Why pendulums swing in harmony – new theory

Maybe I need some more pendulum clocks.

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Perfect harmony? [image credit: homedit] Perfect harmony? [image credit: homedit]

From the believe-it-or-not file, Phys.org reports a possible solution to an old puzzle:

Almost 350 years ago, Dutch inventor and scientist Christiaan Huygens observed that two pendulum clocks hanging from a wall would synchronise their swing over time.

What causes the phenomenon has led to much scientific head-scratching over the centuries, but no consensus to date.

‘But now’ – as Tomorrow’s World presenters used to say…

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2 responses to “Why pendulums swing in harmony – new theory

  1. Has the world totally forgotten about coupled oscillations? Two oscillators with matching frequencies that are able to exchange energy at all (i.e. through the commons support or the surrounding medium) will form ‘normal modes’ of vibration which include ‘combination frequencies’ (e.g. sum and difference frequencies) identifiable via Fourier analysis.
    Perhaps the simplest is the vibrational modes of the water molecule:

    The bonds between the oxygen and the separate hydrogen atoms are independent and have the same frequency, but the molecule itself has two distinct vibrations, depending on whether the O-H bonds are vibrating exactly in phase with each other
    H – – O – – H H – O – H
    or exactly out of phase with each other
    H – – O – H H – O – – H
    A random disturbance of the *system* will generally excite both vibrations to different degrees.
    A disturbance of only one oscillator will excite BOTH modes equally, producing the ‘magical’ exchange of motion between the oscillators.
    The frequency of this exchange depends on how strongly the oscillators are coupled.

  2. Just like females that spend a lot of time together.

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