The 350-year-old mystery of why pendulum clocks hanging from the same wall can influence each other and synchronize over time may hold even more secrets than previously thought, researchers say.

Solving this mystery could shed light on puzzling aspects of a variety of synchronized behaviors, such as how brain cells work together, the scientists added.

In 1665, the inventor of the pendulum clock, Dutch physicist Christiaan Huygens, was lying in bed sick, watching two of his clocks, when he noticed something odd: No matter how the pendulums on these clocks started, they ended up swinging in exactly the opposite direction from each other within about a half-hour. [The 9 Biggest Unsolved Mysteries in Physics]

For centuries, the cause of this effect was unknown. Solving the puzzle could help shed light on the mysterious phenomenon of synchronization, scientists say.

“The synchronization phenomenon is one of the most pervasive drives in nature,” said study lead author Jonatan Peña Ramirez, a dynamicist at the Center for Scientific Research and Higher Education in Ensenada, Mexico. “For example, consider a couple dancing to the rhythm of music, or violinists in an orchestra playing in unison, or a school of fish gracefully swimming.”

In a separate study published last year in the journal Scientific Reports, scientists suggested that the explanation for this phenomenon involvedsound pulses traveling from clock to clock — for instance, through the wall on which the machines hang. However, Peña and his colleagues now suggest that Huygens’ original explanation for this mystery could be the correct one.

The researchers experimented with two complex pendulum clocks known as monumental clocks.”To the best of our knowledge, this is the first time that Huygens’ experiment is reproduced using real monumental pendulum clocks,” Peña told Live Science. “Previous studies have used scaled-down versions of pendulum clocks, or commercial and generic clocks.”

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