This is a large-scale demonstration of the interaction between period and pendulum length, using 16 bowling balls hung from a wooden frame. Here are answers to some common questions: ** What am I seeing? How does this work? ** The length of time it takes a ball to swing back and forth one time to return to its starting position is dependent on the length of the pendulum, not the mass of the ball. A longer pendulum will take longer to complete one cycle than a shorter pendulum. The lengths