Basic physics perpetual motion inventors miss.
Compiled by Donald E. Simanek.
Over some 40 years I've reviewed the literature on the long history of perpetual motion devices. For the last 20 or more years I've recieved proposals for perpetual motion machines via email, and corresponded with their inventors. So I compiled this list of the misconceptions that motivates them and ensures their failure. The list is in no paraticular order, nor is it complete.
Physicists and physics students generally give a blanket dismissal to all perpetual motion and over-unity proposals: "They can't work because they would violate the laws of thermodynames." Laymen will often say, "You can't get something for nothing", or, the flippant, "There's no free lunch". But much can be learned about physics from a detailed examination of why they don't work, and how they violate fundamental laws of classical mechanics. Many of these misconceptions are held by physics students and hinder their understanding of other, useful physicals processes. Perpetual motion devices provide valuable learning experiences for physics students.
Entries labeled "DES" are, so far as I know, my original words of wisdom.
- The overbalance seduction is the oldest mistake made by perpetual motion wheel invenetors. They seek a mechanism that shifts components of a wheel so that there's continually more weight on one side of the axle. This can be accomplished, but the wheel won't turn on its own; it turns only when it is continually pushed by an external agent. The same is true of force overbalance and torque overbalance. This misconception results from failure to consider all of the forces and torques of the entire movable system and on each and very part of it. Also it overlooks the simple fact that the work required to shift the masses toward one side of the axle is at least as great as the energy gained as they fall in the gravitational field. See: Baskara, Villard Honnecort.
- Energy is not a material substance. It does not flow (like liquids). It has no mass. It is a convenient accounting tool for describing and predicting how material bodies interact.
- Momentum is not a material substance. It, too, is a convenient conceptual tool for describing and predicting how material bodies interact.
- Fields, gravitational, electric, and magnetic, are not material things. They are convenient mathematical tools for visualizing and calculating how material bodies interact.
- Gravity is not a source of energy. Gravitry facilities energy exchange between material bodies. Falling water can drive a waterwheel to do work, work from the water's potential energy difference due to height of the source reservoir, that potential energy being due to solar radiant energy that evaporated water, causing water vapor to rise to clouds, then fall as rain.
- Buoyancy is not a source of energy. It is a facilitator of energy exchange between material bodies, gases and liquids.
- Magnetic fields are not sources of energy. Magnets are not energy sources. Magnets do have the small amount of energy given them during the process of magnetising them when they were fabricated. Magnetic fields are convenient mathematical models for describing interactions between magnets, and and between magnets and materials, as well as moving charges.
- Chemical reactions do not produce any more energy than they had initially. They conserve both mass and energy.
- Only nuclear reactions can convert mass to energy and vice versa. The total mass-energy is conserved in such a reaction. One could say that mass is a form of stored (potential) energy. But this conversion of mass to energy does not occur in the machinery of everyday life.
- Perpetual motion is defined as motion that persists without diminution of speed over time, without any energy input. This would not violate any basic laws of physics, but is not achievable because of the elastic properties of materials which cause the machine to lose energy through dissipative processes: heat and sound.
- If all friction and dissipative processes in a wheel were eliminated, it could, when given a push, run with no diminution of speed indefinitely. Such a perpetual motion machine would be perfectly silent and emit no thermal energy (heat). This would not violate any physics laws but would not output any useful work.
- A hypothetical perpetual motion machine is sometimes called a "self-motive" device. If you extract energy from it, it will slow to a stop. But the useful work you could get from it is no more than the energy it had initially when you did work to set it into motion.
- If such a supposedly self-motive device (wheel, belt, pendulum or other cyclic device) were to increase its speed over time, you could extract energy from it to keep it moving at constant speed. Such a hypothetical device is called "over-unity", meaning its ratio of energy out to energy in any given time in is greater than one. No such working device has ever been made.
- The "performance" of a rotating wheel can be measured by how long it takes to come to a stop after it has been given an initial rotation by an external agent.
- The fundamental reason perpetual motion proposals fail is geometry—the geometry of space and time.
- Stevin's principle. If a cyclic device (wheel, belt, etc.) remains unchanged in all respects after each revolution, it cannot produce excess energy.
- The "bigger is better fallacy". If a PMM device doesn't work in a small prototype, making it larger won't improve its performance. See: Aldo Costa, RAR Energia.
- The "heavier is better fallacy". See the previous item.
- The friction fallacy assumes that failure of a PMM to achieve over-unity performance is solely due to friction and other energy-dissipative processes. This is false. Remove all of these and it still won't create energy.
- The imperfect materials fallacy assumes that failure of a PMM is solely due to warping, bending, or flexing of its material parts. Even if all parts were perfectly rigid, undeformable, frictionless materials it still wouldn't work.
- The closest thing to a perpetual motion wheel is a rotating flywheel on a fixed axle, both made of rigid, frictionless materials. Any clever gimmicks you add to such a wheel: falling hammers, shifting weights, levers, gears, belts—all will reduce its performance, bringing it to rest sooner.
- The "configuration fallacy" assumes that the configuration of parts in a PMM somehow magically creates energy that initiates and sustains motion. If this were so, you'd have to construct it carefully, including a brake, for as you assembled the last physical part, it would immediately "take off", moving on its own. I.e., you wouldn't have to give it a push to get it moving. Since its motive energy comes from its configuration, this energy would be created continually, causing the device to accelerate till it tore itself apart. You'd need to extract that excess energy whenever the brake was not engaged. Needless to say, this has never been achieved.
- The previous scenario is sometimes rationalized by supposing that a perpetual motion machine could be tapping "free energy", a fantasized energy that fills all of space and is there for the taking. It used to be identified as "energy of the luminiferous aether", later dark energy and dark matter were invoked as the energy source. This is idle speculation about hypothetical concepts that are still controversial in physics. To claim a machine runs on "free energy" is like claiming it runs when sprinkled with "magic pixie dust".
- Closing the loop. If the power output of a machine were greater than the input power (an over-unity device) then the output could be fed back to the input (closing the loop) to sustain its motion forever. This has never worked. Perpetual motion believers rationalize that the output energy is of a "different kind", incompatible to the requirements of the input.
- Many PMM inventors have only a naive understanding of physics. They think force, energy and power are the same thing. Some even think work and torque are synonyms because they are both the product of force and distance. They have no understanging of vector algebra, required for dealing with displacement, velocity, accelerataion, force, torque and momentum. They simply do not have the conceptual tools to design and test a machine properly.
- Cherry-picking laws. Typically PMM inventors say they accept the laws of physics, with one exception: the conservation of energy. They do not realize that energy (and momentum) conservation laws are logically derivable from Newton's laws (which inventors claim they accept). So if conservation of energy is wrong, then Newton's laws and all the other laws of mechanics would be wrong as well. This is not supported by any experiment ever done. These laws are continually tested, and verified in the machinery of our technology, and have never failed us.
- Momentum is almost totally ignored by PMM inventors. If their machine worked as they claim, laws of momentum and angular momentum would both be violated. They do not address this because they don't understand it. Momenum is a vector quantity, just as important as energy (a scalar quantity), but PMM inventors typically can't do vector algebra.
- Gravity shields are often designed into PMM. There is no such thing as a shield that can block gravity, or even reduce its strength.
- Magnetic shields are often designed into PMM proposals and are considered essential to their operation. Such shields can significantly reduce electromagnetic fields, but not steady magnetic fields. Shielding materials can, however, alter the shape of magnetic fields near them, but materials (magnets and shields) still obey Newton's laws. Inserting shields into a magnetic field requires work. But see the next item, which applies to all fields, of any shape.
- What goes around... Most PMM proposals are cyclic devices—masses moving around closed paths. This motion is in the earth's gravitational field. The energy gained from a mass falling is never greater than the energy required to lift it up again to repeat the cycle to its previous starting point, whatever the shape of its path. The same applies to bodies moving in electric or magnetic fields and pressure fields in liquids or gasses.
- Reactionless thrusters are hypothetical devices that move without application of force. They violate the conservation of momentum. These are rarely proposed, and those that have been built as working models only seem to violate conservation laws. They move only when lying on a flat surface (floor, table), and have a motor in them driving a rotating eccentric mass. The stick-slip process of friction then moves them across that surface. They cannot work in a vacuum. See: Dean Drive, and the next entry.
- Perpetual motionists have sometimes been seduced by an interesting slip-stick phenomenon of mechanical friction. A motor placed on a mechanical balance scale may register a different weight reading when the motor is running than when it is at rest. This is a quirk of the scale's mechanism.
- Be suspicious of any PMM device that only runs continuiually when a person is holding it, or any component of it, or holding a magnet near it. Substitute a rigid structure to hold that part steady, and the device will come to a stop. This is the physiological ideomotor effect, a muscle-nerve feedback process that senses slight motion of what you are holding, and tries to correct it (to hold it steady). There's a small reaction delay time, which results in you unconsciously doing work on the system to sustain its motion. See: Minato motor, spiritualism table tilting, ouija spirit board.
- The "anything is possible" seduction. There are many impossible things in nature. (1) You cannot lay out a walking trail in a closed loop, downhill all the way around—in either direction. (2) You cannot make a triangle on a flat plane with equal sides and unequal angles. Laws of geometry and of nature describe what can happen, but they also tell us what can not happen—if we understand how to apply them correctly.
- Fundamenetal laws of nature are intimately connected. You cannot deny or violate one without violating all the others. You can't pick and choose those you deny while accepting the others.
- Designer hubcaps do not improve the performance of square wheels. —DES.
- Leonardo da Vinci (1452 – 1519). Advice to perpetual motion machine inventors: "Go and join the seekers after gold [alchemists]".
- Jacob Leupold (1674 – 1727). "...this desire [to achieve perpetual motion] is, even today, so deeply anchored in so many that they would rather let themselves be beaten to death than confess that they failed. The reason is that these people have no foundation in mechanics. Many do not know how to calculate motions, and therefore, because of that, start construction based on imagination and haphazard experimentation."
- Johann Bessler (a.k.a. Orffyreus) (1680 – 1745), commenting on someone else's perpetual motion proposal. "The only way to get horsepower from it is to hitch it to a horse."
- The superposition principle of perpetual motion devices: Two unworkable devices combined do not yield a workable one.
- Appeal to exotic hypothetical physics theories, still speculative and not yet confirmed experimentally or accepted. Dark matter, dark energy, multiple universes, quantum wierdness and string theory, are no help to the perpetual motion inventor, for all of them incorporate conservation of energy and momentum as an integral and essential part of their mathematical structure, or are a logical consequence of it.
- Conservation laws are such fundamental facts of nature that we might say that the most important law in physics is: "Nature abhors perpetual motion". I.e., nature cannot allow it. —DES.
- Appeal to other unworkable processes. Time travel, teleportation, gravity shields and other science-fiction notions would, even if possible, not facilitate perpetual motion. See: Paul Davies, How to Build a Time Machine.. Penguin Books, 2001.
- Failure to realize that forces are vectors, and vector algebra must be used when combining them. See: any elementary physics textbook.
- Newton's second law: Fnet = ma is a vector equataion (with vector quantities boldface). Fnet is the vector sum of all forces acting on the mass m and only those.
- Failure to understand centripetal force and the distinction between "real" forces and "fictitious" forces. Centripetal force is a conceptual tool, a ficitious force introduced to faciliate analysis of rotating systems. But it is only used when you choose to analyze a physical process using a non-inertial rotating or accelerating coodinate system.
- Inertia is not a force. It is only a fancy word for mass.
- Newton's third law correctly stated is: "If body A exerts a force on body B, then B exerts an equal oppositely directed force on A." A common mistake is failure to realize that these two forces act on different bodies.
- Work is not simply force multiplied by displacement. It is W = F d cos θ, where W is work, F is the force doing the work, d is the displacement of the body acted upon, and θ is the angle between the vectors F and d. It follows that if a force acts on a body perpendicular to its displacement, that force does no work during the displacement. If a force acts on a body but the body has no displacement in the direction of the force, that force does no work. Study: work, vector algebra, constraint forces.
- The production of useful work is strictly limited by the laws of thermodynamics. The production of useless work seems unlimited. —DES.
Naive and false notions about perpetual motion.
- The fact that all perpetual motion machines throughout human history have failed proves that perpetual motion isn't possible.
Every failed perpetual motion machine demonstrates the correctness of the laws of physics that apply to it. No perpetual motion machine has ever violated any physics laws. Only fraudulent perpetual motion machines seem to work—until their fakery is exposed.
This is not a "proof". Science doesn't deal in proofs, the word "proof" is only appoprite in mathematics and logic. Scientists who declare that perpetual motion is impossible do not use this as an argument and certainly not as a proof. Their reasons for that conclusion are far stronger.
- We know perpetual motion is possible in nature. Planets go around the sun forever. Electrons go around an atomic nucleus without losing energy.
Planets continually lose energy through tidal force effects, and will not move forever. A spinning rigid flywheel on a rigid axle loses kinetic energy very, very slowly by electromagnetic radiation.
The naive picture of the atom as a nucleus surrounded by a cloud of orbiting electrons was abandoned many years ago. The Heisenberg Uncertainty Principle tells us that electrons in an atom are not discrete material objects, and we cannot say how or if they move. An undisturbed stable atom loses no energy, but we can't say anything in it is in "motion".
- Science cannot declare anything to be impossible, for science is incomplete and imperfect.
Some folks justify this with an example, such as: "They said that locomotives would just spin their smooth wheels on the smooth rails and go nowhere." Or: "They said man would never fly." And: "Rockets couldn't work in space, for the rocket's exhaust has no air to push against."
These are statements of naive skepticism, as contrasted with informed skepticism. We now have flying machines, and railroad trains, and space travel, but their invention did not change any of the basic laws of physics, did not equire any modification of physics laws, and did not lead to any new physics laws. Understanding of physics laws was essential for their development, and their success confirmed those laws. Such naive skeptical judgements arise from incomplete or flawed understanding of basic physics laws by people who have had little or no education in physics.
- Perpetual motion inventors should keep trying. Don't discourage them with negativity.
Not one perpetual motion inventor has ever discovered anything new or useful. But that fact will not discourage them.
Everyone needs a hobby. However, if they were better educated in physics they might avoid wasting time repeating past mistakes by inventing square wheels.
© 2019 by Donald E. Simanek.