Iron Filings

The Random Oscillating Magnetic Pendulum (ROMP) is a popular desktop toy. It consists of a pendulum, with a small magnet attached to the end, which can swing freely over a metal base. On the base there are nine numbers of strong, disc-shaped magnets, which act on the pendulum with either an attractive or repulsive force. When the pendulum is displaced and released, it tends to swing in an erratic, unpredictable pattern. Due to friction, the pendulum eventually comes to rest over one of the magnets.