Compare between Ptolemy and Post-Ptolemy systems.

Ptolemy's geocentric model, developed around the 2nd century AD, posited Earth as the stationary center of the universe, with celestial bodies moving in complex epicyclic orbits around it. This model successfully explained the observed motions of planets but became increasingly cumbersome as astronomical observations grew more precise.

The Post-Ptolemaic systems, particularly the heliocentric model proposed by Copernicus in the 16th century, revolutionized our understanding of the cosmos. Copernicus suggested that the Sun, not the Earth, was at the center of the solar system, with planets orbiting it. This heliocentric model simplified the explanation of planetary motion and provided a more elegant framework for understanding celestial phenomena.

Johannes Kepler, building on Copernicus's work, proposed elliptical orbits for planets, and Galileo Galilei's telescopic observations supported the heliocentric model. Ultimately, Isaac Newton's laws of motion and universal gravitation provided a theoretical foundation, explaining not only the observed planetary motions but also unifying celestial and terrestrial mechanics.

In contrast to Ptolemy's Earth-centered model, the Post-Ptolemaic systems marked a paradigm shift, emphasizing simplicity, accuracy, and a sun-centered view of the cosmos, setting the stage for the scientific revolution and the development of modern astronomy.