1145.Jabir Ibn Aflah

Jabir Ibn Aflah (1145 M)

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Jabir Ibn Aflah is a mathematician Islamic nation Spain. However, Jabir had come to give color da contribution in the development of the science of astronomy., Was the first scientist who created the horizon sphere easily moved to measure and describe the movement of celestial objects. One of his popular is the Kitab al-Hay'ah.

Abū Muḥammad Jābir ibn Aflaḥ (Arabic: أبو محمد جابر بن أفلح‎, Latin: Geber/Gebir; 1100–1150) was a Muslim astronomer andmathematician 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 theMoon 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]

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 promotetrigonometry 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]

Jabir ibn Aflah is often known by the Latinised form of his name, namely Geber. Although not he was not in the first rank of Arabic mathematicians, he is important in the development of mathematics since his works were translated into Latin, and so became available to European mathematicians, whereas the work of some of the top rank Arabic mathematicians such as Abu'l-Wafa were not translated into Latin.

Very little information is available regarding Jabir ibn Aflah's life. That he came from Seville is known from two sources. Firstly he is described as "al-Ishbili" in manuscripts containing his treatises; this means "from Seville". The other source gives us not only the information that he came from Seville, but also a good estimate for the period in which he lived. The information comes from Maimonides.

Moses Maimonides, whose Arabic name was Abu 'Imran Musa ibn Maymun ibn 'Ubayd Allah, was a Jewish philosopher, jurist, and physician who was born in Córdoba in 1135. Among many important works he wrote The Guide of the Perplexed in Arabic in which he writes of:-

... ibn Aflah of Seville, whose son I have met ...

Jabir ibn Aflah invented an observational instrument known as the torquetum, a mechanical device to transform between spherical coordinate systems (see [3] for further details). He also gave his name to a theorem in spherical trigonometry, and his criticisms of Ptolemy's Almagest are well known. These criticisms appears in Jabir ibn Aflah's most famous work Islah al-Majisti (Correction of the Almagest). One sees that ibn Aflah even puts his argument regarding errors made by Ptolemy into the title of the work. In [4] Lorch explains Jabir ibn Aflah's most famous criticism, namely Ptolemy's placement of Venus and Mercury below the Sun. Ptolemy claimed that these planets could never be on a line between an observer on Earth and the sun., but ibn Aflah states that this is an error, and that Venus and Mercury are above the Sun.

It is a little difficult to establish the exact degree of originality of Correction of the Almagest. Certainly its general approach bears considerable similarity to the work of Abu'l-Wafa, but it may not be based on Abu'l-Wafa's work. Both may be based on the work of Thabit ibn Qurra, or the work of ibn Aflah, Abu'l-Wafa, and Thabit ibn Qurra may all be based on some still unknown source.

The influence of ibn Aflah is quite remarkable. In [4] his influence on astronomers in both the East and West is studied. In particular the author looks at his influence on the Persian astronomer Qutb al-Din al-Shirazi, who was a pupil of Nasir al-Din al-Tusi; on the Hispano-Arabian philosopher ibn Rushd, who is often known as Averroes, was born in Córdoba in 1126 and integrated Islamic traditions and Greek thought; and on Levi ben Gerson (sometimes known as Gersonides). One of ibn Aflah's more infamous influences was on Regiomontanus who copied large parts of ibn Aflah's work in the fourth book of his publication De triangulis. Regiomontanus did not acknowledge that ibn Aflah was the source of the material and this caused Cardan to strongly criticise Regiomontanus.