Perpetual motion

Perpetual motion

Overview
Perpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, whether they might operate indefinitely or not.

There is undisputed scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...

 that perpetual motion in a closed system would violate the first law of thermodynamics
First law of thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.The law states that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed...

 and/or the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

. Machines which extract energy from seemingly perpetual sources - such as ocean currents - are indeed capable of moving "perpetually" (for as long as that energy source itself endures), but they are not considered to be perpetual motion machines because they are consuming energy from an external source and are not closed systems. Similarly, machines which comply with both laws of thermodynamics but access energy from obscure sources are sometimes referred to as perpetual motion machines, although they also do not meet the standard criteria for the name.

Despite the fact that successful closed system perpetual motion devices are physically impossible in terms of our current understanding of the laws of physics, the pursuit of perpetual motion remains popular.

There is an undisputed scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...

 that perpetual motion in a closed system violates either the first law of thermodynamics
First law of thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.The law states that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed...

, the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

, or both.
Discussion
Ask a question about 'Perpetual motion'
Start a new discussion about 'Perpetual motion'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia
Perpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, whether they might operate indefinitely or not.

There is undisputed scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...

 that perpetual motion in a closed system would violate the first law of thermodynamics
First law of thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.The law states that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed...

 and/or the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

. Machines which extract energy from seemingly perpetual sources - such as ocean currents - are indeed capable of moving "perpetually" (for as long as that energy source itself endures), but they are not considered to be perpetual motion machines because they are consuming energy from an external source and are not closed systems. Similarly, machines which comply with both laws of thermodynamics but access energy from obscure sources are sometimes referred to as perpetual motion machines, although they also do not meet the standard criteria for the name.

Despite the fact that successful closed system perpetual motion devices are physically impossible in terms of our current understanding of the laws of physics, the pursuit of perpetual motion remains popular.

Basic principles


There is an undisputed scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...

 that perpetual motion in a closed system violates either the first law of thermodynamics
First law of thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.The law states that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed...

, the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

, or both. The first law of thermodynamics is essentially a statement of conservation of energy. The second law can be phrased in several different ways, the most intuitive of which is that heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 flows spontaneously from hotter to colder places; the most well known statement is that entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

 tends to increase, or at the least stay the same; another statement is that no heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

 (an engine which produces work while moving heat between two separate places) can be more efficient than a Carnot heat engine
Carnot heat engine
A Carnot heat engine is a hypothetical engine that operates on the reversible Carnot cycle. The basic model for this engine was developed by Nicolas Léonard Sadi Carnot in 1824...

.

In other words:
  1. In any closed system, you cannot create new energy (first law of thermodynamics)
  2. You always lose a little energy (second law of thermodynamics)
  3. Therefore a machine cannot make more energy than it uses or even enough to keep itself operating.


Machines which comply with both laws of thermodynamics by accessing energy from unconventional sources are sometimes referred to as perpetual motion machines, although they do not meet the standard criteria for the name. By way of example, clocks and other low-power machines, such as Cox's timepiece
Cox's timepiece
Cox's timepiece is a clock developed in the 1760s by James Cox. It was developed in collaboration with John Joseph Merlin . Cox claimed that his design was a true perpetual motion machine, but as the device is powered from changes in atmospheric pressure via a mercury barometer, this is not the case...

, have been designed to run on the differences in barometric pressure or temperature between night and day. These machines have a source of energy, albeit one which is not readily apparent so that they only seem to violate the laws of thermodynamics.

Machines which extract energy from seemingly perpetual sources - such as ocean currents - are indeed capable of moving "perpetually" until that energy source runs down. But they are not considered to be perpetual motion machines because they are consuming energy from an external source and are not closed systems.

Classification


One classification of perpetual motion machines refers to the particular law of thermodynamics the machines purport to violate:
  • A perpetual motion machine of the first kind produces work
    Work (thermodynamics)
    In thermodynamics, work performed by a system is the energy transferred to another system that is measured by the external generalized mechanical constraints on the system. As such, thermodynamic work is a generalization of the concept of mechanical work in mechanics. Thermodynamic work encompasses...

     without the input of energy
    Energy
    In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

    . It thus violates the first law of thermodynamics: the law of conservation of energy.
  • A perpetual motion machine of the second kind is a machine which 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 second law of thermodynamics
    Second law of thermodynamics
    The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

     (see also entropy
    Entropy
    Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

    ). 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.


A more obscure category is a perpetual motion machine of the third kind, usually (but not always) 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 third law of thermodynamics
Third law of thermodynamics
The third law of thermodynamics is a statistical law of nature regarding entropy:For other materials, the residual entropy is not necessarily zero, although it is always zero for a perfect crystal in which there is only one possible ground state.-History:...

. Although it is impossible to make such a machine, as dissipation can never be 100% eliminated in a mechanical system, it is nevertheless possible to get very close to this ideal (see examples in the Low Friction section). Such a machine would not serve as a source of energy but would have utility as a perpetual energy storage device.

Use of the term "impossible" and perpetual motion


While the laws of physics are incomplete
Beyond the Standard Model
Physics beyond the Standard Model refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the origin of mass, the strong CP problem, neutrino oscillations, matter–antimatter asymmetry, and the nature of dark matter and dark energy...

 and stating that physical things are absolutely impossible is un-scientific
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

, "impossible
Epistemic possibility
In philosophy and modal logic, epistemic possibility relates a statement under consideration to the current state of our knowledge about the actual world: a statement is said to be:* epistemically possible if it may be true, for all we know...

" is used in common parlance to describe those things which absolutely cannot occur within the context of our current formulation of physical laws.

The conservation laws are particularly robust from a mathematical perspective. Noether's theorem
Noether's theorem
Noether's theorem states that any differentiable symmetry of the action of a physical system has a corresponding conservation law. The theorem was proved by German mathematician Emmy Noether in 1915 and published in 1918...

, which was proven mathematically
Mathematical proof
In mathematics, a proof is a convincing demonstration that some mathematical statement is necessarily true. Proofs are obtained from deductive reasoning, rather than from inductive or empirical arguments. That is, a proof must demonstrate that a statement is true in all cases, without a single...

 in 1915, states that any conservation law can be derived from a corresponding continuous symmetry of the action
Action (physics)
In physics, action is an attribute of the dynamics of a physical system. It is a mathematical functional which takes the trajectory, also called path or history, of the system as its argument and has a real number as its result. Action has the dimension of energy × time, and its unit is...

 of a physical system. This means that if the laws of physics (not simply the current understanding of them, but the actual laws, which may still be undiscovered) and the various physical constants remain invariant over time — if the laws of the universe are fixed — then the conservation laws must hold. On the other hand, if the conservation laws are invalid, then much of modern physics would be incorrect as well.

Scientific investigations as to whether the laws of physics are invariant over time use telescopes to examine the universe in the distant past to discover, to the limits of our measurements, whether ancient stars were identical to stars today. Combining different measurements such as spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...

, direct measurement of the speed of light in the past and similar measurements demonstrates that physics has remained substantially the same, if not identical, for all of observable history spanning billions of years.

The principles of thermodynamics are so well established, both theoretically and experimentally, that proposals for perpetual motion machines are universally met with disbelief on the part of physicists. Any proposed perpetual motion design offers a potentially instructive challenge to physicists: one is almost completely certain that it can't work, so one must explain how it fails to work. The difficulty (and the value) of such an exercise depends on the subtlety of the proposal; the best ones tend to arise from physicists' own thought experiment
Thought experiment
A thought experiment or Gedankenexperiment considers some hypothesis, theory, or principle for the purpose of thinking through its consequences...

s and often shed light upon certain aspects of physics.

The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation. — Sir Arthur Stanley Eddington
Arthur Stanley Eddington
Sir Arthur Stanley Eddington, OM, FRS was a British astrophysicist of the early 20th century. He was also a philosopher of science and a popularizer of science...

, The Nature of the Physical World (1927)

Techniques


Some common ideas recur repeatedly in perpetual motion machine designs. Many ideas that continue to appear today were stated as early as 1670 by John Wilkins
John Wilkins
John Wilkins FRS was an English clergyman, natural philosopher and author, as well as a founder of the Invisible College and one of the founders of the Royal Society, and Bishop of Chester from 1668 until his death....

, Bishop of Chester
Bishop of Chester
The Bishop of Chester is the Ordinary of the Church of England Diocese of Chester in the Province of York.The diocese expands across most of the historic county boundaries of Cheshire, including the Wirral Peninsula and has its see in the City of Chester where the seat is located at the Cathedral...

 and an official of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

. He outlined three potential sources of power for a perpetual motion machine, "Chymical Extractions", "Magnetical Virtues" and "the Natural Affection of Gravity".

The seemingly mysterious ability of magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...

s to influence motion at a distance without any apparent energy source has long appealed to inventors. One of the earliest examples of a system using magnets was proposed by Wilkins and has been widely copied since: it consists of a ramp with a magnet at the top, which pulled a metal ball up the ramp. Near the magnet was a small hole that was supposed to allow the ball to drop under the ramp and return to the bottom, where a flap allowed it to return to the top again. The device simply could not work: any magnet strong enough to pull the ball up the ramp would necessarily be too powerful to allow it to drop through the hole. Faced with this problem, more modern versions typically use a series of ramps and magnets, positioned so the ball is to be handed off from one magnet to another as it moves. The problem remains the same.

Gravity also acts at a distance, without an apparent energy source. But to get energy out of a gravitational field (for instance, by dropping a heavy object, producing kinetic energy as it falls) you have to put energy in (for instance, by lifting the object up), and some energy is always dissipated in the process. A typical application of gravity in a perpetual motion machine is Bhaskara's wheel in the 12th century, whose key idea is itself a recurring theme, often called the overbalanced wheel: Moving weights are attached to a wheel in such a way that they fall to a position further from the wheel's center for one half of the wheel's rotation, and closer to the center for the other half. Since weights further from the center apply a greater torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

, the result is (or would be, if such a device worked) that the wheel rotates forever. The moving weights may be hammers on pivoted arms, or rolling balls, or mercury in tubes; the principle is the same.

Yet another theoretical machine involves a frictionless environment for motion. This involves the use of diamagnetic or electromagnet levitation to float an object. This is done in a vacuum to eliminate air friction and friction from an axle. The levitated object is then free to rotate around its center of gravity without interference. However, this machine has no practical purpose because the rotated object cannot do any work as work requires the levitated object to cause motion in other objects, bringing friction into the problem. Furthermore, a perfect vacuum is an unattainable goal since both the container and the object itself would slowly vaporize, thereby degrading the vacuum.

To extract work from heat, thus producing a perpetual motion machine of the second kind, the most common approach (dating back at least to Maxwell's demon
Maxwell's demon
In the philosophy of thermal and statistical physics, Maxwell's demon is a thought experiment created by the Scottish physicist James Clerk Maxwell to "show that the Second Law of Thermodynamics has only a statistical certainty." It demonstrates Maxwell's point by hypothetically describing how to...

) is unidirectionality. Only molecules moving fast enough and in the right direction are allowed through the demon's trap door. In a Brownian ratchet
Brownian ratchet
In the philosophy of thermal and statistical physics, the Brownian ratchet, or Feynman-Smoluchowski ratchet is a thought experiment about an apparent perpetual motion machine first analysed in 1912 by Polish physicist Marian Smoluchowski and popularised by American Nobel laureate physicist Richard...

, forces tending to turn the ratchet one way are able to do so while forces in the other direction aren't. A diode in a heat bath allows through currents in one direction and not the other. These schemes typically fail in two ways: either maintaining the unidirectionality costs energy (Maxwell's demon needs light to look at all those particles and see what they're doing), or the unidirectionality is an illusion and occasional big violations make up for the frequent small non-violations (the Brownian ratchet will be subject to internal Brownian forces and therefore will sometimes turn the wrong way).

Buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

 is another frequently-misunderstood phenomenon. Some proposed perpetual-motion machines miss the fact that to push a volume of air down in a fluid takes the same work as to raise a corresponding volume of fluid up against gravity. These types of machines may involve two chambers with pistons, and a mechanism to squeeze the air out of the top chamber into the bottom one, which then becomes buoyant and floats to the top. The squeezing mechanism in these designs would not be able to do enough work to move the air down, or would leave no excess work available to be extracted.

Invention history




The 8th century Bavarian "magic wheel" was a disc mounted on an axle powered by lodestones, claimed to be able to rotate forever.

India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

n mathematician
Indian mathematics
Indian mathematics emerged in the Indian subcontinent from 1200 BCE until the end of the 18th century. In the classical period of Indian mathematics , important contributions were made by scholars like Aryabhata, Brahmagupta, and Bhaskara II. The decimal number system in use today was first...

-astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

, Bhāskara II, described a wheel, dating to 1150, that would run forever.

Villard de Honnecourt
Villard de Honnecourt
Villard de Honnecourt was a 13th-century artist from Picardy in northern France. He is known to history only through a surviving portfolio of 33 sheets of parchment containing about 250 drawings dating from the 1220s/1240s, now in the Bibliothèque Nationale, Paris...

 in 1235 described, in a 33 page manuscript, a perpetual motion machine of the first kind. His idea was based on the changing torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 of a series of weights attached with hinges to the rim of a wheel. While ascending they would hang close to the wheel and have little torque, but they would topple after reaching the top and drag the wheel down on descent due to their greater torque during the swing. His device spawned a variety of imitators who continued to refine the basic design.

Following the example of Villard, Peter of Maricourt
Peter of Maricourt
Pierre Pelerin de Maricourt , Petrus Peregrinus de Maricourt or Peter Peregrinus of Maricourt; was a 13th century French scholar who conducted experiments on magnetism and wrote the first extant treatise describing the properties of magnets...

 designed a magnetic globe which when mounted without friction parallel to the celestial axis would rotate once a day and serve as an automatic armillary sphere
Armillary sphere
An armillary sphere is a model of objects in the sky , consisting of a spherical framework of rings, centred on Earth, that represent lines of celestial longitude and latitude and other astronomically important features such as the ecliptic...

.

In 1607 Cornelius Drebbel
Cornelius Drebbel
Cornelis Jacobszoon Drebbel was the Dutch builder of the first navigable submarine in 1620. Drebbel was an innovator who contributed to the development of measurement and control systems, optics and chemistry....

 in "Wonder-vondt van de eeuwighe bewegingh" dedicated a Perpetuum motion machine to James I of England
James I of England
James VI and I was King of Scots as James VI from 24 July 1567 and King of England and Ireland as James I from the union of the English and Scottish crowns on 24 March 1603...

. It was described by Heinrich Hiesserle von Chodaw in 1621. Also in the 17th century, Robert Boyle
Robert Boyle
Robert Boyle FRS was a 17th century natural philosopher, chemist, physicist, and inventor, also noted for his writings in theology. He has been variously described as English, Irish, or Anglo-Irish, his father having come to Ireland from England during the time of the English plantations of...

's proposed self-flowing flask purports to fill itself through siphon
Siphon
The word siphon is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes. But in the English language today, the word siphon usually refers to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir,...

 action and Blaise Pascal
Blaise Pascal
Blaise Pascal , was a French mathematician, physicist, inventor, writer and Catholic philosopher. He was a child prodigy who was educated by his father, a tax collector in Rouen...

 introduced a primitive form of roulette
Roulette
Roulette is a casino game named after a French diminutive for little wheel. In the game, players may choose to place bets on either a single number or a range of numbers, the colors red or black, or whether the number is odd or even....

 and the roulette wheel in his search for a perpetual motion machine.

In the 18th century, Johann Bessler
Johann Bessler
Johann Ernst Elias Bessler was a German entrepreneur who demonstrated a series of devices that he claimed exhibited perpetual motion.-Life and career:...

 (also known as Orffyreus) created a series of claimed perpetual motion machines. In 1775 the Royal Academy of Sciences in Paris issued the statement that the Academy "will no longer accept or deal with proposals concerning perpetual motion".

In the 19th century, the invention of perpetual motion machines became an obsession for many scientists. Many machines were designed based on electricity. John Gamgee developed the Zeromotor, a perpetual motion machine of the second kind. Devising these machines is a favourite pastime of many eccentrics, who often devised elaborate machines in the style of Rube Goldberg
Rube Goldberg
Reuben Garrett Lucius Goldberg was an American cartoonist, sculptor, author, engineer and inventor.He is best known for a series of popular cartoons depicting complex gadgets that perform simple tasks in indirect, convoluted ways. These devices, now known as Rube Goldberg machines, are similar to...

 or Heath Robinson. Such designs appeared to work on paper, though various flaws or obfuscated external energy sources are eventually understood to have been incorporated into the machine (unintentionally or intentionally).

Patents


Proposals for such inoperable machines have become so common that the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...

 (USPTO) has made an official policy of refusing to grant patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

s 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 won't 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. Even if a patent is granted, it doesn't mean that the invention actually works; it just means that the examiner thinks that it works, or that he couldn't figure out why it wouldn't work.

The USPTO maintains a collection of Perpetual Motion Gimmicks as Digest 9 in Class 74

The USPTO has granted a few patents for motors that are claimed to run without net energy input. Some of these are:
Howard R. Johnson, U.S. Patent 4,151,431
  • Johnson, Howard R., "Permanent magnet motor", April 24, 1979
  • Baker, Daniel, "Magnetic propulsion device", February 14, 1978
  • Hartman; Emil T., "Permanent magnet propulsion system", December 20, 1977 (this device is related to the Simple Magnetic Overunity Toy
    Simple Magnetic Overunity Toy
    The Simple Magnetic Overunity Toy is 1985 invention by Greg Watson from Australia that claims to show "over-unity" energy — a route to purported perpetual motion.-Overview:...

     (SMOT)),
  • Flynn; Charles J., "Methods for controlling the path of magnetic flux from a permanent magnet and devices incorporating the same", July 31, 1998
  • Patrick, et al., "Motionless electromagnetic generator
    Motionless Electrical Generator
    The motionless electromagnetic generator is a proposed device which claims over-unity operation, which would violate the first law of thermodynamics. Allegedly, the device can eventually sustain its operation in addition to powering a load without application of external electrical power, by...

    " , March 26, 2002
  • Green, Willie A., "Piston Driven Rotary Engine", March 4, 2003 "Fluid driven device utilizing a leveraged system with minimal displacement"
  • Goldenblum, Halm, "Energy generation mechanism, device and system", November 8, 2005 "A chamber with a partition which lets gas molecules flow one way and not the other. The pressure which builds up on one side of the partition is used to drive a generator."
  • Flynn, Joe, "Methods for controlling the path of magnetic flux from a permanent magnet and devices incorporating the same", June 12, 2001
  • Gates; Glenn A., "Spring driven apparatus", February 23, 2003 "Energy is stored in the springs and power is generated by way of the various forces which cause the springs to wind and unwind."
  • McQueen; Jesse, "Internal energy generating power source", August 22, 2006 "An external power source such as a battery is used to initially supply power to start an alternator and generator. Once the system has started it is not necessary for the battery to supply power to the system. The battery can then be disconnected. The alternator and electric motor work in combination to generate electrical power." Examiners: Schuberg, Darren ; Mohandesi, Iraj A.
  • Haisch, et al. "Quantum vacuum energy extraction", May 27, 2008 "[...] converting energy from the electromagnetic quantum vacuum available at any point in the universe to usable energy in the form of heat, electricity, mechanical energy or other forms of power. [...] When atoms enter into suitable micro Casimir cavities a decrease in the orbital energies of electrons in atoms will thus occur. Such energy will be captured in the claimed devices. Upon emergence form such micro Casimir cavities the atoms will be re-energized by the ambient electromagnetic quantum vacuum. [...] process is also consistent with the conservation of energy in that all usable energy does come at the expense of the energy content of the electromagnetic quantum vacuum."


In 1979, Joseph Newman
Joseph Newman (inventor)
The Energy Machine of Joseph Newman is a DC motor which the inventor claims will produce mechanical power exceeding the electrical power being supplied to it. In the 1980's, Newman attempted to patent the device, but was rejected by the United States Patent Office...

 filed a US Patent application for his "energy machine" which unambiguously claimed over-unity operation, where power output exceeded power input; the source of energy was claimed to be the atoms of the machine's copper conductor. The Patent Office rejected the application after the National Bureau of Standards measured the electrical input to be greater than the electrical output. Newman challenged the decision in court and lost.

Other patent offices around the world, such as the United Kingdom Patent Office
United Kingdom Patent Office
The Intellectual Property Office of the United Kingdom is, since 2 April 2007, the operating name of The Patent Office. It is the official government body responsible for intellectual property rights in the UK and is an executive agency of the Department for Business, Innovation and Skills...

, have similar practices. 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:
Decision BL O/044/06, John Frederick Willmott's application no. 0502841
Decision BL O/150/06, Ezra Shimshi's application no. 0417271


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 ...".

Recent examples


In the late 19th century the term "perpetual motion" increasingly became associated with fraud
Fraud
In criminal law, a fraud is an intentional deception made for personal gain or to damage another individual; the related adjective is fraudulent. The specific legal definition varies by legal jurisdiction. Fraud is a crime, and also a civil law violation...

 and since then inventors have referred to perpetual motion devices using various alternatives such as "over-unity", "free energy", "zero point energy". Here are some representative examples of contemporary proposed perpetual motion designs:
  • Motionless Electromagnetic Generator, a device that supposedly taps vacuum energy
    Vacuum energy
    Vacuum energy is an underlying background energy that exists in space even when the space is devoid of matter . The concept of vacuum energy has been deduced from the concept of virtual particles, which is itself derived from the energy-time uncertainty principle...

    .
  • Perepiteia
    Perepiteia
    Perepiteia is claimed to be a new generator developed by the Canadian inventor Thane Heins. The device is named after the Greek word for peripety, a dramatic reversal of circumstances or turning point in a story. The device was quickly attributed the term "perpetual motion machine" by several media...

    , a device that claims to utilize back EMF.
  • There continue to be frequent claims of water powered cars, which purportedly work by converting water into hydrogen
    Electrolysis of water
    Electrolysis of water is the decomposition of water into oxygen and hydrogen gas due to an electric current being passed through the water.-Principle:...

     and harnessing the energy of hydrogen combustion. The combustion process, in turn, reproduces water vapor, thus qualifying the process as perpetual motion.


Apparent perpetual motion machines


Even though they fully respect the laws of thermodynamics, there are a few conceptual or real devices that appear to be in "perpetual motion." Closer analysis reveals that they actually "consume" some sort of natural resource or latent energy, such as the phase changes of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 or other fluids or small natural temperature gradients. In general, extracting large amounts of work using these devices is difficult to impossible.

Resource consuming


Some examples of such devices include:
  • The drinking bird
    Drinking bird
    Drinking birds, also known as dippy birds and dipping birds, are toy heat engines that mimic the motions of a bird drinking from a fountain or other water source. They are sometimes incorrectly considered examples of a perpetual motion device....

     toy functions using small ambient temperature gradients and evaporation.
  • A capillarity based water pump functions using small ambient temperature gradients and vapour pressure differences.
  • A Crookes radiometer
    Crookes radiometer
    The Crookes radiometer, also known as the light mill, consists of an airtight glass bulb, containing a partial vacuum. Inside are a set of vanes which are mounted on a spindle. The vanes rotate when exposed to light, with faster rotation for more intense light, providing a quantitative measurement...

     consists of a partial vacuum glass container with a lightweight propeller moved by (light-induced) temperature gradients.
  • Any device picking up minimal amounts of energy from the natural electromagnetic radiation
    Electromagnetic radiation
    Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

     around it, such as a solar powered motor.
  • The Atmos clock
    Atmos clock
    Atmos is the brand name of a mechanical clock manufactured by Jaeger-LeCoultre in Switzerland which does not need to be wound manually. It gets the energy it needs to run from temperature and atmospheric pressure changes in the environment, and can run for years without human intervention.Its...

     uses changes in the vapor pressure of ethyl chloride with temperature to wind the clock spring.
  • A device powered by radioactive decay
    Radioactive decay
    Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...

     from an isotope with a relatively long half-life
    Half-life
    Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

    ; such a device could plausibly operate for hundreds or thousands of years.

Low friction

  • In flywheel energy storage
    Flywheel energy storage
    Flywheel energy storage works by accelerating a rotor to a very high speed and maintaining the energy in the system as rotational energy...

    , "modern flywheels can have a zero-load rundown time measurable in years."
  • Once spun up, objects in the vacuum of space—stars, black holes, planets, moons, spin-stabilized satellite
    Spin-stabilized satellite
    A spin-stabilized satellite is a satellite which has the motion of one axis held fixed by spinning the satellite around that axis, using the gyroscopic effect.The attitude of a satellite or any rigid body is its orientation in space...

    s, etc.—continue spinning almost indefinitely with no further energy input. Tide
    Tide
    Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

     on Earth is dissipating the gravitational energy of the Moon/Earth system at an average
    Average
    In mathematics, an average, or central tendency of a data set is a measure of the "middle" value of the data set. Average is one form of central tendency. Not all central tendencies should be considered definitions of average....

     rate of about 3.75 terawatts.
  • In certain quantum-mechanical systems (such as superfluidity and superconductivity
    Superconductivity
    Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...

    ), dissipation-free "motion" is possible.

Thought experiments


In some cases a thought (or "gedanken") experiment appears to suggest that perpetual motion may be possible through accepted and understood physical processes. However, in all cases, a flaw has been found when all of the relevant physics is considered. Examples include:
  • Maxwell's Demon
    Maxwell's demon
    In the philosophy of thermal and statistical physics, Maxwell's demon is a thought experiment created by the Scottish physicist James Clerk Maxwell to "show that the Second Law of Thermodynamics has only a statistical certainty." It demonstrates Maxwell's point by hypothetically describing how to...

    : This was originally proposed to show that the Second Law of Thermodynamics
    Second law of thermodynamics
    The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

     applied in the statistical sense only, by postulating a "demon" that could select energetic molecules and extract their energy. Subsequent analysis (and experiment) have shown there is no way to physically implement such a system that does not result in an overall increase in entropy
    Entropy
    Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

    .
  • Brownian Ratchet
    Brownian ratchet
    In the philosophy of thermal and statistical physics, the Brownian ratchet, or Feynman-Smoluchowski ratchet is a thought experiment about an apparent perpetual motion machine first analysed in 1912 by Polish physicist Marian Smoluchowski and popularised by American Nobel laureate physicist Richard...

    : In this thought experiment, one imagines a paddle wheel connected to a ratchet. Brownian motion
    Brownian motion
    Brownian motion or pedesis is the presumably random drifting of particles suspended in a fluid or the mathematical model used to describe such random movements, which is often called a particle theory.The mathematical model of Brownian motion has several real-world applications...

     would cause surrounding gas molecules to strike the paddles, but the ratchet would only allow it to turn in one direction. A more thorough analysis showed that when a physical ratchet was considered at this molecular scale, Brownian motion would also affect the ratchet and cause it to randomly fail resulting in no net gain. Thus, the device would not violate the Laws of thermodynamics
    Laws of thermodynamics
    The four laws of thermodynamics summarize its most important facts. They define fundamental physical quantities, such as temperature, energy, and entropy, in order to describe thermodynamic systems. They also describe the transfer of energy as heat and work in thermodynamic processes...

    .

Free energy suppression


Because perpetual motion claims have been around for some time, conspiracy theories
Conspiracy theory
A conspiracy theory explains an event as being the result of an alleged plot by a covert group or organization or, more broadly, the idea that important political, social or economic events are the products of secret plots that are largely unknown to the general public.-Usage:The term "conspiracy...

 are often invoked to explain the lack of acceptance and/or availability of such technology.

External links