Perpetual motion machine, 19th century illustration. Perpetual motion is the motion of bodies that continues forever. A perpetual motion machine is a hypothetical machine that can do work infinitely without an energy source. This kind of machine is impossible as it would violate the first or second law of thermodynamics. Copperplate engraving from the Encyclopaedia Londinensis, or Universal Dictionary of Arts, Sciences, and Literature; Volume XVI; Edited by Wilkes, John. Published in 1819.