|Calvo|2007}}

One substantial change Jābir made to Ptolemy's account is that he placed the orbits of [[Astronomy:Venus|Venus]] and [[Astronomy:Mercury (planet)|Mercury]], the minor planets, outside that of the [[Astronomy:Sun|Sun]], rather than between the [[Astronomy:Moon|Moon]] and the Sun as had been the case in the original work.{{sfn|Calvo|2007}}

==Inventor==
[[File:GNM - Torquetum.jpg|thumb|The Torquetum was invented by Jabir ibn Aflah.]]
He invented an observational instrument known as the [[Engineering:Torquetum|torquetum]], a mechanical device to transform between spherical coordinate systems.<ref>{{Cite journal|first=R. P.|last=Lorch|title=The Astronomical Instruments of Jabir ibn Aflah and the Torquetum|journal=Centaurus|volume=20|issue=1|date=1976|pages=11–34|doi=10.1111/j.1600-0498.1976.tb00214.x|bibcode=1976Cent...20...11L}}</ref>

==Influence==
Several later Muslim authors were influenced by Jābir, including [[Biography:Averroes|Ibn Rushd]] (Averroes) and Nur ad-Din al-Betrugi, both of whom worked in al-Andalus. The work was transmitted to [[Place:Egypt|Egypt]] in the 12th century by [[Biography:Maimonides|Maimonides]] and further east by the end of the 13th century.{{sfn|Calvo|2007}}

The work was translated from the [[Social:Arabic|Arabic]] into both Hebrew and [[Social:Latin|Latin]], the latter by Gerard of Cremona, who [[Social:List of Latinised names|Latinized]] his name as "Geber". Through this translation, it had a wide influence on later [[Earth:Europe|Europe]]an mathematicians and astronomers and helped to promote [[Trigonometry|trigonometry]] in Europe.{{sfn|Calvo|2007}}

Much of the material on spherical trigonometry in [[Biography:Regiomontanus|Regiomontanus]]' ''On Triangles'' (c.1463) was taken directly and without credit from Jābir's work, as noted in the 16th century by Gerolamo Cardano.<ref>{{Cite book
  | editor = Victor J. Katz
  | title = The Mathematics of Egypt, Mesopotamia, China, India, and Islam: A Sourcebook
  | publisher = Princeton University Press
  | date = 2007
  | url = http://press.princeton.edu/chapters/i8583.html
  | isbn = 978-0-691-11485-9
  | access-date = 2008-03-16
  | archive-date = 2016-10-01
  | archive-url = https://web.archive.org/web/20161001214903/http://press.princeton.edu/chapters/i8583.html
  | url-status = dead
  }}, p.4</ref>

== Notes ==
{{reflist}}

== References ==
* {{cite encyclopedia | editor = Thomas Hockey| last = Calvo | first = Emilia | title=Jābir ibn Aflaḥ: Abū Muḥammad Jābir ibn Aflaḥ | encyclopedia = The Biographical Encyclopedia of Astronomers | publisher = Springer | date = 2007 | location = New York | pages = 581–2 | url=http://islamsci.mcgill.ca/RASI/BEA/Jabir_ibn_Aflah_BEA.htm | isbn=978-0-387-31022-0 |display-editors=etal}} ([http://islamsci.mcgill.ca/RASI/BEA/Jabir_ibn_Aflah_BEA.pdf PDF version])

==External links==
* {{cite encyclopedia | last = Lorch | first = R. P. | title=Jābir Ibn Aflah Al-Ishbīlī, Abū Muḥammad  | url=http://www.encyclopedia.com/doc/1G2-2830902148.html |  encyclopedia = Complete Dictionary of Scientific Biography | publisher = [[Encyclopedia.com]] | orig-year=1970-80 | date = 2008 }}


{{Islamic astronomy}}
{{Islamic mathematics}}

{{DEFAULTSORT:Ibn Aflah, Jabir}}
[[Category:12th-century mathematicians]]

{{Sourceattribution|Jabir ibn Aflah}}