In scientific terms, kinetic energy is the energy possessed by a body by virtue of its motion, and kinetic art, which peaked from the middle 1960s to the middle 1970s, produces movement, often through machines activated by the viewer. Kinetic Art overlaps with the optical art or Op Art of the 1960s, in which artists such as Victor Vasarely, Julio Le Parc, and Nicolas Schöffer used patterns to create optical illusions of movement, vibration and warping. The term first appeared in print in Time magazine in October 1964, but works falling into the Op Art category were produced much earlier. The influence of the Kinetic and Op Art experiments with ‘machines’ that produced light and movement can be traced in many digital installations today.