The idea of the machine is that it is supposed to operate at ambient temperature, using the ambient temperature to do work. Of course, this is impossible, as any machine that you build will work 50% of the time in the opposite direction, due to the properties of statistical mechanics.Jabbah said:
Perpetual Motion machine... it doesn't work...
- Thread starter zidane1strife
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Oh, I'm pretty sure we can do it now (though did you mean lead into gold?), but it would just be economically infeasible.Tahir2 said:
To turn lead to gold, since lead is more massive, you'd need to get the lead to shed some of its protons. This would involve bombarding the lead with neutrons until it becomes unstable, then allowing it to decay. It may be very difficult to get it to stop decaying at gold, though, once you start it. I'd be rather surprised if some science labs hadn't done this for kicks, with a few micrograms of the stuff.
Actually I did mean lead into gold and retyped it after thinking I had it the wrong way.
Stupid brain.
It has been done AFAIK but the expense of turning lead into gold is considerably more than just buying lead and gold, employing an illusionist and having a magic show with a circus and lions and tigers... erm. And lots of candy.
Stupid brain.
It has been done AFAIK but the expense of turning lead into gold is considerably more than just buying lead and gold, employing an illusionist and having a magic show with a circus and lions and tigers... erm. And lots of candy.
Chalnoth said:
I highly doubt a lab would fund such a a project even for the sake of "gee-whiz" chemistry. It takes a lot of time and money to work with a particle accelerator. You'd probably find trace amounts of gold in nuclear reactors. But we're talking gold in the amount of sub nanomoles. Consider that gold atom to be lost in the vasteness of the universe.
drpepper said:I highly doubt a lab would fund such a a project even for the sake of "gee-whiz" chemistry. It takes a lot of time and money to work with a particle accelerator. You'd probably find trace amounts of gold in nuclear reactors. But we're talking gold in the amount of sub nanomoles. Consider that gold atom to be lost in the vasteness of the universe.
I remember a group of scientist actually doing this. Transmuting lead into gold with a particle accelerator just for the sake of it. If I remember correctly it was a bunch of crazy Russian scientist that tried that as a side-project.
Chalnoth said:
Its the fact that this machine relies on the ambient temperature that makes my point. It cant be a perpetual motion machine if its extracting energy from its surrounding environment. I thought to be a perpetual motion machine it would have to be a self contained system that had no external influence, hence the quotes of the 2nd law. I understand the problem with the ratchet but even if you take that problem away it would still rely on an external energy source (the ambient temperature) and therefore its not a perpetual motion machine.
Wouldnt the ratchet still block rotation in one direction some of the time causing a net rotation in the other direction? Even if it only managed to block rotation one direction 10% of the time its still not blocking the other way and so statistically there would be an overall rotation in a single direction?
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A machine in a fixed-temperature environment is conceptually nearly identical to a closed environment: you cannot extract work from the environment once the system you're studying is of the same temperature as the environment. I think people just talk about a closed system because it's usually a tiny bit easier for thought experiments, but a fixed-temperature environment gives the same results.
Of course, you can extract work from an environment that is out of equilibrium, such as one where the temperature varies over space or over time.
Anyway, the idea is that statistical mechanics (the physics behind thermodynamics) tells us that it is impossible to extract work out of a system that is in equilibrium. Basically, what happens is that whatever mechanism you are using to do work will have the same probability of going forward as back. If you think it doesn't, it's only because you haven't analyzed the system in full (typically because you haven't applied statistical mechanics to one aspect of the system, in this case the extent of the teeth).
Of course, you can extract work from an environment that is out of equilibrium, such as one where the temperature varies over space or over time.
Anyway, the idea is that statistical mechanics (the physics behind thermodynamics) tells us that it is impossible to extract work out of a system that is in equilibrium. Basically, what happens is that whatever mechanism you are using to do work will have the same probability of going forward as back. If you think it doesn't, it's only because you haven't analyzed the system in full (typically because you haven't applied statistical mechanics to one aspect of the system, in this case the extent of the teeth).
zidane1strife
Banned
There'd have to be fluctuations in the magnetic field's strength, or else it's hard to see how an object stretched under the influence of a permanent magnet will be able to vary in length(edit: obviously there'd be some variation as the ratchet vibrated, but the magnet'd be placed at such a location that it's field will influence it at all relevant distance. Such that the minimum tooth length while under the field's influence is still too long to let the pawl/lock over it.), given a constant field.Chalnoth said:
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zidane1strife
Banned
Well the significance of that effect would depend on the number of atoms composing the tooth. I'd imagine past a certain threshold the effect would be minimal at best and shouldn't interfere with our mechanism, the degree of it would probably depend on the strength of the field as well as the number of atoms(I've heard that a new method to order nanoscale polymer fiber and use it in a technic akin to knitting with the application of an electromagnetic field works, so at least we know at a certain scale to field strength ratio we actually manage to control the outcome.).(Also even small nanoscale magnetic elements are useful for memory and computational purposes, iirc.)Chalnoth said:
In any case I don't see how that'd avoid a skew in the movements of the ratchet, the magnetic field's influence would have to be negligible for this particular system in order for it to move in both directions just as easily, that is as easily with or without its influence/presence(bottom vs upper tooth difference).
Mintmaster
Veteran
When I was thinking about this a bit more, magnets and electrostatics don't work. The peak energy of the barrier is the same in both directions. As the ratchet moved towards the next tooth in the allowed direction, the tooth would get longer and the peak energy of the pawl is the same as the peak energy needed in the disallowed direction. If you were relying on time delay, that would mean it's an inelastic system (I think) and you're losing energy.zidane1strife said:
However, imagine if there was a set-reset switch for each tooth position. When the tooth passed the pawl, it would be 'set' and lengthen, and stay that way even if it tried to go back. When it went around to the other side, something would 'reset' it, thus shrinking it. You're not doing any work in this lengthening and shrinking.
Imagine if the tooth was on a spring loaded with some potential energy in the contracted position. Latch #1 holds the tooth down until it passes the pawl, at which point it releases it by some disengagement mechanism. After the tooth goes through a half cycle of SHM, latch #2 holds it (all the kinetic energy of the tooth is stored in the spring again) in the lengthened position. After a half rotation of the ratched, latch #2 is released and latch #1 is engaged again, holding the tooth in the short position. Such a system would exist for each tooth. As mentioned before, no work is done.
I have no idea how to construct such a system, though.
Moreover, there is one bit of information for each tooth, and whenever the tooth passes near the switching points, its state must be measured. It looks like Maxwell's demon. However, the information required seems to be so minute here. In theory a switch could be designed such that it evades measurement unless it's about to be switched, i.e. once a latch is engaged, the engager no longer sees it, and when a latch is disengaged, the disengager no longer sees it.
Googling came up with this page. I suspect this is closely related to where the problem is with the device. The frequency with which one must check the latches is related to random motions of the ratchet, which in turn is related to the temperature. So as usual entropy change and work are intertwined, and you won't win.
zidane1strife
Banned
Well, my solution to the tooth reset was to use a magnetic memory alloy(or if such is not too long lasting, a memory alloy with embedded magnetic particles), it would lengthen while in the presence of the magnetic field but as the ratchet kept moving and it got away from the field(while continuing the circular motion), the tooth would return to its original shape thanks to its memory material properties.Mintmaster said:
Bigus Dickus
Regular
You can't lengthen and shorten a tooth without doing work, regardless of how you attempt to do it (spring/latches, magnetic memory, whatever). Any motion of the tooth will result in losses due to friction or strain energy (or both) in the form of heat. This heat lost will be equal to or greater than any collective bias of thermal energy input into the system that you were hoping to utilize.
zidane1strife
Banned
A shape memory alloy is a material that can return to its original shape after being subjected to a deformation(within certain parameters.). (Example flexon eyeglass frames, you bend them they return to their original shape.). I know this effect can take place countless times, in the materials I've tested, before they wear out. But since I'm not a material engineer I've no clue as to how long they'd last for this particular application or if they'd be practical(hypothetically any possible such material should wear out or change in properties before we can extract any useful energy out of the system... ).Bigus Dickus said:
From my experience with magnets, I've seen you can get something near them and away from them countless times without any problem at all(countless magnets used in many of our electric devices.). Thus you should be able to get a magnetic shape memory alloy(or a shape memory alloy or shape memory material, with embedded magnetic particles) near a magnet and away from it without any trouble. It probably heats a bit while deformed or deforming, but if such deformations are slight(easily within the parameters of the material.), and short in duration(likely) and spaced out, it shouldn't heat up by any significant amount, and in any case it has plenty of time to cool down later on as it completes the revolution.(so in general it should remain at a stable temperature). The collisions of a few molecules, are supposed to be, what's performing the work of moving the ratchet.
Mintmaster
Veteran
There's no reason that the losses from a spring will compare to the gains from random thermal motion. When molecules vibrate they keep on going unless you either have collisions (which on average will only reduce the vibrations if the surrounding material is cooler) or if they have some energy transition like a photon emission. Most importantly, the change in the energy barrier provided by different length teeth has nothing to do with the energy wasted in moving the teeth.Bigus Dickus said:
For example, your ratchet could be a single molecule thick, but your paddles could be huge to generage lots of statistical thermal input. You could encase the ratchet in a vacuum to eliminate external collisions with the teeth. There's no energy needed to hold a tooth in a particular position either, but over time you can statistically get enough of a jolt to move over to the next tooth.
Your argument is just based on practical experience about friction, and there's no quantitative reason to say one is bigger than the other. Take a look a the link I gave earlier. All the proofs of infeasibility assume no energy is lost in the moving the door or whatever, because there is no fundamental limit in reducing these losses.
The real reason this is impossible seems to be much more complicated. If I spent enough time I could probably give you a reason the entropy increases using statistical mechanics, but it's tough.
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