WHAT IS IT? ----------- Random Billiards simulates a frictionless billiard table. The balls all move in straight lines and bounce off the walls. A continuous trace is made of the center of mass of the system. The resulting display shows the statistical behavior of the center of mass. HOW TO USE IT ------------- Select the number of ball to be used, then push SETUP. Push WANDER to run the model. The FADING switch makes it easier to see the long-term pattern in the position of the center of mass. THINGS TO NOTICE ---------------- Watch how the center of mass moves for a while. Is there a pattern? Is there a region in the box that it stays within? THINGS TO TRY -------------- Run the model with a lot of turtles, then just a few. What happens to the motion of the center of mass? Why? Let the model run for a while, with the FADING button on (1). What do you notice about how much time the center of mass spends at different distances from the origin (its frequency distribution)? Push SETUP, then in the command center, type "setheading 60" and press ENTER. This points all of the turltles in the same direction. What does the center of mass do now? Try other headings. EXTENDING THE MODEL ------------- Presently the balls don't bounce off each other. If they did, would it make a difference in the behavior of the center of mass? Try it. This model has up to 300 turtles. What if it had thousands?