The Universe simulation allows you to set your own law of gravity. Here are some "made-up" laws to try; just follow the links.
Law A says that each planet's acceleration is at right angles to the sun, and proportional to one over the cube of the distance.
Law B says that each planet's velocity is at right angles to the sun, and proportional to one over the cube of the distance.
Law C says that each planet's acceleration is towards the sun, and proportional to the distance.
How do the planets move? Which of Kepler's Laws are obeyed?
