Wikipedia:Reference desk/Archives/Science/2022 June 15

= June 15 =

Scrutinizing claims about 'child marriage' according to medical sciences
Probably this was needed to be on this sciences board but rest of the connection is with humanities so I have posted  an input request @ Reference desk/Humanities.

Thanks for inputs

&#32;Bookku, &#39;Encyclopedias &#61; expanding information &#38; knowledge&#39; (talk) 09:19, 15 June 2022 (UTC)

Maxwell's Demon
Can someone explain to be how Maxwell's Demon is a useful or meaningful thought experiment? As far as I can see, either the "demon" obeys the laws of physics (requiring energy to perform work, etc), in which case this is no more a violation of the laws thermodynamics than e.g. me pumping air into a tyre. Or alternatively, the demon isn't bound by the laws of physics, in which case all that the thought-experiment proves is that something that breaks the laws of thermodynamics breaks the laws of thermodynamics, which is a pointless tautology. From the article, I see some people have already made similar criticisms, but despite that "The concept of Maxwell's demon has provoked substantial debate in the philosophy of science and theoretical physics, which continues to the present day". Iapetus (talk) 12:09, 15 June 2022 (UTC)
 * Whether it is useful or meaningful is up for debate but even if not it is part of the history of science. We no longer use the phlogiston theory to explain combustion but Wikipedia has an article on the subject because it is notable, not because it is currently useful. Mike Turnbull (talk) 13:49, 15 June 2022 (UTC)
 * That response seems a little misdirected &mdash; I don't see the slightest indication that Iapetus doesn't think Wikipedia should have an article on Maxwell's Demon. --Trovatore (talk) 16:56, 15 June 2022 (UTC)
 * Thought experiments that pose hypothetical questions are valuable in education to encourage reasoning. They include Schrödinger's cat, illustrating quantum indeterminacy through the manipulation of a perfectly sealed environment and a tiny bit of radioactive substance, and Maxwell's demon, which attempts to demonstrate the ability of a hypothetical finite being to violate the 2nd law of thermodynamics. The article is rated C-class, meaning it is substantive but might still be improved. Maxwell's concept of 1867 is still a fruitful sourcee for experimental work that includes an experimental realization of a Szilárd engine. Philvoids (talk) 14:16, 15 June 2022 (UTC)
 * Trovatore is correct - I'm not disputing that Wikipedia should have an article on it. My question is why was it (and apparently still and is) considered worthy of "substantial debate in the philosophy of science and theoretical physics", when it looks to me to be so obviously a flawed concept. Iapetus (talk) 08:51, 16 June 2022 (UTC)
 * The point of a thought experiment is usually to clarify the properties of a model or theory and to clarify hidden assumptions. Therefore, getting the correct result is often less important than understanding how that result comes about. Maxwell's demon seems to show an inconsistency between elementary mechanics and the laws of thermodynamics. Is there really an inconsistency? Why not? What hidden assumptions are being made? How can they be clarified and corrected? Are there other situations where we may be making a similar assumption? Thinking about these questions in the case of Maxwell's demon has led to important developments in understanding measurement, information, and computation as physical processes. --Amble (talk) 16:30, 15 June 2022 (UTC)


 * Einstein's most famous thought experiment, chasing a beam of light, changed the laws of physics of space and time as they were understood at the time. His thought experiment of a person floating in a box and then falling to the floor led to the even much more revolutionary concept of a curved spacetime continuum. His later thought experiments regarding "spooky action at a distance" did not change the laws of quantum physics – which Einstein had helped establish – but were fruitful in helping to push the understanding of the theory and forced theoretical and experimental physicists to be much more precise. When Maxwell conceived of his thought experiment the second law of thermodynamics was not nearly as firmly established as it is now. I think it was triggered by Kelvin's formulation of the law: It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects. [My emphasis by underlining. --L.] Whatever the case, as pointed out by Philvoids above and also explained in our article, Maxwell's thought experiment has proved a fruitful driver for important theoretical and experimental work.  --Lambiam 17:08, 15 June 2022 (UTC)
 * Why would a demonic sorter sorting be useful? Ha. I'm too often not all that helpful, but scientists are well-known, because of a lack of knowledge, for being myopically dead wrong, but slog on because they believe they are not since their work is useful. The noble objective, obviously, was/is simply an entropy-busting sort, but the suggested means to that end, a hypothetical gate-keeping demon, does allow for knocking down their strawman and the promulgation of that knowledge. BTW, I've just started playing Wordle and found that the word "youth" is a nice followup to "raise". -Modocc (talk) 18:43, 15 June 2022 (UTC)
 * Why would chasing a beam of light be useful? The question completely ignores the nature and purpose of a thought experiment and therefore is myopically dead wrong, perhaps because of a lack of knowledge. Many people are myopically dead wrong because of a lack of knowledge. This is so common that it usually does not draw any attention, unless, of course the mistaken person is a scientist. --Lambiam 20:56, 15 June 2022 (UTC)
 * Thought experiments are common too, but note that "The noble objective, obviously, was/is simply an entropy-busting sort..." It's why the demon has drawn attention. Modocc (talk) 21:26, 15 June 2022 (UTC)
 * The undisguisedly ignoble objective of the EPR paradox was to bust quantum mechanics.  While not successful in that respect, it instigated, among other things, the discovery of Bell's theorem.  --Lambiam 10:53, 16 June 2022 (UTC)
 * First Einstein, now another one? Sorry, but such appeals don't impress. My not so subtle point above is that the demon is likely too constrained to bust the 2nd law. In other words, in spite of the derived no-go theorems on account of the demon, the 2nd law can be wrong. --Modocc (talk) 12:25, 16 June 2022 (UTC)
 * The E in EPR stands for Einstein. --Lambiam 14:01, 16 June 2022 (UTC)


 * I think that the Maxwell demon is a bad illustration of a good point. The better illustration is the Brownian ratchet, unfortunately that one was produced later and is therefore less famous. The point is that if you apply macroscopic intuition to microscopic events, you can easily imagine a device that violates the second law. Introducing a "demon" muddles the waters, because the demon needs to violate certain rules (of biology for starters) to exist, and the argument becomes "yes but ignore that, just look at thermodynamics and there is a problem". Tigraan Click here for my talk page ("private" contact) 09:21, 16 June 2022 (UTC)
 * I think is not rational to treat the laws of thermodynamics as sacrosanct. To call the second law into question makes one sound like a crank with a perpetual motion machine to sell, but this is a shame, because everything should be amenable to criticism. Second_law_of_thermodynamics contains the words the ability of living organisms to grow and increase in complexity, as well as to form correlations with their environment in the form of adaption and memory, is not opposed to the second law – rather, it is akin to general results following from it: Under some definitions, an increase in entropy also results in an increase in complexity, which sounds defensive to me, and like special pleading: certain organizing effects don't count as organization, apparently, if they spoil our laws to which we are wedded. I enjoy vaguely thinking of information and matter and energy as the same thing, and thinking of the potential for information processing to defy entropy (and for humans, or whatever follows, to ultimately escape the heat death of the universe, if there is one), and Maxwell's demon is relevant to that. Card Zero  (talk) 12:03, 16 June 2022 (UTC)
 * There is extensive literature on Maxwell's demon that shows why and how it cannot work. Nevertheless, as fate would have it, I can use the equipment on my kitchen table to demonstrate that the 2nd law is toast. At the macro level there appears to be no gate-keeper(s) involved. Go figure. Modocc (talk) 14:53, 16 June 2022 (UTC)
 * Feel free to give us your experimental setup that disproves the 2nd Law of Thermodynamics. --OuroborosCobra (talk) 14:08, 17 June 2022 (UTC)
 * I could, but not today. Later this summer perhaps, after I've ensured that my invention(s), patent applications and eventual public disclosures are robust, sufficient and necessary, such as no extraneous apparatuses that hinder their costs and utility. Modocc (talk) 16:07, 17 June 2022 (UTC)
 * You've been saying that for years now. Nil Einne (talk) 02:37, 21 June 2022 (UTC)
 * I don't think that's special pleading. I suspect its more likely just a pre-emptive counter to Creationist claims that growth or evolution etc violate the second law.  (I haven't run into too many creationists recently, but 10 years ago or so, they were all over any discussion vaguely evolution-related, posting the same disproven claims about e.g. biological processes allegedly violating the laws of thermodynamics, which in turn lead to a lot of articles about such things getting written in very pedantic ways to counter that). Iapetus (talk) 08:53, 17 June 2022 (UTC)