Ibn al-Shatir

Ibn al-Shatir (or Ibn ash-Shatir) (1304–1375) was a Muslim astronomer of Damascus. He worked as timekeeper in the Umayyad Mosque there, and constructed a magnificent sundial for its minaret in 1371/72. His work kitab nihayat as-sul fi tashih al-usul ("A Final Inquiry Concerning the Rectification of Planetary Theory") in treating the motion of the Moon eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicus later also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. Copernicus at one point used the same model as al-Shatir for removing equants; it temains controversial whether Copernicus was directly influenced by al-Shatir's work.

Related Topics:
1304 - 1375 - Muslim - Astronomer - Damascus - Umayyad - Moon - Equant - Epicycle - Ptolemaic - Copernicus

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The discovery and the whole concept of planetary motion is attributed to Kepler and Copernicus while not crediting the contribution of Ibn Al-Shatir, this while the models of Ibn al-Shatir are mathematically identical to those of Copernicus.

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Ibn al-Shatir also wrote a treatise called "Hidayat al-'amil bi 'l-rub' al-kamil".

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