<P> In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe with Earth at the center . Under the geocentric model, the Sun, Moon, stars, and planets all orbited Earth . The geocentric model served as the predominant description of the cosmos in many ancient civilizations, such as those of Aristotle and Ptolemy . </P> <P> Two observations supported the idea that Earth was the center of the Universe . First, from the view on Earth, the Sun appears to revolve around Earth once per day . While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day . The stars appeared to be on a celestial sphere, rotating once each day along an axis through the north and south geographic poles of Earth . Second, Earth does not seem to move from the perspective of an Earth - bound observer; it appears to be solid, stable, and unmoving . </P>

Who used the geocentric system to explain planetary motions