nov 19, 130 - Ptolemy

Description:

Developed a complex mathematical system based on Aristotle's ideas with nine regions called spheres, including the seven heavenly bodies, which are perfectly spherical, the firmament, the Primum Mobile and the Empyrean.

All the spheres are centered around earth (geo-centric). These spheres containing the heavenly bodies rotate around the earth every 24 hours.

Corruption and change only exist on earth.

Observation of the night sky shows retrograde motion, where a planet has forward motion against the background of the stars and then seems to back up. Ptolemy accounts for changes with a system of some 80 different epicycles.

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