<P> While the sphericity of the Earth was widely recognized in Greco - Roman astronomy from at least the 3rd century BCE, the Earth's daily rotation and yearly orbit around the Sun was never universally accepted until the Copernican Revolution . </P> <P> While a moving Earth was proposed at least from the 4th century BCE in Pythagoreanism, and a fully developed heliocentric model was developed by Aristarchus of Samos in the 3rd century BCE, these ideas were not successful in replacing the view of a static spherical Earth, and from the 2nd century CE the predominant model, which would be inherited by medieval astronomy, was the geocentric model described in Ptolemy's Almagest . </P> <P> The Ptolemaic system was a sophisticated astronomical system that managed to calculate the positions for the planets to a fair degree of accuracy . Ptolemy himself, in his Almagest, points out that any model for describing the motions of the planets is merely a mathematical device, and since there is no actual way to know which is true, the simplest model that gets the right numbers should be used . However, he rejected the idea of a spinning earth as absurd as he believed it would create huge winds . His planetary hypotheses were sufficiently real that the distances of moon, sun, planets and stars could be determined by treating orbits' celestial spheres as contiguous realities . This made the stars' distance less than 20 Astronomical Units, a regression, since Aristarchus of Samos's heliocentric scheme had centuries earlier necessarily placed the stars at least two orders of magnitude more distant . </P> <P> Problems with Ptolemy's system were well recognized in medieval astronomy, and an increasing effort to criticize and improve it in the late medieval period eventually led to the Copernican heliocentrism developed in Renaissance astronomy . </P>

First to present the heliocentric model of the universe