Kids Research Express

The major premises of Copernicus's theory are that the earth rotates daily on its axis and revolves yearly around the sun. He argued, furthermore, that the planets also circle the sun, and that the earth precesses on its axis (wobbles like a top) as it rotates. The Copernican theory retained many features of the cosmology it replaced, including the solid, planet-bearing spheres, and the finite outermost sphere bearing the fixed stars. On the other hand, Copernicus's heliocentric theories of planetary motion had the advantage of accounting for the apparent daily and yearly motion of the sun and stars, and it neatly explained the apparent retrograde motion of Mars, Jupiter, and Saturn and the fact that Mercury and Venus never move more than a certain distance from the sun. Copernicus's theory also stated that the sphere of the fixed stars was stationary. Another important feature of Copernican theory is that it allowed a new ordering of the planets according to their periods

Copernican System, systematic explanation of the movement of the planets around the sun; advanced in 1543 by the Polish astronomer Nicolaus Copernicus . The Copernican system advanced the theories that the earth and the planets are all revolving in orbits around the sun, and that the earth is spinning on its north-south axis from west to east at the rate of one rotation per day. These two hypotheses superseded the Ptolemaic system , which had been the basis of astronomical theory until that time. The Copernican system first described the precession of the equinoxes (see Ecliptic ) but did not explain it. Publication of the Copernican system stimulated the study of astronomy and mathematics and laid the basis for the discoveries of the German astronomer Johannes Kepler and the British astronomer Sir Isaac Newton.