Entropy

I just don't think it could work. I mean, the thing you described earlier-the box with the partition, well the chances of that ever happening are infinitesmal, though I admit chances exist. But when/if it eventually happened, it would only be for the slightest fraction of a millisecond, and in that time the partition would have to be dropped. that's got to be one fast moving partition to work. Consequently, when it closes the box, trapping the particles, and comes to a stop, it's gonna release a lot of heat [large change in velocity, small amount of time]. wouldn't this heat increase the entropy of the system? [but like I said earlier, I know very little about this]. Also, as for Maxwell's demon itself, the idea doesn't quite work, in my mind. meh. I'm tired. I'll go into it later.

As far as the infinitesmal chance of all the particles moving to 1 half of the box, that's why we have theory. Theories don't always work in reality. (and sometimes reality doesn't seem to fit into theories) For instance a sphere of arbitrary radius COULD be disassembled into infinitesmal parts and reassembled, as a continuous mass, into a sphere of radius 2. This mathematical theory falls apart when we take into consideration a little thing known as the atom (no pun intended).

As far as sliding the partition in, if you shape your box so it is narrow in height (for less velocity when inserting), and use some good lubricants, then heat from friction could be minimised. Although technology these days allows for superconductors, allowing for lossless transmission of electrons, so why not say it is theoretically possible to transmit larger particles, such as a partition? Then heat is eliminated altogether.

Sorry for my verbosity, verging on verbocidal-ness.

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ok, what I wrote last time doesn't even make sense and I was hoping to get here and edit it before anyone read it, but since you already have, I'll leave it be and say that in my tired state when I wrote system what I meant was surroundings. Listen: this partition thing. Firstly, the chances of the molecules even filling one side are ridiculously small [as I already said] secondly, even if they only filled one side, it would be for the tiniest fraction of a second. A few milliseconds-MAYBE. Ok, I'm going to assume you're familiar with the average speeds of molecules in a gas,* which are generally assumed to be around the speed of sound in air (but are often faster). I'm getting to my point. So, for this partition to trap these molecules, it's got to go from 0m/s to over the speed of sound and back to stationary in the space of less than a second. [unless you can predict the movement of gas molecules, which you can't] Firstly, you probably can't do this. Secondly, that sort of acceleration could never be achieved by gravity. thirdly, even if you could do this, it would require a relatively large amount of energy. Whatever machine moves the partition, it's bound to give off large amounts of heat to the surroundings. this'll increase the entropy of the surroundings, but also the fact it needs so much energy means that the whole box thing could never solve the problem of our energy needs.




*If you're not, you can calculate it with v=square root of (3RT/M), R=8.314, T=kelvins, M=molecular mass. I'm not putting calculations up here. Yes, it is an average.Some will be going slower, but then again, some will be travelling much faster.


ok, now as for the demon, I wanted to argue it couldn't work even in theory. By saying it doesn't exist and wastes no energy, abdo's inadvertantly done that for me. I hope someone understands what I mean in my ramble.

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the demon couldn't work for other reasons too. It would need to use energy to observe the molecules, and wouldn't both the demon and the trap door increase in entropy as it opens and closes? Doesn't that increase the total entropy of the system. Then there's other stuff about the demon itself..... [I'm not sure I know enough about it to properly refute it]

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Quote:

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Originally posted by AbdoRinbo
Maxwell's demon is a relay mechanism that responds in a certain way to information concerning the state of a particular system. It is not a living a being, but it is intelligent. Its only purpose is to violate the second law (entropy); and accordingly, the imagined results would have a profound impact on our existence.

Unfortunately though, for a Maxwell's demon to work (if it's even possible) would take 10^10^10 years.

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Uhm, yes, a demon watching billions of fast moving gas molecules and operating a little trap door for 10^10^10 years [from info abdo himself gave above] is bound to use up less energy than could be gained from a box of gas. there's no chance. there will be a decrease in total useful energy-an increase in entropy. the more I think about it, the more Maxwell's demon strikes me as a total load of b.s.

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But if no such being can exist, then don't you have to admit it couldn't work, on the grounds you could never have such a 'ghost'? The demon itself would have to defy the laws of thermodynamics to not expend energy. It's sorta like saying, 'well if we can make a being defy the laws of thermodynamics, we can defy the laws of thermodynamics. Breakthrough!!'

The demon it self isn't (at least in classes) supposed to be the issue. It's the function the demon performs. Sorta like Schrödingers cat. No one ever put a real cat into a box, with a decaying particle and a vial of poison. They are both just things to think about to focus thinking in a certain direction.

Abdo: I realize I said Atom, while there are many smaller particles. I was just trying to demonstrate a difference between mathematical reality, and physical reality. Also, I've been under the impression that anything smaller than the electron/quark level is still under debate, with the possible exception of the neutrino (which has debatable mass).

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It is true that we have never seen electrons and neutrinos, although these much more widely accepted. (ie. nobel prizes have been given out for particle theories (bose-einstein condensate), while I know of none given for string theory)

Looking back to previous posts, I'm not to sure you quite know the theory I was talking about with the sphere. The radius units don't matter, it could be 2 angstroms or 2 terrameters. Looking from a purely mathematical perspective (ignoring scientific principles such as quantization of matter) you find that it is possible to deconstruct it and reconstruct it with the same amount of matter to have twice the radius (and the same density, although density means something different in this case, since it ignores modern principles altogether). What this is intended to point out, however, is that theories are quite nice as theories, but in the real world we have to have some sort of observability. No one has ever observed an orange being deconstructed and reconstructed time and again, until it is the size of the sun. Although certain theroies allow it to work. People have noticed the effects of electron transmission, (TV's, computers, telephones, anything that requires electricity to run.) to my knowledge, which is at times quite flawed, no one has ever observed the effects of strings. Or of anything smaller than quarks/electrons, for that matter (saving the photon and the hotly debated neutrino).

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I'm not going to ask myself anything. I'll ask around to find the name of/writer of this theory I'm refering to. It's quite odd, and the implications would be astounding if it weren't for physics.

Obviously, this doesn't happen in nature, but it DOES in fact happen in theory.

The point is still that what works in theory doesn't necessarily happen in reality, and what works in reality doean't always work in theory. (for example of the latter, we have the humble bumble-bee (or am I mistaking that for another bee?), which theoretically can't fly)