Why Do Pendulum Clocks Swing Together?

Since Dutch scientist Christiaan Huygens first invented the pendulum clock back in 1656, the world has been captivated by the perfectly synched time keeping devices. At the time of creation the pendulum clock was hailed as the most accurate timepiece on the planet, with an error margin of less than 10 seconds. Time is measured using a pendulum suspended from a wire, rod or string. The speed at which the pendulum swings is determined by its length which should be adjusted to suit the dimensions of the clock.

Huygens noted that when two pendulum clocks are hung side by side their pendulums would eventually swing in unison, yet in opposite directions. The conundrum has spanned for over 350 years and now, a pair of physicists has busted the phenomenon in a write up published in Scientific Reports journal. They claim a sound pulse triggers an energy transfer which then causes the clocks to synchronise.

Portuguese scientists unravel pendulum mystery

The revelation was discovered by a pair of Portuguese scientists who assert that these sound pulses jump from clock to clock. As they transfer they disquiet the swing of the pendulums which eventually causes them to harmonise. Regardless of how or when they start, they’ll always swing in unison within 30 minutes! To put forward the watertight hypothesis the scientists developed a bespoke complex mathematical model. They then fixed two clocks to a wall and started to observe. Both the theoretical predictions and pendulum synchronisation came to light.

Co-author Luis Melo of Lisbon University’s physics department explains, “We could verify that the energy transfer is through a sound pulse.” He maintains that as well as solving “an old, fundamental problem,” the discovery also enhances the scientific world’s understanding of other oscillator types.

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Images sourced via Flickr Creative Commons. Credits: kbrookes