Misplaced Pages

Latest revision as of 15:09, 5 September 2024

This is a list of interesting articles on wacko theories; unfortunately, these attract wacko and crank edits, and various shades of subtle vandalism. These articles should be watched for inappropriate edits.

The list of pseudoscientific theories is a target of frequent crank edits. So are many articles in Category:Pseudoscience; physics topics should be categorized in Category:Pseudophysics.

Famous historical blunders

Blunders involving famous academicians and institutes.

• Polywater is a supposed polymerized form of water.

Semi-legit topics

Compelling ideas that attract both legit academic and crank/original research.

• Quantum brain dynamics - I am currently working on reviewing the literature for this article, but most scientists agree that the brain is simply not a quantum system. Watch out for one researcher who is editing this article and quantum mind with his own work.

• Electron black hole - idea that fundamental particles are somehow black holes. (I accidentally channeled this mess, sorry. linas 1 July 2005 00:55 (UTC))

• Afshar experiment is an idea that is out there.

• Many articles in Category:Quantum measurement have long-running edit disputes.

• Generalized theory of gravitation -- describes researches done by Einstein late in life (which he really did do)... but the article attracts edits claiming that the theory is now classified top secret by the US Navy because it can make ships invisible, etc.

Discussion for Misplaced Pages:Pages needing attention/Physics

Notice to members of WikiProject Physics: Pages needing attention (PNA) is being reconfigured as a bot-maintained list of cleanup, expansion, and expert attention requests, as well as one-stop shopping for relevant portal, wikiproject, category, and stub category links. As such, comments on PNA must be moved to talk pages or to wikiprojects. As such, the following are moved here. Alba 12:56, 10 April 2006 (UTC)

Listed since December 2005 CE, most recent first

New Articles:

• Electrotherapy full of pseudo-science. Thehalfone 11:26, 12 November 2007 (UTC)
• Exploded Planet Hypothesis Seems at first glance a certain pseudo-science theory.. Danski14 05:23, 6 March 2007 (UTC)
• Photon Structure.. possible AfD or Speedy or Prod candidate. Danski14
• Relativistic Variable Mass Synchrotron possible promotional essay. Danski14 20:37, 21 February 2007 (UTC)

• Three articles in particular,

• Dirac equation in the algebra of physical space,
• Algebra of physical space, and
• Paravector,

have all been created and written by two users which may or may not be the same person:

Cabrer7 (Contributions) and

137.207.80.65 (Contributions)

The sentence that triggered my suspicions came from the introduction to the Paravector article,

This name was given by J. G. Maks, Doctoral Dissertation, Technische Universiteit Delft (Netherlands), 1989.

JabberWok 17:08, 9 December 2006 (UTC)

• In Fundamental interaction before in the chart, it said the Strong interaction has a range of "1.4 x 10^-15 m". Now it says "infinite". Is this difference significant? I know someone said, I can't recall who, "Just because it's infinite doesn't mean it's zero", but what about in this case? --GangofOne 03:41, 15 April 2006 (UTC)

This is a confusing one. It doesn't seem as though there is any disagreement about the physics of the range. The effect, which everyone seems to agree on, is that there is a nuclear force with a short range. But some users seem to draw a distinction between the nuclear force, which I guess they consider to be carried by pions (which are massive and unstable) and some abstract notion of chromodynamics, where the carrier is the gluon (which is massless and stable). I don't know if this distinction is standard among lattice gauge theorists.

The trouble with this abstract notion of chromodynamics is that experimentally the gluons appear to be confined. If this can be proved theoretically, whoever does the proof wins a million US dollars from the Clay foundation. But the experimental evidence at the temperatures and pressures typically encountered on Earth (less than 5 trillion degrees or so) is pretty overwhelming that the gluons are indeed confined. So, at everyday temperatures and pressures, there isn't any force mediated by gluons because gluons can't ever get themselves free. Effectively (and approximately), they're always bound to pions. So this distinction that the authors create between chromodynamics and the nuclear force is really all a bit artificial, there's only a nuclear force (except for very extreme environments, such as perhaps the interior of a neutron star and for brief periods in some laboratories) since pions can freely move around transmiting forces (in the 10^-23 seconds before the decay) whereas gluons are only some abstract virtual internal excitation.

Besides the range, the scaling has also been changed to 1, a scaling of 1 and range infinite would be correct if one considers, as was popular during the early 70s (but replaced by the chromodynamics in the standard model) the action of the strong force on two particles to be described by a string which connects them. However, both the 1 and the infinity fail even in this picture when one realizes that such strings would break when, for example, a quark and antiquark pair create in the middle. This effect is refered to as screening, and I feel that it invalidates the recent changes made to the table.

Perhaps to resolve these two issues one can specify that the table is only valid in one particular region of the QCD phase diagram, say, temperatures below 5 trillion and reasonable pressures, and put back the old values of the scaling and range?JarahE 01:07, 18 April 2006 (UTC)

• Check this out: Edward Seykota. Until I happend along, this article read like an advert, but Seykota is not hiding his physics claims; see . Probably my infobox summary of his claims can be improved. ---CH 22:10, 1 April 2006 (UTC)

My understanding was that a significant amount of the lift produced over an airfoil was due to the Coandă effect, not just Bernoulli's principle. Among other things, this is why it isn't impossible for stunt aircraft to fly upside-down. However, I'm not an aerospace engineer, so it's quite possible that I'm wrong about the degree to which the effect is relevant under normal flying conditions. --Christopher Thomas 22:24, 1 April 2006 (UTC)

Is there an aerospace engineer in the house? ---CH 00:50, 2 April 2006 (UTC)

• User:Haselhurst has uploaded a number of images which I believe to by copyrighted (e.g. by the Emilio Segre Visual Archive) but which he credited to his own website, which appears mostly devoted to Wave Structure Matter. Haselhurst has edited a number of articles including Wave Structure Matter, History of the Wave Structure of Matter, Milo Wolff which extensively discuss Wolff's collaboration with Ronnie Haselhurst on this fringe theory, and he has cited a work by himself which is published by Apeiron Press, which says of itself, Apeiron Press specializes in the publication in electronic form of books that could not otherwise be published. Indeed, one of their other authors is Tom Van Flandern; see citations in Le Sage's theory of gravitation. This raises (at least in my mind) questions of WP:RS, WP:AUTO, and WP:NPOV. ---CH 04:21, 29 March 2006 (UTC)
• User:Kopeikins has created some new articles in which he argues his (minority) viewpoint in the Kopeikin "speed of gravity" controversy, which need to be WP:NPOV'd:
  1. Aberration of gravity
  2. Post-Newtonian expansion
• Speed of gravity: User:Tomvf and 24.113.28.179 (Tomvf seems to say that this anon was acting on his behalf; he has a fan club so this is quite possible) is once again trying to make POV-pushing edits of the section dealing with his cranky ideas. See this archive of past arguments with TVF by Steve Carlip and myself, and see also this eprint by Carlip rebutting TVF's claims. Also, User:Skopeikin has been editing the section dealing with the controversy in which he is a direct participant, so far no flagrant POV pushing that I have seen but this bears monitoring. Note that TVF is trying to introduce his personal (cranky) notion of speed of gravity. I am unwilling to waste any more of my time "arguing" with TVF (see the archive just cited to see why I found this so frustrating and ultimately pointless), and in fact am disengaging from WP article space, so it will be up to others to try to maintain WP:NPOV in this article.---CH 17:18, 23 March 2006 (UTC)
• Oersted,Centimetre gram second system of units in my humble opinion those article should at least contain the same information as the appendix of Jackson's electrodynamic --LN2 05:46, 18 February 2006 (UTC)
• Genealogy of Theoretical Physicists proposed deletion. fix it or lose it. GangofOne 01:55, 8 February 2006 (UTC) Deletion attempt thwarted. Was C- quality, now B-; polishing is still possible. If everyone adds just one fact, then there will be 6e9 new facts on it. GangofOne 03:41, 15 April 2006 (UTC)
• Zitterbewegung -- target for edits that insert pseudoscience refs. linas 21:29, 29 December 2005 (UTC)
• Zero-point energy -- mish-mash of phsyics and pseudoscience. Of course, these days, zero-point energy is about both, but each of these topics should be treated distinctly. linas 21:29, 29 December 2005 (UTC)
• Black hole. It seems like about once every two weeks someone has an epiphany, decides that it's impossible for black holes to form due to gravitational time dilation approaching infinity as collapsing material approaches the horizon radius, and posts about this on the talk page. If someone more eloquent than I am could put a layman-convincing explanation of why this is _not_ the case somewhere prominent in the article, that would be extremely helpful. --Christopher Thomas 08:18, 28 December 2005 (UTC)

Maybe the recurring epiphanies people are having are due to the fact that it's a perfectly viable reflection of reality? Denial ain't just a river in Africa. (Sorry I'm just having a ball with this thing, nothing personal.) David Ashley 05:00, 29 December 2005 (UTC)

The reasons why this interpretation isn't accurate are presented at Schwarzschild metric. I'm sure any of the GR physicists lurking here can give you a more detailed explanation. Short version is that the visual effect is an illusion caused by the fact that light emitted near the horizon can take an arbitrarily long time to escape the hole, and that the mathematical effect that gives you the "frozen star" interpretation is an artifact of the coordinate system Karl Schwarzschild used the first time he did the analysis. This is discussed in detail at Schwarzschild metric. I've given this overview enough times to get really sick of doing it, so we need something in the article that explains it more convincingly (showing it, as opposed to saying it, because people apparently don't want to just take the word of all of the textbooks on the subject). --Christopher Thomas 17:45, 29 December 2005 (UTC)

• Entering a black hole

The paragraph states: "A black hole's gravity as described by the Theory of Relativity causes a number of peculiar effects. An object approaching a simple causes a number of peculiar effects. An object approaching a simple Schwarzschild-type (non-rotating) black hole's center will appear to distant observers as having an increasingly slow descent as the object approaches the event horizon. This is because photons emitted as the object approaches the horizon take an increasingly long time to escape from the pull of the black hole to allow the distant observer to gain information on the object's fate."

This can be interpreted as if the light was slowed down to a speed less than c, which, as to my understanding, is impossible. Instead, I think the effect is due to the time dilation so that successively emitted photons, all well traveling at speed c, arrive at increasing intervals of time because the points at which they were emitted are seen to have an increasing distance in time by the observer though not by the emitter.

Could someone whit a really firm knowledge of this subject please have a look at the article and the talk page? 84.160.227.124 11:21, 6 January 2006 (UTC)

This can be interpreted... is wrong; please see for example Geroch, Relativity from A to B, which offers an excellent nontechnical illustrated discussion of basic Schwarzschild vacuum geometry, focusing on the black hole property (the event horizon) not on the maximal extension, of course. ---CH 17:22, 23 March 2006 (UTC)

If people took textbook's words for things science wouldn't make very much progress. The arguments above for the existence of black holes rely on general relativity. Here's an argument championed by John Preskill about why this approximation cannot be trusted in the case of black holes. General relativity is a classical approximation to our world, which is valid at energies far below the Planck scale. The validity of this approximation is at best poorly understood in the case of objects falling into a blackhole, because the redshift of the light emitted by such objects goes to infinity as the object approaches the black hole. This means that very high energy physics (above the Planck scale) from the point of view of the infalling object must be understood in order to understand the light which an outside stationary observer measures to be sub-Planckian. In other words, the infinite Doppler-shift invalidates the usual approximation that super-Planckian physics (ie quantum gravity) can be ignored to calculate low energy effects and so it puts in doubt the applicability of general relativity to the horizon, despite the fact that the curvature is quite small at the horizon of a large black hole.

This means that it is very possible that the existence of black holes depends on which quantum gravity theory describes our world, and that in some quantum gravity theories they do not exist (see also fuzzballs). Some of the leading relativistists have proposed in the past that this is the case, see for example Evanescent Black Holes by Curtis Callan, Steven B. Giddings, Jeffrey A. Harvey and Andrew Strominger who proposed that black holes evaporate before they form, which is another version of the scenario criticized above. JarahE 19:18, 25 March 2006 (UTC)

The debates aren't about whether the GR description of black holes is completely accurate - it's assumed by most scientists that it _isn't_, and this is prominently noted in the article. The problems occurring are with misinterpretations of the _GR description_, especially in the specific ways outlined above. The majority of the black hole article is concerned with the GR description of black holes, as it's the best uncontroversial description we have to date. The reason it's listed here is that we're getting people regularly showing up saying "statement X about (GR) black holes is incorrect because of (handwaving argument)!", and not taking sketched explanations or "read this stack of references" for an answer.

Does this make clearer what these threads are about? --Christopher Thomas 07:08, 29 March 2006 (UTC)

Ok, yeah I admit I was playing devil's advocate. I agree with you that people who say that GR and black holes are inconsistent have a faulty argument, and that obviously such faulty arguments shouldn't be put on the page.

But at the same time, I think a more serious problem among people who should know better is that they think that black holes must exist in the quantum theory because the curvature is small near the horizon and so quantum effects should be small. But invariably their arguments have a step, like a transformation to Finkelstein coordinates, which is singular and lets the quantum physics back in. I think that as a result people in general aren't cynical enough about black holes. This is compounded by astronomers claiming to have seen them (which of course is impossible, black holes being black and all, they just see cosmic rays so intense that were GR to be a valid description would indirectly imply the existence of a black hole.) In my opinion this skepticism should be conveyed at least on the trans-Planckian problem page, if not on the black hole page. JarahE 18:10, 29 March 2006 (UTC)

• Gravitational interaction of antimatter -- Could use vetting by experts in particle physics and relativity, as it presently comes across as a pitch for antigravity, and I'm not well-versed enough to evaluate the cited references. --Christopher Thomas 06:17, 21 December 2005 (UTC)

References to this article have been added to a large number of other articles by Intangir (talk · contribs). Vetting some of these additions might not be a bad idea. --Christopher Thomas 19:45, 26 December 2005 (UTC)

I find the current state of the article "acceptable" from the physics point of view. Last I looked at it, it was not cranky, and discussed legit physics in a legit way. I'd even suggest de-listing it here; while the article could be improved, its not (currently) bad. (It may, however, become the target of the pseudosciene crowd, and thus should be watched over). linas 21:29, 29 December 2005 (UTC)

If we can get one or two additional people signing off on it, then it should be safe to de-list it and remove its "disputed" template. Hillman (talk · contribs) should probably be one of these, as he'd had several concerns about the article's content. --Christopher Thomas 22:00, 29 December 2005 (UTC)

I think I addressed the only factual accuracy concern which Hillman actually stated. In fact, I just deleted the disputed content. However, I'd rather not have it un'disputed' until Hillman has had a chance to respond with any potential new factual accuracy complaints. Also, both of us have plenty of non-fact-oriented issues with the current state of the page, and it will probably have a clean-up tag for some time. However, this can probably be delisted from here after Hillman comes back from wikivacation. --Intangir 02:47, 31 December 2005 (UTC)

• Cosmic censorship hypothesis - As far as I know (and I'm not an expert, which is why I've tagged it as needing expert attention) determinism isn't considered factual, just a theory (and disputed by chaos theory). This article reads like determinism is a fact and therefore cosmic censorship must exist. — Preceding unsigned comment added by 63.26.24.223 (talk • contribs) (18 December 2005)
  • (moved from old threads) Cosmic censorship hypothesis - the article is not very well written, the narration is weak, I had to reread it a few times before I noticed some of the factual statements (even though it's very small and relatively simple). For example, in one place it says "special situations just mentioned", but it's not clear, what are these situations. Paranoid 19:41, 20 Nov 2004 (UTC)
• Project Orion - Currently under very enthusiastic revision by Flying fox (talk · contribs). At minimum the revisions need editing for tone, and fact-checking would be a very good idea as well. --Christopher Thomas 06:44, 8 December 2005 (UTC)
• Talk:Autodynamics -- I'd proposed an infobox to summarize AD's departures from mainstream science, and there is now debate over exactly what AD is claiming. If any relativity experts want to contribute, that would be great, as I really don't feel up to getting back into that debate again myself. --Christopher Thomas 23:08, 20 December 2005 (UTC)

Commented on within the past month

• Measurement in quantum mechanics

"I think this is a mess but I lack the skills to fix it. Someone who knows QM well might comment" from cleanup >2 months, needs someone knowledgeable on subject. rhyax 06:24, 10 Sep 2004 (UTC)

I've gone over the grammar, and made a suggestion for dealing with it more thoroughly on the article's talk page Bth

I moved this from the "mathematics" section. Paul August ☎ 18:33, Jun 5, 2005 (UTC)

I updated this page in the light of quantum decoherence, cleaning up a lot of obsolete and incorrect statements. Dave Kielpinski 00:35, 19 December 2005 (UTC)

• Infrared fixed point - is this article for real? RJFJR 19:59, Apr 30, 2005 (UTC)
  • It seems to be a real term, as far as Google can tell; it's used in journal articles by many different authors (unlike crackpot science, which tends to be cited among a small circle of authors). I didn't find peer-reviewed publications on the first search, but I spent all of 5 minutes on it. The article needs cleanup by a particle physicist, though. --Christopher Thomas 20:14, 30 Apr 2005 (UTC)
  • Yes its real. Comes from renormalization group theory, though the article needs to be rewritten. I have to think about it more , but I started to fix it upSalsb 1 July 2005 18:23 (UTC)
    • There seems to be some duplication at cutoff scale. I've added "see also" links, but this could use attention from a physicist. --Christopher Thomas 01:46, 8 December 2005 (UTC)
• Proximity Effect Please help! I created the stub because it was originally an article about a comic book, but I'm a clueless idjit when it comes to Physics and prolly wrote nonsense, although I tried hard not to. KillerChihuahua 13:46, 19 September 2005 (UTC)

I believe that proximity effect is now in reasonable shape although I still haven't made up my mind about the atomic physics section. Alison Chaiken 05:06, 29 December 2005 (UTC)

Archive

I'm moving discussion threads from PNA/Physics here once they wind down to reduce clutter. Some of the pages are still in the PNA/Physics list, while others have been removed but have discussion that may still be relevant. Discussion that's no longer relevant to PNA/Physics should be moved to the talk pages of the articles in question. Discussions that are still active should stay on PNA/Physics.--Christopher Thomas 18:40, 26 Jun 2005 (UTC)

Negative energy

(Comments moved here for further discussion/archiving. --Christopher Thomas 18:40, 26 Jun 2005 (UTC))

• Negative energy - Article says it needs attention, but was not listed here before now. I do not understand the article at all.
  • As far as I can tell, it was pure gibberish. I've replaced it with a redirect to exotic matter (the same place negative mass redirects to). --Christopher Thomas 16:12, 26 May 2005 (UTC)
  • The concept of "Negative energy" is used to explain the Casimir effect and is not directly related to negative mass. The best option for now is to either re-write that article completly or VfD it for now. Awolf002 16:10, 4 Jun 2005 (UTC)
    • I'm not convinced that the Casimir effect's definition of "negative energy" is a better reference than the one presented at exotic matter. Exotic matter has negative kinetic energy when in motion, and also has negative energy density in the way that term is used in general relativity. Thus, I consider it a better redirect point, for now. --Christopher Thomas 22:56, 6 Jun 2005 (UTC)

Various topics relating to quantum mechanics

(Comments moved here for further discussion/archiving. --Christopher Thomas 18:40, 26 Jun 2005 (UTC))

• Clauser and Horne's 1974 Bell test is incomprehensible to someone who doesn't already know what the article's talking about. ] 17:42, 2004 Aug 7 (UTC)
  • Not knowing any better, I tried linking to a book which is a popular treatment on the subject. The article's main author disagrees with the book, and subsequently reverted. Thus the article and related articles and comments currently serve as balance for quantum entanglement, for which the author states there is no experimental basis, in contradiction with the book I referenced. By the way, the experiment examines a consequence of a POV which Albert Einstein tried to use, to disprove quantum mechanics. The issue is local reality versus non-local reality. Teleportation is a consequence of non-local reality. It's an important subject. Ancheta Wis 01:05, 17 Aug 2004 (UTC)

Given that Quantum entanglement now says that the phenomenon has been proven, it's probably OK to add that reference back in. -- Beland 01:27, 19 Aug 2004 (UTC)

One of my objections to that reference was that it was clear that it did not deal specifically with the CH74 test, which is the subject of the article. It could perhaps be given as a ref from Quantum entanglement. However, I suspect it of factual inaccuracy, e.g. in relation to Aspect's experiments. Probably it is no worse than other popular books though.

Incidentally, contradictory though it may seem, "quantum teleportation" does not necessarily (according to Braunstein, one of the experts) involve nonlocal effects. Caroline Thompson 21:18, 22 Aug 2004 (UTC)

I've added a little "background reading" to Bell's theorem. Other popular books can be added here. I don't see the need to suggest other reading from pages such as Clauser and Horne's 1974 Bell test as these are not intended to be treated as anything other than subpages of the Bell's theorem page.

The book list is preceded by a caveat regarding the likely accuracy of the information on actual experiments. This may perhaps be seen as presenting a biased view, but this is only right in the context. Bell's theorem is based on the local realist point of view and it is only fair that the world should be warned that popular books are riddled with mistakes. Contact me for refs.Caroline Thompson 10:45, 24 Aug 2004 (UTC)

• The following articles should be checked for factual accuracy and NPOV by someone familiary with quantum theory and who believes in the dominant professional scientific view: Bell's theorem; CHSH inequality; Clauser and Horne's 1974 Bell test; Bell test experiments; Local hidden variable theory. -- Beland 01:27, 19 Aug 2004 (UTC)
  • A question: Is someone who "believes in the dominant professional scientific view" likely to have made a specific study of the loopholes in Bell test experiments, or know the difference between the assumptions behind the various Bell tests? These are not subjects covered in standard physics courses. I'm afraid there's a problem here: knowing the facts it's impossible to have a neutral point of view! I very much doubt if any of the material in the new Bell's theorem page is wrong. It has been checked by an expert who has been involved in the subject since Bell's time. Caroline Thompson 21:18, 22 Aug 2004 (UTC)

Actually, teleportation obeys locality, but not "reality" (in its technical sense). Most popular treatments are pretty poor on this point. This is due to abuse of language in the quantum physics community. It's surprisingly easy to argue most quantum measurement folks out of calling anything "nonlocal" by invoking quantum field theory, widely considered the most successful theory in all of physics, which takes locality as an axiom.

Furthermore, amateur contributors should be aware that local realism and denying the validity of Bell test experiments are views held by a small minority of physicists. Dave Kielpinski 00:28, 19 December 2005 (UTC)

• (Consolidated the QM topics into a list, moved discussion to PNA/Physics talk page. Concerns were expressed about accuracy and POV bias for these articles. --Christopher Thomas 18:44, 26 Jun 2005 (UTC))
  • Bell's theorem
  • CHSH inequality
  • Clauser and Horne's 1974 Bell test
  • Bell test experiments
  • Local hidden variable theory.

Cosmology

• Big Bang, Ultimate fate of the universe, Plasma cosmology, and other pages. Big Bang has been in an edit war for about a week as of this writing, Ultimate fate of the universe has recently been dragged in, and my understanding is that the long-standing dispute over content at Plasma cosmology boiled over again in a similar timeframe. The core issue seems to be the degree to which the views of Plasma cosmology are included in Big Bang and Ultimate fate of the universe, and what an appropriately neutral description of Plasma cosmology itself would involve. I'm not touching any of this until the relevant RFCs and RFAs have been settled. However, having more editors contribute to the RFCs and talk pages and check for bad edits/reversions would probably help establish what consensus is for these pages. --Christopher Thomas 22:47, 22 November 2005 (UTC)

Crackpot topics

Ideas lacking a critical foundation. This list may be superfluous, as all of these, and much, much more, already appear in Category:Pseudoscience.

• Autodynamics (AD)' is a theory proposed as a replacement for special relativity, which is claimed to have been based on erroneous assumptions.
• Creationist cosmologies offer by Young Earth Creationists as alternative ideas about cosmology to allow for a universe that is only thousands of years old.
• Dynamic theory of gravity
• Heim Theory (see also Burkhard Heim), a Theory of everything with small, mostly german and austrian following.
• HHO gas magical fuel making all sorts of unsupported claims.
• Hydrino theory proposes the hydrino, or miniature hydrogen atom with the electron pushed closer than usual to the nucleus.
• Kirlian photography is high-voltage contact print photography. Its existence is not disputed, however the paranormal interpretations of some images thus produced are.
• Modern geocentrism, citing uniform gamma ray bursts distribution as evidence that we are at the center of the universe, and other ideas of this liking.
• Wilhelm Reich's Orgone energy is an unproven form of energy.
• Perpetual motion machines
• Polarizable vacuum
• Synchronicity refers to the alignment of forces in the universe to create an event or circumstance.
• Time Cube, the idea that we live 4 actual days for every 1 perceived day, a fact not apparent to us because of a vast academic conspiracy.

Pages to watch out for

These are legitimate topics that nevertheless may attract strange edits.

• Unsolved problems in physics

• WikiProject Physics