You may recall from a Mechanics course that the period of a pendulum is proportional to the square root of the length of the line suspending the weight - i.e., the longer the pendulum, the slower it swings.
Harvard students built a device with a series of 15 pendulums in a row, each one slightly longer than its neighbor, then set them in motion and filmed the result.
The resulting patterns in this short video are quite fascinating to watch.
The above words were from an email sent me from a good friend. I don't know if he wrote them or not, but he could have.