perpetual motion

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.

perpetual motion

noun

1. Also calledperpetual 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 calledperpetual 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

Word History and Origins

Origin of perpetual motion¹

First recorded in 1585–95

Example Sentences

For instance, a counterfactual property imposed by the laws of physics is that it is impossible to build a perpetual motion machine.

From Nautilus

In the current approach to physics, some laws already have this counterfactual structure — the conservation of energy, for example, is the statement that it is impossible to have a perpetual motion machine.

From Quanta Magazine

For an artist in perpetual motion, that doesn’t sound like a stretch at all.

From Washington Post

I want to always be in a state of perpetual motion: going somewhere, doing something.

From The Daily Beast

It is a potent part of the Sarkozy brand: he is tireless and in perpetual motion.

From The Daily Beast

The poor soldier had one of those eccentric souls which need perpetual motion.

From Project Gutenberg

I suppose I am growing old, for I begin to dislike perpetual motion.

From Project Gutenberg

Of course, such a doctrine cannot be true; it would amount to a perpetual motion!

From Project Gutenberg

In fact, it is the old story illustrated, that perpetual motion is impossible.

From Project Gutenberg

Or, perhaps, a still more lively illustration to some readers may be the idea of perpetual motion.

From Project Gutenberg