Kepler's Laws

Johannes Kepler's laws of planetary motion:

1. 1. The orbit of every planet is an ellipse with the Sun at one of the two foci, i.e. planetary orbits are not circluar but eliptical
2. 2. A line joining a planet and the Sun sweeps out equal areas during equal intervals of time, i.e. motion of the planet is faster when closer to the sun
3. 3. The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. Captures the relationship between the distance of planets from the Sun, and their orbital periods

Kepler published his first two laws in 1609, having found them by analyzing the astronomical observations of Tycho Brahe. Kepler published the third law in 1619.