Astronomy · a Light

A mosque timekeeper's lunar model matches Copernicus exactly

Ibn al-Shatir kept the prayer times at the Umayyad Mosque in Damascus and built the sundial for its minaret. He also rebuilt planetary astronomy, discarding Ptolemy's equant and off centre circles and assembling his models from uniform circular motions only. In 1957 Victor Roberts, working with E. S. Kennedy in Beirut, showed that Ibn al-Shatir's model of the moon is mathematically identical to the one Copernicus published in 1543, and that several parameters match. What nobody has found is a route. No Latin translation of Ibn al-Shatir is known and Copernicus never names him. Some scholars argue for transmission through Byzantine Greek manuscripts, others for two men solving the same problem the same way. Ibn al-Shatir kept the earth at the centre. Copernicus moved it.

Ibn al-Shatir · Damascus, c. 1304-1375