A study in the journal Scientific Reports has proposed a solution: the pendulums transfer energy to one another through sound pulses.
A pair of Portuguese scientists hypothesised that these pulses might move from clock to clock, perturbing the swing of the pendulums and eventually causing them to synchronise. They developed a complex mathematical model before conducting experiments with a pair of clocks attached to a rail fixed to a wall. The theoretical predictions and simulation matched, they found.
“We could verify that the energy transfer is through a sound pulse,” said co-author Luis Melo, from Lisbon University’s physics department. This not only solves “an old, fundamental problem,” it also boosts understanding of other types of oscillator, he said.