This video doesn’t, on the surface at least, seem like the most exciting clip in the world. But keep watching right to the end and you’ll see something amazing happen.

These metronomes are all set off at different times, but slowly and surely they align until they’re all keeping time together in unison. It’s a mesmerizing display.

The reason for this effect is the flexibility of the surface they’re sitting on. The collective movement forces the reluctant metronomes to all fall into line.

A similar force can be seen at work on bridges. The Millennium Bridge in London was nicknamed the Wobbly Bridge as pedestrians walking across it caused it to sway, which in turn caused the people to walk in time with each other, which in turn exacerbated the swaying.