Talk:Perpetual motion

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Perpetual motion describes "motion that continues indefinitely without any external source of energy; impossible in practice because of friction." ... There is a scientific consensus that perpetual motion is impossible, as it would violate the first or second law of thermodynamics.

I don't think that this wording is adequate. It's easy to read it as saying that motion continuing indefinitely is theoretically impossible according to the laws of thermodynamics, which is not true at all. (talk) 17:23, 22 June 2013 (UTC)

Can you give an example of macroscopic motion that will actually continue indefinitely without any external source of energy? --ChetvornoTALK 17:51, 22 June 2013 (UTC)
Firstly, there is no mention in the definition of "macroscopic". If you want a macroscopic example, though, an orbiting body will, ignoring exotic effects, continue orbiting forever in a vacuum. The laws of thermodynamics do not preclude this, and, in fact, one could argue that the laws of thermodynamics say the exact opposite: that motion always will continue forever. (talk) 18:01, 22 June 2013 (UTC)
It would have to be a perfect vacuum without a single subatomic particle, which doesn't exist in the universe. The rest of the universe would have to be empty of other objects, because if there are any other objects in the universe at a temperature above absolute zero, the momentum carried by their black body radiation will slow the orbiting object. Even then a body orbiting another one will radiate energy in the form of gravitational waves and will slowly spiral in. --ChetvornoTALK 18:12, 22 June 2013 (UTC)
Actually, I have a problem with the above definition, too. That definition, from the word perpetuum mobile, comes from a time before the concept of energy was understood. In modern physics, the idea of perpetual motion has expanded to include devices that produce electrical, chemical or other forms of energy besides mechanical energy. The modern definition is: a device that produces energy without any energy input, or (in the limiting case) a device that runs without input of energy. The definition of "motion that continues indefinitely" has to remain the primary definition in the article because it is in most WP:RSs, but I'd like to add an explanation of the modern energy definition, if I can find a source. --ChetvornoTALK 01:51, 24 June 2013 (UTC)
I would support that. The current definition actually isn't bad, but the more precise the definition, the easier it will be for readers to understand that over-unity is actually possible if you are drawing energy from another source, but that the "rules of physics" forbid an over-unity device if it tries to create energy out of nothing. The sooner we update this definition the better. Wdford (talk) 07:53, 24 June 2013 (UTC)

The current 'scientific' definition is a bit of a fudge, as it assumes that the definition of energy is 'energy know to science' to the exclusion of any unknown-undiscovered energy source.(See cold fusion) This further assumes that no new energy source is possible because science knows all possible energy sources. This is surely not in the spirit of science as it assumes that science knows everything about energy. Therefore: it is impossible for a machine to run on an energy source unknown to science, now or at any future date? What became of logic? — Preceding unsigned comment added by (talk) 22:40, 13 October 2013 (UTC)

As the article says, new physics may be discovered tomorrow. All it is saying is that the impossibility of perpetual motion (based on conservation of energy and the 2nd law) is the closest thing to a universal law we know. It is one of the oldest (dating back to the Renaissance) and has been the most challenged. In its 400 year history it has been continually attacked and has not only stood up, but has been found to lie at the foundation of all modern physics.
All the physical laws we know about, back to the Big Bang, are based on conservation of energy and therefore do not permit perpetual motion. Any "undiscovered sources of energy" that can be explained by known physical laws must be "limited" sources and not "unlimited, perpetual" sources. This would have included cold fusion, if it had panned out, which was not "perpetual motion" but merely a new way of burning the limited fusion fuel available on Earth. Of course new physical laws may be discovered. But Noether's theorem makes it pretty difficult even for any new physics to permit perpetual motion. It says any law of physics, known or future unknown ones, which obeys time symmetry, meaning it is unchanging in time (which is what makes it a "law"!!) must conserve energy and therefore prohibit perpetual motion. This is all explained in the article; did you read it? --ChetvornoTALK 08:47, 14 October 2013 (UTC)
Surely at atomic level, the motion of matter cannot actually stop. I think the problem is with the term 'perpetual motion', when what is actually meant is that a machine carrying out 'work' indefinitely is impossible. I think the movement of stars etc is perpetual motion, if not, then when and how are they going to stop? Theories about the ultimate fate/future of the universe vary, with talk of heat death on one hand, and accelerating expansion due to dark energy on the other. Gomez2002 (talk) 11:45, 28 July 2014 (UTC)
You're right about the motion at the atomic level; any matter at a temperature above absolute zero has thermal energy. If we could tap that, it would be a truly "perpetual" source of energy, because all energy ultimately degrades into thermal energy, so it would be a closed cycle; a self-renewing source. That is what a "perpetual motion machine of the 2nd kind" claims to do. The 2nd law of thermodynamics forbids this; in order to extract useful energy from thermal motion you need a reservoir at a lower temperature, and any process that extracts work from the higher temperature reservoir exhausts heat into the lower temperature reservoir. So even though there is atomic motion, useful energy cannot be extracted from a system at a constant temperature.
In addition to any extraction of useful work by us, due to "entropy" spontaneous processes slowly degrade and dissipate any "nonequilibrium" reservoirs of energy, for example temperature differences, or moving objects like planets, until eventually the universe will reach "equilibrium"; there will be motion on the atomic scale, but no usable energy; the heat death you mentioned. The motion of celestial bodies has been discussed on this page repeatedly; processes like drag due to interstellar gas, tidal distortion, and gravity waves will dissipate the kinetic energy of orbiting stars and galaxies, so they will eventually "spiral in"; it just takes a long time (a LOONG time). Dark energy MIGHT be an exception, but it is only active on a very large scale; anything the size of a galaxy or smaller is going to suffer heat death; I would assume it would slowly collapse and end up as a black hole.
I absolutely agree that the problem is the term "perpetual motion"; as you say, what most people mean by the term is a machine that will produce work with no energy input. --ChetvornoTALK 14:21, 28 July 2014 (UTC)

More clarification of terms needed?[edit]

There are a few things that could potentially be in perpetual motion based on some of the definitions on the page:

1 Any object in space - An object moving through space will continue to move (perpetually) unless something gets in the way. As far as I know two objects that orbit each other could orbit perpetually if they are in a stable configuration (but I don't know if tidal effects would always end up destroying the stable state?

2 When you create a superfluid you can, as far as I understand it, create a perpetual fountain - the fluid will keep moving so long as the temperature remains low enough. — Preceding unsigned comment added by (talk) 12:43, 24 January 2014 (UTC)

The motion of celestial bodies has been discussed repeatedly on this page - see "Definition" above. There are various sources of drag, such as interstellar gas, tidal deformation, and gravitational waves, which dissipate the energy as heat, so orbiting bodies will eventually "spiral in"; it just takes a long time. Superfluidity might be an example; the similar example of perpetual superconductive electric currents is already mentioned in the introduction. However I have read that in practice superconductive currents don't actually flow forever, but dissipate energy by several small mechanisms which cause the currents in devices like superconductive magnets to decay to zero on a time scale of months, so perhaps superfluid motion also decays. It would have to be sourced. Just observing a superfluid's motion requires light to reflect off of it, and the light photons will carry off momentum from the fluid in the form of a tiny Doppler shift - in the real world there are all kinds of tiny dissipative effects that prevent a motion from being truly "perpetual". --ChetvornoTALK 18:24, 24 January 2014 (UTC)
It's true to say that in theory an object could continue to spin or move in a straight line at constant velocity perpetually - but in practice, you can't ever quite manage it. With relativity, it's arguable that an object doesn't move at all when it's going at constant velocity because it is an equivalent statement to say that the entire universe is simply moving the other way. An object that appears to be "stationary" is it all gets very tangled when you try to argue purely theoretically. SteveBaker (talk) 19:49, 8 July 2014 (UTC)

"Free Energy"[edit]

The disambiguation page for Free Energy points here as the only source of information for devices based on "alternative" physics - and as such the description "Perpetual Motion" is incomplete.

At the heart of quantum theory is the concept that energy/matter is constantly being created and destroyed. Researchers have therefore considered "energy from the vacuum" devices. In the realm of electricity, researchers have found ways of setting up asymmetry so that for instance back EMF in a transformer secondary or motor is cancelled out.[1] Whilst references to this field should be guarded, arguably they should not be dismissed. Dollist (talk) 19:46, 7 July 2014 (UTC)

I'm afraid you've been taken in by pseudoscience. The source you gave is quite wrong. Quantum theory is based on conservation of energy, and does not allow energy/matter to be created or destroyed, only changed in form. The motion of electrons and zero-point energy cannot be tapped due to the second law of thermodynamics. "Alternative" physics is bogus physics. The "energy from the vacuum" theories of John Bedini, Tom Bearden, Gabriel Kron, etc. are horse manure. Not a single paper by any of them has been accepted by any reputable scientific journal. Their claim that the reformulation of Maxwell's equations by Oliver Heaviside around 1900 ignored asymmetric solutions that allow back EMF in a motor to be cancelled is laughable to any real physicist. None of the devices on that page work. They sound convincing though, don't they?

Decomposing the scalar potential between the end charges of a dipole reveals a harmonic set of EM waves flowing into the dipole from the complex plane. The well-known broken 3-space symmetry of the dipole in its energy exchange with the vacuum thus releases 3-symmetry in EM energy flow, while conserving 4-symmetry. The dipole thus becomes a universal kind of negative resistor extracting electromagnetic energy from the vacuum.

— Tom Bearden

These people have learned to dress up their fantasies by mixing them with real physics so they sound like real physics papers, so they deceive a lot of uneducated readers. --ChetvornoTALK 22:05, 7 July 2014 (UTC)
Tom Bearden is the absolute master of technical-sounding gobbledegook. In addition to all the stuff he's written, he loves the sound of his own voice, and you can find hours of him talking on YouTube. If anything uses him as a reference, it's safe to stop reading. The fact that people keep falling for his nonsense is why I argued strongly NOT to delete the Wikipedia article about him, but I was outvoted, because the fact is, he really isn't "notable". KaturianKaturian 19:03, 8 July 2014 (UTC)
...but back on topic: Your reference (Patrick Kelly's "Guide to Free Energy Devices") is nowhere near a WP:RS; however, it is extremely useful as a comprehensive list of fallacious claims.KaturianKaturian 19:11, 8 July 2014 (UTC)

jul 29, 2014, Almost Perpetual Machines,[edit]

jul 29, 2014, How is this working then? , , — Preceding unsigned comment added by Nayanmipun (talkcontribs) 07:32, 29 July 2014 (UTC)

They are (as their titles and comments tell you) examples of overbalanced wheels. This is one of the older (and now less-novel) well-known failures to be actually perpetual motion. It's easily debunked by basic physics, as already discussed in our article. DMacks (talk) 08:04, 29 July 2014 (UTC)
The overbalanced wheel seems to be the only example which isn't explicitly debunked, in the article - until I copyedited it, it just said "the result is (or would be, if such a device worked) that the wheel rotates". Is there a snappy explanation of why the expectation of perpetual rotation is incorrect? --McGeddon (talk) 08:31, 29 July 2014 (UTC)
The caption in the gallery section seems like a good sound-bite: "The "Overbalanced Wheel". It was thought that the metal balls on the right side would turn the wheel because of the longer lever arm, but since the left side had more balls than the right side, the torque was balanced and the perpetual movement could not be achieved. That's in keeping with the explanation in footnote #22 (doi:10.1016/j.physrep.2012.10.007) cited in the main article where you were editing. DMacks (talk) 09:06, 29 July 2014 (UTC)
Oh, I missed the gallery. Seems unhelpful to be splitting such text between a section and the gallery, I'll try cleaning it up. --McGeddon (talk) 09:16, 29 July 2014 (UTC)
I agree. Thanks for your work on it! DMacks (talk) 09:21, 29 July 2014 (UTC)

Given that two of the gallery images could usefully illustrate two paragraphs, I've moved them. This just leaves File:Perpetuum1.png in the gallery, which seems a bit lost by itself. Should this replace the other image of the overbalanced wheel, File:Perpetuum mobile villard de honnecourt.jpg? The newer image is clearer, but the older one may be of historic significance, and at least conveys the age of the idea. --McGeddon (talk) 09:30, 29 July 2014 (UTC)

Another problematic statement[edit]

As an outcome of the above discussion (I believe), the opening definition now reads much better. However, there is a similar problem at the start of the next section:

"There is a scientific consensus that perpetual motion in an isolated system violates either the first law of thermodynamics, the second law of thermodynamics, or both."

This is simply not true. Perpetual motion (as it is defined in the opening sentence) does not violate any physical laws. (talk) 20:49, 24 September 2014 (UTC)

... though I said that the opening definition read much better, now I am wondering. Is this distinction between "perpetual motion" and a "perpetual motion machine" actually real, or just someone's invention to fudge the wording? (No offence.) Does a "perpetual motion machine" not do "perpetual motion"? (talk) 20:58, 24 September 2014 (UTC)

The issue is really a historical and linguistic one. The term "perpetual motion" from the Latin perpetuum mobile originated in the Middle Ages, before the concept of energy was understood. People tried to build a machine that would turn "by itself", indefinately. The repeated failure of these efforts led to the concept of energy and conservation of energy, which explained why they were unsuccessful. The modern meaning of perpetual motion in physics has expanded beyond a machine that will turn forever. It means a machine that produces more energy than it consumes, in other words a machine that produces energy from nothing (or in the case of a perpetual motion machine of the 2nd kind, one that produces energy from thermal motion at equilibrium). The term is extended to other types of energy than motion; an electrical generator that produces electric energy with no input fuel would also be called a perpetual motion machine.--ChetvornoTALK 00:25, 25 September 2014 (UTC)
The anachronistic term "perpetual motion" has led to an enormous amount of confusion on this page; people bring up examples like the motion of the Moon or planets, and ask "is this not perpetual motion?" The answer is no it's not, because it doesn't produce energy from nothing. These are just examples of motion with very little friction. A moving object only has a certain amount of energy. Every form of motion is subject to some form of friction, which dissipates its energy, so unless it can produce energy from nothing, it will eventually stop moving. For example, the Moon circling the Earth is subject to drag from the thin interplanetary gas as well as tidal deformation, so it will eventually "spiral in" and collide with the Earth. If you want to show that perpetual motion is possible, you have to show that energy can be produced from nothing. --ChetvornoTALK 00:25, 25 September 2014 (UTC)
Thanks, but I stand by my original comments. Firstly, I do not believe that the distinction between "perpetual motion" and "perpetual motion machine" as made in the opening sentence is valid (or widely recognised), and secondly I do not believe that the statement at the beginning of the "Basic principles" section is true, given the definition at the start of the article. Probably we should focus specifically on what should be done to fix these two issues, if it is agreed that they need fixing. (talk) 02:40, 25 September 2014 (UTC)
What exactly is your objection? I don't see that there is much of a distinction being made between the terms. --ChetvornoTALK 03:04, 25 September 2014 (UTC)

Fix, don't delete[edit]

After spending considerable time attempting to clean up the mess that the LEDE had become, I found all my hard work RVed with a nice note about how it was wrong and unsourced. Neither statement was true, but I guess that's why I'm now here, having to ask what precisely was wrong with it so that I can fix those statements and re-implement. Maury Markowitz (talk) 20:01, 18 October 2014 (UTC)

"Perpetual motion, in the strict sense of the term, is both theoretically possible and seen in practice. The galaxies in the universe will move forever, by any practical definition," is something that caught my eye as being incorrect, unless you have a specific definition of "practical definition" in mind. "Runs a long time" is definitely not "perpetual", especially if there are multiple possible end-states, such as heat death of the universe--essentially, their motion was initiated by energy input (Big Bang or something) and will eventually wind up being converted to other forms rather than motion. It's only perpetual in a sense similar to the next discussed ideas, such as hydroelectric power or other beyond-Earth sources. DMacks (talk) 20:42, 18 October 2014 (UTC)
I agree with DMacks. Point taken, Markowitz; I probably should have discussed before reverting. Here are my issues with the rewrite:
  • "Perpetual motion, in the strict sense of the term, is both theoretically possible and seen in practice."
The biggie. Wrong and misleading. Many, many sources state that perpetual motion is impossible. Perpetual motion of the third kind, frictionless motion, which is what is being referred to in the "galaxies" example, is almost possible, but as has been discussed many times on the Talk page, is not actually possible because it is not possible to have motion without some friction or energy loss.
  • "The exact nature of the failure of these devices was different in every case - the endless waterwheel fails for different reasons than the overbalanced wheel"
This is misleading for nontechnical readers. The most important fact in this article is that all perpetual motion machines fail for one or the other of the same two reasons: They either violate conservation of energy (the first law of thermodynamics) or the second law of thermodynamics. These points should be up near the top. The quote above encourages the common view that all it takes for perpetual motion is for someone to find a better linkage or a different method. Maybe instead make the point that the fact that so many different designs failed led Enlightenment scientists to the idea that a general principle was involved - conservation of energy. Plus the readers haven't been told what a "endless waterwheel" or "overbalanced wheel" is.
  • "...a device that continues to operate with no external inputs while producing useful work"
What kind of "inputs"?
  • "Designs for such devices were popular for centuries..."
I feel this wording may be misinterpreted to mean the ancients had the "secret".
  • "Many perpetual motion machines fail because the design inherently requires more energy to run than the system contains..."
This should be reworded; a perpetual motion machine of the first kind requires an "infinite" amount of energy.
  • "More modern designs, especially those that do not provide physical motion directly, tend to be based on the conversion of energy from one form to another."
Something should be said here about heat or thermal energy; the defining characteristic of perpetual motion machines of the 2nd kind is that they convert thermal energy to work. Also I wouldn't say they were "more modern designs" but that they are a different class or type because they fail for a different reason.
--ChetvornoTALK 23:00, 18 October 2014 (UTC)
Many, many sources state that perpetual motion is impossible Sources talking about perpetual motion machines'. If you do not believe the galaxies are in perpetual motion, you might want to read up a bit more on dark energy. As to "practical definition", anyone can state that anything is not "perpetual" because it had a beginning in time, yet such a definition is not practical. A practical definition would have to include provisions for the time that the device starts and may be deliberately stopped. But adding such distinctions is precisely the sort of overcomplicating that confuses more than
This is misleading for nontechnical readers. I say the exact opposite. The Browning Ratchet doesn't work because of the 2nd law, that simply tells you that you're probably not looking hard enough. The actual reason that it doesn't work is described in the article. And that reason is different than the reason the overbalanced wheel doesn't work, or the waterwheel example. All of these fail for different reasons, and simply saying "2nd law" is far, far more confusing than pointing out the actual reasons.
If you think the wording is unclear, or too wordy (guilty!) then by all means fix it. But the current lede is a shitstorm of far more confusing terminology. One issue pointed out above is introducing things the reader hasn't seen before, but the current version has a whole section about superconductivity that adds nothing but confusion and apparently is an attempt to demonstrate a counterexample and then explain it away. Come on.
Chetvorno has some excellent suggestions at the end there. So here goes...

Perpetual motion is motion that continues indefinitely without any external source of energy.[1] The term is most commonly used to refer to a perpetual motion machine, a device that continues to operate with no external inputs while producing useful work.

Proposals for perpetual motion machines have been made for centuries, although they all failed in practice. Early examples generally used basic mechanical systems to produce closed loop motion, using falling water to power a water pump for instance. Later examples tended to be based on any new scientific discovery; magnets, electrical systems and various materials effects have all been proposed. Before the mathematical understanding of the concepts of work and energy had been developed, there was no obvious reason why these devices would not work, and the failure of one design was not taken as an indication that another would not work. The development of modern physics, especially the concept of energy and the science of thermodynamics, has demonstrated that any such device is physically impossible.

Many perpetual motion machines fail because the design inherently requires more energy to run than the system contains, and once the initial store is used up the output will end. Such devices are said to fail the first law of thermodynamics, a specific case of the law of conservation of energy. Other designs are based on the conversion of energy from one form to another, or the use of different energy levels from which work can be extracted. The second law of thermodynamics demonstrates that all such process are inherently lossy, and these systems will leak away energy and eventually stop.[2][3][4]

Perpetual motion, in the strict sense of the term, is theoretically possible. The galaxies in the universe will move forever, by any practical definition, but no work is being extracted so they are not machines. Likewise, there are any number of common examples of machines that run for long times; a hydropower dam produces electricity from a seemingly endless supply of water, but the water is being provided by an enormous evaporation process powered by the Sun. It is important to contrast these examples with the concept of a perpetual motion machine in the sense that it is used here.

Despite the fact that successful perpetual motion devices are impossible in terms of the laws of physics, the pursuit of perpetual motion remains popular. Modern examples often claim to comply with both laws of thermodynamics but access energy from obscure source. These are sometimes referred to as perpetual motion machines, although they also do not meet the criteria for the name.

  1. ^ "Dictionary - Definition of perpetual motion". Retrieved 2012-11-27. 
  2. ^ Derry, Gregory N. What Science Is and How It Works. Princeton University Press. p. 167. ISBN 1400823110. 
  3. ^ Roy, Bimalendu Narayan (2002). Fundamentals of Classical and Statistical Thermodynamics. John Wiley & Sons. p. 58. ISBN 0470843136. 
  4. ^ "Definition of perpetual motion". 2012-11-22. Retrieved 2012-11-27. 
The link is busted. That site itself now identifies as, and does not have an entry for the phrase "perpetual motion". If we're looking for lay-language definition (or meta-search of several other lay-reader sites), maybe [2]? DMacks (talk) 04:48, 19 October 2014 (UTC)
Metric expansion of space is a different thing than objects themselves simply/actually physically moving apart. Dark energy describes itself as some sort of field or type of energy that causes the acceleration; therefore there is energy input involved, which contradicts the definition. I don't know enough about this topic to figure out what would happen (or if it's knowable, or even reasonable to ask) to the motion if the effect of dark energy were removed ("would it be perpetual even without it?"). DMacks (talk) 04:48, 19 October 2014 (UTC)
And astronomers differ about what will happen at the end of the Universe. A major possibility is the heat death of the universe, in which everything "runs down". Rather than debate cosmology, the introduction should make the point that all these systems are losing energy to friction or other losses, so they cannot continue moving "perpetually". --ChetvornoTALK 13:07, 19 October 2014 (UTC)
Which is a useless definition of perpetual in this context, and I admonish myself for saying anything because I knew it would turn into this sort of definitional BS. Maury Markowitz
  • "...but no work is being extracted so they are not machines."
This is characteristic of all perpetual motion machines of the 3rd kind, they serve as energy-storage devices, yet most are still called "machines". You would not call a gyroscope or a superconductive magnet a "machine"? --ChetvornoTALK 13:07, 19 October 2014 (UTC)
Sure you would, if they perform work. What do you think the definition of a machine is? Maury Markowitz
Both gyroscopes and superconductive magnets have been used to store energy and when the energy is extracted they do work, but by your definition if they are not producing work they would not be called "machines". I don't see that thermodynamics makes this distinction between "perpetual motion" and a "perpetual motion machine". Any system which has the potential to produce work indefinitely (or in the case of machines of the 3rd kind, store energy indefinitely) could be a "perpetual motion machine". --ChetvornoTALK 14:13, 19 October 2014 (UTC)
  • "Perpetual motion, in the strict sense of the term, is theoretically possible."
Unless you can find enough WP:RSs to refute the many sources that say perpetual motion is impossible, this can't be included. --ChetvornoTALK 13:07, 19 October 2014 (UTC)
Newton's First Law of Motion: "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Every counterexample being offered here is a practical counterexample, hand waving at its worst... "well, eventually it will hit something". However, that lies outside the definition in the article as that is clearly an external source, and has no basis in the underlying physics. This is why it is vital that the idea of perpetual motion, and the concept of a perpetual motion machine should be clearly separated. Maury Markowitz
But you can't find a system in physics which is not acted on by an outside force. The above statement would require WP:RSs that "perpetual motion" is different from a "perpetual motion machine", and that perpetual motion is possible. I don't see significant support in physics for this view. --ChetvornoTALK 14:40, 19 October 2014 (UTC)
  • "The Browning Ratchet doesn't work because of the 2nd law, that simply tells you that you're probably not looking hard enough."
No, that's the wonderful thing about the thermodynamics laws. You don't have to look further. No machine, regardless of construction, can produce work from a system at equilibrium. That's what we're trying to get across to readers. The reason they fail is not due to their individual construction, but to general laws. The text does make this point but it needs to be clearer. --ChetvornoTALK 13:07, 19 October 2014 (UTC)
The article goes on to explain a twelve year hunt for the actual mechanism. Why do you think they bothered then?Maury Markowitz (talk) 12:33, 19 October 2014 (UTC)
From the article: "Any proposed perpetual motion design offers a potentially instructive challenge to physicists: one is certain that it cannot work, so one must explain how it fails to work. ...during that twelve-year period scientists did not believe that the machine was possible. They were merely unaware of the exact mechanism by which it would inevitably fail." --ChetvornoTALK 14:40, 19 October 2014 (UTC)
  • "a perpetual motion machine, a device that continues to operate with no external inputs while producing useful work."
Again, this is sloppy. It is a machine that continues to produce work without any external energy input. --ChetvornoTALK 13:07, 19 October 2014 (UTC)
Fine, energy. Maury Markowitz
The first law of thermodynamics is the law of conservation of energy. --ChetvornoTALK 13:07, 19 October 2014 (UTC)
No its not, or we would call it that. It is a specific sub-case of conservation of energy expressed in thermodynamics terms. Navel oranges are a type of orange, they are not equivalent to oranges. Maury Markowitz
My feeling is that this could be a good introduction, but the errors and misleading statements have to be corrected. It needs to be clear for the non-technically-educated readers. --ChetvornoTALK 13:07, 19 October 2014 (UTC)
What, like a completely unsupported statement about apparent perpetual motion in superconductors, which then tries to explain it away but utterly fails to do so? Maury Markowitz
I agree the present introduction is lousy.--ChetvornoTALK 14:13, 19 October 2014 (UTC)
The most important thing is that it has to state in no uncertain terms that perpetual motion is impossible, due to the two thermodynamics laws. --ChetvornoTALK 06:26, 19 October 2014 (UTC)
No, the most important thing is to state in no uncertain terms that perpetual motion 'machines are impossible, due to the two thermodynamics laws. These laws say nothing whatsoever about motion. Maury Markowitz (talk) 12:33, 19 October 2014 (UTC)
I personally don't think the lede needs all of these descriptions of "this isn't p.m. because x, that isn't p.m. because y". If you want a quick fix, it could be vastly improved by simply truncating it after "... (as occurs in energy harvesting)."
But for a better fix: the lede is supposed to summarize the article. The content and sequence of the lede, after the opening sentence, should be at least closely guided by that of the article body. Go through the article and start with one sentence per level two and level three section, then augment as necessary. If that doesn't produce a good lede, then the problem is not with the lede, it's with the article. Jeh (talk) 10:07, 19 October 2014 (UTC)
Whoa, logic to the rescue! Maury Markowitz (talk) 12:33, 19 October 2014 (UTC)
Yes, that could work. But I don't see a distinction in the article between "perpetual motion" and "perpetual motion machines", or anywhere that it says perpetual motion is possible. --ChetvornoTALK 14:13, 19 October 2014 (UTC)