Geocentrism is the belief that the Earth is fixed at the centre of the Universe. Geocentrists accept that the earth is round. Before the 16th century most people believed in the theory of geocentrism. From Earth, it looks like the Sun and stars are moving across the sky. In about 150 AD the Greek astronomer, Ptolemy wrote a book to explain in great detail how the spherical Earth is surrounded by things that move in the sky. From the time of Ptolemy through to the 16th Century AD educated people who knew the earth is round almost always believed the Geocentric theory of Ptolemy.
- Kunitzsch, Paul (2008). "Almagest: Its Reception and Transmission in the Islamic World". In Selin, Helaine (ed.). Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures (2008 ed.). Dordrecht: Springer. doi:10.1007/978-1-4020-4425-0. ISBN 978-1-4020-4960-6. Archived from the original on 2018-06-10. Retrieved 2021-04-08.
Around AD 150, Ptolemy wrote his great handbook of astronomy called Mathematike Syntaxis...