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Perpetual motion

Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, since its existence would violate the first and/or second laws of thermodynamics.[2][3][4][5]

For other uses, see Perpetual motion (disambiguation).

These laws of thermodynamics apply regardless of the size of the system. For example, the motions and rotations of celestial bodies such as planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy, such as solar wind, interstellar medium resistance, gravitational radiation and thermal radiation, so they will not keep moving forever.[6][7]


Thus, machines that extract energy from finite sources cannot operate indefinitely because they are driven by the energy stored in the source, which will eventually be exhausted. A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out.


In 2016,[8] new states of matter, time crystals, were discovered in which, on a microscopic scale, the component atoms are in continual repetitive motion, thus satisfying the literal definition of "perpetual motion".[9][10][11][12] However, these do not constitute perpetual motion machines in the traditional sense, or violate thermodynamic laws, because they are in their quantum ground state, so no energy can be extracted from them; they exhibit motion without energy.

A perpetual motion machine of the first kind produces without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy.

work

A perpetual motion machine of the second kind is a machine that spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However, it does violate the more subtle in a cyclic process (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.

second law of thermodynamics

A perpetual motion machine of the third kind is defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever due to its mass inertia (third in this case refers solely to the position in the above classification scheme, not the ). It is impossible to make such a machine,[20][21] as dissipation can never be completely eliminated in a mechanical system, no matter how close a system gets to this ideal (see examples at § Low friction below).

third law of thermodynamics

Decision BL O/044/06, John Frederick Willmott's application no. 0502841

[34]

Decision BL O/150/06, Ezra Shimshi's application no. 0417271

[35]

Proposals for such inoperable machines have become so common that the United States Patent and Trademark Office (USPTO) has made an official policy of refusing to grant patents for perpetual motion machines without a working model. The USPTO Manual of Patent Examining Practice states:


And, further, that:


The filing of a patent application is a clerical task, and the USPTO will not refuse filings for perpetual motion machines; the application will be filed and then most probably rejected by the patent examiner, after he has done a formal examination.[31] Even if a patent is granted, it does not mean that the invention actually works, it just means that the examiner believes that it works, or was unable to figure out why it would not work.[31]


The United Kingdom Patent Office has a specific practice on perpetual motion; Section 4.05 of the UKPO Manual of Patent Practice states:


Examples of decisions by the UK Patent Office to refuse patent applications for perpetual motion machines include:[33]


The European Patent Classification (ECLA) has classes including patent applications on perpetual motion systems: ECLA classes "F03B17/04: Alleged perpetua mobilia" and "F03B17/00B: [... machines or engines] (with closed loop circulation or similar : ... Installations wherein the liquid circulates in a closed loop; Alleged perpetua mobilia of this or similar kind".[36]

The toy functions using small ambient temperature gradients and evaporation. It runs until all water is evaporated.

drinking bird

A -based water pump functions using small ambient temperature gradients and vapour pressure differences. With the "capillary bowl", it was thought that the capillary action would keep the water flowing in the tube, but since the cohesion force that draws the liquid up the tube in the first place holds the droplet from releasing into the bowl, the flow is not perpetual.

capillary action

A consists of a partial vacuum glass container with a lightweight propeller moved by (light-induced) temperature gradients.

Crookes radiometer

Any device picking up minimal amounts of energy from the natural around it, such as a solar-powered motor.

electromagnetic radiation

Any device powered by changes in air pressure, such as some clocks (, Beverly Clock). The motion leeches energy from moving air which in turn gained its energy from being acted on.

Cox's timepiece

A , due to it having a COP above 1: the energy it consumes as work is less than the energy it moves as heat.

heat pump

The uses changes in the vapor pressure of ethyl chloride with temperature to wind the clock spring.

Atmos clock

A device powered by induced nuclear reactions or by from an isotope with a relatively long half-life; such a device could plausibly operate for hundreds or thousands of years.

radioactive decay

The and the Karpen Pile are driven by dry pile batteries.

Oxford Electric Bell

Anti-gravity

Faster-than-light

Incredible utility

Johann Bessler

Pathological science

Time travel

at Curlie

Perpetual motion

Archived 2018-09-14 at the Wayback Machine

The Museum of Unworkable Devices

Maruyama, Koji; Nori, Franco; Vedral, Vlatko (2009). "Colloquium: The physics of Maxwell's demon and information". Reviews of Modern Physics. 81 (1): 1–23. :0707.3400. Bibcode:2009RvMP...81....1M. doi:10.1103/RevModPhys.81.1. S2CID 18436180.

arXiv

Popular Mechanics, January 1954, pp. 108–111.

"Perpetual Motion - Just Isn't."

BBC discussion with Ruth Gregory, Frank Close and Steven Bramwell, hosted by Melvyn Bragg, first broadcast 24 September 2015.

In Our Time: Perpetual Motion

What is known about perpetual motion in detail, Published on USIIC May 21, 2023