The persuance of perpetual motion is to physics and mechanical engineering what alchemy is to modern chemistry, which is to say that it is seeking after the unrealizable. The earliest written description of a perpetual motion machine dates to the fifth century A.D. Manuals and scientific treatises abounded throughout the Middle Ages and the Renaissance that described various perpetual motion devices. As late as the early 1800s, a miller in Ohio poured his life savings into building a three-story mill house that was supposed to run perpetually by means of a closed system powered by 500 gal (1,890 L) of water. It didn't work.

Perpetual motion, when defined by its literal meaning, is an impossibility according to Classical physics. A perpetual motion device, when set in motion, never stops and never requires further input of energy. Another way of saying that is, it puts out more energy...