PERPETUAL MOTION: AN IMPROBABLE
DREAM
Kirk Straughen
(Investigator 145, 2012 May)
Kirk Straughen
(Investigator 145, 2012 May)
Introduction
A perpetual motion machine is an imaginary device that, once set in motion will continue to operate indefinitely. The illustration in Figure 1 of an overbalancing wheel mechanism is based on a drawing from the notebooks of Villard de Honnecourt (1235), and is testimony to the antiquity of the idea. The underlying assumption is that the weighted arms fall in the direction of the turning wheel (as indicated by the arrow) thereby ensuring one side is always heavier than the other, thus engendering a continuous rotary motion. The purpose of this essay is to explain why this and other devices claimed to be perpetual motion engines will not work.
Perpetual Motion and Thermodynamics
Figure 1
Unfortunately, the laws of nature forbid the possibility of constructing perpetual motion machines, of which there are three types:
The first type of perpetual motion machine is one whose efficiency is claimed to exceed 100%. In other words the inventor claims it creates energy from nothing. An example of this kind of device is Garabed Giragossian's flywheel (1917). This engine consisted of a huge flywheel that was hand-cranked by an assistant, and then kept in motion by an electric motor.
Using a dynamometer (a device used to measure the power output of a machine), Giragossian measured the energy needed to bring the flywheel to a stop and found that it was 200 times greater than what the electric motor supplied.
Unfortunately, Giragossian failed to realize there is a difference between power and energy (energy is the measurement of the capacity to perform work, whereas power is the rate at which work is performed). The energy supplied by his assistant's muscles and the electric motor was stored as kinetic energy in the flywheel as it was brought up to speed over time, and when the flywheel was brought to an abrupt stop, the stored energy was instantly expended.
A perpetual motion machine of the first kind cannot work because it attempts to violate the First Law of Thermodynamics that states, in part, that matter and energy can neither be created nor destroyed, merely transformed (the conservation of matter and energy).
The second kind of machine is one that the inventor claims will take heat from the environment and convert it wholly into work. An example of this kind of device is Professor John Gamgee's Zeromotor (1880). This engine was supposed to operate in the following way: A reservoir of ammonia, which boils at minus 33° C, would be vaporized by ambient heat producing a vapor pressure of four atmospheres that would drive a piston. As the vapor expanded it would also cool, condense and be returned to the reservoir for the next cycle.
These kinds of engine will not work because whatever working fluid is used cannot expand to the point of condensation due to the resistance of the piston. Furthermore, the Second Law of Thermodynamics (in Clausius' formulation) states that heat cannot be transferred from a colder to a hotter body. Consequently, in order for the working fluid to be condensed, it must be cooled by refrigeration, which requires more energy than what the engine is capable of generating.
The third type of perpetual motion machine is one that does no work but merely continues in motion forever. An example of this kind of device is shown in Figure 1.
Unfortunately, the Second Law of Thermodynamics does not permit the operation of these kinds of engine because energy is always lost through the conversion of kinetic energy (the energy of motion) to heat energy through friction generated by the moving parts. In the absence of a continuous power source all machines, like spring driven clocks, will eventually run down. Entropy — the measure of the unavailable energy of a system and its resulting disorganization — increases over time.
Misguided Minds
The creators of perpetual motion machines are, generally speaking, individuals who have little, if any, sound understanding of physics. Rather, they are usually backyard inventors with some practical knowledge of mechanics and a boundless sense of self-confidence in their own ability. This is a potentially dangerous combination.
If the inventor is sincere in his belief that the machine will work, he may waste large sums of his own and other people's money in pursuit of an impossible dream, thus running a considerable risk of financial ruin for himself and his investors. When the inventor realizes that the machine will not work, what started out as a delusion may degenerate into outright fraud — having to admit he was wrong may be deemed too humiliating, especially when fantastic promises have been made and other people's money is involved.
Indeed, the history of perpetual motion is littered with examples of outright fraud. For example, in 1813 Charles Redheffer of Philadelphia displayed (for a fee) what he claimed was a perpetual motion machine whose main component was a large gearwheel driven by a small pinion. The secret of the device's continued operation, however, lay not in some esoteric energy, but in the power of a hidden clock spring.
About fifty years later John E. W. Keeley fleeced those who invested in his Hydropneumatic Pulsating Vacu-engine, a complicated mechanism of pipes, valves, metal globes, nozzles and gauges that allegedly converted water into 'inter atomic ether.' Unfortunately, it was only after his death that investigators discovered the device was powered by compressed air carried in concealed pipes.
A more recent example of perpetual motion is Joe Newman's Energy Machine, a kind of generator that he claims produces more power that it takes to run. Newman, a self-taught man, appears to have made the mistake of thinking that by continually increasing the number of turns of copper wire around the armature of an electric motor, a point would eventually be reached where the motor would produce more power than what it would take to run. Unfortunately, this is not possible:
"What he ended up with was a motor that ran on a very small current — but a huge voltage was needed to supply that current. Since the power drawn by the motor is given by the product of the current and the voltage, the increase in voltage, as you would expect from the law of conservation of energy, just offsets the lower current. There is no increase in efficiency." (R. Park: Voodoo Science, page 102)
During the 1986 US Senate hearing concerning the Patent Office's refusal to grant him a patent, Newman refused to have the device tested when his claims were challenged. If it worked why refuse the test? Perhaps it is because patents will only be granted if the applicant submits a working model of the device that can withstand scientific scrutiny. Needless to say, this has not happened to date.
Conclusion
The laws of nature do not permit the possibility of perpetual motion machines because energy can be neither created nor destroyed, merely transformed, and what energy does exist is always dissipated due to friction. Consequently no system can remain in operation forever. This also applies to celestial bodies whose motions are subjected to dissipative forces such as tidal friction and gas friction as they move through the extremely tenuous interstellar dust and gas that exists in space. Indeed, the entire universe is winding down — as it cools entropy increases due to the unavailability of energy and eventually all things will come to an end. Perpetual motion, like eternal life, is an impossible dream.
Bibliography:
Bernal, J.D. Science in History, Vol. 1 The Emergence of Science, Penguin Books, England, 1969.
Grant, J. A. Directory of Discarded Ideas, Corgi, London, 1981.
Park, R. Voodoo Science, Oxford University Press, Oxford, 2000.
Pyke, M. Dr Magnus Pyke's Dictionary of Fallacies, Willow Books, London, 1983.
Yule, J.D. (Ed.) Concise Encyclopedia of Science and Technology, Crescent Books, New York, 1985.
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