<P> According to the geometers (or engineers) (muhandisīn), the Earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to the motion of the Earth and not the stars . </P> <P> Early in the 11th century Alhazen wrote a scathing critique of Ptolemy's model in his Doubts on Ptolemy (c. 1028), which some have interpreted to imply he was criticizing Ptolemy's geocentrism, but most agree that he was actually criticizing the details of Ptolemy's model rather than his geocentrism . </P> <P> In the 12th century, Arzachel departed from the ancient Greek idea of uniform circular motions by hypothesizing that the planet Mercury moves in an elliptic orbit, while Alpetragius proposed a planetary model that abandoned the equant, epicycle and eccentric mechanisms, though this resulted in a system that was mathematically less accurate . Alpetragius also declared the Ptolemaic system as an imaginary model that was successful at predicting planetary positions but not real or physical . His alternative system spread through most of Europe during the 13th century . </P> <P> Fakhr al - Din al - Razi (1149--1209), in dealing with his conception of physics and the physical world in his Matalib, rejects the Aristotelian and Avicennian notion of the Earth's centrality within the universe, but instead argues that there are "a thousand thousand worlds (alfa alfi' awalim) beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has ." To support his theological argument, he cites the Qur'anic verse, "All praise belongs to God, Lord of the Worlds," emphasizing the term "Worlds ." </P>

What scientists challenged the geocentric view of the universe