CBSE Class 9 Answered

 A Polish astronomer, Nicolaus Copernicus proposed that the earth revolve around sun and not the sun around the earth.This model in which sun is at the centre of the solar system with planets revolving around sun is called the Heliocentric system. But he did not have a mathematical proof for the same.Later a German mathematician Johannes Kepler came up with the idea of planets moving around the Sun in an elliptical paths and it was known as the Kepler's laws of planetary motion. Later Sir Isaac Newton formulated the Universal Law of Gravitation with which he explained the physics of planetary motion.