-
Members of the previous forum can retrieve their temporary password here, (login and check your PM).
Real perpetual motion??
- Thread starter SWIMfriend
- Start date
I do get it, really, you are proposing there could be a system where the work you get out of the mechanical part [which would be less than (the density of the water) x (acceleration due to gravity) x (the volume of the object) x (the height of the water column); i.e., buoyant force x distance--which is the amount of work needed to get the buoyant object to the surface, if you try to extract more work from that part of the cycle the object will not rise] is greater than the work required to either disassemble or reassemble the object (because only one of those can be spontaneous without running afoul of thermodynamics) plus the work required to transport it back down so the cycle can start over (otherwise you are relying on either "magic" or an external force, i.e., either impossible or not really perpetual motion).SWIMfriend said:
Without details about the (dis/re)assemble process it is impossible to calculate the work needed there. However, we can assume that the work required to transport the formerly buoyant object back down to the bottom, regardless of its form, will at least be equal to the work it took to get it to the surface because the same amount of mass needs to be moved the same distance. So, even if you are able to do the transport without doing more work than it took to get the object to the surface, you are likely going to end up with a deficit because of the (dis/re)assemble process.
It doesn't really matter if the connection between the proposed mechanical and chemical parts of the system are direct/"causal" or indirect, because unless it is a closed system you don't have perpetual motion (as entropymancer pointed out).
Now, if you were to back away from the perpetual motion claim and try to use the ocean (or atmosphere) as an infinite capacity heat sink you would be in much the same game as the wave->energy and wind->energy people... and the question becomes, `can it be done more efficiently?'
HTH
SWIMfriend said:
I guess I'm just not sure how it's relevant if we're looking at it from the view of energy in the system.
Running the machine does work, but in so doing removes energy from the system. This work cannot be used to put more energy back into the system than it has taken out (I assume you accept this premise?) so this represents a net decrease of energy in the system (the reservoir). And recall that we haven't actually returned the system to its starting state, which would involve moving the buoyant object back to the main surface of the reservoir, which would take more energy to accomplish.
Repeatedly changing the phase of the buoyant material will also cost energy from the system. The difference in the energy of the buoyant material as it transitions from its solid to liquid states is the same as the difference as it transitions from liquid to solid. But again, there is no perpetual motion. Regardless of how the phase change happens, this costs energy from the system.
Even if the work done by the machine were sufficient to pay for the phase change, the system is still losing energy as the machine runs.
Tsehakla said:
Exactly.
Very interresting idea to use that tube with water and a buoyant object.
SWIMfriend, you approach this subject with the additude of "let's see how we can debunk this".
Could you perhaps leave some room for the possibility that it cannot/need not be debunked and that there IS a possibility to create such an energy device?
Don't just assume it's impossible, even if all known laws of physics indicate that.
That pipe-water-buoyancy-idea inspires me greatly to start experimenting.
I wanna urge you to experiment too. Who knows what you may find.
SWIMfriend, you approach this subject with the additude of "let's see how we can debunk this".
Could you perhaps leave some room for the possibility that it cannot/need not be debunked and that there IS a possibility to create such an energy device?
Don't just assume it's impossible, even if all known laws of physics indicate that.
That pipe-water-buoyancy-idea inspires me greatly to start experimenting.
I wanna urge you to experiment too. Who knows what you may find.
Oops. That's wrong. The water would end up DISPLACING air--and the result would be the same that The Traveler advised about.
Tsehakla said:
No, I disagree there (and of course, if you're correct, the entire idea COMPLETELY fails). If the buoyant object is buoyant because of its FORM, and the form dissolves--you can then claim it can diffuse evenly throughout the water. Styrofoam (polystyrene) is just C and H--which can surely disperse and diffuse throughout any body of water; but put 'em together right, and you have something that's very buoyant, i.e., far less dense than water (I know I'm not strictly talking about "dissolving" in this case--but the logical principle is the same).
The main idea I'm trying to investigate is changing the LOGIC of the operation of a PM machine (or an apparatus that can produce work) such that you can circumvent the "work in = work out--at OPTIMUM" ultimate thermodynamic brick wall.
I'm not really trying to SELL this idea, so much as I am trying to remark that the scenario that I've outlined is QUALITATIVELY DIFFERENT from all other "traditional" PM attempts. I find the difference intriguing; that's all.
Entropymancer said:
Again, I think I understand these points. My interest is the IDEA. Let me rephrase it.
Suppose it happened that, in this world, the energy cost of chemically assembling C and H into styrofoam, and disassembling them BACK into C and H was VERY SMALL. "Small" is always a RELATIVE term, after all. And I don't think anything about the atomic energetics of chemistry has to relate to GRAVITY forces in a way that MUST foil my apparatus.
As it happens, the cost of the styrofoam stunt WILL foil my apparatus (I'm totally ASSUMING that, but I don't think you're going to disagree with me). THEN, the apparatus wouldn't work. But (again) I say that failure is mere BAD LUCK. Why? Because the energy derived from the apparatus (from "using" the force built in to it) is in NO WAY DERIVED from the chemistry involved in making styrofoam. See what I mean?
The damn thing would WORK. REALLY WORK. If it weren't for the UNFORTUNATE FACT that styrofoam is a little HARDER to make, rather than a little EASIER to make. That's all I'm saying.
And I've never THOUGHT of the problem/question quite that WAY before, and I find it INTERESTING. And, in fact, it has given me an idea (which, hehe, I'm keeping to myself) about an approach (in a completely different sort of apparatus--nothing even to do with buoyancy) that, dammit, I'm thinking MIGHT ACTUALLY FREAKING WORK to make a PM-type device--and I'm a guy who would have chopped MY OWN HEAD OFF two weeks ago for saying something like that!
Questioning the LOGICAL UNDERPINNINGS of the problems of PM to me suggests areas of thought for CIRCUMVENTING the thermodynamic problems...and I KNOW how stupid that sounds!
I'm not sure that you are understanding... no matter how small the energetic cost to assemble the object, you're not going to have perpetual motion as long as the system is closed. You're losing energy in two places: doing work with the machine takes energy from the system, and assembling the object takes energy. No matter how small the energy to assemble the object is, you're never going to be able to use the work produced by the machine to replace the energy lost operating it if the system is closed.
You can only produce perpetual motion by opening the system to the environment so the lost energy can be compensated (in any of a variety of ways). And while this produces perpetual motion, it's not a perpetual motion machine. Perpetual motion is easy; I've got a solar powered flower gadget that perpetually bobs back and forth... but it's not a perpetual motion machine. It just gets the energy from an external source (the sun).
You can only produce perpetual motion by opening the system to the environment so the lost energy can be compensated (in any of a variety of ways). And while this produces perpetual motion, it's not a perpetual motion machine. Perpetual motion is easy; I've got a solar powered flower gadget that perpetually bobs back and forth... but it's not a perpetual motion machine. It just gets the energy from an external source (the sun).
Entropymancer said:
I disagree. Ignoring the energetic cost of disassembling and reassembling the buoyant object, the rest of the apparatus supplies FREE ENERGY (ignoring friction, etc.). The cost of energy is pushing the buoyant object slightly under water, and the return is the full trip upward (AND, if you could figure out how to get it OUT at that height, your could drop IT, in addition to the weight you lifted via the pulley apparatus, for a bonus--but that bonus has been expired by The Travelers observation that there's no way to do it without allowing air into the system [or using energy to, of course, push it all the way back down against its buoyancy force]).
The analogy to "typical" PM machines is that they would work JUST DANDY if one could "turn off" forces at no cost (like gravity or magnetism). In this case, you can easily get energy, if only you can get a buoyant object "out of the way,"i.e., if you can turn off an OBJECT rather than a FORCE. Yes, the buoyant object is at the point of lowest potential energy of the apparatus, but if it could DISSOLVE, it could return to the area of HIGHEST potential energy (near the bottom of the tube) at no energy cost, via random diffusion in a liquid.
The difference between this and other PM devices is that, in the others, there's a need to "turn off" static forces (for no cost in energy), that no one could IMAGINE being able to do--they seem like fundamental constants of the universe). In this, there's a need only to DISSOLVE AN OBJECT--a common occurrence, which, it probably JUST SO HAPPENS, costs slightly too much energy.
But, if one takes an extreme example--say at the bottom of the thousand mile deep ocean...then I'm not so sure (but in that case, even the slightest friction in one's pulley mechanism--not to mention a thousand miles of monofilament
--would be it's undoing). Strangely, it might turn out in that case that there IS NO, and perhaps CANNOT BE, any practical way to actually harvest the work created.EDIT: Oh, wait. There WOULD be a way: instead of having a thousand mile pulley system, you have convenient stages on the way up, where the object is attached to new pulleys, and the work is harvested at each stage, a bit at a time. That would obviate the need for a thousand mile big dynamic harvesting apparatus (and change it to shorter dynamic apparati, combined into a large "static" configuration).
EDIT: One more thing, to be clear: I personally FREELY EQUATE the terms "perpetual motion" and "free energy." So, if one has a machine that provides free energy, then I feel free to call that a "perpetual motion machine," and vice versa. Sorry if that has caused any confusion.
OK. So that's the best way to express my idea. In traditional attempts, PMs could easily work if one could turn off "inconvenient" FORCES at the right time. In this idea, the PM could work if one could turn off an inconvenient OBJECT at the right time.
Of course, you can turn on and off an electromagnetic force, but it costs energy to do so--and in THAT case, it obviously fits right in as part of the calculation. One can't turn permanent magnets on and off (without lots of energy), however, nor gravity.
Objects can be "turned off and on" at, we're aware, somewhat more energy cost than we'd all like. But unlike examples of traditional PMs, the energy of turning on and off a buoyant object is not RELATED (or only related LOGICALLY) to the energy one can harvest from this machine.
The situations have a similar form, but for me it's a revelation that one can substitute OBJECTS for FORCES when thinking about PMs. To me that opens at least some considerations that I don't think are often analyzed.
Of course, you can turn on and off an electromagnetic force, but it costs energy to do so--and in THAT case, it obviously fits right in as part of the calculation. One can't turn permanent magnets on and off (without lots of energy), however, nor gravity.
Objects can be "turned off and on" at, we're aware, somewhat more energy cost than we'd all like. But unlike examples of traditional PMs, the energy of turning on and off a buoyant object is not RELATED (or only related LOGICALLY) to the energy one can harvest from this machine.
The situations have a similar form, but for me it's a revelation that one can substitute OBJECTS for FORCES when thinking about PMs. To me that opens at least some considerations that I don't think are often analyzed.
This is where you start relying on "magic"... if the object spontaneously disassembles it will not spontaneously reassemble, you will be left with its components dispersed throughout the medium--and it will be necessary to apply a force to do the work needed to "put 'em together right."SWIMfriend said:
Logic is an abstract thing and doesn't apply any usable force; if it is sound it will lead you from truth to truth though. Keep in mind that thermodynamics is already discussed/expressed logically, using the language of mathematics (which is a sound logical system), so if it it wrong in some way you will be able to prove it using mathematics... that will most likely be easier and less error-prone than fiddling with mechanical and/or chemical systems.
I suspect that "all" is too strong, but it really depends on how you define "traditional PM attempts." AFAICT, traditionally, all attempts at PM have failed.
If you do happen to rewrite the laws of thermodynamics, whether by mathematical proofs (i.e., logic) or by constructing a perpetual motion machine, make sure you put "swim" somewhere in the title so we know it was you.
I'm fully granting that there's an energy cost to make the object disappear and reappear. I fully grant that it could be calculated exactly. And I fully grant (from my own experience) that in this case, it would no doubt require more energy than one can harvest just from the buoyant object going up the tube. What I'm saying is that it's only COINCIDENCE that things balance that way. It's only COINCIDENCE that more energy is required to MAKE things, than SOME of the contraptions those things could be a part of that produce energy.Tsehakla said:
I think I expressed best how I see the problem in my last post. I'm not trying to say that thermodynamics is illogical. I guess what I'm saying is, that in such problems, one never includes calculations for the energy required to PRODUCE the elements used in the apparatus--when examining the thermodynamics of a process of the apparatus. In that way I mean that those elements of the apparatus exist almost AS abstractions--and the thermodynamic calculations don't end up addressing them.Tsehakla said:
hehe. I DO have an idea I want to investigate (when I get what I'm working on NOW off my table!). If it works, you will be among the FIRST to know, I promise. And if it FAILS, I will also describe it here and discuss where it fails, and what I didn't see. It's similar in that it depends on some aspects of change in the object, when subjected to static forces. In my mind it's very DIFFERENT from anything I've seen or heard approached or discussed; and the idea arose in the discussion of this business. But I'm not NEARLY in a position to understand how it would reflect on thermodynamics as it is now. Probably it's nothing. We'll see. I'll be happy to describe it as soon as I determine why it MUST fail. It doesn't involve anything as complex as producing objects--just "modifying them" during the process.Tsehakla said:
btw, let's idealize the apparatus:
The mechanical work collector:
One can forget about air pressure, if one has a tube closed on both ends, filled with water, and set upright in a gravitational field. At the bottom of the tube is a magical, frictionless, weightless connection apparatus such that, when a buoyant object (an object less dense than the least dense portion of the water--at the top) starts from the bottom of the tube and moves to the top, the work generated is used to pull up a weight on a pulley on the outside. It's obvious that, each time a run is made, a weight could be pulled higher and higher--or new weights could be added to the first weight. The outcome would be that one could produce and store as much energy as one wanted, in this gravitational field, by repeated runs of allowing a buoyant object to run up the tube. The TALLER the tube, the more work that can be harvested in a single run.
The object synthesis cost:
The buoyant object "magically" dissolves at the top of the run (by magic I mean let's not think about ACTUALLY doing the chemistry, and the apparatus needed to do the chemistry), and is magically reconstituted at the bottom. The atoms or molecules required are COLLECTED at the bottom, after they had dissolved, AS THEY APPEAR FOR USE, by the random process of diffusion. This process of reconstituting the object will COST energy. But there is NO COST for the atoms and molecules of the object to randomly diffuse throughout the water, and eventually end up at the bottom (but, of course, there's an ENTROPY issue of re-ordering randomly placed objects). Because there's no cost to the diffusion (other than time, with a VERY tall pipe, you would have a VERY long wait before all the molecules visited the bottom of the tube), there's NO DIFFERENCE in synthesis cost related to the height of the tube.
Now let's eliminate one factor right away: it IS necessary that the temperature of the system is maintained. It's not going to work at absolute zero. But normally, ALL PM machines are granted "room temperature," so let's grant that here. With that granted, I think we can allow for permanent random diffusion of the molecules.
The challenge:
The question then becomes this: Is there NO HEIGHT POSSIBLE where the work created by the long trip up could be greater than the synthesis cost of the object--which remains the same no matter what the height of the column is? I don't see how someone could prove there IS no such height possible. It seems to me that with ENOUGH height, it would surely be possible to harvest more mechanical work than the synthesis energy cost.
EDIT: One thing I think we should avoid: The idea that the synthesis cost would be greater with higher tubes, because the water pressure would be greater. I already made the case in an earlier post that sea creatures (and even bacteria) live at the bottom of the sea, and surely manufacture the full range of biological molecules that land creatures manufacture. I don't really KNOW, but I'm quite sure, that it doesn't require VASTLY MORE ENERGY for the sea creatures to perform these syntheses than is does for land creatures. I think we can approximate that the synthesis cost will remain the same no matter what the height of the tube. Heck, it might even DECREASE as the tube gets higher--who's to say? The only thing that would seriously change, as far as I can tell, is the TIME it would take for the dissolved components to diffuse back down to the bottom. So...I guess, while changing the height will work well for changing the amount of WORK accomplished, it probably wouldn't change the work per TIME very much: the POWER would be limited.
The mechanical work collector:
One can forget about air pressure, if one has a tube closed on both ends, filled with water, and set upright in a gravitational field. At the bottom of the tube is a magical, frictionless, weightless connection apparatus such that, when a buoyant object (an object less dense than the least dense portion of the water--at the top) starts from the bottom of the tube and moves to the top, the work generated is used to pull up a weight on a pulley on the outside. It's obvious that, each time a run is made, a weight could be pulled higher and higher--or new weights could be added to the first weight. The outcome would be that one could produce and store as much energy as one wanted, in this gravitational field, by repeated runs of allowing a buoyant object to run up the tube. The TALLER the tube, the more work that can be harvested in a single run.
The object synthesis cost:
The buoyant object "magically" dissolves at the top of the run (by magic I mean let's not think about ACTUALLY doing the chemistry, and the apparatus needed to do the chemistry), and is magically reconstituted at the bottom. The atoms or molecules required are COLLECTED at the bottom, after they had dissolved, AS THEY APPEAR FOR USE, by the random process of diffusion. This process of reconstituting the object will COST energy. But there is NO COST for the atoms and molecules of the object to randomly diffuse throughout the water, and eventually end up at the bottom (but, of course, there's an ENTROPY issue of re-ordering randomly placed objects). Because there's no cost to the diffusion (other than time, with a VERY tall pipe, you would have a VERY long wait before all the molecules visited the bottom of the tube), there's NO DIFFERENCE in synthesis cost related to the height of the tube.
Now let's eliminate one factor right away: it IS necessary that the temperature of the system is maintained. It's not going to work at absolute zero. But normally, ALL PM machines are granted "room temperature," so let's grant that here. With that granted, I think we can allow for permanent random diffusion of the molecules.
The challenge:
The question then becomes this: Is there NO HEIGHT POSSIBLE where the work created by the long trip up could be greater than the synthesis cost of the object--which remains the same no matter what the height of the column is? I don't see how someone could prove there IS no such height possible. It seems to me that with ENOUGH height, it would surely be possible to harvest more mechanical work than the synthesis energy cost.
EDIT: One thing I think we should avoid: The idea that the synthesis cost would be greater with higher tubes, because the water pressure would be greater. I already made the case in an earlier post that sea creatures (and even bacteria) live at the bottom of the sea, and surely manufacture the full range of biological molecules that land creatures manufacture. I don't really KNOW, but I'm quite sure, that it doesn't require VASTLY MORE ENERGY for the sea creatures to perform these syntheses than is does for land creatures. I think we can approximate that the synthesis cost will remain the same no matter what the height of the tube. Heck, it might even DECREASE as the tube gets higher--who's to say? The only thing that would seriously change, as far as I can tell, is the TIME it would take for the dissolved components to diffuse back down to the bottom. So...I guess, while changing the height will work well for changing the amount of WORK accomplished, it probably wouldn't change the work per TIME very much: the POWER would be limited.
SWIMfriend said:
I had thought you were just trying to violate the second law of thermodynamics... but from this statement it seems that you are trying to violate the first law as well!
Remember, energy cannot be created or destroyed. Even if we assume an ideal process where no energy is lost to heat, we still have ΔU = -W. There is no such thing as "FREE ENERGY". That work has come out of the system in the form of energy. Am I reading correctly, that you are actually contending that this is not the case, that energy can in fact spontaneously appear? That would contradict the principle of law of conservation of energy, which would be quite a revolutionary thing to overturn; All of physics would have to be rewritten. Is there any evidence I should be aware of indicating that this is the case?
This is why I say that the energy to disassemble and reassemble the object (lets call that energy ΔU2) is irrelevant. That it takes any energy at all means that with each cycle, the system is losing some ΔU+ΔU2, such that |ΔU+ΔU2|>|W|. Even if you could convert 100% of that work into energy and add it back into the system, the system would still have less energy than when it started. Unless you're allowing energy to be introduced to the system from some external source, then you're necessarily going to be depleting a finite amount of energy that was present in the system at the start.
In this argument, I'm not invoking the second law of thermodynamics at all. I am simply taking your premise and applying the first law of thermodynamics to it. Even with all process idealized beyond what's possible in reality (i.e. nothing lost as heat when converting between work and energy), your contraption still fails as a perpetual motion machine based on only the first law of thermodynamics. The only way to make it work indefinitely is to allow energy to be added to the system from an external source.
Entropymancer said:
Well, OK, sure. When you do the FIRST TRIAL, you are getting energy that had to be SET UP by lifting the tube full of water against gravity, etc.
But IT IS TRUE: IF the object can be made to "disappear," and it you can have ANOTHER object handy (that you claim doesn't "cost anything," then you can keep putting buoyant objects into the tube, and they will KEEP DOING WORK each time. And you can STORE that work each time. I don't need to do calculations, or think about laws of thermodynamics, to know that. I just have to look at the apparatus.
It's no different than saying your apparatus is dropping bowling balls from a ladder. Of course it's ridiculous if you don't CONSIDER that you have to lift the bowling ball UP each time--but then again, if you could arrange for bowling balls to simply APPEAR at the top of the ladder--then, yes, you could generate FREE ENERGY, as much as you pleased.
It's the same here, but instead of the very IMPROBABLE feat of magic bowling balls appearing at points of high potential energy, we're talking about the more MUNDANE phenomenon of dissolving objects, and re-crystallizing them. Yeah, if the cost of that is LOW, then you can generate as MUCH FREE ENERGY AS YOU PLEASE from this apparatus. No question about it. That's my whole point--and it's obvious. I mean it's obvious to me--unless I've made a silly mistake in thinking that pushing the object into the water only a CENTIMETER is going to take as much energy as the object can generate moving up the entire column. I really don't think so. I think the amount of energy that can be harvested by the object floating to the top of the column would equal the amount of energy you would have to use to push it DOWN the length of the column. In this case, we have to push it down only a tiny fraction of that distance.
Yes, if one ignores the COST of disassembling and reassembling a buoyant object, then one can generate an infinite amount of "free energy" from this system--but you're right, for the first (let's say, "few" ) trials you would be paying for the work necessary to lift the tube of water in a gravitational field. Once you paid that, then its ALL FREE!
EDIT: BTW, I'll be away tomorrow. It'll be about 24 hours before I can respond to posts again.
I think you're still misunderstanding me. The energetic cost of pushing that first object underwater is negligible. I'm not concerned with it in the slightest.
For simplicity, let's consider the (basically impossible) case where the initial cost to submerge the object is zero, and even the cost of disassembling and reassembling the objects is zero. I'm talking about a situation where there is no energetic cost to initiate either the first cycle or any subsequent cycle. And again, we'll idealize the machine further and assume that no energy is lost to heat as the object rises in the tube. I contend that you still will not have a perpetual motion machine that can do useful work or provide you with a source of energy.
Even with all of these idealized assumptions, we are still faced with the first law of thermodynamics... basically the law of conservation of energy. We still have ΔU = -W. That is, when we do some quantity of work, W, with the machine, the internal energy of the system (which in this case is the water reservoir and tube) decreases by that same amount of energy, W. The work isn't free, because we cannot spontaneously create energy out of thin air (recall that work is a form of energy). That energy has to come from somewhere, and in this case "somewhere" means the water reservoir/tube system.
Even if we imagine that it costs absolutely no energy to create another object at the bottom of the tube and run the process a second time, we're again going to have a decrease in the internal energy of the system equal in magnitude to the work done by the system. No matter how many times we do this, the sum of all the work extracted from the system will always be equal to the total decrease in the internal energy of the system. But there is only a finite amount of energy contained in the system; when this is exhausted, we can extract no more work.
I will grant that in this magical hyper-idealized system (where we ignore all energetic costs in initiating each cycle, and imagine that no energy is ever lost in the form of heat), you could have perpetual motion... if after each cycle you feed all of the work energy you obtained back into the system (and none of it is lost to heat), then at the end of each cycle the internal energy of the system would equal its value at the beginning of the cycle. But you could never obtain any useful work from this perpetual motion device, because every iota of work you obtain must be fed back into the system in order for it to be perpetual. In order to obtain useful work (or any other sort of energy) we are, by definition, removing energy from the system. And once we start removing energy from the system (which contains a finite quantity of energy), we no longer have a perpetual motion machine. This is a fundamental consequence of the law of conservation of energy.
As a sidenote, I would contend that you could not create such a hyper-idealized system in reality. There is no way to prevent some energy being lost to heat in a real system like this, so even if there was zero energetic cost to initiate each cycle and you were feeding all work back into the system you would not have perpetual motion. But that's just a sidenote, a mere tangent to the point that I'm trying to make.
My main point, which you do not seem to be grasping, is that energy (whether it's work or any other form of energy) cannot simply appear out of thin air. With reference to work specifically, if we ignore any and all possible ways in which energy might be lost in the process, we are still left with ΔU = -W. That equation is crucial.
Put another way: If a closed system has an internal energy of 100 joules, we cannot extract 200 joules of energy from that system, much less ∞ joules.
You're no longer talking about perpetual motion; you're talking about literally free energy, which we can simply magick into existence through a clever loophole. To justify this, you must provide evidence indicating that the law of conservation of energy is incorrect.
For simplicity, let's consider the (basically impossible) case where the initial cost to submerge the object is zero, and even the cost of disassembling and reassembling the objects is zero. I'm talking about a situation where there is no energetic cost to initiate either the first cycle or any subsequent cycle. And again, we'll idealize the machine further and assume that no energy is lost to heat as the object rises in the tube. I contend that you still will not have a perpetual motion machine that can do useful work or provide you with a source of energy.
Even with all of these idealized assumptions, we are still faced with the first law of thermodynamics... basically the law of conservation of energy. We still have ΔU = -W. That is, when we do some quantity of work, W, with the machine, the internal energy of the system (which in this case is the water reservoir and tube) decreases by that same amount of energy, W. The work isn't free, because we cannot spontaneously create energy out of thin air (recall that work is a form of energy). That energy has to come from somewhere, and in this case "somewhere" means the water reservoir/tube system.
Even if we imagine that it costs absolutely no energy to create another object at the bottom of the tube and run the process a second time, we're again going to have a decrease in the internal energy of the system equal in magnitude to the work done by the system. No matter how many times we do this, the sum of all the work extracted from the system will always be equal to the total decrease in the internal energy of the system. But there is only a finite amount of energy contained in the system; when this is exhausted, we can extract no more work.
I will grant that in this magical hyper-idealized system (where we ignore all energetic costs in initiating each cycle, and imagine that no energy is ever lost in the form of heat), you could have perpetual motion... if after each cycle you feed all of the work energy you obtained back into the system (and none of it is lost to heat), then at the end of each cycle the internal energy of the system would equal its value at the beginning of the cycle. But you could never obtain any useful work from this perpetual motion device, because every iota of work you obtain must be fed back into the system in order for it to be perpetual. In order to obtain useful work (or any other sort of energy) we are, by definition, removing energy from the system. And once we start removing energy from the system (which contains a finite quantity of energy), we no longer have a perpetual motion machine. This is a fundamental consequence of the law of conservation of energy.
As a sidenote, I would contend that you could not create such a hyper-idealized system in reality. There is no way to prevent some energy being lost to heat in a real system like this, so even if there was zero energetic cost to initiate each cycle and you were feeding all work back into the system you would not have perpetual motion. But that's just a sidenote, a mere tangent to the point that I'm trying to make.
My main point, which you do not seem to be grasping, is that energy (whether it's work or any other form of energy) cannot simply appear out of thin air. With reference to work specifically, if we ignore any and all possible ways in which energy might be lost in the process, we are still left with ΔU = -W. That equation is crucial.
Put another way: If a closed system has an internal energy of 100 joules, we cannot extract 200 joules of energy from that system, much less ∞ joules.
You're no longer talking about perpetual motion; you're talking about literally free energy, which we can simply magick into existence through a clever loophole. To justify this, you must provide evidence indicating that the law of conservation of energy is incorrect.
Hmm I've been thinking...
If you had such a setup as in the video, you could use a strong magnet connected to a buoyant airfilled balloon.
If the tube was square-shaped instead of cylindrical and attatched to the long side of a rectangulair water-reservoir,
then by letting the magnet-balloon float up in the square-shaped shaft, a metal object (attracted by the strong magnet) could be lifted along the
outside of the square shaft, untill it could be dropped from significant hight to yield energy.
The balloon could be deflated to sink the magnet and restart the cycle.
You'd need a proper magnet though. Perhaps one of those found in busted soundsystems are powerfull enough.
Then I'd need to figure out how to release the metal object from the magnet and inflating/deflating the balloon,
without using more energy than the falling metal objects can yield.
If that would work than it would pretty much be a perpetual motion device giving energy output in the form of electricity.
I should get to my drawing book. =)
If you had such a setup as in the video, you could use a strong magnet connected to a buoyant airfilled balloon.
If the tube was square-shaped instead of cylindrical and attatched to the long side of a rectangulair water-reservoir,
then by letting the magnet-balloon float up in the square-shaped shaft, a metal object (attracted by the strong magnet) could be lifted along the
outside of the square shaft, untill it could be dropped from significant hight to yield energy.
The balloon could be deflated to sink the magnet and restart the cycle.
You'd need a proper magnet though. Perhaps one of those found in busted soundsystems are powerfull enough.
Then I'd need to figure out how to release the metal object from the magnet and inflating/deflating the balloon,
without using more energy than the falling metal objects can yield.
If that would work than it would pretty much be a perpetual motion device giving energy output in the form of electricity.
I should get to my drawing book. =)
Entropymancer said:
That's right. Because, it's true, the potential energy of the buoyant object at the bottom of the tube is EQUIVALENT to the work produced as it rises up the tube (that's what your equation states). So, when you get that work OUT, normally, to reset the mechanism, you could have to do the exact amount of work in the OPPOSITE direction, to put the object back at it's original point of potential energy.
But if the object DISAPPEARS, and another one APPEARS at the point of higher potential energy, then SURE, you simply get "W" amount of work each time you "allow" the object to spontaneously move from higher to lower potential energy. As I said before, it's the same as dropping bowling balls: if they just spontaneously APPEAR at the top of the ladder, then you can collect as much work AS YOU PLEASE by simply continuing to drop them. You don't have to "drain" any energy from your system. If effect, you're "mysteriously" being given "free" energy by the genie who is making the bowling balls appear at the top of the ladder.
So, the PHYSICS KEY to my scenario is this: the ATOMS from the disassembled object can DIFFUSE through the water BACK TO THE POINT OF HIGH GRAVITATIONAL POTENTIAL ENERGY. So you BYPASS that problem--that is part of ALL other PM machines.
Sure, the water temp would need to remain constant; and I see no reason it wouldn't, if you declare the entire apparatus a "system," so no heat can be "lost" to the surroundings. In fact, the water would probably heat up (from the friction of the object rising), and you could INCLUDE that in the energy produced (all of this, of course, is not counting the COST of disassembling and reassembling the object.
So, normally you would have to PUSH the object back down after it produces work while floating up. And the HIGHER THE TUBE, the MORE WORK it would take to push it back down--it would also equal (ideally) the work achieved as it rose. But height DOESN'T MATTER when we're talking about the diffusion of atoms in a liquid. Thus, the work you could collect by the rise of the object will INCREASE linearly with the height of the column, but the cost of retrieving the atoms at the point of high potential energy will remain ZERO. So, if the synthesis/destruction costs are CONSTANT (approximately), but the work can be INCREASED as much as you please, there must come a point where the work created can be GREATER than the constant synthesis costs.
To refute that you can't retreat to "thermodynamic formulas." Those formulas don't RECKON with disappearing objects (just as they don't reckon with forces that can be turned on and off at no cost).
How about answering this: Do you agree with me that, if one could turn the magnetic force on and off at no cost, that it would be child's play to develop a PM machine--or a machine that would supply infinite free energy? The machine could simply be a suspended magnet over a metal object. When the magnet turns on the object is lifted in a gravitational field, and when turned off it falls in a gravitational field. Force over a distance is work. One could harvest an infinite amount of work/energy from such an apparatus.
So, the relevant "laws" don't take into account forces that can be turned on and off for free, or (as in the example under discussion) objects that can disappear and reappear at different places within a system of static forces (i.e., varying potential energies).
SKA said:
We are just "abstracting away" the need for the magnet apparatus--for the purposes of the discussion; although it IS a way to avoid the inefficiencies in my "pulley system."
But your idea of inflating the balloon presents one strong problem: The higher the column, the MORE WORK that will be required to fill the balloon at the bottom of the tube. That problem doesn't work around the PROPORTIONALITY issue as well as an actual CHEMICAL SYNTHESIS of an object--we can suppose that it wouldn't require significantly more amounts of energy for synthesis at the bottom of a high tube (and it MIGHT even require less energy--"pressure" usually has the same directional effect as "heat" in the rate and direction of chemical reactions.
Depending on how that statement is meant to be interpreted, it's either completely false or completely pointless: If you consider an object dissolving to be a form of "disappearing", it's totally false. Thermodynamic formulas account for things such as dissolving materials and phase changes. If you mean literally disappearing, then it's completely pointless. The only way for matter to cease to exist is to turn into energy.SWIMfriend said:
Regardless, no matter which way you meant that claim, the law of conservation of energy still applies. Regardless of whether you consider thermodynamics relevant, a closed system contains a finite amount of energy, and you cannot extract more than that finite quantity unless you open the system and allow external forces to compensate for the extracted energy.
I'm not saying that the basic idea wouldn't work; I'm just saying that it would not work with a closed system, which is to say that it would not be a perpetual motion machine, just an ordinary machine capable of producing motion perpetually.
SWIMfriend said:
It's a completely null point. If you could turn a magnetic force on and off at no cost, then that force could not be capable of producing work. What you're talking about is magic. If I could put on a pointy hat, wave my magic wand, and say "Abracadabra Alakazam" to make three toes sloths materialize from thin air, then I could use their mass and potential energy to make a perpetual motion machine. It's true in a facile sense, but still totally irrelevant.
That's because forces that can turn on an off for free must necessarily be incapable of applying any force. Objects that can disappear and reappear at different places (without applying the appropriate compensating energy) must necessarily be objects which are incapable of having any potential energy (which is to say, they must have no mass).
SWIMfriend, I find you to generally be a rational member of this forum. Obviously you find this notion very intriguing, but I really think you need to take care that it does not run off with your common sense. To make this notion physically feasible, the system must be open, or else there is only a finite quantity of energy that can be tapped from it. It simply cannot work as a closed system.
The system that you're describing is founded on entirely fictional principles, and entirely neglects the reality of physics. You're basically saying, "If we imagine that the world did not operate in accordance with the law of conservation of energy, we could have perpetual motion and free energy." Well yes, we could. But unless you can provide some compelling reason why we should disregard a law that has shown itself to be 100% in accordance with every single physical observation ever made, then this is purely magical thinking.
And one small aside:
No. The equation states that the work produced is equal to the difference between the total internal energy of the object, reservoir, and tube combined, before and after the buoyant object rises. It seems that you're still missing that point: The work energy is not extracted from the buoyant object only, but from the water reservoir as well. And in a closed system, dissolving the buoyant object restores none of the internal energy of the system that has been lost to work.SWIMfriend said: