Perpetual Motion

PERPETUAL MOTION, taken literally, refers to movement that goes on forever. However, the term most commonly refers to any particular device or system that indefinitely produces more energy than it consumes, resulting in a net output of energy for infinity. The law of conservation of energy,  which states that energy cannot be created or destroyed, explains that such a perpetual motion machine cannot exist. The most commonly contemplated type of perpetual motion machine is a mechanical system which sustains motion indefinitely, despite losing energy to friction and resistance.  Another type of impossible "Perpetual Motion Machine" is one which does not violate conservation of energy, but produces work by extracting heat from its surroundings, thereby cooling them down, and converting the heat energy into mechanical work.