Hickory, dickory, dock
Have you heard of the Beverly Clock?
Gracing the foyer of the Department of Physics at the University of Otago in Dunedin, New Zealand, this mechanical marvel is powered by the planet – or variations in daily temperature and atmospheric pressure to be precise.
So how does the 153 year old clock, which has only ever been wound once, actually work? Inside the clock there is a one cubic-foot air-tight box. And inside that there’s air, which expands or contracts throughout the day, pushing on a diaphragm. In practice, a six-degree Celsius temperature variation is all that’s required to raise a one-pound weight by one inch. As the weight descends, it powers the clock for another day.
One of the longest-running scientific experiments in the world, the Beverly Clock looks set to go on ticking long after your or our time’s up. Except for occasional stoppages for cleaning, relocation and when the temperature and atmospheric pressure have remained stubbornly steady, this is the closest any of us will see to a perpetual motion machine. Unless you know better of course…
