perpetual motion

American  

noun

Mechanics.

1. the motion of a theoretical mechanism that, without any losses due to friction or other forms of dissipation of energy, would continue to operate indefinitely at the same rate without any external energy being applied to it.

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perpetual motion British  

noun

1. Also called: perpetual motion of the first kind.  motion of a hypothetical mechanism that continues indefinitely without any external source of energy. It is impossible in practice because of friction

2. Also called: perpetual motion of the second kind.  motion of a hypothetical mechanism that derives its energy from a source at a lower temperature. It is impossible in practice because of the second law of thermodynamics

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Etymology

Origin of perpetual motion

First recorded in 1585–95

Example Sentences

"Perpetual motion" machines are the patent examiner's biggest annoyance.

From Time Magazine Archive

Perpetual motion stands at the head of the absolute impossibilities of life; therefore, the government has never offered a prize for the solution of this mythical problem.—Ranger.

From Golden Days for Boys and Girls, Vol. XIII, Nov. 28, 1891 by Elverson, James

Perpetual motion has been the dream of scientific visionaries, and a pretended but cheating realization of it has been exhibited by scamp after scamp.

From The Humbugs of the World An Account of Humbugs, Delusions, Impositions, Quackeries, Deceits and Deceivers Generally, in All Ages by Barnum, P. T. (Phineas Taylor)

Perpetual motion, or squaring the circle, would baffle Gregory.

From The Face and the Mask by Barr, Robert

Perpetual motion by a drum with one vertical half in mercury, the other in a vacuum: the drum, I suppose, working round forever to find an easy position.

From A Budget of Paradoxes, Volume I by Smith, David Eugene