Alice Aycock's kinetic sculpture is made of aluminum plates and blades within a steel frame, with a small motor attached at the base.

Aycock's early sculptures were built of wood. In 1979 she began to exhibit machines with moving metal parts-wheels and axles propelled by electric motors. When set in motion, The Theory of Twilight creates a dramatic, impressive, abstract tableau that may inspire feelings of danger.

For conservation purposes, The Theory of Twilight operates for five minutes on the hour and half hour.