Way cool video!
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.
- Simple Harmonic (and non-harmonic) Motion § Harvard Natural Sciences Lecture Demonstrations