The Geocentric and Heliocentric Models of the Universe
In the Ptolemaic system, the universe is a series concentric spheres -- spheres one inside the other. Earth is fixed, or motionless, at the center these spheres. The spheres are made of crystal-like, transparent substance, in which the heavenly bodies -- pure orbs of light are embedded. For example, the Moon is embedded in the first sphere, Mercury in the second, Venus in the third, and the Sun in the fourth. The rotation of the spheres makes these heavenly bodies rotate about the death and move in relation to one another.
In the tenth sphere in the Ptolemaic system was the "prime mover," which moved itself and gave motion to the other spheres. Beyond the tenth sphere was Heaven, where God and all the saved souls resided. God was at one end of the universe, then and humans were at the center. Humans had been given power over earth, but their real purpose was to achieve salvation. |
In May 1543, Nicholas Copernicus, a native of Poland, published his famous book, On the Revolutions of the Heavenly Spheres, a mathematician, felt that geocentric system was too complicated. He believed that his heliocentric, or sun-centered, conception of the universe offered a more accurate explanation that did the Ptolemaic system.
Copernicus argued that the Sun, not the Earth, was at the center of the universe. The planets revolved around the Sun. The Moon, however, revolved around the Earth. Moreover, according to Copernicus, the apparent movement of the Sun around the Earth was recalled caused by the daily rotation of the Earth on its axis and the journey of the Earth around the Sun each year. |