Final answer:
The Ptolemaic system is a geocentric model developed by Ptolemy where Earth is at the center of the universe, with celestial bodies in complex circular paths around it. It used epicycles and deferents to explain observed motions and was the accepted model before the heliocentric Copernican system.
Step-by-step explanation:
The Ptolemaic system is a geocentric system of planetary motion, which places the Earth at the center of the universe.
Developed by the Greek philosopher Ptolemy in the second century AD, this model includes the Moon, the planets, the Sun, and the stars revolving around Earth in complex superpositions of circular paths - a concept.
To account for the observed celestial motions, Ptolemy's model used epicycles, smaller circles on which the planets moved, which in turn moved along larger circles called deferents.
According to history, before the heliocentric model proposed by Copernicus and validated by subsequent scientific discoveries, the Ptolemaic view represented the prevalent understanding of the cosmos, despite its lack of simplicity and explanations based on physical laws.
The replacement of this view by the Copernican system, which is centered around the Sun and governed by Newton's laws of gravitation, marked a significant paradigm shift in astronomy and the beginning of modern science.