From such a long time, the scientists are trying to get more and more information about the universe. Basically their interest is to study the motion of the heavenly bodies. Ptolemy was the first Greek astronomer to start the study of the planetary motion of the heavenly bodies. He gave a theory called Geocentric Theory of Planetary Motion. According to his theory, all the heavenly bodies like sun, star, moon, etc are moving around the earth, which is stationery and is taken as the center of the universe. So, according to his theory ‘geocentric’ means a system in which earth is taken as the center. So, it was called with the name geocentric theory. After the passage of time famous scientist Copernicus challenged this theory.
As the time passes, great Indian scientist Arya-Bhatt gives the decisions about some important facts. He said that like lunar and solar eclipse, formation of day-night can be defined with no difficulty by simply supposing that the earth revolves around the sun and also rotating along its own axis. Due to the less development in that time proper ways of exchanging information and ideas with the other philosophers were almost negligible.
Again in 1953 Copernicus said that it will be easier to describe the motion of the heavenly bodies if we simply assume that the sun is stationary, the earth and the other planets are revolving around the sun. The name of this theory was heliocentric theory. After the experiments of Copernicus, Galileo started his experiments on planets as well as on moon. After his success he also started supporting the theory of Copernicus.
