perpetual motion machine

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As a perpetual motion ( lat. , Constantly shattering 'majority Perpetua mobilia ) are referred to different categories being covered, not existing devices, which - once set in motion - remain without further supply of energy eternally moving and then, depending on the underlying definition may also work should perform. What they all have in common is that they contradict at least one main thermodynamic principle and therefore cannot be implemented.

Categories of Perpetua mobilia

Perpetual motion machine with water wheel

Perpetua mobilia are categorized according to which thermodynamic law they violate. The classification therefore gives no indication of the intended functional principle of the perpetual motion machine.

First kind of perpetual motion machine

A perpetual motion machine of the first kind is a machine that contradicts the law of conservation of energy (analogous to the 1st law of thermodynamics ). It should thereby provide at least the energy necessary for its own operation and in some cases additional useful energy. Such a machine would generate energy out of nothing and thus contradict the law of conservation of energy.

Examples of perpetua mobilia of the first kind:

  • A pump that pumps water upwards and is driven by part of this water via a water wheel .
  • A lamp lights up, the light is captured by a photo element ("solar cell") and converted into electrical current, which should make the lamp shine again.

Even the "simple" closed energy cycle without providing additional useful power is not possible because of the inevitable losses (for example due to friction, deformation or other heat dissipation to the environment).

Physical impossibility of the perpetual motion machine of the first kind

Experience shows that the law of conservation of energy is valid without exception. In theoretical physics it follows from the definition of energy z. B. in Hamiltonian mechanics or correspondingly with the help of the Hamilton operator of quantum mechanics . According to the mathematical Noether theorem , the energy defined in this way is retained in a closed system if the nature of the physical interactions does not change over time. Conversely and more precisely: If the physically defined total energy of a system changes, e.g. B. increases, then the associated mathematical model necessarily contains an energy contribution that is not determined by the measured variables of the system alone, but explicitly depends on the time. This energy contribution is then based on an influence from outside the system. It is therefore not a closed system that includes all interacting components. The term "perpetual motion machine" in the physical and patent legal sense, however, refers solely to a closed system in which, by definition, the conservation of total energy applies, i.e. no energy can arise or disappear, which makes a perpetual motion machine impossible.

Any mechanism that measurably increases the energy in the universe known today , instead of merely redistributing it, would therefore indicate an as yet unexplained influence from outside the physically described universe. While such a situation may appeal to a mystic , science would have to expand the definition of energy in a more comprehensive theory with more or different measures. In such a case, one would first look for interactions with the environment, such as B. radiation, or looking for internal degrees of freedom, e.g. B. (sub-) molecular interactions, until the observed energy gain can be understood as a conversion from a previously not considered form of energy. In this way, however, still unknown basic forces could be discovered and described.

Theories that claim the existence of a perpetual motion machine are therefore pseudoscientific , since they do not understand the same thing as “energy” as physics, but use the physical term in their statements. Today's proponents of such theories therefore often use other names, e.g. B. "Converter for Free Energy". Here, the esoteric concept of “ free energy ” must not be confused with the scientific- thermodynamic concept of free energy .

Perpetual motion machine of the second kind

A perpetual motion machine of the second kind violates the second law of thermodynamics . The machine is supposed to gain work from the ambient heat without a (constantly maintained) temperature gradient being necessary. Since their own operation in turn generates heat, the "energy cycle" would be infinitely possible. Part of its thermal energy is to be withdrawn from the environment and (partly) converted into the (drive) energy required to operate the machine (and possibly some additional useful energy). Such a machine does not violate the law of conservation of energy, but violates the second law of thermodynamics, because the conversion of work into heat is always irreversible . It is therefore impossible to convert evenly distributed thermal energy into unevenly distributed energy (which could be used to drive machines) without using additional energy. To quantify this irreversibility, entropy was defined in the middle of the 19th century .

The concepts for Perpetua mobilia of the second kind are based on a misunderstanding of the principle of a heat engine . According to the second law, this must work with a hot and a cold point or reservoir. The machine converts part of the (thermal) energy flowing from hot to cold into a higher-value form of energy; the rest of the thermal energy is passed through to the cold point. If the heat cannot at least partially flow away via the machine in the direction of the cold point, then the machine stops.

The temperature difference between the hot and the cold point determines the achievable ratio between higher-quality energy and transmitted heat (see Carnot efficiency )

Examples of Perpetua mobilia of the second kind:

  • A saucepan that collects heat from the air in the room and thereby heats up. On its side walls and above it in turn warms the room air.
  • A wheel that turns by being supplied with drive energy from the warmth of the room. Its friction in turn generates heat.
  • A submarine that crosses a body of water and cools the surrounding water to propel it. Its journey in turn generates frictional heat.

A thought experiment, Maxwell's demon , illustrates aspects of the perpetual motion machine type 2. It is particularly noteworthy because it creates a direct connection between physics and information processing: A minimum amount of energy must be applied in order to process n bits of information.

Another example is the Smoluchowski-Feynman ratchet ( molecular ratchet ). An electronic analogy to Maxwell's demon would be the rectification of the thermal noise of the electrons in an electrical conductor by a semiconductor - Diode , but also from energy can not work reasons ( Brillouin paradox ).

Many of the ideas about molecular motors and machines that were originally pure thought experiments are now being achieved by the synthetic capabilities of modern chemistry. Kay u. M. presented old and current ideas and discussed the technical problems and physical principles. According to an idea by Fritz Vögtle , topologically chiral rotaxanes (small propellers whose front and back have different shapes) should rotate in thermal equilibrium with a chiral gas (e.g. H 3 C-CHClF), preferably in one direction. This hypothetical phenomenon, which would apparently violate the 2nd law, has not yet been experimentally confirmed.

In 2000, possible violations of the second law in quantum mechanical systems were discussed. Allahverdyan and Nieuwenhuizen calculate the Brownian motion of a quantum particle, which is strongly coupled to a quantum heat bath, and showed that at low temperatures energy can be obtained from a heat bath through cyclical variation of parameters and thus an apparent violation of the 2nd law due to Quantum coherence phenomena. Your work met with criticism.

According to Capek and Bok (1999), Maxwell's demon is capable of self-organization under certain conditions. This leads to an explicit thought construct of a perpetual motion machine of the 2nd kind.

Third type perpetual motion machine

The term perpetual motion machine of the third kind is not used consistently. According to the definition given above, a perpetual motion machine of the third kind violates the 3rd law of thermodynamics , i.e. That is, the idea is that it uses a heat reservoir with a temperature of 0 K (or less).

Sham perpetual motion machine

A dummy perpetual motion machine uses z. B. small pressure or temperature fluctuations in its environment similar to energy harvesting . For example, a sensitive seismograph is always in motion, but still not a perpetual motion machine. Typical of all false perpetua mobilia is the low power density, i. That is, a large and heavy apparatus is required in order to be able to use at least a small amount of energy.

The impeller of a light mill. On the left the un-blackened side of a mica plate, on the right the blackened one.

Examples of such devices, which appeared earlier as perpetua mobilia, are:


Perpetuum mobile of Villard de Honnecourt (around 1230)

Already early civilizations and peoples were fascinated by the perpetual celestial mechanics and started "physical" attempts at explanation at all times. The first reports of mechanical perpetua mobilia come from India and the Orient. The Indian astronomer Lalla describes a perpetual motion wheel in his work Sysyadhivrddhida Tantra in 748 . Around 1150, the Indian mathematician Bhaskara II describes a perpetual motion machine, which consists of a wheel with mercury-filled spokes.

Around 1230, the French builder Villard de Honnecourt devised a perpetual motion machine, which consisted of pendulum hammers suspended from a wheel. Honnecourt mentions mercury in his description as a filler, so it is assumed that he knew the work of Bhaskara directly or indirectly. Konrad Gruter , a medieval cleric, led at the court of Pope Boniface IX. in Rome in the last decade of the 14th century carried out attempts at hydrotechnology and the construction of a perpetual motion machine.

During the Renaissance , Francesco di Giorgio , Leonardo da Vinci and Vittorio Zonca designed Perpetua mobilia, but without practical implementation. Da Vinci was the first to formulate that a mechanical perpetual motion machine belongs in the realm of impossibility.

In the Baroque period , interest in perpetual machines was fully awakened. In addition to the universal scholars Athanasius Kircher and Caspar Schott , many others dealt with the theory and occasionally also the practice (for example Johann Bessler , artist name Orffyreus) of the perpetual motion machine.

As early as 1775, the Paris Academy of Sciences decided not to accept any more patent applications for a perpetual motion machine for examination, as continuous movement was not possible. With the formulation of the law of conservation of energy by Julius Robert von Mayer and Rudolf Clausius in the middle of the 19th century, the theoretical ground was removed from the perpetual motion machine. Nevertheless, the idea of ​​the perpetual motion machine is not dead; inventors are still trying to come up with an eternally moving machine.

Physics in transition

The basic concept of energy describes the ability to do work and has changed over time with the growing state of knowledge: Thousands of years ago, heat could be generated from dead material by combustion ; At that time the term energy was not yet coined for this. With the discovery of gunpowder at the end of the Middle Ages , it became clear that this heat , pressure and movement can be converted into one another - energy is released. In the 18th century the steam engine showed the thermodynamic relationships between pressure, heat and movement and that “heat somehow enables energy and movement” . At the end of the 19th century, the photo effect was discovered and a connection between the frequency of light and the kinetic energy of the electrons detached from a metallic surface by the light was established. This effect was interpreted quantum mechanically by Albert Einstein in the 20th century . In his special theory of relativity , the equivalence of mass and energy is postulated, which can be expressed with the frequently cited formula E = mc² . The fact that mass and energy can be converted into one another is known today as reliable knowledge. To date, the mass is the most fundamental form of energy, while over time, new forms of energy storage and conversion have been found.

The different energy terms, especially the equivalence to mass, resulted from completely different areas of physics than thermodynamics. Nevertheless, they satisfied the law of conservation of energy insofar as newly discovered forms of energy cannot be converted into known forms of energy with an efficiency of 100% or higher.

For example, a nuclear power plant - viewed with the physics of the 19th century - looks like a perpetual motion machine at first glance. It violates the rules of energy conservation known in the 19th century. However, since the initial and final states are not identical, even 19th century physics gives no reason to assume that a nuclear power plant can do an infinite amount of work. The elemental composition of the fuel rod changes, so that at some point it stops doing work. After that, the initial state can no longer be established, so that the defining cyclicity of the process of a perpetual motion machine is not given.

According to Noether's theorem , physical models or theories that meet certain requirements must contain a law of conservation of energy, since in physics every symmetry also has a conservation quantity. This is confirmed by the formation of phenomena or structures on the macro level of its system "which in turn is based on the interplay of its elements". This would make the validity of the law of conservation of energy understandable, since it follows from the plausible temporal invariance of the physical laws.

Misinterpreted effects and principles

Perpetua mobilia were or are often conceived from the following real-life effects and principles:

Thermal machines

A widespread type of apparent perpetua mobilia is based e.g. B. on a smoothly mounted wheel, which experiences a weight shift due to a spatial temperature difference, which sets it in rotation (without external drive via the central shaft). This class includes: B. a flexible wheel with rubber band spokes that contract on the warm side and relax again on the colder side ( Gough-Joule effect ), a wheel whose circumference is occupied by weights hanging on bimetallic handles, or a wheel made of opposing pairs Pressure vessels, in which, similar to a heat pipe, a liquid gas that evaporates through heat rises and thus shifts the weight. In the past, numerous wheels constructed in this way were repeatedly mistaken for perpetua moblia, as they could actually turn in a mysterious way, often over a long period of time (with little power output), without a drive being found. Small Stirling engines that run on the hand using body heat alone are also particularly impressive .

Solution: Since the machines transport heat from the warm to the cold side or the media in the components run through a cycle, it is ultimately heat engines that utilize the smallest temperature differences.

Water evaporation

A number of functioning devices take advantage of the increase in entropy in the evaporation of water. The enthalpy of evaporation has to be applied, which leads to a temperature difference between the water and the surrounding air - the water becomes colder. Energy can actually be obtained from this temperature difference (e.g. drinking bird ). Energy can also be obtained from other effects of evaporation, such as the shortening / lengthening of wet and dry ropes (the increase in entropy also works against the capillary force here ). Constructions with sponges on a wheel, which work by shifting weight during evaporation, are similarly known.

Solution: The energy that enables an increase in entropy comes from the atmospheric imbalance that is caused by solar radiation on the earth. In a closed system, the relative humidity would soon approach 100%, which would stop the evaporation.


You can increase the voltage with a transformer . E.g. with adjustable model train transformers , the train travels faster at higher voltages. Couldn't you build a machine that inverts the voltage of a battery → transforms it to a higher voltage with a transformer → rectifies it again → so that several batteries can be charged at the same time? No - when transforming, the product of current and voltage (the power) remains constant. So when the voltage is stepped up, the maximum current on the side of the higher voltage drops at the same time. So the power for charging does not get bigger - it gets even smaller because it is multiplied by the efficiencies of the transformer, inverter and rectifier, which are all less than one. Losses in the transformer would be z. B. the electrical resistance of copper and magnetic losses of the iron core.


There are a number of proposals for a perpetual motion machine that works with permanent magnets or additionally with an electric current generated by them. Attempts are made again and again to shield a stationary magnetic field locally. Here it is mostly disregarded that each workpiece is made of a material that can shield magnetic fields, e.g. B. Mu-metal , in turn generates strong magnetic fields at its edges, which make the realization of the inventive idea impossible in principle.

Simple example: A magnetic vehicle places a strong magnet in front of it via a linkage. The magnet attracts the vehicle and is also moved at the same time, so that the vehicle is pulled behind the magnet all the time and pushes it in front of it all the time (for example the "Perpetumobile" in Michael Ende's Jim Knopf and the Wilde 13 ). This can be compared with the well-known story of the Baron von Münchhausen , who wants to have pulled himself out of the swamp by the hair - without a fixed (force reference) point. Such ideas for perpetua mobilia not only violate the law of conservation of energy (kinetic energy from nowhere), but also the law of conservation of momentum, the principle of actio and reactio of Newtonian mechanics . Another example is the magnet motor , a concept of a motor that has been propagated by various hobbyists, which is supposed to be set in rotation solely by the force of permanent magnets.

Gravity and gas kinetics

In the 19th century there was a scientific dispute due to a small calculation error in a work by James Clerk Maxwell , according to which the temperature of gases in gravity fields is not constant and therefore a heat flow should theoretically take place. Even after Maxwell himself had cleared up the error in the same work, the dispute continued, for example between Ludwig Boltzmann and Loschmidt .

The basic idea of ​​this erroneous view is that in a Knudsen gas the potential energy of the gas - molecules increases with increasing height in the gravitational field , while their kinetic energy decreases with increasing height to the same extent, similar to what would be the case with jumping, ideally elastic balls . This leads to the wrong assumption that gases have to become cooler with increasing altitude in the gravitational field, because when the molecules rise, the molecules lose kinetic energy (cool down), but the lowest-energy (coldest) ones stay at the bottom, or the slow molecules rarely reach a great height than the fast ones.

From a relativistic point of view, however, there is a temperature gradient in the atmosphere in equilibrium. The general theory of relativity provided a solution . She provided the explanation why no heat flow can take place in a gravitational potential despite a temperature gradient : The energy that is more available on the ground also causes an increase in mass - warm gases are slightly heavier than cold ones and thus convert more kinetic energy into potential energy in a field around. A relativistic formula for the heat flow applies here.

But there still seem to be open questions. According to theoretical considerations, the effect in some systems should be significantly greater than the general theory of relativity predicts.

Ilya Prigogine comments on the problem in his book:

“In fact, we do not know today whether the Second Law is compatible with all the known interactions between particles, namely with the gravitational interaction. ... In other words, we do not know whether gravity can be included in the Second Law. However, as far as the short-range forces of molecular interactions are concerned, we currently have no reason to doubt the validity of the Second Law ... "

- Ilya Prigogine


The German Patent and Trademark Office rejects patent applications that have a perpetual motion machine as their subject matter, with reference to the lack of feasibility of the invention (commercial applicability) according to § 1 PatG . The potential inventor could only obtain protection for his invention by presenting a working prototype to the German Patent and Trademark Office.

A patentable invention requires that a teaching on technical action is given and that this leads to concrete success. If this is impossible because the teaching cannot be objectively implemented, then there is no invention. In particular, an invention does not exist if it violates recognized physical laws (see BGH BlPMZ 1985, 117, 118).

Although most patent offices expressly advise (e.g. on their homepage) not to accept any proposals for Perpetua mobilia, countless patent applications are still filed every year; the German Patent Office reports about a hundred applications annually.

Visual arts

In the field of fine arts , especially in the 20th century, there are - after many forerunners in antiquity, the Renaissance, the Baroque and the 19th century - different approaches for a metaphorical representation of the principle of permanent movement of artistic forms. Examples are the kinetic art of Alexander Calder or the large sculptures by George Rickey .

Web links

Wikisource: Perpetuum Mobile  - Sources and Full Texts
Commons : Perpetuum Mobile  - collection of images, videos and audio files
Wiktionary: Perpetuum mobile  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. For example, an extensive collection of supposed perpetua mobilia is contained in: Patrick J. Kelly: A Practical Guide to Free Energy Devices . Carol Publishing Group, 2009 (English).
  2. Kay, Leigh, Zerbetto: Synthetic Molecular Motors and Machines . In: Angew. Chem. , 2007, 119, pp. 72-196.
  3. Angew. Chem. Int. Ed. , 2003, 42, pp. 4542-4545.
  4. Allahverdyan, Nieuwenhuizen: Extraction of work from a single thermal bath in the quantum regime . In: Physical Review Letters , 2000, 85, pp. 1799-1802. Allahverdyan, Nieuwenhuizen: Extraction of work from a single thermal bath in the quantum region . In: Phys. Rev. Letters , Volume 85, 2000, pp. 1799-1802, arxiv : cond-mat / 0006404 . Allahverdyan, Nieuwenhuizen: Quantum brownian motion and its conflict with the second law . In: Proc. Quantum limits of the 2nd Law , San Diego 2002, arxiv : cond-mat / 0208564
  5. ^ Peter Weiss: Lasers act on cue in electron billiards . In: Science News . tape 157 , no. 4 , 2000, pp. 55 , doi : 10.2307 / 4012071 .
  6. Capek, Bok: A thought construction of working perpetuum mobile of the second kind . (PDF; 114 kB) In: Czechoslovak Journal of Physics , 1999, 49, pp. 1645–1652.
  7. Landsberg. In: J. Phys. A , 10, 1977, p. 1773.
  8. ^ Dietrich Lohrmann: The machine book of Konrad Gruter for Erich VII., King of Denmark (1424). In: German Archive for Research into the Middle Ages . Volume 63, 2007, pp. 78-79, ( digitized version ).
  9. for example Wolfgang Bürger in Perpetuum mobile. In: NZZ Folio . 1995
  10. ^ Maxwell: On the dynamical theory of gases . In: Phil. Trans. Roy. Soc. , Volume 157, 1866, p. 534, correction in an addition to this article.
  11. Wolfgang Dreyer, Wolf Weiss: Stories of Thermodynamics and Obscure Applications of the Second Law . 1997, online
  12. ^ Rolf Freitag: Effects of simulated surfaces on Knudsen gases in a homogeneous field and the second law of thermodynamics . (PDF; 355 kB) 1997
  13. Rolf Freitag: Investigation of the altitude dependence of temperature and density in Knudsen gas in thermal equilibrium . (PDF; 236 kB) 1997
  14. Ilya Prigogine, Isabelle Stengers: Dialogue with nature . Piper Verlag, Munich 1981, p. 210 ff.
  15. "Patents are granted for inventions [...] provided they [...] are commercially applicable."
  16. Annual Report 2011 (PDF) German Patent and Trademark Office, p. 16.
  17. ^ Frank Popper: Kinetic art: light and movement, environmental art and action, DuMont, Cologne 1975. ISBN 9783770107681 . [1]
  18. ^ Peter Anselm Riedl: George Rickey - Kinetic Objects, Phillip Reclam Jun., Stuttgart 1970. [2]