Over at The Kids Should See This, a video from the Ikeguchi Lab in Japan demonstrates how 32 metronomes match up in synchronous play after each being tapped at different instances. It’s a pretty difficult feat to sync 2 metronomes–let alone an extra 30!
It’s Okay To Be Smart explains the physics behind it:
When the arm of any metronome hits the side, it exerts a force on the blue platform. Normally friction would make that unnoticeable. But this platform is special. It’s set up on rollers so that it can move from side to side.
When any two metronome arms hit, their forces on the platform either cancel out or add together, depending on how out of or in sync they are. Any arms that are out of sync will experience a force in the opposite direction that inches them closer to the pack.