METRONOMES SYNC — The weights of the pendulums on the metronomes are being swung back and forth by the rolling back...

METRONOMES SYNC — The weights of the pendulums on the metronomes are being swung back and forth by the rolling back and forth motion of the cans. The metronomes only go the rate they are set at IF under ONLY the downward (perpendicular) force of gravity. As soon as there is an acceleration along the line of swinging, that acceleration may largely override that of Earth's gravity. Of course, that back and forth motion of the cans is actually started by the pendulum weights themselves; whichever side the majority of the weights are on at the start, will cause a roll in that direction (thereby influencing the minority pendulums whose weights are on the opposite side). It's a progressive process with each roll back and forth.

Video 1:
https://youtu.be/W1TMZASCR-I

Some beautiful Math:
http://www.math.pitt.edu/~bard/classes/mth3380/syncpapers/metronome.pdf

Video 2 - And now, 32 metronomes:
https://youtu.be/7PHSkoPGoFg

{ via Ismael Cordeiro, Marcio Pinto e Fabiano Vianna }
https://youtu.be/W1TMZASCR-I