This is simple. And lovely. Math in motion …
Per the YouTube page:
Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and (seemingly) random motion.
For more details see http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa…
The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations.
Our apparatus was built from a design published by Richard Berg [Am J Phys 59(2), 186-187 (1991)] at the University of Maryland. The particular apparatus shown here was built by our own Nils Sorensen.
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Video courtesy of Harvard Natural Sciences Lecture Demonstrations, © 2010 President and Fellows of Harvard College
A few years ago there was some construction on campus and a number of sawhorse barriers were erected to keep people from falling in the excavation. To accommodate the handicapped, the flashing lights on top of the sawhorses had little beepers. The time period was probably determined by something like the discharge of a capacitor (inexpensive old-school timing circuits worked that way) instead of a digital count, but in any case there was slight variation between beeps from one to the next. I closed my eyes and stood, listening as complex patterns emerged from the array. The fact that they were arranged in space as well as time made it fascinating and strangely musical.
Later I brought my music-major son back and we listened. He was amazed – loved it.
Heck, I get fascinated by the flashers on the barriers in just that way. (It’s a good thing I’m not prone to epileptic seizures.)