This article originally appeared in The Skeptic, Volume 3, Issue 3, from 1989.
The promise of a machine which runs forever, a perpetual motion machine, is irresistible. Perpetual motion was a hot topic in the last century, because the age of the engineer was at its height and the demand for new energy sources great. It is no coincidence that the science involved was worked out at this time; yet even today, over a century later, people continue to propose machines which don’t work.
The reason for the enduring popularity of perpetual motion is of course the dream of conjuring energy from nothing. Were this feasible, all coal-fired power stations, with their carbon dioxide and sulphurous emissions, could be closed; likewise, nuclear fission power plants, with their radioactive waste; and the need to disfigure the landscape with arrays of solar cells or windmills would vanish. The enormous sums spent on energy research could be redeployed, and cheap energy made readily available to developing countries. The inventor of a free energy source would be feted throughout the world.
Perpetual motion proposals are of two types, and the distinction is crucial. A Perpetual motion machine of the first kind actually creates energy. Some of this is inevitably rendered inaccessible through friction losses in bearings, or air drag on moving parts, or the like; but the rest is available to the world as free energy. By contrast, a perpetual motion machine of the second kind neither creates nor destroys energy. It runs forever by completely eliminating friction in the bearings, air drag, and such; but any attempt to extract energy from it causes it to slow down.
These two types of machine respectively contravene the first and second laws of thermodynamics. The first law states that energy is conserved, and the second that entropy increases. More on these in a moment.
Most publicity attaches to perpetual motion proposals of the first kind. Their proponents generally agree with scientists as to the laws of force and torque operating within their machines. The law of force was first elucidated by Isaac Newton three centuries ago, and states that Force=Mass x Acceleration. Similarly, angular acceleration is proportional to the applied torque.
Once it is accepted that undisturbed motion is a body’s natural state, that it alters its velocity (i.e., accelerates) only when a force is acting on it, and that slowing down is not the natural state but the result of frictional forces, the path to Newton’s laws is easy and intuitive. It nevertheless took a genius of Newton’s magnitude to overthrow the Aristotelian model of space and time.
But, crucially, the same people do not accept that the force and torque laws also imply conservation of energy. This makes good sense: no force, no velocity change, no energy change. But in a complicated machine the same principle is one step further removed from the forces and torques which people can feel, and is often beyond untutored intuition. I am told, with a don’t-blind-me-with-science look, ‘Maybe, but what is wrong with my machine?’ Perpetual motion advocates, having once got into a physicist’s office, are reluctant to leave until a lengthy impasse is reached.
One catch occurs so often it is worth singling out. Perpetual motion machines, in common with many others, a.re almost invariably cyclic; after sufficient operation, called a cycle, the machine returns to its initial configuration. A wheel making one complete turn is the simplest example. (Cyclicity is a matter of convenience, since a non-cyclic machine would be difficult to exploit.) In evaluating cyclic machines, it is essential to consider the energy balance over a complete cycle. Cyclic machines with an obvious acceleration mechanism in one part of the cycle, but a subtle deceleration process in another, are particular favourites.
Even more subtle are those machines which interchange energy between its various forms: motion, heat, latent heat of evaporation (the ‘drinking bird’, a popular toy), electromagnetism, and so on. Some of the subtleties are quite ingenious, but if physics is operating as it has been understood for three centuries, the catch is inevitably there somewhere.
Perpetual motion machines of the second kind, though less commercially attractive, are no less interesting. Moreover, they exist! From Newton’s laws it follows that an isolated system in motion, with no forces or torques acting on it, exhibits precisely perpetual motion of the second kind. How can this be reconciled with the running down of a top due to the friction at its tip? The answer is that the energy has not been destroyed, but converted into heat at the tip. Since heat is motional energy of the atoms in the tip, we could still see continuing motion if our eyesight were good enough. The motion is therefore perpetual, though on an atomic scale rather than an everyday one. We say the energy of the top has degraded into heat, and this process translates into physics through the second law of thermodynamics. It is a consequence of our inability to see things on the atomic scale, rather than a fundamental property of nature like the first law.
A further subatomic example of the second kind is electrons orbiting the atomic nucleus. Obviously, there is no air resistance! Because of the peculiarities of the quantum theory of atomic processes, we can no longer picture the process simply. Nevertheless, the criterion for perpetual motion of the second kind is still satisfied: verifiable predictions are not altered unless the system is disturbed. In other words, the electron does not ‘run down’. Energy conservation still holds good in quantum mechanics.
A large-scale example is the earth orbiting the sun. Meteorite strikes and other external influences, which affect the motion, are separate issues. Clearly perpetual motion of the second kind is common on celestial and atomic scales, but rare on Earth. However, we now know how to set up a simple quantum state as large as we like. The secret is to cool the system sufficiently near to absolute zero. The most famous example is superconductivity, currently in vogue, in which an electric current circulates in a wire loop with zero resistance, needing no battery to drive it. Although the current itself is still invisible, its effects are observable. Another example is superfluidity, in which a liquid flows up the inside of a tube immersed in it, and back down the outside, indefinitely.
How do these systems beat the second law? This law is ultimately only probabilistic reasoning, used in the absence of detailed information about each atom. Since we normally ask questions only about large-scale quantities, the enormous number of atoms being averaged over guarantees our answers accurate with almost total certainty. (Entropy relates to the amount of information needed to specify the system at the atomic level.) In the examples just given, we are dealing not with millions of particles, but with one electron, one planet, one known quantum state. Our reasoning then is exact; the second law is a different form of reasoning used in different circumstances. Proposals which violate the second law, all ultimately equivalent to impossible heat engines, tend to be more subtle than proposals of the first kind.
Finally, for theory, conservation of energy still holds in Einstein’s theory of relativity, provided that mass m is seen as a further form of energy E, related by the famous equation E = mc2 where c is the speed of light. Because this is so large, mass is a very concentrated form of energy: we can do 300 million times better by converting the mass of a tank of petrol than by burning it! The complexity of nuclear reactors indicates the difficulty of transforming mass into accessible energy. But if, conversely, we invest energy in making antimatter, we have the perfect fuel, for antimatter spontaneously converts to readily accessible energy when mixed with matter. Just one tenth of a gram of antimatter, safely confined, would propel a car for life!
We now turn to the entertaining history of perpetual ‘motion. Arthur Ord-Hume’s book, Perpetual Motion: the History of an Obsession (Allen & Unwin, 1977), gives a modern survey.
Today it is difficult to imagine a time when energy conservation was not firmly established, and the equivalence of different forms of energy, particularly heat, was fiercely debated. Yet that was the situation up to the middle of the last century; and earlier still, before Mayer, Joule and Helmholtz settled the first law, and Carnot and Clausius the second, perpetual motion proponents should be judged by their own times.
A Sanskrit manuscript from the first half of the fifth century refers to a wheel, free to rotate about a horizontal axis, with sealed holes drilled in radially from the circumference, part filled with mercury. Once started. the wheel was supposed to maintain its rotation. Presumably its inventor fell for the ‘cyclic’ fallacy, believing that the extra moment, due to the mercury on the descending side of the wheel moving under centrifugal force to the circumferential end of the tube, provides sufficient impetus to keep the whole thing going.
This is the earliest known coherent suggestion for perpetual motion. It is also the prototype of many proposed in Europe, in which weights attached to the circumference of the wheel dispose themselves further from the axis on the descending side of the wheel than the ascending.
Some of these were marvellously intricate, and the Marquis of Worcester; who is believed to have constructed the first practical steam engine, claimed success for one in 1655. (‘Worcester’s biographer, Henry Dircks, published in 1861 a comprehensive survey of the preceding three centuries of perpetual motion.)
This was pre-dated by the Italian philosopher Zimara, who in 1518 proposed a crank (inoperable, incidentally) for linking a windmill to a set of bellows aimed at it. Interconversion between forms of energy, here wind and mechanical energy, is a characteristic concept of perpetual motion. Perpetual motion was eminently respectable during the Renaissance: contemporary with Zimara, Leonardo da Vinci was involved in drafting sketches for six designs. By far the most common proposals concerned self-propelling water wheel. The water mill was the dominant mechanical device in Europe; what could be more natural than to harness its power to raise the water once more. The aptly named Robert Fludd ‘1574-1637), an English physician, and Georg Bockler, of Nurnberg, were two leading visionaries of this kind. It mattered little that John Wilkins, Cromwell’s brother-in-law and later Bishop of Chester, tested a similar scheme unsuccessfully during the Civil War, and pronounced his scepticism in 1648. Perpetual motion was in the air of the time. Wilkins, in fact, continued to be fascinate by perpetual motion to the end of his life.
The decline of a great many superstitions in the Age of Reason left perpetual motion untouched, for it could still be phrased as a scientific hypothesis. Indeed, proposals proliferated from the 1720’s onwards. The 18th century also saw the first clock to be powered by changes in atmospheric pressure, giving an illusion of perpetual motion, by the London clockmaker James Cox. It now rests in the Victoria & Albert Museum.
In the last century, while the laws of thermodynamics were being established, the harnessing of electromagnetism led to a new series of proposals. These all essentially coupled motors back to generators. In fact, the earliest coherent magnetic proposal goes far as back as 1570, when a Jesuit priest suggested that an iron ball, rolling down a ramp under gravity, could be drawn back along a different path by a magnet. We now know that any magnet strong enough to do this would keep the ball from rolling in the first place.
The combination, last century, of the mechanic explosion and popular ignorance led to exploitation and fraud. E.P. Willis, a machinist of Connecticut, charged admission to view an asymmetrical-wheel machine, which he set up in New Haven and subsequently New York. It was maintained in a glass case and was actually powered by compressed air passed up a strut and over one of the gears. Willis simply challenged viewers to state hew the machine could run, rather than claim perpetual motion.
No such constraints attached to Charles Redheffer, who in 1812 set up a machine in Philadelphia which ran unceasingly. Needless to say, viewing was not free of charge. A team of experts sent to examine it in connection with Redheffer’s application for funding detected that the wear on two connected gears was on the wrong side, and were satisfied that fraud was involved. They did not detect its nature, but instead built a similar machine with concealed clockwork, and a winder disguised as an ornamental knob. Redheffer privately offered its owner, Sellers, a large sum to reveal his secret. Instead, Sellers denounced Redheffer. Worse was to come in New York, where Redheffer, undaunted, built a further machine. The submarine pioneer, Robert Fulton, recognised its uneven speed through one cycle as characteristic of a crank (appropriately), and denounced it on the spot. He then dismantled a suspicious-looking support strut to reveal a catgut-belted drive, run by a man turning a wheel in a nearby room. The crowd, which had paid $5 a man, then a large sum (ladies free, for some reason) demolished the remainder, and Redheffer fled.
Perhaps the finest fraud was perpetrated by John Keely, again of Philadelphia, In 1875 he unveiled a complicated variant on the steam engine, into which he would blow for half a minute and then pour in five gallons of water. After a whizzbang show of manipulating various valves and taps, he would then announce that the apparatus was charged with a mysterious vapour, at a pressure of 10,000 pounds to the square inch. Keely claimed that the power source was the disintegration of water. Latterday enthusiasts prefer, like Keely, to tap new forms of energy, rather than deny its conservation. This is theoretically possible but it is highly unlikely that easily exploitable new forms will be found.
The main reason for Keely’s success—he raised over a million dollars to set up the Keely Motor Company—was showmanship. Keely was an imposing figure with an air of honesty, who was given to baffling the uninitiated with phrases like ‘hydropneumatic pulsating vacu engine’, ‘sympathetic equilibrium’, and ‘quadruple negative harmonics’. Such pseudoscientific terms are often used by today’s charlatans; plus ca change! With men of science Keely was more guarded, and took pains to ensure none cot examine his machines closely.
In the 1880’s the Keely Motor Company, discouraged by his failure to produce a commercial motor, cut off his funding. He found an alternative source in a wealthy widow, and promptly unveiled a new idea: vibrating energy in the aether, which underlay the disintegration of water. The Motor Company sued him for reimbursement, but he claimed his latest idea was unrelated to earlier ones and refused to pay. After a spell in prison, he succeeded in satisfying the courts of this. Keely was forced to tread warily when his benefactress attempted to have leading scientific figures validate his device. Testa and Edison declined, but a visit in 1805 led the engineers involved to suspect compressed air sources. They were right. After Keely’s death three years later, the son of one of his backers promptly rented the house, and found it was comprehensively ‘wired’ to a three-ton air tank in the basement.
The first patent on a perpetual motion proposal was granted in Britain in 1635. only twelve years after patenting was introduced. By 1775, the Parisian Academy of Sciences was refusing to accept schemes. Since this was long before the establishment of energy conservation, the gentlemen of Paris can only have been disillusioned by the repeated failure of all such devices in practice. Nearly a hundred years later, the US Patent Office decreed that a working model should be submitted within one year of the initial application; but enthusiasts still gummed up the works, and finally, in 1911, a working model was demanded from the start.
This rule has, inevitably, been challenged in the courts within the last decade, with inventor Howard Johnson finally winning US patent 4151431 on his `magnetic motor’. Nevertheless, the world hardly waits with bated breath. The current furore over Joseph ‘Newman’s motor, which supposedly taps into hitherto unknown gyroscopic fields associated with sub-atomic particles, further demonstrates that perpetual motion will never die away entirely. (Present-day physics successfully predicts the spin properties of elementary particles to a staggering one part in a hundred million, which is as far as experiments have gone.) However, Newman’s device runs, it has proved subtle enough to confound several scientists. The story of perpetual motion exemplifies the entire human endeavour: an upward crawl to enlightenment, with theory and practice advancing side by side; momentous discoveries by pioneers, which become the bedrock on which the next advances are built; gradual diffusion of the new ideas into general awareness; and ever the self-deluded, and the charlatans preying on ignorance.
The story has been presented here as a case history rather than a warning, but if any lesson is to be drawn it is that the best insurance against nonsense is a scientifically educated public. It is faintly credible that the US Navy came close to backing one machine in 1881; but astounding that less than four years ago a jury acquitted a perpetual motionist of fraudulently raising $685,000, because (the attorney later found) it believed perpetual motion and energy creation possible. The sooner that cannot happen, anywhere, the better.
