Information icon.svg At All things in moderation, we are currently voting on restrictions on the use of LLMs (chatbots) in RationalWiki. Reminder: you need to have at least 75 edits and to have been registered for at least three months to be eligible to vote.

Talk:Maxwell's demon

From RationalWiki
Jump to navigation Jump to search

Is it really pseuodoscience? I thought it was a valid thought experiment. Is Schrodinger's cat, then, pseuodoscience?--User:Brxbrx/sig 15:41, 13 December 2011 (UTC)

Do you have a mental deficiency that prevents you from reading wikipedia? ArchieGoodwin (talk) 15:58, 13 December 2011 (UTC)
I think he's probably just incapable of sitting still for the 2 seconds it takes to think things through or refrain from holding court on every single inane thing that pops into his head. It's probably pseudoscience but the point is broader. The article presents it as an illustration of a principle of pseudoscience at work, e.g. the demon is only capable of effecting a violation of the 2nd Law of Thermodynamics if that's how you define it. According to Maxwell's original formulation, the demon is not considered part of the closed system of the divided box, thus he is capable of changing the temperature and regulating pressure "without expenditure of work." The standard criticism, and I think the way this article intends to present the issue albeit poorly, is that it's inaccurate to describe a being interacting with a system without affecting its net energy. Thus, the broad point is that it's analogous to the kind of slippery games creationists play in essentially assuming into existence the conclusions they've put at issue by building them into the definitions they (mis)use in debating their positions. I'm sure there are more profound ways to put it but that's what you get while I'm sitting here waiting to get out of an appt. Nutty Roux100x100 anarchy symbol.svg 16:28, 13 December 2011 (UTC)
I've taken out references to pseudoscience. I'm not Jesus (talk) 16:57, 13 December 2011 (UTC)
I did read the wikipedia article, long before I'd read this one and again before I left my comment. Maxwell's demon, while disproved, is still a valid part of science and is used in lessons even today. Just because it was found to be false doesn't mean it's pseudoscience. Science corrects itself. Also, it doesn't fit a stricter definition of pseuodscience- the guy who came up with it was a physicist himself who presented it to other physicists.--User:Brxbrx/sig 19:18, 13 December 2011 (UTC)
I take it back. You're a cretin and you have the attention span and focus of a gnat. Nutty Roux100x100 anarchy symbol.svg 20:09, 13 December 2011 (UTC)


I can see why this can be considered pseudoscience, but I'm under the impression Maxwell wasn't aware of the solution. If people still try to push this thought experiment as pseudoscience today then I think we should keep the category, but if we don't document that in the article I don't think we need the category. True, it gave rise to pseudoscientific Morton's demon, but it isn't Morton's demon, so I don't feel at the moment that we need the category. Sam Tally-ho! 04:19, 15 December 2011 (UTC)

Any theory involving demons is not science today and was not science in Maxwell's time. Mjollnir.svgListenerXTalkerX 04:21, 15 December 2011 (UTC)
But it's a though experiment. Was he actually trying to make a scientific theory involving demons? Sam Tally-ho! 04:24, 15 December 2011 (UTC)
(edit conflict) It was a thought experiment. Maxwell didn't deny Thermodynamics, he was just questioning it (and no, he wasn't JAQing off, he ws legitmately curious). The thought experiment remains in physics education today and can help to understand the subject. Just because it was proven wrong doesn't mean it was pseudoscience. Only if people had kept propounding it, which they haven't.--User:Brxbrx/sig 04:25, 15 December 2011 (UTC)
Stop edit warring, Brxbrx. Who cares if he was curious or not. Maxwell's idea is discredited as hokum. It's used, if at all, as an example of hokum. He couldn't have known why it was hokum, but that's also irrelevant. Redefining terms to create such an alternate reality is the very essence of pseudoscientific hokum. I have no idea what your prior point about Maxwell being a physicist presenting the idea to other physicists has to do with the issue. And your final assertion that it's not pseudoscience unless people continue propounding it is idiotic. If you were right, we'd never be able to cover one off cranks pretending they've got cold fusion all worked out. Knock it off. Nutty Roux100x100 anarchy symbol.svg 04:30, 15 December 2011 (UTC)
Scientific thought experiments still have to stay within the bounds of methodological naturalism, at the very least; Schrödinger's Cat, for example. Mjollnir.svgListenerXTalkerX 04:33, 15 December 2011 (UTC)
Wasn't Schrödinger's Cat making fun of quantum theory, though? As in, it was less a legitimate thought experiment and more a parody of a particular line of thought. Star of David.png Radioactive afikomen Please ignore all my awful pre-2014 comments. 04:39, 15 December 2011 (UTC)
My understanding is that it's a legitimate illustration of at least the Copenhagen interpretation of quantum theory that has it possible to calculate the probability that photons will pass through either slit in the double slit experiment as if they were in 2 places at one, based on theoretically tracing the path of a particle as if it were a wave function by its amplitude. This makes sense to me but I'm sure I'm getting it desperately wrong. Nutty Roux100x100 anarchy symbol.svg 05:10, 15 December 2011 (UTC)
It would be hokum if Maxwell said "there is a demon that can do this to violate thermodynamics". Thought experiments don't have to stay within the bounds of methodological naturalism, because you can use them to prove points about why methodological naturalism has to be maintained. That the demon does do work in opening a gate wasn't the relevant point; it was that the demon would have to be processing information to complete the task. This started the ball rolling to get information tied into thermodynamics and entropy. To call it "discredited" is really to miss the point entirely. Scarlet A.pngpathetic 16:46, 15 December 2011 (UTC)
Thank you! I was worried that if you did come into this discussion, you'd get your whole obtuse on, but I'm glad I was wrong.--User:Brxbrx/sig 16:49, 15 December 2011 (UTC)
This article might help. Scarlet A.pngbomination 16:50, 15 December 2011 (UTC)
Wait a sec... did people seriously think Maxwell was trying to invent a perpetual motion engine by summoning up an genuine supernatural demon? Scarlet A.pngbomination 17:18, 15 December 2011 (UTC)
That's the Diskworld version. Bad Faith (talk) 17:31, 15 December 2011 (UTC)
Give me a break. Maxwell never said there is a "demon" (and actually never used that term) because the "demon" was merely a means of discussing the actual question he was asking, which gets left out of the thought experiment as it's commonly quoted. Beyond the conceit of the illustration, he was absolutely proposing a possibility that he viewed as within the bounds of methodological naturalism. The actual question he asked was whether the Second Law of Thermodynamics was something that emerged from a statistical understanding of the motion of molecules rather than from the motions of individual molecules. You point relates to subsequent understandings of the problem, but has nothing to do with what Maxwell's actual point was, a point that we obviously now know is bunk.

Let's look at exactly what Maxwell says since people seem to be looking at only part of the section from his 1872 book Light and Heat, and I think missing the actual point he was making:

One of the best established facts in thermodynamics is that it is impossible in a system enclosed in an envelope which permits neither change of volume nor passage of heat, and in which both the temperature and the pressure are everywhere the same, to produce any inequality of temperature or of pressure without the expenditure of work. This is the second law of thermodynamics, and it is undoubtedly true as long as we can deal with bodies only in mass, and have no power of perceiving or handling the separate molecules of which they are made up. But if we conceive a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are still as essentially finite as our own, would be able to do what is at present impossible to us. For we have seen that the molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the swifter molecules to pass from A to B, and only the slower ones to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics.

This is only one of the instances in which conclusions which we have drawn from our experience of bodies consisting of an immense number of molecules may be found not to be applicable to the more delicate observations and experiments which we may suppose made by one who can perceive and handle the individual molecules which we deal with only in large masses.

In dealing with masses of matter, while we do not perceive the individual molecules, we are compelled to adopt what I have described as the statistical method of calculation, and to abandon the strict dynamical method, in which we follow every motion by the calculus.

It would be interesting to enquire how far those ideas about the nature and methods of science which have been derived from examples of scientific investigation in which the dynamical method is followed are applicable to our actual knowledge of concrete things, which, as we have seen, is of an essentially statistical nature, because no one has yet discovered any practical method of tracing the path of a molecule, or of identifying it at different times.[1] (my emphasis)

The actual question Maxwell asked has been answered in the negative in a variety of ways; but allowing the possibility of perpetual energy, as Maxwell did, is now known to be pseudoscience. The entire point of discussing the thought experiment now versus then is to illustrate what became a well-known principle that was unknowable, or at least unknown, to Maxwell. The pseudoscience category refers to the fact that the thought experiment admits of a possibility that we now know doesn't exist. It's not pejorative; it simply is what it is: no agent can act upon a system without doing work as part of the system ("the system enclosed in an envelope"). Nutty Roux100x100 anarchy symbol.svg 17:49, 15 December 2011 (UTC)

Yes, but "wrong" is not the same as pseudoscience and neither is "falsified". Things that are "wrong" or "falsified" are just that. I don't think it fits the description as outlined in our article on Pseudoscience.--BobSpring is sprung! 20:53, 15 December 2011 (UTC)
(EC, but also "what Bob said") So any time a scientist says "hmm, here's an idea..." it's pseudoscience if it doesn't work? We have no proof that the laws of thermodynamics are truly unbreakable, they're empirically observed and more than likely they are unbreakable - but there's nothing that says they CERTAINLY cannot be broken if we find the right method. That was true when Maxwell was working, it's still pretty much true now. It's asking the question "Could this work? And if not, why not?" and science does this all the time. Our understanding of mass-energy equiverlence and how information theory ties into entropy didn't exist when Maxwell asked that. So I don't see why the pseudoscience tag is there, no one else describes it as bunk psuedoscience as it's a question, not "this will work and I don't care what evidence you're going to put in front of me" as cranks do. If you presented Maxwell with mass-energy equivalence and information-entropy relationships to disprove the conjecture he'd be pretty happy with that. If that's pseudoscience then all of science is pseudoscience. Scarlet A.pngpathetic 20:58, 15 December 2011 (UTC)
I think his hate-on for me was making him want to prove me wrong. He can't be that dense--User:Brxbrx/sig 21:17, 15 December 2011 (UTC)
I think Brxbrx just called me dense because a few people disagree with me. The irony meter supplier will be exhausted of his remaining stock. Anyway, once again I'm not suggesting that Maxwell was engaged in pseudoscience. I would have preferred it in the pseudoscience category because, while Maxwell didn't know he was wrong, redefining the laws of physics as he proposed very nicely illustrates the kind of thinking that goes into pseudoscience and the category provided a good jumping off point from which to explore the subject. The mention of perpetual motion machines amplifies that point but could be strengthened. Nutty Roux100x100 anarchy symbol.svg 22:03, 15 December 2011 (UTC)

Subtle problem with our discussion[edit]

We make mention that in the real world, Maxwell's demon would have to use energy to determine the speed of things, but this bypasses an important problem. You could duplicate the demon's behavior with particularly lucky random openings and closings of the door, with no observation. That is to say there exists a random door usage that mimics any particular universe of the demon's behavior.

As far as any sort of perpetual motion pseudoscience goes, this isn't relevant, because you're going to net lose potential. But as far as a deconstruction of the second law in principle, as a thought experiment, you still have trouble. Ikanreed (talk) 20:30, 16 January 2015 (UTC)

Well yes and no. Something would have to regulate the opening and closing of the door, and the physical solution to the thought experiment is just to point out that when considering the full system (in your example, including the door and the mechanism required to open/close it in any particular pattern) any lowering of entropy within the box will still be accounted for with a corresponding increase in entropy somewhere else in the system. I'm not sure it's entirely necessary to explicitly say this though. - Grant (talk) 20:58, 16 January 2015 (UTC)
Yeah, but in this case you just made a completely random pre-programmed pattern, and it happened to match the high energy particles. The likeliehood of that happening are infinitesimal, but it not-the-less highlights an avenue by which, strictly hypothetically, entropy of a closed system could decrease. In the end, the law is a statistical one. Ikanreed (talk) 21:01, 16 January 2015 (UTC)
The law is a statistical one, sure, in that it's derived from statistical mechanics. However, at some point, to create this completely random pre-programmed pattern, some entropy-increasing process had to be performed. The trick about the Second Law is that it applies to the net increase in entropy across the entire system, where the "entire system" is defined as any and all processes involved. If we ignore, for example, the processes I mention here, then sure, that system can decrease in entropy. That still isn't a violation of the Second Law, however. - Grant (talk) 21:07, 16 January 2015 (UTC)
I mean if you want to be really pedantic it's accurate to say that the universe (provided nothing exists outside of it) is the only system that truly respects the Second Law in its absolute entirety, since it's remarkably difficult to generate a perfectly closed system. Still, it's not necessarily a statistical thing, per se. - Grant (talk) 21:10, 16 January 2015 (UTC)
I know, it's just the article's discussion of the matter tries to present otherwise. Ikanreed (talk) 21:12, 16 January 2015 (UTC)
Hmm, interesting. I didn't find that, but I'm also not the most observant about these sorts of things. Perhaps there's a place we can insert clarification. I don't believe my statements as written are necessarily good to add, but perhaps a note that the "closed system" part of the Second Law is critical would be a good idea. Thoughts? - Grant (talk) 21:18, 16 January 2015 (UTC)

This would violate the laws of thermodynamics as perpetual motion is impossible - you cannot get more energy out than you put in. Yet the demon of the thought experiment, given the ability to look at a molecule and open a gate, would consume far less energy than the entire system generated. This apparently simple way to get around the fixed laws of thermodynamics puzzled James Clerk Maxwell and many other scientists of the era. How to prove that Maxwell's demon could not work (leaving the laws of thermodynamics intact) had to wait some time.

Here's the problematic phraseology to me. It's just little bit absolutist. I sort of realize I'm pushing to muddy the waters when snarky-point-of-view should be the guideline, though. Ikanreed (talk) 21:40, 16 January 2015 (UTC)

Well my personal view is that as it relates to science, SPOV should take a backseat to accuracy whenever possible. Throwing a note in there to point out that this isn't actually a closed system (and thus it can decrease in entropy locally) might be a good idea. I would certainly support it. - Grant (talk) 21:47, 16 January 2015 (UTC)
I'm going to be picky here and say I'm not a huge fan of your wording. The Second Law is always true (inasmuch as any scientific law can be "true") because the Second Law applies only to closed systems. If your system is closed, it will obey the Second Law, regardless of statistical outcomes. If your system is not closed, then the Second Law no longer applies (but instead applies to the broader closed system containing your open system). While I think I understand the point you're getting at, "statistically true" has the connotation that there's some chance the Second Law will be violated; this is inaccurate, as there's a significant difference between a law being violated and simply not applying. - Grant (talk) 21:53, 16 January 2015 (UTC)
(That said, I'm mulling over what I would say to replace it, but haven't yet decided exactly how to word it or where it would be best to place it.) - Grant (talk) 21:58, 16 January 2015 (UTC)
I'd be happy to pull it out if it makes the article worse as is. Ikanreed (talk) 22:02, 16 January 2015 (UTC)
I'm not sure I would go so far as to say it makes the article worse; just that it replaces the original wording issue with a slightly different one. I'll think on it some more. - Grant (talk) 22:03, 16 January 2015 (UTC)


"RAM chips that store information are, in fact, ever so slightly heavier than RAM chips without information because of the relationship between energy and information"

This sounds incorrect to me. Is there anything that can be cited? — Unsigned, by: / talk / contribs 12:02, 24 February 2015 (UTC)

Energy expended and gate open-close time[edit]

The thought experiment of Maxwell's demon only considers the energy expenditures of the demon in control of the gates… but the opening and closing of the gates would itself be a process that consumes energy (an object in motion stays in motion unless it collides with something and/or a force such as friction removes its kinetic energy (and an object in motion stays in consistent motion unless geography or some force modifies the motion; an object at rest stays at rest without the action of an outside force)). Furthermore, no gate can open or close completely instantaneously; there must be an array of "partially open" transitional states between "open" and "closed", and even if those transitional states only occupy a microsecond each, they must still exist, and a molecule, being a very tiny piece of matter, could feasibly slip through a partially-opened gate, especially if it was moving quickly. Thus, how do we guarantee that all fast molecules are kept out of the slow molecule room? The demon would have to act well in advance of the fast molecule's approach to keep it out, and might cut off a slow molecule that it intended to grant passage to in the process.

Am I the first person to consider these disproofs of perpetual motion, or was the "processing energy requirement" really the very first hole punched in the idea of hypothetical perpetual motion? --Luigifan18 (talk) 16:22, 7 July 2022 (UTC)