Using the Planetary System Builder

Studying the process of planetary system evolution is not an easy task. Trying to figure out how just 3 mutually interacting objects will behave is more than paper and pencil methods can handle. Some of the greatest minds in science tried heroically but could make only limited progress with the so-called 3-body problem because of the complexity of the motions. To really see what can happen when lots of planets interact you need a computer and that is what this Interactive is all about. The tool you are playing with here would have been considered state of the art science just decades ago when computers first became research tools.

Here are the steps you need to follow to get started:

Notice the text on the screen that gives you information about size, time and mass "scales" used in the simulations. Notice on the lower left hand side there are labels that show the current position of the cursor on the screen.

1. Press "presets". You will get a menu of possible systems to begin with. You may start with just the Sun, the Sun and Earth, the entire solar system out to Saturn or a random distribution of planets. There are 2000 random distributions to choose from. To change your random distribution change the number in the box labeled "System #" and hit Enter on your keyboard. Click the "Crowded" button to make random systems with the planets packed together. These tend to get more interesting behavior early on in their evolution. You can add a new planet to any of these preset systems. Just choose the new planet's mass by moving the MASS slider-bar. You can go all the way from Mercury sized masses up to "Hot Jupiter" mass bodies.

2. Use the mouse to locate the position where you want to place the planet. Left-click on the mouse and a circle appears whose size is proportional to the planet's mass. This planet will begin on a circular orbit. You can have up to 20 planets in a system at once. You can also choose a planet's initial speed and direction by right-dragging on the mouse and "pulling" the velocity arrow outward from the planet.

**** Note: Preset planets always begin on circular orbits ****

3. Press "Play" to begin watching the system evolve. Use the speed slider-bar to speed-up or slow-down the evolution (this is good for when you want to recreate a system and watch it evolve more slowly).

4. You can hit "Pause" to stop the evolution at any time. You can add planets while the evolution is running or paused.