Infographysics: Physics of the water clock

Water clocks are among the most ancient time-measuring instruments in human history. They have been found in many shapes and formes, from a simple pair of containers—where water goes from one bowl to the other in a fixed amount of time, while the passing of time is measured via ticks drawn on the walls of each bowl — to the more complex design shown here. In its simplest form, a water clock can be thought as a hourglass where water replaces sand. In the above, a piston is designed following Archimedes’ buoyancy principle so that, taking advantage of the pressure coming from the rising level of water, a rotation is induced in the hand of a Clock.