Aug 3, 2013
"The clock is controlled by a valve that inflates and deflates a foil balloon inside a glass capsule. Users can set the deflation rate in intervals of 10 minutes, all the way up to a half hour, with Schmidt noting that “30 minutes is not too long or too short for a step in time; it gives only an orientation.” When the clock runs out of air, it can be reset as many times as needed, which, Schmidt says, is to prevent people from totally losing track of time."