Waves in the pendulum system

HOW

1. Using a handle connected to a metal comb, gently swing the balls out of balance. The strings must not be tangled.
2. Then move the comb back to the lower position with a quick movement, releasing the balls.
3. Observe the behaviour of the balls over an extended period of time.

WHY

You are dealing with an arrangement of sixteen independent pendulums of carefully selected lengths. The equal tilting of the balls out of equilibrium at the same time (with equal phase and amplitude) causes their motion to reproduce successively different moving and standing waves when the pendulums are released. After a full cycle, it returns to its initial state. So, you observe an arrangement of independent objects that
behave as if there is a coupling between them.