What are the postulates of Non-Copernican system?

The Non-Copernican system refers to pre-Copernican models of the solar system, primarily the geocentric model proposed by Ptolemy in the 2nd century AD. The postulates of the Non-Copernican system are based on the Earth-centered view of the universe:

1. Geocentricity: The fundamental postulate of the Non-Copernican system is the belief that Earth is the stationary center of the universe, and all celestial bodies, including the Sun, Moon, and planets, orbit around it.

2. Uniform Circular Motion: In the Ptolemaic system, celestial bodies move in uniform circular motion along epicycles—smaller circles whose centers move along larger deferents. This elaborate system aimed to account for the observed retrograde motion of planets.

3. Celestial Spheres: The Non-Copernican model posited a series of nested, concentric celestial spheres, each associated with a particular celestial body. These spheres served as the paths along which planets and other celestial objects moved.

4. Epicycles and Deferents: The introduction of epicycles and deferents was a crucial postulate. Epicycles were smaller circles upon which planets moved, while deferents were the larger circles carrying the epicycles, creating a complex system to explain the irregularities in planetary motion.

These postulates aimed to provide a comprehensive framework for understanding the apparent motions of celestial bodies while maintaining the Earth-centric perspective. The Non-Copernican system, though later superseded by the heliocentric model, represents a significant historical stage in humanity's evolving understanding of the cosmos.