What is Perpetual motion: Definition and 111 Discussions

Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, as it would violate either the first or second law of thermodynamics or both.These laws of thermodynamics apply regardless of the size of the system. For example, the motions and rotations of celestial bodies such as planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy, such as solar wind, interstellar medium resistance, gravitational radiation and thermal radiation, so they will not keep moving forever.Thus, machines that extract energy from finite sources will not operate indefinitely, because they are driven by the energy stored in the source, which will eventually be exhausted. A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out. Machines powered by more obscure sources have been proposed, but are subject to the same inescapable laws, and will eventually wind down.
In 2017, new states of matter, time crystals, were discovered in which on a microscopic scale the component atoms are in continual repetitive motion, thus satisfying the literal definition of "perpetual motion". However, these do not constitute perpetual motion machines in the traditional sense or violate thermodynamic laws because they are in their quantum ground state, so no energy can be extracted from them; they exhibit motion without energy.

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  1. russ_watters

    Insights Why We Don’t Discuss Perpetual Motion Machines (PMM)

    Continue reading...
  2. J

    Perpetual motion idea

    Hi all, Minimal math/physics background here, so bare with me. Imagine a smooth track or tube that tightly spirals downwards into smaller and smaller circles. Now imagine if a ball rolls down that spiral, gaining speed. At the bottom/end of the spiral the track/tube goes underneath the...
  3. Negatratoron

    Discussion Thread on the "Massless Charge" Perpetual Motion Machine

    Imagine a massless (or very light-weight) charge that is glued to a rod undergoing sinusoidal motion along an axis. The acceleration of this charge produces electromagnetic waves, which can be harvested for energy, and this energy can be used to power the continued sinusoidal motion as well as...
  4. W

    Disproving perpetual energy and perpetual motion machines.

    Hi, I was having a discussion with somebody who was trying to convince me of these things which I don’t believe. However I kept trying to think of the physics laws that make these things impossible. To my mind came resistance and friction. But I feel there are other science laws that I have...
  5. E

    B How does this osmotic system reach equilibrium?

    [Mentor's note - this post has been edited to ask the interesting physics question while not falling afoul of the forum rule prohibiting discussions of perpetual motion] On the left is pure water (blue), and on the right is concentrated salt water (green). The red walls in the middle are...
  6. O

    Almost perpetual motion?

    Perpetual motion is fundamentally impossible. But almost perpetual motion is possible. The list of toys or devices designed to run for a very long time is short: crookes radiometer (photons, cheap), the drinking bird (heat engine, cheap), the Atmos clock (temperature, expensive), Beverly Clock...
  7. mollwollfumble

    I Connection between entropy and time travel?

    My background is that I'm an applied mathematician and engineer, self-taught in GR and QFT. It's an old idea, in some dozen or so SciFi books. But I'm looking for a mathematical framework for handling it. The second law of thermodynamics, that entropy always increases in a closed system, can be...
  8. E

    B Can the moon orbit be used as perpetual motion?

    I'll attach a picture of what I mean but essentially I wanted to know if it was possible to (under circumstances where the Earth and moon do not change angle of rotation when orbiting the sun) create a perpetual motion machine using orbit as a means to turn a giant gear circling the Earth in...
  9. Jazzyrohan

    Perpetual motion machines can't exist (Feynman's lectures)

    I have been reading Feyman Lectures Volume 1 and I am stuck on the example or proof given in the book about how no machine can be more efficient than a reversible machine. http://www.feynmanlectures.caltech.edu/I_04.html Section 4-2 A very simple weight-lifting machine lifts weights three...
  10. Happyholland

    Suspend a magnet on a pendulum above a repelling magnet

    Hi, I was pondering a question after seeing a video about chaotic magnetic pendulums. If you were to suspend a magnet on a pendulum above a repelling magnet, would it stop moving or would you get perpetual motion? My guess is it would stop moving but I can't think of how. Gravity would try to...
  11. P

    Perpetually driven electric car

    I would think that using every bit of energy that a moving electric car produces, it would be able to sustain itself. Geared alternators on each wheel, pinwheels to use wind energy to power the interior electronics, plus solar panels. Even putting stators on the rims with a coil in the hub...
  12. Aleoa

    Perpetual motion machine - Intuitive meaning

    I'm reading the first Feynman volume on physics. In the chapter about Conservation of Energy, the author explains with the following sentence what is a perpetual machine ( in this case a weight-lifting machine). "If, when we have lifted and lowered a lot of weights and restored the machine to...
  13. SchroedingersLion

    Feynman: Reversible machines, no perpetual motion?

    Greetings, I have begun reading the Feynman Lectures to repeat the most important ideas from my undergraduate studies and to improve my intuitive understanding of physics. In one of the first chapters, the one about the conservation of energy, he demonstrates that the conservation of energy is...
  14. A

    B Reversible Machine

    I am no able to understand the reasoning of Feynman in deducing that it is impossible to build a machine that will lift a weight higher than it will be lifted by a reversible machine. I am also not able to understand what reversible machine is. So, please help me.
  15. ramzerimar

    Explain to me the flaw in this perpetual motion scheme

    Someone showed this to me, and I'm struggling to explain why this perpetual motion scheme is impossible. A picture: Basically, this is a cylinder within a large reservoir, with water at the level of the reservoir water level. The mass would be dropped and then reach the bottom of the cylinder...
  16. TMT

    Machine 2nd degree or

    Concerning Global warming; Can we cool atmosphere by converting it's heat content to electricity? if we do so is it became a perpetual machine in 2nd degree or not? I'm not so good in thermodynamics. But I'm sure it will not violate 1. rule energy is not created from noting, energy converted...
  17. dkotschessaa

    Leonardo’s Perpetual Motion Machines

    Obviously they don't work, perpetually, but they're really cool anyway: http://www.leonardodavincisinventions.com/mechanical-inventions/leonardo-perpetual-motion-machine/
  18. Ziknich

    Can we mimic a perpetual motion machien?

    Good day to all! I read a small article in MIT's engineering.edu page. The article talks about perpetual motion machines, it says that we cannot create one, but we can mimic it. My question is: how can we mimic this perpetual motion machine? Has it been mimicked before? And if yes, how? I...
  19. H

    Non-Linear optics vs The 2nd Law of Thermodynamics

    Hi, rank newbie here, with my first post. This one is something I figure every first year student comes up with at some point, but I don't know enough keywords to Search for an answer. (I'm not a student except in the category "of life": this isn't assigned homework) I figger, using a bit of...
  20. R

    Superfluid Perpetual Motion?

    Yes, I'm aware of the countless threads about perpetual motion here. Not sure if this idea has been considered with superfluids, though. I'm no physics expert (basically a laymen), but the idea of a superfluid in perpetual motion intrigues me because I can't imagine why it wouldn't be possible...
  21. J

    I William skinner Machine gravity

    Could someone explain under which principle does Skinner's machine operate? Is it just a free falling mass that's taken back to it initial position by very little input energy, thus generating a constant gradient or potential difference, and generating energy, or is it just storing kinetic energy?
  22. Theoden

    What are we striving towards with fusion reactors?

    Hi, I have heard that fusion can generate power and potentially make breeder reactors obsolete; but to even bring atoms close enough to fuse, wouldn't take a significant amount of energy in the first place? I feel like we are allotting high voltage toward fusion and getting a lesser...
  23. W

    Non-Solar Power Station in Space

    I have read about Japan's solar power plant in space. Would it not be easier to build a plant similar to the huge circular spinning space stations you see in movies that create their own gravity/downward force? Once something that large is spinning in space could you not use the motion to...
  24. Zlelik

    Is Hydroelectric power plant a perpetual motion machine?

    Is Hydroelectric power plant a perpetual motion machine of second kind from this classification https://en.wikipedia.org/wiki/Perpetual_motion#Classification ? or not? If not which kind of perpetual motion machine is it? :)
  25. E

    A perfect machine?

    What are the odds that humans will come up with a 100% (or extremely close to) efficient machine within the next couple centuries. If so, what principle do you think it would work on? How about a perpetual motion machine? Share your thoughts.
  26. GiantSheeps

    Planetary motion as perpetual motion?

    Could a planet orbiting around a sun be considered an example of perpetual motion? I know that the planet wouldn't be doing any work, since it goes back to the same spot every year, but does an object have to be performing for it to be considered perpetual motion? The two might have nothing to...
  27. A

    Perpetual Motion: Can Mono Polar Magnets Create It?

    I am wondering if perpetual motion is possible using mono polar magnets and magnets that do not depolarize (these are hypothetical magnets) If you had a magnet that used opposing polarities to spin a wheel that had no pivot points, but instead used magnets to levitate the design and it was in a...
  28. heterotictype1

    Idea for a perpetual motion machine

    If someone were to send a probe out to interstellar space, bring it to a full stop and start rotating, would it continue rotating eternally? Or would drag from errant plasma slow it?
  29. L

    Perpetual Motion From Satellite Revolution

    "Perpetual Motion" From Satellite Revolution This is going to sound very far fetched, and I know very little about the laws of physics, admittedly (I don't even know if I'm posting this in the right area), but curiosity compels me. I was wondering if it would be possible to harvest energy...
  30. P

    Perpetual Motion: Is it Possible?

    According to the second law of thermodynamics, perpetual motion is impossible, right? But how do gas molecules in a closed container move perpetually?
  31. S

    Perpetual motion machine

    perpetual motion machine ! i read many of this papers but it violates the first law of thermodynamics . can it come true one day
  32. R

    Is this perpetual motion?

    Hi Experts I am wondering if my understanding of perpetual motion is correct. I use solar energy to supply energy needed to reset the cycle of a motion. In short, the extra energy needed to reset a cycle is provided by another source of free energy. This way, the motion is kept...
  33. K

    Why perpetual motion machine wouldn't work.

    I'm trying to explain to my friend why the following would not work, but embarrassingly, I'm having trouble. You have a ramp that allows a ball bearing to roll up, and a strong magnet at the top which is able to pull the ball up the ramp. But there is a hole halfway up the ramp, and so the...
  34. A

    Refuting Perpetual Motion with Magnets

    My friend believes that he's able to create a perpetual motion machine using carefully arranged magnets and the repelling force between them in order to spin a turbine. To refute this, I argued that perpetual motion is against the laws of thermodynamics and that friction would eventually...
  35. iVenky

    When can we have perpetual motion?

    I was reading Feynman's lectures Vol I. There he says it is possible to have perpetual motion ideally. Considering everything is ideal what is the condition to have perpetual motion? For example if you take a weighing machine, is it possible to have perpetual motion for all weights on both panes...
  36. J

    Why isn't a hydroelectric dam considered perpetual motion?

    I am familiar with the second law of thermo, so i realize that there is an answer. My reasoning is that the water is flowing because of gravity, which turns the dam turbines. So where is the energy being removed from the flowing water? I mean its not changing the Earth's gravity right?
  37. samsara15

    Perpetual Motion: Particle Spin & Earth's Role

    Elementary particles spin. So does the Earth. Spin does work. The spin of electrons and other elementary partlces never stops, or slows down. Why isn't the spin of particles considered to be perpetual motion? Doesn't particle spin violate the laws of Thermodynamics?
  38. P

    Perpetual Motion In The Gravitational Field

    Can perpetual motion be possible in a gravitational field? If I take an object and into space from earth, the potential energy increases but as we go further away from the Earth the forces which contribute in the work done decreases, thus it seems to me as if energy is destroyed. Because the...
  39. P

    Perpetual motion and Newton's first law

    This might be a very stupid question. But let me still ask. :) Perpetual motion is not possible. But by Newton's first law, a body remains in its state of motion unless an external force acts on it. Now, I wonder if the statement "perpetual motion is not possible" is true only in a practical...
  40. S

    Perpetual Motion.

    I am completely fascinated with it, but my only question is if perpetual motion is achievable in space why don't we connect huge wire's to a machine lifted into space that constantly creates a giant force and never stops then is converted and sent down to earth? I am not sure if I shed my...
  41. Q_Goest

    Perpetual Motion Disease

    Ralf is in a wheel chair now. He’s an old guy, over 80 but still has a strong desire to do things like run his machine shop and invent stuff. His shop only consists of himself and one other guy though he’s not able to work in the shop any longer due to his age and failing health. He’s got this...
  42. T

    Perpetual Motion (explain why it's impossible)

    Obviously it's impossible, but no one on a different forum understood why not in terms of forces. Also the solution doesn't need to be quantitative. Homework Statement The one thing I'd change from the troll science picture below would be to change the balls full of air on a string to a...
  43. T

    Perpetual motion (please just give me a chance, it's just a few questions)

    I realize just from the title a lot of people are going to shoot me down very quickly, but these are just questions to help my basic understanding. I'm definitely not a physics buff. I just want to know a couple of things pertaining to gravity and permanent magnets. Technically speaking are...
  44. S

    Perpetual Motion using Brownian Motion?

    Let me start off by saying that I very well know that PM is impossible. Thermodynamics aren't just good ideas-they're the law. :) I have heard that Brownian Motion will go on infinitely, but you can't harness it and it is useless perpetual motion. Is this true?
  45. T

    My Perpetual Motion - Would it work?

    I think of some pretty crazy ideas when I'm half asleep. I keep a notebook and pencil by my bed, randomly wake up and write jibberish down. Sometimes great ideas, but most of the time crazy nonsense that I have to wonder what the hell I was thinking, even though they seemed like the greatest...
  46. E

    Using Magnets to Create Perpetual Motion?

    Let's say I have permanent magnets set up in a sort of half sphere with the inside of the sphere pointing up and it laying flat on a table and then I have a ball with, let's say, half the radius of the half sphere. The ball has the same permanent charge as the half sphere. I place the ball over...
  47. H

    Isn't gravitational orbit perpetual motion?

    I was wondering... Suppose that the mass that was being orbited, in place of the earth, was stable and constant - then substitute the moon with another constant but suppose the orbit is the same as the mass and distances between them are the same - would/could this be an example of perpetual motion?
  48. G

    Atoms and the law of perpetual motion

    Please someone, answer this question for me...Do atoms exist in perpetual motion? I have heard we have never discovered anything capable of perpetual motion, but aren't atoms always moving? Please answer.
  49. A

    Perpetual Motion: Exploring the Possibilities

    I am sorry if this is a weird or stupid question, as I am currently in college and majoring in physics, but have not taken any physics classes yet. The weird thing I was thinking about was the impossibility of perpetual motion. Are not atoms a form of perpetual motion? What about solar systems...
  50. A

    Perpetual motion through magnetized water?

    if you mixed water with a feromagnetic metal and then ran it through permanent magnets (giving it a charge or allign it correctly) , then heated it up into stem and ran it through a coil of copper wire (in some way as to cause electrons to flow). waited for it to condensate (perhaps using the...