How many times has this happened to you? You have five metronomes and they’re all out of sync with each other! How do you correct this problem? Thankfully the folks at Lancaster University have the solution: two soda cans and a plank. Why does it work?
Metronomes (or “pendula”) when on table, oscillate with random phases, since that is how they started and they are “uncoupled” (no energy/information flows from one to other so they do not “know” each other.) When they are all together on the cans, notice that the cans themselves oscillate little, providing coupling/information crossover. which forces “synchronization” in periodic systems (discovered by Huygens in 17th century).