Ibn al-Shatir (1304 – 1375) (Arabic: ابن الشاطر) was an Arab Muslim astronomer. He worked as muwaqqit (موقت, religious timekeeper) in the Umayyad Mosque in Damascus and constructed a magnificent sundial for its minaret.
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, while eliminating the eccentrics and equant by introducing extra epicycles.
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 Nicholaus Copernicus’s De revolutionibus. It is thus believed that Ibn al-Shatir’s model was adapted by Copernicus into a heliocentric model. Though this remains uncertain, it is known that Byzantine Greek manuscripts containing the Tusi-couple which Ibn al-Shatir employed had reached Italy in the 15th century.
Ibn al-Shatir’s model for the appearances of Mercury, showing the multiplication of epicycles in a Ptolemaic enterprise
Y. M. Faruqi writes:
“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.”
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