We're used to seeing pendulum waves generated on tiny scaffolds with itty-bitty balls. But as this awesome demonstration points out, the same physics applies even at the largest scales.
The key to pendulum waves — and understanding why the balls appear to move in and out of synch with each other — is that the strings are at different lengths. This causes each ball to swing at a different rate. Eventually, as the balls move back and forth, they eventually "match up" and produce a wave-like pattern, like the one seen at about 2:40.
This pendulum was built by Appalachian State University teacher and artist Jeff Goodman.
H/t This Is Colossal.