Geocentric Model

In astronomy, the geocentric model also known as "geocentrism", is the superseded theory, that the Earth is the centre of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece and ancient China. Most Ancient Greek philosophers assumed that the Sun, Moon, stars, and naked eye planets circled the Earth, including the systems of Aristotle and Ptolemy.

Two commonly made observations supported the idea that the Earth was the centre of the Universe. The first observation was that the stars, sun, and planets appear to revolve around the Earth each day, making the Earth the centre of that system. The second common notion supporting the geocentric model was that the Earth does not seem to move from the perspective of an Earth bound observer, and that it is solid, stable, and unmoving. In other words, it is completely at rest. The geocentric model was usually combined with a spherical Earth by ancient Greek and medieval philosophers. It is not the same as the older flat Earth model implied in some mythology. However, the ancient Greeks believed that the motions of the planets were circular and not elliptical, a view that was not challenged in Western culture before the 17th century through the synthesis of theories by Copernicus and Kepler.

Heliocentric Model

The Heliocentric model also known as Heliocentrism or Heliocentricism, is