The suspended balls swing back and forth at slightly different rates, determined by the length of the strings. Each ball completes a set number of swings in 30 seconds, from the longest (15 swings in 30 seconds) to the shortest (24 swings in 30 seconds). Set in motion together, the balls go in and out of several interesting patterns before they line up again after 30 seconds.
Ivars Peterson is a freelance writer and editor. He was Director of Publications at the Mathematical Association of America from 2007 to 2014. As an award-winning mathematics writer, he previously worked at Science News for more than 25 years and served as editor of Science News Online and Science News for Kids. His books include The Mathematical Tourist, Islands of Truth, Newton's Clock, and Fragments of Infinity: A Kaleidoscope of Math and Art.