4 ms·

Totally aside, but funnily enough two pendulums can synchronize through weak vibrations, e.g. pendulum clocks hanging on the same wall. Observed by Huygens in 1

• dhimes 11y ago
  A cool thing to do is to hang two pendula next to each other and couple them via, say, a pencil (loop each pendulum's string once around the pencil, so the pencil is horizontal and is able to transfer energy from one to the other). Set one in motion. Eventually wonder where the rest of the day went :)