Decoded: How two pendulum clocks always oscillate in synchronicity

Two pendulum clocks, hung from the same wooden structure, will always oscillate in synchronicity. Called "Huygens synchronisation" after the renowned Dutch physicist Christiaan Huygens, the secret behind this 350-year-old phenomenon has now been solved.

Researchers from Eindhoven University of Technology along with Mexican colleagues have presented the most accurate and detailed description of "Huygens synchronisation' to date.

The insights help us understand synchronisation in all kinds of oscillating systems such as the biological rhythms of the human body, they noted.

Lacking the requisite mathematics at the time, Huygens contended that the effect was being caused by tiny vibrations in the wooden structure on which the clocks were hanging.

Henk Nijmeijer, professor of dynamics and control at Eindhoven University, found that Huygens explanation was right.

In the journal Scientific Reports, the team described the most comprehensive study undertaken to date on the effect.

"An odd sympathy" was the way Huygens termed the unexpected discovery he made at home in The Hague in 1665.

The team performed a modern variant of Huygens' experiment whereby two pendulum clocks specially made for the purpose by the Mexican clock manufacturer Relojes Centenario were placed on a wooden undersurface.

In addition to taking extensive measurements, they analysed and simulated the effect using the most detailed mathematical model developed for this experiment.

This enabled them to dissect the mechanism behind the synchronisation correctly and in detail and consign to the bin the theory proposed two years ago that the synchronisation was attributable to acoustic pulses.

The team also discovered what variables determine whether the clocks swing in parallel with or counter to each other, something that Huygens did not observe.

"Another new discovery is that pendulum clocks are not only synchronous but also move more slowly over time and thus are not very reliable timekeepers," they noted.

The scientists believe many similar occurrences of synchronisation are present in engineering and in nature like imbalanced rotor motion or the human heartbeat.

There are also indications that certain epileptic attacks are caused by the synchronisation of neurons that takes place in the brain.