sentences:  Copernicus held that the Earth is another planet revolving around the fixed Sun once a year, and turning on its axis once a day.But while Copernicus put the Sun at the center of the celestial spheres, he did not put it at the exact center of the universe, but near it.Copernicus' system used only uniform circular motions, correcting what was seen by many as the chief inelegance in Ptolemy's system.