The sympathy of two pendulum clocks: beyond Huygens’ observations

In an era when science relied heavily on observation, experimentation, and reflection, the Dutch scientist Christiaan Huygens made a serendipitous discovery: two of his recently invented pendulum clocks—which were hanging from a common wooden beam placed at the top of two chairs—were showing an ‘odd sympathy’. Namely, the pendula of the clocks were oscillating in perfect consonance but in opposite directions, i.e. the clocks were synchronized in anti-phase. He reported this odd phenomenon first to R. F. de Sluse, on February 22, 1665 and two days later to his father and to a member of the Royal Society of London.

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In the last years, Huygens’ synchronization has become a relevant topic among scientists and researchers. By designing novel experimental platforms and/or by conducting theoretical analyzes, further understanding about the exciting phenomenon described by Huygens has been obtained. In particular, the aforementioned studies somehow convey the same message: the key element in Huygens’ setup of pendulum clocks is the coupling structure and its mechanical properties.

Nevertheless, Huygens’ synchronization is still an open problem. This claim may be surprising, specially if one considers the fact that the behavior associated to pairs of coupled oscillators has been extensively and exhaustively studied and nowadays, the focus is not on pairs of oscillators but rather in networks of oscillators.

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English Translation of Horologium Oscillatorium: http://www.17centurymaths.com/contents/huygenscontents.html

I think I've been under appreciating Huygens: https://en.wikipedia.org/wiki/Christiaan_Huygens