httpv://www.youtube.com/watch?v=yVkdfJ9PkRQ
Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and (seemingly) random motion.
Apparently, apart from being lovely to behold, the phenomenon is a good demonstration of quantum revival, (formerly Creedence Clearwater Revival).
Pendulum Waves (Harvard Natural Sciences Lecture Demonstrations)
