Copernican system
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Copernican system
(kŏ-per -nă-kăn) A heliocentric system of the Solar System that was proposed by Nicolaus Copernicus and eventually published in 1543 in his book De Revolutionibus . It uses some of the basic ideas of the Ptolemaic system, including circular orbits and epicycles, and was no more accurate in its predictions. Copernicus, however, maintained that the planets move around the Sun (in the relative positions accepted today), the Sun's position being offset from the center of the orbits. The apparent motions of celestial bodies such as the Sun were explained in terms of the rotation of the Earth about its axis and also the Earth's orbital motion.The planetary motion can be represented by two uniform circular motions: one is an epicyclic motion of the planet about a point D on the circular orbit; the other, unlike that of the Ptolemaic system, is a uniform circular motion of D about the center, C, of the orbit. This requires that the rate of motion of D about C is exactly half that of the epicyclic rate of motion with respect to a fixed direction.
There was a strong and prolonged reaction – especially by the Church – to the Copernican system, which effectively displaced the Earth as the center of the Universe. There was also a sudden revival in astronomical observation in order to test the theory, notably by Tycho Brahe. Tycho's detailed observations, which showed the inadequacies of the Copernican system, were used in the formulation of Kepler's laws of planetary motion. The heliocentric cosmology became firmly established after Galileo had made telescopic observations of the phases of Venus.