Check out this fascinating video of numerous metronomes set off at random times at random frequencies. Slowly but surely the clicks begin to merge, motions come closer and then eventually spontaneous synchronisation is there before your very eyes.
This only works on raised floors, where the group with the greater combined metronome direction will slowly influence the others, bringing them together synchronised in one motion. The cans placed under the system allow this to happen quicker as metronomes synchronize through small motions of the base on which they are placed.
There is a mathematical model explaining this phenomenon. It was formulated by Yoshiki Kuramoto, a Japanese physicist at Kyoto University. It models the behavior of a large set of coupled oscillators that each have their intrinsic natural frequency, and each is coupled equally to all other oscillators.. Watch the video below to undestand its principles. Read more about it on Wikipedia.
Video by Stewart Heitmann.