Law 1: The planets move in an ellipse around the Sun as centre.
Law 2: The orbits of the planets sweep out equal areas in equal times. If the planet takes the same time to move from p to q as from r to s, the areas A and B will be equal.
Law 3: The square or the time for a complete orbit of a planet around the Sun is proportional to the distance cubed:
This can be proved using Newton's Law of Gravity.