Built from 15 billiard balls, this pendulum wave demonstration provides an excellent example of “visual traveling waves, standing waves, beating, and random motion.” The apparatus cycles through these patterns because of each pendulum string’s calculated length. An explanation from Harvard.edu’s Science Demonstrations:
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. When all 15 pendulums are started together, they quickly fall out of sync—their relative phases continuously change because of their different periods of oscillation. However, after 60 seconds they will all have executed an integral number of oscillations and be back in sync again at that instant, ready to repeat the dance.
These pendulum wave science project instructions can help you make your own hypnotizing apparatus.
Watch more videos from TKSST’s collection of pendulums, including this wave apparatus made from bowling balls, making Lissajous patterns with DIY sand pendulums or light, and this art installation favorite: Nowhere and Everywhere at the Same Time, No. 2.