Kepler's Laws of Planetary Motion

In Astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. 

The three laws state that: 

1. The orbit of a planet is an ellipse with the Sun at one of the two foci. 

2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. 

3. The square of a planet's orbital period is proportional to the cube of the length of the semi-major axis of its orbit.