Name: Anonymous 2008-04-21 21:45
Around 500 CE, Indian astronomer Aryabhata presented a mathematical system that took the Earth to spin on its axis and considered the motions of the planets with respect to the Sun. He also made an accurate approximation of the Earth's circumference and diameter, and also discovered how the lunar eclipse and solar eclipse happen. He gives the radius of the planetary orbits in terms of the radius of the Earth/Sun orbit as essentially their periods of rotation around the Sun. He was also the earliest to discover that the orbits of the planets around the Sun are ellipses.