Perpetual Motion

In the foyer of the Department of Physics at the University of Otago in Dunedin, New Zealand, sits the Beverly Clock, invented in 1864 by Arthur Beverly. An airtight box inside the clock expands and contracts throughout the day running on atmospheric pressure and changes in temperature, and the contractions then push on a diaphragm. It takes only a few degrees of variation over a day to raise a one pound weight one inch. This in turn descends, powering the clock. One of the world's longest running experiments, the Beverly Clock has never been wound.