Ibn al-Shatir
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Ala Al-Din Abu'l-Hasan Ali Ibn Ibrahim Ibn al-Shatir (1304 – 1375) (Arabic: ابن الشاطر) was an Arab Muslim astronomer, mathematician and engineer who worked as muwaqqit (موقت, religious timekeeper) in the Umayyad Mosque in Damascus.
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[edit] Astronomy
His most important astronomical treatise was the Kitab nihayat al-sul fi tashih al-usul (The Final Quest Concerning the Rectification of Principles), in which he drastically reformed the Ptolemaic models of the Sun, Moon, and planets, by his introducing his own non-Ptolemaic models which eliminates the epicycle in the solar model, which eliminate the eccentrics and equant by introducing extra epicycles in the planetary models via the Tusi-couple, and which eliminates all eccentrics, epicycles and equant in the lunar model.
While previous Maragha school models were just as accurate as the Ptolemaic model, Ibn al-Shatir's geometrical model was the first that was actually superior to the Ptolemaic model in terms of its better agreement with empirical observations. Other achievements of Ibn al-Shatir include the separation of natural philosophy from astronomy and the rejection of the Ptolemaic model on empirical rather than philosophical grounds. Unlike previous astronomers before him, Ibn al-Shatir was not concerned with adhering to the theoretical principles of cosmology or natural philosophy (or Aristotelian physics), but rather to produce a model that was more consistent with empirical observations. His model was thus in better agreement with empirical observations than any previous models produced before him. His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance".[1]
[edit] Testing
Unlike previous astronomers, Ibn al-Shatir generally had no philosophical objections against Ptolemaic astronomy, but was only concerned with how well it matched his own empirical observations. He would usually test the Ptolemaic models, and if any did not match his observations, then he would formulate his own non-Ptolemaic model in its place which did match his observations. For example, it was Ibn al-Shatir's concern for observational accuracy which led him to eliminate the epicycle in the Ptolemaic solar model, as he describes below:[2]
"As for the Sun having an epicycle, that is acceptable. But that did not match with accurate observations as you will see below in the configuration of the Sun, for we have found the solar anomaly, which is the equation, not in agreement with accurate observations at the midpoints of the zodiacal belt."
Ibn al-Shatir was also the earliest astronomer to introduce experiments into planetary theory, in order to test the Ptolemaic models on empirical grounds. For example, while testing the Ptolemaic solar model, Ibn al-Shatir "tested the Ptolemaic value for the apparent size of the solar disk by using lunar eclipse observations." His work on his experiments and observations, however, has not survived, but there are references to this work in his The Final Quest Concerning the Rectification of Principles.[3]
[edit] Influence
Although his system was firmly geocentric, he had eliminated the Ptolemaic equant and eccentrics, and the mathematical details of his system were identical to those in Nicolaus Copernicus' De revolutionibus.[4] His lunar model was also no different from the lunar model used by Copernicus.[5] It is thus believed that Ibn al-Shatir's model was adapted by Copernicus into a heliocentric model. Though it remains uncertain how this may have happened, it is known that Byzantine Greek manuscripts containing the Tusi-couple which Ibn al-Shatir employed had reached Italy in the 15th century.[6] It is also known that Copernicus' diagrams for his heliocentric model, including the markings of points, was nearly identical to the diagrams and markings used by Ibn al-Shatir for his geocentric model, making it very likely that Copernicus may have been aware of Ibn al-Shatir's work.[7]
Y. M. Faruqi writes:[8]
"Ibn al-Shatir’s theory of lunar motion was very similar to that attributed to Copernicus some 150 years later".
"Whereas Ibn al-Shatir’s concept of planetary motion was conceived in order to play an important role in an earth-centred planetary model, Copernicus used the same concept of motion to present his sun-centred planetary model. Thus the development of alternative models took place that permitted an empirical testing of the models."
[edit] Engineering
Ibn al-Shatir constructed a magnificent sundial for the minaret of the Umayyad Mosque in Damascus. Ibn al-Shatir also invented the first astrolabic clock.[9]
[edit] See also
[edit] References
- ^ George Saliba (1994), A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam, p. 233-234 & 240, New York University Press, ISBN 0814780237.
- ^ George Saliba (1994), A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam, p. 234, New York University Press, ISBN 0814780237.
- ^ George Saliba (1994), A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam, p. 238, New York University Press, ISBN 0814780237.
- ^ The model Copernicus used in his earlier Commentariolus differs in minor detail from that of Ibn al-Shatir. V. Roberts and E. S. Kennedy, "The Planetary Theory of Ibn al-Shatir", Isis, 50(1959):232-234.
- ^ George Saliba (1994), A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam, p. 236, New York University Press, ISBN 0814780237.
- ^ A. I. Sabra (1998). "Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy", Perspectives on Science 6 (3), p. 288-330.
- ^ George Saliba (2007), Lecture at SOAS, London - Part 4/7 and Lecture at SOAS, London - Part 5/7
- ^ Y. M. Faruqi (2006). "Contributions of Islamic scholars to the scientific enterprise", International Education Journal 7 (4), p. 395-396.
- ^ David A. King (1983). "The Astronomy of the Mamluks", Isis 74 (4), p. 531-555 [545-546].
[edit] References
- Fernini, Ilias. A Bibliography of Scholars in Medieval Islam. Abu Dhabi (UAE) Cultural Foundation, 1998
- Kennedy, Edward S. "Late Medieval Planetary Theory." Isis 57 (1966):365-378.
- Kennedy, Edward S. and Ghanem, Imad. The Life and Work of Ibn al-Shatir, an Arab Astronomer of the Fourteenth Century. Aleppo: History of Arabic Science Institute, University of Aleppo, 1976.
- Roberts, Victor. "The Solar and Lunar Theory of Ibn ash-Shatir: A Pre-Copernican Copernican Model". Isis, 48(1957):428-432.
- Roberts, Victor and Edward S. Kennedy. "The Planetary Theory of Ibn al-Shatir". Isis, 50(1959):227-235.
- Saliba, George. "Theory and Observation in Islamic Astronomy: The Work of Ibn al-Shatir of Damascus". Journal for the History of Astronomy, 18(1987):35-43.
- Turner, Howard R. Science in Medieval Islam, an illustrated introduction. University of Texas Press, Austin, 1995. ISBN 0-292-78149-0 (pb) ISBN 0-292-78147-4 (hc)
[edit] External links
- http://faculty.kfupm.edu.sa/phys/alshukri/PHYS215/Islamic%20astronomy.htm
- http://www.riifs.org/review_articles/review_v1no2_sliba.htm
- http://www.angelfire.com/il/Fernini/ifscience.html
- http://www.cs.sfu.ca/~anoop/weblog/archives/000080.html
- http://www.bookrags.com/research/ala-al-din-abul-hasan-ali-ibn-ibrah-scit-021234/
