The First Ball Bearing

This may be the first design of a ball bearing. In a ball bearing, smooth balls roll between two surfaces, reducing the friction between then. Leonardo used this design to construct a revolving stage for a theater production at the court of Milan. Today, the descendants of Leonardo's ball bearing are found in many mechanisms, from skateboards to computer hard drives, conveyor belt rollers to Lazy Susans, automobile transmissions to bar stools.