Kepler's Laws of Motion

The three laws which explain the motion of objects in elliptical orbits, developed by Johannes Kepler and announced by him in 1609 and in 1618. The rules apply to any body in circular or elliptical orbit around the Sun. Equally, the rules also apply to satellites, both natural and artificial, in orbit around a planet. The first rule states that planets move in elliptical orbits with the Sun placed at one focus. Rule two states that equal areas are swept out in equal times, so the planets must be travelling faster when they are closer to the Sun. Rule three states that the square of the planet's orbital period is proportional to the cube of its mean orbital radius from the Sun. More and more .