Johannes Kepler was born in Weil-der-Stadt, Germany. He studied at Tubingen, and in 1593 was ap-pointed professor of mathematics at Graz. He corresponded with the astronomer Tycho Brahe, who was then in Prague, and for a short time worked with him.

Kepler was the first to search for a physical explanation for planetary orbits and he discovered that the orbits are elliptical with the sun at one focus.

He announced his first and second laws of planetary motion in Astronomia nova (1609), which formed the groundwork of Isaac Newton's discoveries. Kepler also founded modern optics by postu-lating the ray theory of light to explain vision.

Image : Kepler's laws