Metronomes started randomly synchronize after a short period of time as they influence each other through the side-to-side motion of their shared base.

Source: UCLA Physics & Astronomy
https://demoweb.physics.ucla.edu/content/160-spontaneous-synchronization

160. Spontaneous Synchronization | UCLA Physics & Astronomy

@wonderofscience slightly unrelated, does anyone knows which metronome is the one on this video? I have been looking for a clean looking one, and I really like this one.

@david @wonderofscience

Based on the W tuning fork logo I think it’s a Wittner Taktell Super-mini, a German model
still in production.