Is the concept of a perpetual motion machine feasible in the realm of physics?

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Discussion Overview

The discussion centers on the feasibility of perpetual motion machines within the framework of physics, exploring concepts related to mechanical energy, gravitational effects, and the implications of relativity. Participants examine theoretical models and potential mechanisms, including the role of gears and levers, gravitational time dilation, and energy transmission in gravitational fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that mechanical energy against gravity may not work due to relativistic effects, though the exact nature of these effects remains uncertain.
  • There is a suggestion that light does not accelerate, and while photons may gain energy, the implications for perpetual motion are not fully understood.
  • A participant discusses simplifying gear assemblies into levers and questions whether energy transfer through a gravity gradient affects the system's efficiency.
  • Gravitational time dilation is noted to potentially slow down the bottom gear's rotation, which may offset energy increases, although this is presented as a hypothesis rather than a conclusion.
  • Some participants explore the Ehrenfest paradox and its relevance to the rigidity of gears in gravitational fields, suggesting that perfect rigid-body rotation may not be achievable.
  • There are claims that if the machine operates horizontally, it could function without gravitational energy loss, indicating a distinction between scenarios with and without gravity.
  • Concerns are raised about the implications of energy scaling in different reference frames, particularly regarding kinetic energy and photon energy in gravitational contexts.
  • Participants express uncertainty about where energy loss occurs in the proposed systems and whether energy differences across reference frames can be accurately quantified.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the feasibility of perpetual motion machines, with multiple competing views and hypotheses presented throughout the discussion. Uncertainties about the implications of relativity and gravitational effects remain unresolved.

Contextual Notes

Limitations include assumptions about the rigidity of materials, the dependence on gravitational fields, and the complexities of energy transfer in varying reference frames. The discussion highlights unresolved mathematical steps and the need for further analysis.

  • #91


You correctly assume that as the light energy travels downwards it picks up "energy" due to the gravitational field, but you fail to realize that as the mechanical energy travels back uipwards it loses "energy" due to the gravitational field.

Both light energy and mechanical energy have the same behavior.
 
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  • #92


ApplePion said:
You correctly assume that as the light energy travels downwards it picks up "energy" due to the gravitational field, but you fail to realize that as the mechanical energy travels back uipwards it loses "energy" due to the gravitational field.

Both light energy and mechanical energy have the same behavior.
ApplePion: As there was no specific quoting anyone, I must do a Sherlock Holmes and deduce from the time of your entry it is me you are directing your comment to. If so then I'm afraid you have badly misunderstood what I have been arguing. I'm on your side re above! Have another read of #81 and earlier please, paying close attention to what is actually said. Now if you were referring to someone else well apologies but how would I know that?
 
  • #93
DaleSpam said:
Which is what we did here.

In any case, Feynman is not on PF so you may have to settle for our inferior efforts instead. It is always possible to come up with a scenario so complicated that your audience cannot analyze it (even Feynman).

Since the conservation principles follow directly from the laws then the details of a given machine are irrelevant. As long as it follows the laws it must also follow the conservation principles. At some point you need to stop conjecturing more complicated machines and actually learn the derivation of the conservation law. But again, that is not what was done here.

Oh, I think there are plenty of good Feynmanns going at this question. I just didn't want the deconstruction to stop until Guss got a transparent answer at some level, or I could figure out something for myself. But all good things have an end eventually.
 
  • #94
yuiop said:
Would have been easier to have just posted a link to this youtube video of a plane taking off from a conveyor belt. No one was more surprised than the pilot when the plane took off. LOL


The skeptics don't accept the Mythbusters demo. You wouldn't believe the excuses. But I've gotten us off-topic, and that will get us a warning.
 
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  • #95
ApplePion said:
It *would* be c is one *switched* to inertial coordinates, but when one is working in a system one has to use the coordinates of the actual system.
There is no God-given set of coordinates for a given system. You are always free to use any coordinates you choose. Or do you not believe that coordinate transformations are valid?

ApplePion said:
I live in Florida, and while it is possible that I *could* live in Alaska being that I am an American citizen, I do not actually live in Alaska.
The laws of physics are the same whether you place the origin of your coordinate system in Alaska or Florida.

You are asserting a difference between SR and GR that does not exist. In both theories the speed of light is c in any set of inertial coordinates. In both theories the speed of light may be something other than c in non-inertial coordinates. The difference between the theories in this context being merely that inertial coordinate systems are global in SR and local in GR.
 
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  • #96


ApplePion said:
You correctly assume that as the light energy travels downwards it picks up "energy" due to the gravitational field, but you fail to realize that as the mechanical energy travels back uipwards it loses "energy" due to the gravitational field.

That's a statement, not a deconstruction.
 
  • #97
Q-reeus said:
Guss - re your #79, may I suggest you re-read #56 again. What applies to the spinning shaft there equally applies to your meshing gear setup. Both rotation speed and force are equally affected as measured *locally* in the gravitational potential. At any given height, power in the descending light beam will be exactly matched by ascending power in the meshing gears. Just a glorified 'conveyer belt' in effect. Both values are *equally* greater at the bottom, and lower at the top. The key is to appreciate power is related to the square of redshift (or blueshift depending on datum point chosen) as *locally* measured. And btw, prior argument to the effect that force impulses have to explained as 'photon exchange' is both missing the issue and just wrong. I'm no expert in solid state physics, but can say that solids are *not* held together by electromagnetic forces only - quantum interactions like Pauli exchange interactions are important. Hence covalent bonds, metallic bonds, as well as ionic bonds ,and in any real solid it is a mixture of these. As long as the gears hold together properly, all that matters is how gravity effects the local measure of things.

To the extent there are distinct exchange interactions due to overlapping wave functions, those should be dissected out of the book-keeping and dealt with separately. If they are a significant factor discussed in engineering physics, I'd like to see citations, and if they are, they will certainly complicate things with a classic quantum versus relativity wrestling match.

I don't want to assume that the gears are equivalent to a 'conveyer belt' if that doesn't help Guss. It doesn't help me, because then we have three down/up routes to deal with, rather than just the photons down, mechanical energy up. I don't want to knock down a straw-man, either, with rotors, conveyor belts, electric circuits, and the like, although I suspect there is a unified explanation.

Instantaneously, the gears are acting as a series of levers. I could give a picture as to how this would occur with any geometry of gears, but I'm too lazy.
 
  • #98
danR said:
To the extent there are distinct exchange interactions due to overlapping wave functions, those should be dissected out of the book-keeping and dealt with separately. If they are a significant factor discussed in engineering physics, I'd like to see citations, and if they are, they will certainly complicate things with a classic quantum versus relativity wrestling match.
danR: What I was saying there is that one cannot properly explain the mechanical transmission of power going on by trying to turn it into a chain of photon interactions and then saying those photons are redshifting just like in the downward light beam. It is simply a fact that a solid could never be stable if 'glued' purely by electrostatic interactions. When a solid is deformed, basically one is perturbing the electron cloud distributions within the solid, and that distribution is governed strongly by quantum mechanical rules, not electrostatics. As I say I'm no guru on this, but just Google for solid state physics, or materials science etc, and follow the leads. The crux of the matter is how gravitational potential distorts the metric locally and how this relates particularly here to local measure of frequency, velocity, and force in general. Do you accept that whether a force is of electrical or mechanical origin, it will transform under gravitational potential exactly the same?
I don't want to assume that the gears are equivalent to a 'conveyer belt' if that doesn't help Guss. It doesn't help me, because then we have three down/up routes to deal with, rather than just the photons down, mechanical energy up. I don't want to knock down a straw-man, either, with rotors, conveyor belts, electric circuits, and the like, although I suspect there is a unified explanation.
Agreed it has become somewhat fragmented with links to other threads etc, but I think usefully so, and mostly the metaphors have been apt in context. Conveyor belt simply meant a continuous looping of power with no net effect. Crude but drives home the point that the light and mechanical gear system are reacting to gravity in the same manner re power transmission. In #56 it was explained both transverse acting force and velocity have the same redshift factor - and again I repeat, that is a locally measured thing owing to gravitational potential (not gravitational force). Power is the product of the two. The light beam experiences the same squared redshift dependence. Thus they are always balancing - no net flow at any point.
Instantaneously, the gears are acting as a series of levers. I could give a picture as to how this would occur with any geometry of gears, but I'm too lazy.
What applies to the spinning shaft example will apply to the gears (or equivalent instantaneously oriented levers) since the meshing forces are also transverse. Bottom line: there is no mysterious power deficit to explain, and no mysterious continuous deformations in the gears to worry about. That was an artefact of assuming power was proportional to the redshift only, and not it's square as is the actual case.

I guess the simplest rough analogue I can think of is that of the rolling motion of a car tyre. Pick some white painted spot on the tyre wall. As it rolls downward, it hits a deformation zone (effect of gravity) where distances and stresses alter, but this process fully reverses each full rotation.
 
  • #99
Q-reeus said:
danR: What I was saying there is that one cannot properly explain the mechanical transmission of power going on by trying to turn it into a chain of photon interactions and then saying those photons are redshifting just like in the downward light beam. It is simply a fact that a solid could never be stable if 'glued' purely by electrostatic interactions. When a solid is deformed, basically one is perturbing the electron cloud distributions within the solid, and that distribution is governed strongly by quantum mechanical rules, not electrostatics. As I say I'm no guru on this, but just Google for solid state physics, or materials science etc, and follow the leads. The crux of the matter is how gravitational potential distorts the metric locally and how this relates particularly here to local measure of frequency, velocity, and force in general. Do you accept that whether a force is of electrical or mechanical origin, it will transform under gravitational potential exactly the same?

Agreed it has become somewhat fragmented with links to other threads etc, but I think usefully so, and mostly the metaphors have been apt in context. Conveyor belt simply meant a continuous looping of power with no net effect. Crude but drives home the point that the light and mechanical gear system are reacting to gravity in the same manner re power transmission. In #56 it was explained both transverse acting force and velocity have the same redshift factor - and again I repeat, that is a locally measured thing owing to gravitational potential (not gravitational force). Power is the product of the two. The light beam experiences the same squared redshift dependence. Thus they are always balancing - no net flow at any point.

What applies to the spinning shaft example will apply to the gears (or equivalent instantaneously oriented levers) since the meshing forces are also transverse. Bottom line: there is no mysterious power deficit to explain, and no mysterious continuous deformations in the gears to worry about. That was an artefact of assuming power was proportional to the redshift only, and not it's square as is the actual case.

I guess the simplest rough analogue I can think of is that of the rolling motion of a car tyre. Pick some white painted spot on the tyre wall. As it rolls downward, it hits a deformation zone (effect of gravity) where distances and stresses alter, but this process fully reverses each full rotation.

I had looked briefly into exchange interactions, and found a strong preoccupation with spin/magnetic/ferromagnetic issues, and again, I would want someone with the credentials to either parse out, or integrate, the components (potentially) implicated in the transmission of energy.

Since Guss has given us a photon generator, we're in luck because we can break this contraption down to one-photon at a time emitter, absorber/converter, gear (lever-equivalent in the instantaneous case) system. A rotor will complicate things, but we can treat the photon-quantized impulses as radial/transverse waves still using the forces under the current controversy.

So, I would take the forces issue to a reliable forces-Certified General Accountant, and have them look at Guss' system and return me, for a suitable fee of course, a complete tabularized account of the up-path photon, and quantum interaction, and whether the latter obeys some kind of GR regulations regarding redshifting, or whether they are offshore companies that don't pay GR taxes, or if they're in with the photon exchange particles in some kind of energy-laundering scheme, or whatever.
 
  • #100
Actually, discussion on exchange interaction is rather hard to come by on PF, and its contribution to the transmission of energy even more uncertain. If it is invoked as a factor in the mechanical return path in the present discussion, I think it needs some quantification.

https://www.physicsforums.com/showthread.php?t=208889&page=3
 
  • #101
danR said:
...So, I would take the forces issue to a reliable forces-Certified General Accountant, and have them look at Guss' system and return me, for a suitable fee of course, a complete tabularized account of the up-path photon, and quantum interaction, and whether the latter obeys some kind of GR regulations regarding redshifting, or whether they are offshore companies that don't pay GR taxes, or if they're in with the photon exchange particles in some kind of energy-laundering scheme, or whatever.
Good luck with finding such Certified Accountant - apart from being hard to come by he/she may charge quite a hefty fee!
 
  • #102
danR said:
Actually, discussion on exchange interaction is rather hard to come by on PF, and its contribution to the transmission of energy even more uncertain. If it is invoked as a factor in the mechanical return path in the present discussion, I think it needs some quantification.

https://www.physicsforums.com/showthread.php?t=208889&page=3
And the point driven home there was? Beginning at #33 and ending at #40 all I got was a differing of opinions. I could supply a counter link like here: https://www.physicsforums.com/showthread.php?t=409034 - entry #19 & following. This whole thing can be made infinitely complex if one wishes to chase the fine details of every possible QM/EM/GR interaction involved. And why stop there - wouldn't we need to burrow right down to the Planck scale and even beyond. One might then have to decide whether string theory or LQG or CDT or whatever is the correct TOE before being comfortable our exhaustive accounting is done good and proper. And let's not forget the real world contributions of friction, hysteresis, imperfect 'transducer' conversion efficiencies, finite acoustic wave generation effects, etc etc. What an ungodly mess! But the OP surely intended an idealized gedanken experiment where extraneous issues are ignored. Surely what matters is how gravity effects an otherwise straightforward power loop - sans gravity we agree their is nothing to consider here; just conversion from one form of energy/power to another, and thence recycle continuously. The intention is to find that the gravitational metric transformations top re bottom are consistent, and here we rely on the universality of such transformations.

As I asked you in #98 and repeat here: "Do you accept that whether a force is of electrical or mechanical origin, it will transform under gravitational potential exactly the same?" If you would care to answer that this time around, we can decide whether you still have a real issue. If your answer is no, well straight away I will construct a perpetuum mobile for your consideration from that choice. (I have only just realized there IS a real issue with mechanical transmission in a gravitational field in a more general setting using Schwarzschild metric, but none that applies to the OP's setup and our discussion of that)
 
  • #103
Q-reeus said:
As I asked you in #98 and repeat here: "Do you accept that whether a force is of electrical or mechanical origin, it will transform under gravitational potential exactly the same?" If you would care to answer that this time around, we can decide whether you still have a real issue. If your answer is no, well straight away I will construct a perpetuum mobile for your consideration from that choice. (I have only just realized there IS a real issue with mechanical transmission in a gravitational field in a more general setting using Schwarzschild metric, but none that applies to the OP's setup and our discussion of that)

The question is complex, so I will break it into parts:

The force is electromagnetic whether electrical (deBroglie) or mechanical (bond distortion). (Addendum: I'm satisfied that the exchange interaction is akin to quantum entanglement/correlation, is not a force, is FTL-instantaneous, cannot do work, cannot carry a signal, etc. and is not a significant component in this machine.)

Its exchange particle is the photon.

The photon solus, or part of a photon/bond domino cascade up the GR field, will lose energy exactly as the down photon gains.

I think we have to swap pronouns: you have to decide whether we have an issue. I think the matter is resolved, and answers to Guss' machine: the down and up photon energies are GR-symmetric. It will make a fine mobile, but not a classical perpetual motion machine that will solve our energy needs.
 
  • #104
danR said:
...I think we have to swap pronouns: you have to decide whether we have an issue. I think the matter is resolved, and answers to Guss' machine: the down and up photon energies are GR-symmetric. It will make a fine mobile, but not a classical perpetual motion machine that will solve our energy needs.
As long as we all agree we have a mobile and not a perpetuum mobile then if you and I are happy with our different perspectives, fine. No big deal - time for a kit-kat.:rolleyes:
 
  • #105
Q-reeus said:
As long as we all agree we have a mobile and not a perpetuum mobile then if you and I are happy with our different perspectives, fine. No big deal - time for a kit-kat.:rolleyes:

Also, all the big kids seem to have left the playground; but at least if we're both wrong, nobody important seems to care.:biggrin:
 

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