Chaotic Pendulum contains a deceptively simple set of pendulums in a steel and Plexiglas case. A central, T-shaped bar supports three bearing-mounted bars from its ends. The “T” is itself bearing mounted at the intersection of the upright and the cross arm. The visitor gives an initial twist to the pendulums with a protruding knob. Intuition says that the resulting motion of this system should be, if not simple, at least predictable. Intuition, however, does not work with this device since its motion is chaotic, extremely complicated and long-lived.