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Ramiel
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Mine was a hypothetical question t_pyro, I asked it for fun, to see if anyone could find it's solution - for fun, not as a "practical"
solution to perpetual motion... the solution to this problem pretty much proves the whole theory's impossibility.
Jeez, calm down a bit man. ; )
[edit - "t_flex" changed to "t_pyro"]
[Edited on 28-3-2004 by Ramiel]
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t_Pyro
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Geomancer:
Sorry, I don't think I'm visualising your machine correctly. I don't quite get what you mean by saying that the "ascending side
will always be overbalanced by the descending one". The ascending side will have more water in its capillaries than the descending side, hence
will be heavier. Work has to be done to raise the water against the force of gravity, and this water, once "squeezed out" at the highest
point, falls back. How is energy being produced from nothing?
Regarding the uncertainty principle, it is incorrect to speak of "density of the working fluid". What we're talking about here are
discrete particles, not a homogenous accumulation of particles. In order to separate the particles in the manner described, we have to analyse the
particles individually, not as an accumulated "fluid". For example, an electron cannot be confined within a volume equal to that of the
nucleus of an atom. To prove this, we consider the mass of a single electron, not the "average" mass density of an electron cloud.
Ramiel, sorry, I think I got carried away... I think the heat's getting to me!
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Geomancer
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It seems that we are having difficulty communicating. I'll try to draw a picture of my device and post it later. Capillaries tubes are not
involved. Since you like the things so much, though, try this:
Two identical beveled wheels, like the cutters for a can opener or a pizza cutter, are placed so as they are free to turn on an axle. The axle is
bent slightly so as on one side the two wheels are very close together, almost touching. On the other side, then, they are more separated. Submerge
the device halfway in water, with the axle in the plane of the liquid. Due to the close proximity of the plates one side, the fluid will be drawn up
between them by capillary action. On the other side, the wheels are far apart, so this won't happen. The weight of this fluid will then unbalance
the wheels.
If I understood correctly, your arguement from uncertainty went like this:
You need to determine the energy of the incoming particles to whithin some precision, say m
By having the particles pass through a gate, you determine the position to a certain precision, p
It is impossible to satisfy both of these precision requirements
Clearly, the conclusion holds for certain m and p. What you fail to realize is that m and p are completely arbitrary. Let's say the size of your
gate gives you energy uncertainty of m. All you need to know about the particle's energy is whether it is greater than the average energy (E) in
its pool. But, under thermal equilibrium, eventually you can find particles of arbitrarily high energy; in particular, you can find particles with
energy greater than E+2m. Similarly, with very low density working fluids (like a soft vacuum), you can safely make the gate quite large.
Try thinking from the standpoint of microscopic reversibility instead.
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axehandle
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Aren't we violating the 1st law of thermodynamics here?
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
\"Verbing nouns weirds the language!\"
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Geomancer
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My devices, if they were to work, yes. Showing why these machines don't work is still an instructive puzzle.
Ramiel's demonic contraption, OTOH, does not violate the first law. The problem is, what stops it from violating the second?
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t_Pyro
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I was not talking about any capillary <i>tubes</i>. I said that the water would rise up the <i>capillaries</i> of the
material. Without any such capillaries, the material would be entirely solid, hence would not absorb any fluid.
Regarding the uncertainty method:
I'm not sure whether I conveyed my argument well enough. What I said was that during the fraction of time dt, while the particle is passing
through the gate, since the gate itself is of a comparable dimension as the particle, the uncertainty of the position of the particle is limited to
the diameter of the gate, which is very small. Hence, the uncertainty in the momentum will be very high. Mass and density cannot be arbitrary. Mass is
quantised. You can have a particle of 1 amu, 2 amu and so on, but not 0.231 amu or 0.1 amu. By my calculations, if the particle is a proton for
example, the uncertainty in its velocity while passing through a gate twice its diameter is approximately 15.7623x10<sup>6</sup> m/s. The
corresponding uncertainty in energy is very high.
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Geomancer
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Partially submerge a metal spoon in water. Observe closely, it does lift a small amount of water.
I dont trust your calculation. My body has quite a few gated proton channels in it, and I seriously doubt that it has that many protons moving at
millions of m/s.
Also, you arbitrarily assume that the size of the gate must be twice the particle diameter. In a vacuum (or even a gas), you could get away with
much larger gates. Moreover, you falsely assume that it is impossible to find very high energy particles in your system. It's only extremely
unlikely. Wait a few billion years.
[Edit: I never wrote that mass was arbitrary. I was using the symbol m for permissible energy uncertainty. The density of a gas is is arbitrary (more
precisely, it is a natural multiple of (particle mass)/(container volume); I suppose there is an upper limit, but that's not important here).]
[Edited on 27-3-2004 by Geomancer]
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t_Pyro
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What you're talking about regarding the spoon is due to surface tension, whereas the belt concept uses the ability of water to rise up fine
capillaries. Although the basic reason for the phenomena are the same (surface tension of water), the former method cannot be applied to your first
gadget, since then the "squeezing" of the belt would have no effect...
I arbitrarily chose twice the diameter of the proton as the gate size since any gate larger than that would not be able to allow specific protons to
pass without other protons being able to pass through, also. No, there are no vessels/gates/openings/pores which have a diameter comparable to that of
a proton, at least none that I'm aware of. Hence, the idea of any particle in your body having the stated velocity is absurd.
I did not say that it is impossible for particles to have such high energy. I said that if the particle <i>does</i> have such a high
energy, it's defeated the purpose of segregation by the gate on the basis of energy. The energy of the particle while entering the gate, and
while passing through the gate are therefore worlds apart.
If you want to check my calculations:
The diameter of a proton is approx. 10<sup>-15</sup>m.
Mass of proton= 1.67262x10<sup>-27</sup> Kg.
Therefore, dv=(h/(4pi))/(1.67262x10<sup>-27</sup> * 2*10<sup>-15</sup>
=15.76226x10<sup>6</sup> m/s.
[Edited on 28-3-2004 by t_Pyro]
[Edited on 28-3-2004 by t_Pyro]
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Geomancer
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| Quote: | Originally posted by t_Pyro
What you're talking about regarding the spoon is due to surface tension, whereas the belt concept uses the ability of water to rise up fine
capillaries. Although the basic reason for the phenomena are the same (surface tension of water), the former method cannot be applied to your first
gadget, since then the "squeezing" of the belt would have no effect... |
Where did you get this squeezing out stuff stuff from? Take a solid strip of rubber, partially submerge it in water. It will lift a certain
amount. Take a strip twice as wide, and it will lift about twice as much. Take the first strip, stretch it to be twice as wide, and it will lift a
similar amount to the second one. To make the PM, partially submerge a loop of rubber, with one side stretched and one side not. I've included a
drawing.
| Quote: | | I arbitrarily chose twice the diameter of the proton as the gate size since any gate larger than that would not be able to allow specific protons to
pass without other protons being able to pass through, also. |
I really don't see why you need the gate to be so tiny. If atoms naturally got anything like this close, fusion power would be no problem. As
I've noted, the human body contains plenty of gated channels that seem to work just fine.
[Edit: You also seem to state that the energy of the particle entering the gate and the energy of the particle in the gate are different. What do you
mean by this? PS, sorry about the svg, it's the only format my program would output.]
[Edited on 29-3-2004 by Geomancer]
Attachment: pm.svg (7kB)
This file has been downloaded 1007 times
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Marvin
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The answer to the first problem is that the surface gives out a different amount of energy when it relaxes than it required to stretch because it is
displacing molecules of the liquid from its surface.
The second problem is instantly recognisable as the Maxwells Demon problem, in which a very small demon opens and shuts a small gate to collect fast
moving molecules of a gas in order to create a thermal difference from a boltzman distribution of molecules in a gas at a 'constant'
temperature. The thought experiment lead to the development of the concept of Entropy.
Ultimatly the answer to the second problem, is that for an active system, however well we build the gate system with its sensor/gate open/close
mechanism we cannot make a machine that requires less power than it can produce from the thermal difference. The mathematics for this is based
entirly on the 'information' the system requires to work, and the unavoidable power cost of this.
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Ramiel
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Okay, kudos to Marvin and Geomancer.
It is in fact an adaptation of the <html><a href="http://www.maxwellian.demon.co.uk/">maxwelian demon</a></html>
problem... (don't ask me what the naked demons are all about, apparently the author was big on them)
| Quote: |
Posted by Geomancer:
"demonic contraption"
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I had a laugh when I saw that.
The answer is pretty obtuse if you ask me. Another reason it won't work is the demon must "see" the particles with photons in the
system. And you know what THAT means. 
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Geomancer
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| Quote: | Originally posted by Ramiel
The answer is pretty obtuse if you ask me. Another reason it won't work is the demon must "see" the particles with photons in the
system. And you know what THAT means. |
It's pretty simple if you take microscopic reversibility to be axiomatic. Consider making a movie of the demon at work. When running the
movie backwards, consider a place where a high energy molecule approaches the gate from the high temperature side. In forward time, this could have
arisen in one of two ways: either the particle was originally on the hot side, and bounced off the closed gate, or it was on the cold side, and went
through the open gate. In order to retain microscopic reversability, then, the demon (in reverse time) must have a way of distinguising these two
conditions. In other words, the forward demon must have a way of remembering every decision it makes.
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