I shamelessly stole this video from a post by Julianne Dalcanton at Cosmic Variance because it’s so cool. 32 metronomes start out ticking asynchronously, buit miraculously fall into synchrony. Why? It’s based on the platform on which they’re standing, but go to Cosmic Variance to see the answer.
If you’re a physics geek, try to answer by watching the video before you read Julianne’s explanation.