There was one strong issue with the Ptolemaic model – it didn’t adequately explain the retrograde motions of the planets, even with epicycles. This is what lead Copernicus to propose the ...

Ibn al-Shatir’s Mercury model, with its multiplication of epicycles to eliminate eccentrics ... as well as penetrating critiques of Ptolemaic astronomy. Ibn al-Shatir’s use of the Tusi ...

Unfortunately, the original Copernican model was loaded the Ptolemaic baggage. The Copernican planets still travelled around the solar system using motions described by the superposition of ...

In “The Case against Copernicus,” authors Dennis Danielson and Christopher Graney detail the evidence-based reasons why 17th-century astronomers doubted the Copernican model of the universe ...

were strongly suggestive of the epicycles of Ptolemaic astronomy. It was obvious that there was some inherent defect in the theory and nothing less than a radical change of outlook was required.