Mesmerizing Pendulum Waves


(Video Link)


This simple but beautiful video from Harvard University shows fifteen pendulums of increasing length swinging to and fro. Sometimes they appear to be in sync, but at other times, not. Here's why:

The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations. When all 15 pendulums are started together, they quickly fall out of sync—their relative phases continuously change because of their different periods of oscillation. However, after 60 seconds they will all have executed an integral number of oscillations and be back in sync again at that instant, ready to repeat the dance.


Link via Kottke

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Blatant edits on Wikipedia are annoying, but they're not as dangerous as subtle (but very wrong) edits - I once encountered a series of articles that are legit on the outset but turn out to be completely nonsensical. My trust on Wikipedia hasn't been the same ever since.
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I have an idiot boss who likes to use the phrase "that wouldn't be prudent". Every once in a while me and my co-workers will go on to Wikipedia and change the picture on the entry for prudence to a picture of our boss. It gets changed back within a day, but it's always good for a laugh-filled afternoon!
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