Wikipedia talk:WikiProject Physics/Archive February 2011

An old merge proposal

If anyone is interested, it appears that a merge was proposed, in July 2010. It was proposed that thsee two articles [1], [2], be merged into this article [3]. No discussion appears to have taken place, hence there appears to be no objection for this set of merged articles. ---- Steve Quinn (talk) 05:04, 23 January 2011 (UTC)

If there hasn't been any discussion, take a straw poll here before declaring it closed for or against. I'll set up a sub-heading for that. Ideally it'd be on one of the article pages (probably that of the merge-to target), but the templates should have automatically listed it for discussion already. --Christopher Thomas (talk) 06:43, 23 January 2011 (UTC)

In terms of procedure, if the merge tags have been there for 6 months with nobody disagreeing, it seems perfectly reasonable to just go ahead and merge them! Djr32 (talk) 11:51, 23 January 2011 (UTC)

Lack of comment doesn't indicate a consensus in either direction. While you could make an argument for WP:BOLD favouring a merge, the usual action in a "no consensus" situation is to leave things as they are. In practice, the right thing to do if one feels a merge is warranted is exactly what Steve Quinn actually did: bring it up in a venue where discussion will be generated. --Christopher Thomas (talk) 18:39, 23 January 2011 (UTC)

Straw poll for the Boltzmann merge

• Merge both as proposed, due to strong overlap of existing content. --Christopher Thomas (talk) 06:43, 23 January 2011 (UTC)
• Merge, as per Christopher Thomas. -- cheers, Michael C. Price ^talk 10:27, 23 January 2011 (UTC)
• Merge, as per Christopher Thomas. PAR (talk) 11:28, 23 January 2011 (UTC)
• Merge Boltzmann's entropy formula, not so sure about Boltzmann entropy, which seems to be more about a specific approximation, so could either be a section within the main entropy article or a separate article. Djr32 (talk) 11:51, 23 January 2011 (UTC)
• Oppose - the proposed target article is already pretty horrible. /Pieter Kuiper (talk) 11:59, 23 January 2011 (UTC)

  Sorry, but why exactly is that an argument against merging?TR 16:37, 23 January 2011 (UTC)

• Merge, as per Christopher Thomas.TR 16:38, 23 January 2011 (UTC)
• Merge, per above discussion. The formula doesn't warrant a separate treatment from the concept which it relates. Headbomb {talk / contribs / physics / books} 20:58, 23 January 2011 (UTC)
• Merge to get rid of the shorter Boltzmann entropy article, which can be a sub of any one of a number of articles, including Boltzmann's entropy formula. Regarding the last, it is a semi-historical treatment of a formula, and we do have semi-historical articles on formulas, for example Balmer's formula, Rydberg equation, and so on. The lapidary version of Boltzmann's equation on his tombstone after his suicide sets us up for a more historical treatment of this equation (otherwise it would be trivia in a physics-only article). So I vote to keep Boltzmann's entropy formula and content, if only as a repository to keep some of the history of the physics, like the wonderful example in Dirac equation. More of the story of this equations development will eventually go here, and meanwhile it can be used as a main or subarticle whenever the subject comes up. SBHarris 22:33, 23 January 2011 (UTC)
• Comment If this merge is done, it might be an idea to also add work in some of the material that used to be at Gibbs entropy formula, which was lost when that article was similarly turned into a redirect. Jheald (talk) 14:16, 2 February 2011 (UTC)

Fields in Physics

Should Force field (physics) be merged to Field (physics)? If so, let's do it. Biophys (talk) 20:04, 31 January 2011 (UTC)

Maybe it should be merged into the examples on Classical field theory? I'm not sure why there are so many different articles about fields? Shouldn't they all be merged?--Dudemanfellabra (talk) 22:12, 31 January 2011 (UTC)

I tried to rewrite the article earlier today, I think it's worthwhile and shouldn't be merged. A force field is just a position-dependent force. For example, when an object is attached to a spring, the spring's force is described by a force field, but there's no "field" there in the physics sense. When an object travels while subject to a force field, the work done by the force is calculated with a line integral, an important theorem taught in introductory calculus courses and physics courses. This is not a complicated topic, and there's not too much to say, but it's worth an article, and definitely different from a "classical field" in physics. It is also important background for more advanced discussions, for example the article conservative force includes many links to force field. --Steve (talk) 07:34, 1 February 2011 (UTC)

I agree that the spring example can be modelled as a force field, but it isn't actually a force field because the spring is in direct contact with the object; there is no "action at a distance" (i.e. the force doesn't have to propagate through free space to reach the object as it does in the gravitational/electric force). Even if all these articles aren't merged (and I still think a few of them should be), they should at least include links/subsections with {{Main}} templates to each other. Reading through Field (physics), I never once see a link to force fields, and I never once see a link to conservative fields. Basically I guess my gripe is with the Field article (just now noticing it is Start-Class). It should be expanded/restructured to include mention of all these types of fields/field-like forces.--Dudemanfellabra (talk) 16:10, 1 February 2011 (UTC)

I think that the definition of force field is wrong. It is not the force, it is the field which is multiplied by the charge (or mass or whatever) of the particle to get the force. In other words, the force fields depend on the environment of the particle, not the particle itself. And it is not just any field, but only those fields which produce forces on particles. JRSpriggs (talk) 16:30, 1 February 2011 (UTC)

This is very basic. As explained in electric field, for example, "The strength or magnitude of the field at a given point is defined as the force that would be exerted on a positive test charge of 1 coulomb placed at that point; the direction of the field is given by the direction of that force." There is nothing else.Biophys (talk) 17:59, 1 February 2011 (UTC)

JRSpriggs, I would say that the thing you are talking about is a (normal physical) field, not a force field. Since you're talking about something different, of course you will disagree with the definition. But the definition in the article is actually a definition that many people use, as proven by the citations that I put in. It's not the only definition, but it is a valid definition. This situation is hardly unusual, which is why we have disambiguations. Certainly you can find textbooks that agree with your preferred definition, where "force field" just means electric field or any other physical field. Maybe we can add some more disambiguation-type text to clarify that "force field" may mean other things even within physics and math.

Biophys, of course there is a close relationship between, say, an electric field and its associated force field: The force field F is the electric field E times the charge of the particle under discussion. Certainly it would be silly to discuss the "electric force field" as if it needed to be explained from scratch, when there's already a very nice article on the electric field. In the article there is only one line defining and discussing the electric force field, in terms of the electric field. It just serves as an example of a force field.

The important part of the article, which could be expanded more, is that a line-integral of a force field equals the work moving a particle along that path, and also that the divergence of a force field is zero or nonzero depending on whether or not it is a conservative force. Again, these things form an important and standard part of introductory vector-calculus or mechanics courses. In my first vector-calculus course many years ago (if I recall correctly), the relationship between force fields and work was the main example that motivated the definition of a line integral, long before I knew anything about the physics of electric fields or gravitational fields. --Steve (talk) 22:50, 1 February 2011 (UTC)

In my usage, E and B are parts of the electromagnetic force field while D, H, A and φ are other electromagnetic fields. Γ is the gravitational force field while g and R are other gravitational fields. JRSpriggs (talk) 11:13, 2 February 2011 (UTC)

No, E and B are parts of electromagnetic field, whereas electromagnetic force field is something very different, as Steve explained here. No merging, I guess.Biophys (talk) 18:58, 2 February 2011 (UTC)

astrophysics and dashes

See WT:AST, a person who deals with languages has asked about why astronomy articles are not using English grammar forms for dashes and hyphenation in terms, instead of spaces. Seems like another WP:DASH headache. 64.229.101.119 (talk) 04:35, 3 February 2011 (UTC)

Spark

Hey everyone, there's a small debate going on over the naming of the article Spark (fire) at its talk page. Any helpful and accurate input is much appreciated. Thanks so much!--Yaksar (let's chat) 14:05, 3 February 2011 (UTC)

• There's now a request for outside comment as well. Thanks again.--Yaksar (let's chat) 16:36, 4 February 2011 (UTC)

A move request

Hi everyone, there's a move request being debated here: Talk:Spark_(fire) as to whether it's accurate to refer to all sparks (of the heated particle kind) as types of fire. Since this seems to be a place where knowledgable science editors would be I ask anyone who potentially knows about the topic to come and give input. Thanks!--Yaksar (let's chat) 19:03, 6 February 2011 (UTC)

Tom van Flandern

I've tried to make same changes to this article, especially as regards the strange claims as regards the speed of gravity. Maybe other editors should look at it as well. It seems, that there was already an edit war on this article, so someone else should look at it as well. --D.H (talk) 21:29, 5 February 2011 (UTC)

The tone on that talk page is very bad and I think it looks like ownership mentality. I would not recommend to go there alone. This is definitly a page which need help.--Stone (talk) 12:20, 8 February 2011 (UTC)

Antichristos is back as Jsdhgsdjhg

As was to be expected, indef blocked user Antichristos (talk · contribs) is back as Jsdhgsdjhg (talk · contribs). See these edits. All the sources and most of the text is taken literally from the above collapsed section Wikipedia talk:WikiProject Physics#Speed of gravity. Left a message at blocking admin talk page. DVdm (talk) 22:03, 7 February 2011 (UTC)

Jsdhgsdjhg has been blocked. -- Crowsnest (talk) 00:32, 8 February 2011 (UTC)

Consciousness Causes Collapse

I recently posted these questions on the talk page for Consciousness Causes Collapse section of Quantum mind–body problem: Does this really mean that a creature's consciousness is somehow creating reality? How many serious physicists believe this?

I also appeal to anyone with knowledge of physics to make pages like this more accessible. The fact is, as a young scientist, I have to care which views scientists in other fields (i.e. physics) rate as most likely to be true, second most likely to be true, etc. So for one, any polls would be of great service.

On the other hand, I like to have as much of an ideas as possible, but sometimes 'explanations' are in deep need of metaphor or simpler summaries that follow them. Maybe someone could do something about this one: "The interpretation identifies the non-linear probabilistic projection transformation which occurs during measurement with the selection of a definite state by a mind from the different possibilities which it could have in a quantum mechanical superposition." It's just sort of left hanging there.

Thanks for your time-Tesseract2 (talk) 18:35, 1 February 2011 (UTC)

The collapse problem is a longstanding issue and was discussed seriously by physicists, especially in first half of the 20th century. And it still is discussed to this day, but in physics circles, it is referred to as the "collapse problem". However when you hear the "Quantum mind/body problem", it almost exclusively refers to the new age pseudoscience crap pushed in such books as The Tao of Physics or What the Bleep Do We Know!?. Headbomb {talk / contribs / physics / books} 19:02, 1 February 2011 (UTC)

Well, Roger Penrose's work is not, er..., ‘conventional’ but I wouldn't call it “new age pseudoscience crap”, either. (But he doesn't believe that consciousness causes collapse, either; at best, that collapse causes consciousness or something like that.) A. di M. (talk) 19:14, 1 February 2011 (UTC)

Did Penrose not have some idea such as that gravity is an exception, the one field which is classical rather than quantum in nature. So collapse of the wave function occurs when an effect is large enough to make a significant change in the gravitational field. In other words, the curvature of space-time is the ultimate "observer". Right? JRSpriggs (talk) 19:31, 1 February 2011 (UTC)

Yes, but my point is that he also had some idea such as that quantum superpositions have a fundamental role in the working of the human brain without which consciousness would be impossible. A. di M. (talk) 12:06, 2 February 2011 (UTC)

Note that "Consciousness Causes Collapse" and the MWI are effectively the same. There is no collapse in the latter case, but you have a superposition of different brains who have observed something differently, so you have an effective collapse in each sector corresponding to each outcome with nonzero amplitude. You can then say that being conscious of some result "causes" the collapse of the wavefunction of the rest of the universe. David Deutsch has shown that the reverse is also true. It is obvious that if you can erase the information you gained from the observation in a reversible way, the system would evolve back to the initial state, according the the MWI. The wavefunction would thus "uncollapse". However, you can do this (theoretically) while still retaining the information that a measurement was carried out. So, you reversibly "forget" the result, but you don't forget that you had measured the system, then the system will still uncollapse according to the MWI. Of course, this can only be done in practice using competely isolated systems, so you need to consider simulating an entire human brain using a quantum computer; the measurement would be something that takes place in the virtual world simulated by the quantum computer. Count Iblis (talk) 13:38, 2 February 2011 (UTC)

Some good information to start. Collapse being involved with consciousness is one thing (and not unsurprising, unless I am mistaken in being unsurprised that the small influences the large?) The more "new age" interpretation seems quite different: that it is the developed consciousness (like we see in humans) that causes the collapses of the wave function. At least that's the spooky claim I THINK is sometimes made and is being described.

Anyway, maybe some of you have cite-able sources you could add to the Quantum mysticism page and Quantum mind–body problem#"Consciousness causes collapse" section? To skeptic it up a little? Right now the positive case is presented with little or no negative case (which is, I would assume, the dominant position amongst physicists). Hell, I could do the writing if I knew which physicists we should be listening to that know enough about this sort of thing.-Tesseract2 (talk) 19:57, 2 February 2011 (UTC)

Ok well, in the end I ended up citing the criticisms against some generally uncontested claims over at Quantum mind–body problem#"Consciousness causes collapse". If anyone wants to provide second opinions they would be welcome.-Tesseract2 (talk) 16:08, 10 February 2011 (UTC)

Confused cosmology

Eyes needed at new article Doughnut theory of the universe, where the author seems to written a very confused and badly flawed interpretation of a New York Times popular science article. I have left my comments on the article's talk page. Can anything be salvaged from this, or should it go to AfD ? Gandalf61 (talk) 16:48, 6 February 2011 (UTC)

Looks like it could be merged 'n' redirected to some-other-article-whose-title-I-can't-remember-right-now about that. (Soooo many people assume that zero curvature everywhere must imply infinite spatial extent, so if we can point out that this is not the case citing reliable sources, we should do so somewhere.) A. di M. (talk) 17:44, 6 February 2011 (UTC)

I have now done some cleanup on the article to remove the most obviously incorrect parts. Gandalf61 (talk) 06:51, 11 February 2011 (UTC)

What to do with Particle acceleration, Particle displacement, and Particle velocity?

Stumbled upon these. Not too sure if they should be merged, deleted, or redirected... Opinions? Headbomb {talk / contribs / physics / books} 07:48, 10 February 2011 (UTC)

Particle displacement as the result of passing waves seems to be notable subject, that is used in various ways in the observation of waves in continuous media. (See the results of this gbooks search). I'm not sure if particle velocity and particle acceleration, being the first and second time derivatives of the particle displacement, merit their own articles. I think they could be safely merged into one article.TR 08:25, 11 February 2011 (UTC)

Particle number up for deletion

The article Particle number, which is rated as High-importance on this project's importance scale, has been nominated for deletion.  --Lambiam 12:21, 10 February 2011 (UTC)

The article has been improved and expanded, and the deletion nomination was withdrawn. -- Crowsnest (talk) 23:32, 10 February 2011 (UTC)

BTW, no real need to report these things unless there's something particularly special going on at them. We have Wikipedia:WikiProject Physics/Article alerts for that. Headbomb {talk / contribs / physics / books} 23:53, 10 February 2011 (UTC)

Some of us may not have the "Article alerts" on our watch list, and so would appreciate notification on this talk page of important actions. JRSpriggs (talk) 03:47, 11 February 2011 (UTC)

The article was nominated as a diction definition. Considering the state of Wiktionary, shouldn't WPPhysics set up a task force to maintain dictionary definitions on Wiktionary? 65.94.47.11 (talk) 07:58, 11 February 2011 (UTC)

Wikipedia talk:WikiProject Astronomy#Bibcode cleanup

There's an ongoing discussion about cleaning up bibcodes in citations. Feedback is welcome. Headbomb {talk / contribs / physics / books} 03:15, 12 February 2011 (UTC)

Suspicious edits

Please check out suspicious edits by 217.172.220.186 (talk · contribs). He seems to be pushing a theory "Maximum entropy generation in open systems: the Fourth Law?" by Umberto Lucia. (Obviously a whacked idea.) JRSpriggs (talk) 13:07, 15 February 2011 (UTC)

Antechristos again maybe? Headbomb {talk / contribs / physics / books} 13:27, 15 February 2011 (UTC)

I don't believe so, it seems to be a single purpose account to push that. Anyway we shouldn't be sticking that into Wikipedia without some sort of secondary source. It hasn't reached even the level of notability of Frieden's extreme physical information which I keep hoping might have something in it but I am most certainly not going to stick into those articles. Dmcq (talk) 22:44, 17 February 2011 (UTC)

By the way 79.24.75.132 (talk · contribs) is probably the same editor just at another computer I think. Dmcq (talk) 23:05, 17 February 2011 (UTC)

Hyperconductor

Hyperconductor (edit | talk | history | protect | delete | links | watch | logs | views) is the title of a a new stub-article. I don't see very much in the way of reliable sources for this topic. I found one at Google Books pertaining to Cryogenic Hyperconductors here, another one here, and one that is not WP:RS here. There is also a patent that mentions the word in the body of the proposal, here. ---- Steve Quinn (talk) 03:11, 16 February 2011 (UTC)

It's drivel. Delete it. Xxanthippe (talk) 03:56, 16 February 2011 (UTC).

The article as it stands is indeed drivel. It's not quite far enough into gibberish territory to speedy, but I've stuck a prod tag on it (with rationale). We'll see what happens.

The term itself does seem to have been used (albeit very rarely), for aluminum under certain conditions of temperature and applied magnetic field. As far as I can tell from a Google Scholar search and SQ's links, someone got anomalous measurements that hinted at very high conductivity when working with aluminum in the 1970s, they used the term "hyperconductor" to describe it, and at least one researcher (the one showing up in more recent literature) borrowed the word (though I'm not sure he actually supports the claim itself). It probably doesn't pass the notability threshold for an article (maybe a sentence somewhere in the aluminum article, maybe not). --Christopher Thomas (talk) 04:43, 16 February 2011 (UTC)

Phys. Rev. ST Accel. Beams is under CC-BY now

Just to note, yesterday it was announced that PRST-AB’s entire archive and all future papers will be made available under the terms of the Creative Commons Attribution 3.0 License (CC-BY) starting from 15 February 2011. It means that with proper citation it could be freely used in Wikipedia and other Wikimedia projects. Details here. Dispite it is a primary source it could contain some useful information as well. Artem Korzhimanov (talk) 16:51, 16 February 2011 (UTC)

This sounds like something that would be more useful to WikiSource than Wikipedia, though I agree that it's a good thing. --Christopher Thomas (talk) 19:09, 16 February 2011 (UTC)

Their images might be useful for wikipedia. Materialscientist (talk) 12:52, 17 February 2011 (UTC)

For example, one could use review paper Overview of the Compact Linear Collider and pictures therein in order to rewrite a stub about Compact Linear Collider. Artem Korzhimanov (talk) 13:10, 17 February 2011 (UTC)

Eddington limit

Hi, I don't know where to type this, but isn't the Eddington limit incorrect if stars like R136a1 exist?

The Eddington limit says that stars that are bigger than 120 solar masses (approximately) wouldn't be able to exist... so I thought maybe some mention should be done to this fact.

Thanks.

212.170.135.108 (talk) 12:33, 17 February 2011 (UTC)

It's not so much a case of "can't exist", but "can't exist for long". The Eddington limit actually says that stars heavier than about 150 solar masses are very unstable (shedding their mass rapidly in light-driven solar wind). This turns out to be exactly what's happening to R136a1, as discussed in the "physical characteristics" section.

The paper cited for the mass estimate seems to do a reasonably good job of describing how stars like those in the R136 cluster evolve over their early (and short) lifetimes (section 4 gives an overview and references the stellar models used). Section 5 considers the possibility that this object (or other objects in the R136a component) are binary stars instead of single high-mass stars, but their conclusion is that most of them aren't (otherwise there'd be more x-ray emission from colliding stellar winds). --Christopher Thomas (talk) 20:06, 17 February 2011 (UTC)

OR edits by user Bopomofo?

User Bopomofo (talk · contribs) has been adding what looks like FTL OR to me to various physics articles, but it's outside my area of expertise, and it could do with some more experienced eyes on it.--JohnBlackburne^words_deeds 03:03, 18 February 2011 (UTC)

I had just noticed that at faster-than-light. I don't think it's fair to call it OR; there's a reference that looks genuine, and the abstract does seem to say something like what he's claiming. It's more likely a case of undue weight (extraordinary claims require extraordinary sourcing?). But it isn't my field and I'll wait for physicists to weigh in. --Trovatore (talk) 03:23, 18 February 2011 (UTC)

Again I'm not an expert but I suggested it is OR as the paper is new, dated April 1 2011, so maybe posted by someone involved in it, though it looks more like a misinterpretation or simplification. And yes, as at WP:REDFLAG Exceptional claims require high quality sources. As well as the claim of FTL energy transmission the way the same content has been added to multiple articles, using minor edits, two more since I first noticed it, raised a red flag.--JohnBlackburne^words_deeds 08:31, 19 February 2011 (UTC)

Hey guys, anybody there? This is kind of important, I think. Bopomofo is claiming that energy is transmitted faster than the speed of light. He has a source! If this were real, or even taken seriously, it would be all over the news, right? So it's probably not real (or if it is, then there's some big caveat that needs to be added explaining why it doesn't mean what you might think it does). But I'm not in a position to refute the source given. Someone who is needs to take a look at this. --Trovatore (talk) 07:06, 19 February 2011 (UTC)

I saw those edits, but my response was to unwatch the page. I'm on sabbatical, and this looks like a "will take more than 5 minutes to vet" issue. My feeling is that, much as with some of experiments that showed FTL group velocity, this is a _measurement_ that scientists don't dispute, with an _interpretation_ that they _do_ dispute. I'd have to read the paper to see what's actually going on, but from the sounds of things they're getting a FTL phase velocity (fine) and claiming that it represents FTL energy transfer due to other properties of the system (not so fine).

Long story short, does need to be vetted, ideally by someone with solid state physics experience, but I'm not going to touch it until I'm in a mood to pick up the mop again (ditto with the recent edits to Wormhole). --Christopher Thomas (talk) 07:47, 19 February 2011 (UTC)

Help disambiguate Effective mass

There are a large number of links to this page. I'm currently cleaning several physics disambiguation pages (most have 2-3 links that need cleaning up), but this one has around 50 so help would be appreciated. Headbomb {talk / contribs / physics / books} 20:49, 18 February 2011 (UTC)

BTW, http://toolserver.org/~dispenser/cgi-bin/dablinks.py is a usefull tool for this task. You can also add it to your /monobook.js or /vector.js with this piece of code

var qqToolConfigCustom=true; // We want a custom config
var qqWhichToolBar="tb";     // "cactions" for top, "personal" for very top, or "tb" for sidebar toolbox
// (The following) Which tools? true for yes - false for no
var qqPeerRev=true;
var qqAltImg=true;
var qqDablinks=true;
var qqExtLink=true;

importScript('User:QwerpQwertus/tools.js');

PeerRev, AltImg and ExtLink refer to other usefull tools. You can choose which ones you want with qqFOOBAR=true; and those you don't want with qqFOOBAR=false; .

Dablinks is particularly awesome if you combine it with

importScript('User:Anomie/linkclassifier.js'); // Linkback: [[User:Anomie/linkclassifier.js]]

importStylesheet('User:Anomie/linkclassifier.css'); // Linkback: [[User:Anomie/linkclassifier.css]]

Which colors links according to certain rules (deletion = red, redirect green, disambiguation = beige, ...).

See my own User:Headbomb/monobook.js page for other ideas (like convenient links to the citation bot, etc...). Headbomb {talk / contribs / physics / books} 20:54, 18 February 2011 (UTC)

Right now, ~100% of the links should go to Effective mass (solid-state physics), and ~0% should go to Effective mass (spring-mass system). I suggest redirecting effective mass to Effective mass (solid-state physics) (WP:PRIMARYTOPIC). :-) --Steve (talk) 03:00, 19 February 2011 (UTC)

"Van Allen radiation belt" -- a Wikipedia horror tale ?

Last night I removed an unsourced claim, attributed to Alex Dessler, that the Van Allen radiation belts may be due to volcanic activity. I think this is physically very unlikely, and not at all main-stream, though I am not an expert on Van Allen radiation. A little Google search found ~9000 hits on {'Alex Dessler' 'Van Allen'}, but looking at the top few I see only things that seem to quote our previous Wikipedia article verbatim — almost all having all or part of the phrase:

"while Alex Dessler has argued that the belt is a result of volcanic activity".

Most appear to be blogs & other lightweight material, nothing that looks like a reliable source. A full-text search of the Astrophysics Data System for {"ALEX DESSLER" "VAN ALLEN BELT"} found no hits between 1952 and 2003. (Where would one search for older space physics information, I wonder?)

At first glance it appears to me as if there may have been an avalanche or loop of citations stemming from that very early (~2002) Wikipedia mention. The editor who made the claim was blocked indefinitely in 2008 as a troll, although that was not at first enough to convict the edit. Although "Alex Dessler" is redlinked, he is a reputable worker in space science.

I looked around a bit for a proper source, and commented out the dubious claim, thinking that if there is a peer-reviewed article in a scientific journal that supports the claim, we should probably restore it. But I now it looks like this is a classic Wikipedia horror story.

When I could find no reasonable sources (glancing at only 30 or 40, of course not 9000), I sent an email, to Dessler, who quickly responded:

I am (sort of) shocked that this is what is reported. It is true that I once made a verbal joke at a meeting where I was making fun of someone (Tom Gold as I recall) to make the point that correlations were not proof of physical causality. You need a viable theory to make the connection. For example, I like this quote, "It has been proven by thousands of experiments that the beating of tom-toms during an eclipse will restore the Sun." This is from E. Bright Wilsons's book (which I read as a graduate student in the early 1950s) Introduction to Research. Wilson did not believe this correlation was true, as I did not believe volcanoes could cause or have any effect on the Van Allen Belt. My point was regarded as funny enough that I believe Wilmot Hess, in one of his books, quoted me in the spirit of a physicist having fun. If he did, the book would have been published in the 1960s. I never put such nonsense in print -- OMG!

The edit that did the damage was:

07:44, 18 November 2002 Lir (talk | contribs) (7,275 bytes) (undo)

Lir made many many edits, often on other subjects, for over 6 years before being blocked, many of which probably need to be reviewed carefully. So it is potentially a more general Wikipedia problem. I think this case history needs to be reported (and discussed) on some of the project pages — physics, astronomy, space science,... as many as are relevant, and wherever Lir made many edits.

This is the first clear instance I have encountered of what appears to be an attempt to undermine the integrity of Wikipedia by deliberate covert fallacious editing. It is not trolling, which I think is defined as a deliberate attempt to create destructive conflict by stirring up conflict, outrage & emotion, etc — ie, not hidden.

Some points:

• Covert malicious vandalism is present on Wikipedia to some extent, and because people are so clever, in general it is likely not easy to detect, especially given our essential commitment to assume good faith. (So how much of this is out there? Has anyone done some serious investigation to quantify the extent of the issue?)

• The widespread use of Wikipedia as the reference of first resort means that errors here are likely to be disseminated very rapidly and widely into the Internet and the cultural "information atmosphere".

• Verbatim copying of Wikipedia material is very widespread, at least in some cases. (Probably especially bad where journalists with no deep understanding of a specialized subject are trying to summarize for the lay public.)

• As important as formal criteria for authenticity are, there is probably no substitute for significant understanding of, and expertise in, the subject matter by some minimum number of the editors contributing to any given article.

• The appalling thing is that at this moment there hundreds of "sources" out there on the Internet—and none of them are reliable. It will be interesting to watch the "decay" of this information now that the Wikipedia article has been corrected, but it seems likely that will be very slow, if it decays at all.

• Inaccurate, or even absurd, material may lie undetected for a very long time, and do great damage to our reputation, our project, and even to society.

• Given the central importance of information and the existence of strong political, ideological, and economic drivers, covert attacks on Wikipedia can be anticipated to sometimes be not just mischievous, but strongly motivated: sustained, determined, and even backed by the resources of wealthy and powerful entities, such as powerful authority figures, corporations, religious and ethnic groups, and even nation states.

Thus Wikipedia is at least potentially (and perhaps already extensively) threatened by its own remarkable success.

I am basically a wikignome, by no means very well qualified to address these issues. I am certain there are many other editors in our project who are much more aware than I am. I would appreciate it if they could perhaps give us (me) some advice about how a lay wikipedian can best respond to these challenges, or point to existing WP resources for doing better. Thanks to any who respond.

Cheers, Wwheaton (talk) 02:57, 19 February 2011 (UTC)

Another editor has suggested concentrating all discussion of the above issues for the three related projects on the Astronomy project page, here. I think this sounds like a good idea. Wwheaton (talk) 04:37, 19 February 2011 (UTC)

Question about spacetime

Ok I don't really know if this is proper to ask on the project talk page, but I didn't think the guys at village pump would know as much about this as the people here. The spacetime article says "the interval between two events [in spacetime] is defined as $s^{2}=\Delta r^{2}-c^{2}\Delta t^{2}$." I've seen this millions of times, and I know it defines the metric tensor of the space, but I've never had anyone explain to me why that sign is negative. I'm trying to grasp (even though my university doesn't offer undergraduate differential geometry classes... a shame) the concept of differential geometry in order to apply it to a space in which some number of dimensions are compactified. If someone could explain that minus sign to me, it would help me out a lot. Thanks, and sorry if this isn't the place to ask.--Dudemanfellabra (talk) 22:46, 19 February 2011 (UTC)

Read metric tensor (general relativity) and sign convention#Metric signature. Of course, there is a bug that neither of the two are linked from the "spacetime" article. Incnis Mrsi (talk) 10:12, 20 February 2011 (UTC)

Well, I understand that the minus comes from the metric tensor of the space, but every article I chase down the rabbit hole simply asserts that the metric signature includes a minus sign but never actually states why. The closest I've been able to come is the fact that spacetime is a Pseudo-Riemannian manifold, which only has to be nondegenerate and not positive definite (as an informative aside, both of those articles may as well be written in Chinese to me). Again, though, the Pseudo-Riemannian manifold article simply asserts the fact that the negative sign is ok to have there, but it never really says why it's needed. I'm looking for a "This sign can't be positive because..." type thing. Anyone know where I can find that? Even if it's not on Wikipedia? Sorry if I sound completely ignorant, but trying to teach yourself differential geometry and general relativity is a bit rough. Thanks for the help, though.--Dudemanfellabra (talk) 16:47, 20 February 2011 (UTC)

Er this is the very heart of Relativity, the term must be negative to preserve the constancy of the speed of light for all inertial observers! The interval must be Lorentz invariant (See Lorentz transformation) or it would imply that c varies for different observers. If the sign were positive it would not be Lorentz invariant and the foundation of Einsteinian Relativity would collapse... ChiZeroOne (talk) 18:14, 20 February 2011 (UTC)

Ok I think I've figured out where the negative comes from, but the way I did it brings up a new problem.. I know what the Lorentz transformation is and all of this, but I may just be looking at it from the wrong angle or I may just not see it. This is my way of looking at it: If one realizes that light emanating from the origin at speed c in any direction must traverse a distance cdt in a short amount of time, then you get $|\,d{\vec {r}}\,|=cdt={\sqrt {d{\vec {r}}\cdot d{\vec {r}}}}$ and therefore $dr^{2}-(cdt)^{2}=0$. What I would like to know is where $ds^{2}$ comes from in the equation above.--Dudemanfellabra (talk) 19:36, 20 February 2011 (UTC)

The minus sign cannot be "explained", it is just an empirically observed fact. It is the difference between spatial dimensions and temporal dimensions.

For space-like separations, apply a Lorentz transformation to get to a reference frame where dt'=0, and then observe what the value of |dr'| is! For time-like separations, transform to a reference frame where dr'=0 and then observe what the value of |dt'| is! JRSpriggs (talk) 00:42, 21 February 2011 (UTC)

Continuing difficulties at Talk:Dark matter

An IP user (129.96.220.98 (talk · contribs · WHOIS)) has been aggressively arguing for the inclusion of Process Physics (userspace copy) in the "alternatives to dark matter" section of the Dark matter (edit | talk | history | protect | delete | links | watch | logs | views) article. After adding it and having the addition reverted multiple times a couple of weeks back, they've changed to arguing without apparent rest on the talk page for its inclusion. More eyes might help.

Based on the WHOIS information for the IP, I fear that there may be WP:COI issues as well. This isn't quite a single-purpose account, but it's close.

I'm out of ideas for how to resolve this. --Christopher Thomas (talk) 06:28, 22 February 2011 (UTC)

They now also seem to be editing from 121.45.45.109 (talk · contribs · WHOIS). --Christopher Thomas (talk) 19:29, 22 February 2011 (UTC)

Process physics sounds like Reginald Cahill of Flinders University, and used to be extremely persistent on Usenet under various usernames, all to be traced back directly to Adelaide—haven't checked recently. Google scholar doesn't produce much more than Cahill citing Cahill about his Process Physics Theory of Everything. DVdm (talk) 22:59, 22 February 2011 (UTC)

Please, please be careful to avoid anything that could be construed as WP:OUTING. I've very carefully avoided making any claims that the IPs are, or are acting on behalf of, specific people. Associating IPs or usernames with real-world identities is something that shows up frequently at AN/I, and usually results in swift and unpleasant administrative action. --Christopher Thomas (talk) 03:52, 23 February 2011 (UTC)

(ec) I hadn't looked at the article or at the contributions of these IP's. Just making a general remark about something I recalled from a previous life, related to Process Physics, and not related to any wiki-user or -IP in particular. I had a look now and I understand your concern. Cheers & GL. - DVdm (talk) 08:15, 23 February 2011 (UTC)

Update: They swear up and down that they don't have a conflict of interest, and seem to be reacting positively to further discussion of Wikipedia's guidelines for notability, weight, sourcing, and so forth. I've suggested that they try to pull together enough sources to write a version of Process Physics that would survive an AfD (the old one didn't), and that they ask here for guidance. Please bear with them, as they're still learning the ropes. --Christopher Thomas (talk) 08:03, 23 February 2011 (UTC)

Cold Fusion is very very cold.

Hey Project physics!

You know when you are at a party and after mentioning that you are a scientist you end up listening to some guy tell you his "theories" on how Buddhism and quantum mechanics are actually the same thing? Imagine that guy taking over the editing of a project physics article.

When was the last time any of you looked at the cold fusion article?

I am writing here to suggest that this article be removed from the project's articles and consigned to the "rational skeptics" wikiprojects.

I view Wikipedia science articles as a resource that I and other researchers use to get a quick and accurate overview of a topic. Wikipedia articles reach a broad scientific audience and can actually be beneficial to the research community's progress towards a better understanding of nature. Conversely, because of it's broad reach, Wikipedia can also have a deleterious effect on research. The cold fusion article falls into the latter category and since there is little interest from actual scientists in editing the article why not be rid of it?Crawdaddy74 (talk) 16:11, 22 February 2011 (UTC)

Well, while it is now consigned to rubbish bin of history, the story is important to the history of physics. Similarly, N ray and Phlogiston are in the scope of this project. The tag is not meant to indicate that the topic of the article is considered viable by the physics community, but that this page is a place to go when local editors need a few more eyes or to have a point settled.

That said, it would actually surprise me if that article were not in need of a good trimming with the WP:SCIRS axe. It has needed it for years, honestly, but the highly contentious editing atmosphere tends to drive out everyone who is not willing to babysit the article on a full-time basis. It is also very difficult to get anyone to accept that this one great source they just found simply carries no weight compared to the fact that pretty much nobody considers it a viable hypothesis anymore. I guess the proponents were pretty heavily invested by the time of the DOE report, but the cold fusion community's response to the report continues to boggle.

Alright, in penance for my cynicism I will give the article a read through tomorrow. Anyone else who wants to jump in would be welcome. - 2/0 (cont.) 19:11, 22 February 2011 (UTC)

I just think that if no physicists are actually going to look at the topic then it shouldn't be part of the physics project. I went there trying to browse after hearing about that announcement a month ago about italian's demonstrating a cold fusion device. Not only did I find nothing of value in the article, but when I decided to try and clean it up with some more modern literature that I had to go and look up on my own, there was no one on the discussion board that was even qualified to help determine the appropriate weight of the research. I found it pretty convincing and so was waiting for someone with some expertise to show up and tell me why I was wrong... but nobody did. If no physicists care, what is the point of even having an article, give it to the sociologists and anthropologists. I mean the thing is rated B-Class High importance? — Preceding unsigned comment added by Crawdaddy74 (talk • contribs) 22:39, 22 February 2011 (UTC)

Plenty of physicists will look at the article, and regardless of whether physicists would look at it or not, cold fusion is still very much physics-related (see 2/0's comments above). As for the rest, if you think the article needs editing, see WP:BOLD. Headbomb {talk / contribs / physics / books} 23:27, 22 February 2011 (UTC)

I hear what you are saying and I agree with you. But in this case the editing is dominated by lay people with no understanding of anything besides the popular notion that cold fusion research is of no merit or that "excess heat is real!". But this paper for instance is very interesting and invalidates some claims made in the article but if I added it to the article absent input from someone who could make a valid judgement as to it's relative merit it would be summarily reverted by editors who think that the new scientist is the final word on science topics. They would give more weight to something like this — Preceding unsigned comment added by Crawdaddy74 (talk • contribs) 01:19, 23 February 2011 (UTC)

Perhaps I'm missing something here, but why wouldn't you just consider it to be in the domain of both wikiprojects? That happens all the time with other articles. --Christopher Thomas (talk) 03:54, 23 February 2011 (UTC)

Yes. I guess I am just pointing out that it doesn't meet the standard I am used to seeing from a project physics article (although I only ever consult wiki on topics that are of no interest to the average person). I guess I should just chalk it up to the fact that I was shocked at the poor quality of the article and the general level of science education evident on the discussion page and thought that that made it unsuitable to be marked as a high importance b-class project physics article. If I am wrong please chalk it up to the fact that I am new to the world of wiki editing (I only signed up to try and clean up the cold fusion article). Let's drop the subject then... PS I swear I have been signing these posts!.. one more try...Crawdaddy74 (talk) 16:32, 23 February 2011 (UTC)

New article: particle

Cross posted to Wikipedia talk:WikiProject Chemistry#New article: particle, as this could use an eye from the chemists

Up until recently, we didn't have any article on the concept of a particle, we only had a disambiguation page listing several types of particles, but never a coherent explanation of the concept. It really pissed me off that we lacked a basic explanation of a concept as important as this one, so I got off my ass and fixed that tonight. The "what links here" of particle, particle (disambiguation) and particle physics should probably be cleaned up, so any help doing that would be much appreciated (as well as any expansion of the particle article, of course). Headbomb {talk / contribs / physics / books} 08:33, 7 February 2011 (UTC)

I'm a little concerned that the article seems to be made up of different types of particles and really is a disambiguation page. There does not seem to be anything there which acts as a main citation. Is there anything which actually lumps together particles the way the article does? Dmcq (talk) 14:24, 7 February 2011 (UTC)

The disambiguation page should be restored to the primary position, physics "particle" is in no way clearly primary. Particles is a common topic in language and other subjects, and the current article seems like a grabbag. 65.94.45.238 (talk) 06:53, 8 February 2011 (UTC)

An article about "anything whose size is much smaller than the length scales one is interested in" is not such a far-fetched idea, but I won't pronounce myself on whether this should be considered the primary meaning or the grammatical meaning is also prevalent enough. (In the latter case, just move Headbomb's article to particle (physics) and the disambiguation back to particle.) List of things to do before I die: [...]; use the rhyme between particle and article in a poem; [...]. --A. di M. (talk) 09:54, 8 February 2011 (UTC)

This meaning of "particle" is indeed the primary one. A quick look at the "what links here" gives these mainspace results

• International Union of Pure and Applied Chemistry
• Sputtering
• Verb
• Particles (redirect page)
  • Microfiltration
  • Secondary emission
  • Granular material
  • Dustcap
  • Space Patrol (1962 TV series)
  • Eye protection
  • Botryoidal
  • History of quantum mechanics
  • Electromagnetic brake
  • Creaming (chemistry)
  • Halogenerator
  • Timeline of physical chemistry
  • Friction-plate electromagnetic clutch
  • Air sanitizer
  • Granulation (making of granules)
  • Dan Pero Manescu
  • Antibody labeling
  • Decoding Reality
• List of particles
• Centauro event
• Fluid parcel
• Point particle
• NedFest
• Bulk density
• Magellanic Stream
• Quasiatom
• Russell Stannard
• Kalapas
• Attenuation coefficient
• The God Particle: If the Universe Is the Answer, What Is the Question?
• Configuration entropy
• Particle accelerator
• Behind-armor debris
• Classical mechanics
• Acoustic resonance spectroscopy
• Falling sand game
• Aerosol impaction
• Releasing agent
• List of gamelan ensembles in the United States
• Respirable suspended particle
• Homogeneous (chemistry)
• Flying Other Brothers
• Indoor bioaerosol
• Eight-dimensional space
• Udmurt grammar
• Sockley's model
• Bonded Neo
• Aluminium alloy inclusions
• Contractions of negated auxiliary verbs in English
• Evolutionary Algorithm for Landmark Detection

Out of 54 links, 3 refers to the grammatical concept (verb, Udmurt grammar, Contractions of negated auxiliary verbs in English), 2 refers to some artist (NedFest, Flying Other Brothers), 1 to particle board (List of gamelan ensembles in the United States), and the rest (48) refers to the concept of particles. Headbomb {talk / contribs / physics / books} 12:08, 8 February 2011 (UTC)

Well there are 200+ mainspace articles that link to grammatical particle.TR 12:28, 8 February 2011 (UTC)

And 1250+ that link to particle physics. An alternative measure of things might be what dictionaries say about it, and it's also resoundingly leaning towards the science concept rather that then grammar concept. Headbomb {talk / contribs / physics / books} 12:33, 8 February 2011 (UTC)

From all the data you have provided it is quite obvious that both meanings of the term particle are quite common. Unlike the generic use in physics (which doesn't have a particularly well defined meaning), the term has a very precisely defined meaning in grammar. This makes it very likely that people searching for "particle" on wikipedia actually are looking for grammatical meaning. TR 12:54, 8 February 2011 (UTC)

That's hard to believe. Dauto (talk) 17:55, 8 February 2011 (UTC)

The articles in the list of suggestions I get when typing "particle" in the search box all seem to have to to with the physical, rather than grammatical, meaning. If, as I guess, they are sorted by number of visits, that means that this meaning is what a very large majority of readers are looking for. --A. di M. (talk) 19:32, 8 February 2011 (UTC)

Per Headbomb, and after viewing the sources of this "new" article, it appears that the physics description, or scientific description, of "particle" is by far the primary one. By the way, creating this article is a good idea, and I think that the article, at this point, is very good (imho). ---- Steve Quinn (talk) 00:14, 9 February 2011 (UTC)

Linguistics is not a science?TR 06:55, 9 February 2011 (UTC)

That's a rather irrelevant/pedantic point. Science obviously meaning natural sciences here. Headbomb {talk / contribs / physics / books} 07:43, 9 February 2011 (UTC)

I've just been pointed to particle again today and having had another look at it I feel an urge to stick an AfD on it. There is no book chapter or paper about particles there, it is somebody's random collection of thoughts about different types of particles. I see it being defended above, anybody like to give one reasonable source which covers a reasonable extent of the topic other than some dictionary definition of a particle? Dmcq (talk) 17:09, 24 February 2011 (UTC)

I added some tags to the article and removed the bit about stars being particles when compared to a galaxy which I believe to be essentially incorrect. IvoryMeerkat (talk) 18:06, 24 February 2011 (UTC)

I was promptly reverted! [4]. Does anyone else find this rude? IvoryMeerkat (talk) 18:10, 24 February 2011 (UTC)

Rude or not, the reversion was justified. Xxanthippe (talk) 21:44, 24 February 2011 (UTC).

I have started up an AfD at Wikipedia:Articles for deletion/Particle. Dmcq (talk) 23:17, 24 February 2011 (UTC)

Tension (physics)

I'd like to bring up a comment that an IP editor left at Talk:Tension (physics) because I feel that is true but needs more big picture foresight than will normally be found on the article talk page. If one looks past the expletives of the comment, he/she is correct in that this article is pretty much wrong and useless in its current state (along with compression (physical)). I bring this up here, because the article needs to be steered in the right direction, and I'm not sure what that is. My recommendations are merging it with compression (physical) under the name tension and compression and then having a short article explaining the concepts (it would be similar to ferrous). The problem with this is that it might just be a dictionary entry. Otherwise, I can see deleting it and compression (physical) and redirecting them to stress (physics), but my problem is that that article is extremely complex in comparison to the concepts that are being searched. I'm not sure either is a great recommendation and welcome conversation and other ideas. Wizard191 (talk) 19:04, 25 February 2011 (UTC)

I agree. I left a few general suggestions for a K.I.S.S. re-organization on the talk page. I don't think it needs much expertise to improve it a lot, and steer more ambitious readers on their way to the right place. Wwheaton (talk) 22:13, 25 February 2011 (UTC)

Relativistic Doppler effect

Article Relativistic Doppler effect might need some expert attention w.r.t. new username's Cattlecall1 (talk · contribs) recent edits. I have reverted twice. DVdm (talk) 22:46, 25 February 2011 (UTC)

Another annoying request for input

Hey everyone. So I'm bringing up a topic on this page again, so I want to apologize in advance if I'm being a bother. The article on sparks, referring to the small heated particles of matter, is currently titled Spark (fire), although the sparks it discusses are not fire. I was hoping some of the people here who are more knowledgeable on science would be able to weigh in on other possible suggestions at this page. Thanks so much!--Yaksar (let's chat) 07:31, 24 February 2011 (UTC)

Such a spark may not be fire (a rapid chemical chain reaction of oxidation-reduction). But it is hot enough to glow like a fire and to ignite a fire if it comes in contact with both fuel and oxidizer. So I do not think that the title is inappropriate. JRSpriggs (talk) 06:08, 25 February 2011 (UTC)

But so are electric sparks. It doesn't really ambiguate between the two if the rationale of both being able to ignite a fire applies to both. The subtitle needs to be something that makes clear the difference between the article in question and others with the same name. --Yaksar (let's chat) 06:17, 25 February 2011 (UTC)

I think that electrical sparks are a kind of (fire) spark. So I do not see a need to disambiguate between them. JRSpriggs (talk) 06:30, 25 February 2011 (UTC)

The problem is that they are totally different types of things, as explained at Spark, the disambiguation page. Please refer to this definition: http://www.merriam-webster.com/dictionary/spark . The article in question concerns definition one, while the other types of sparks concern definition two. Other than the fact that both can potentially cause fires, there's no connection between the two beyond the name. I therefore find it especially odd that (fire) would be the way to distinguish between the two of them, considering we both agree it doesn't do the job of distinguishing between the two.--Yaksar (let's chat) 06:34, 25 February 2011 (UTC)

Hi, I think those sparks really are very commonly "fire", in that oxidation usually sustains their incandescence to some extent after the initial energy input. There is of course a balance between heat loss and the energy input from oxidation, which can go either way, and also the fuel source (carbon, iron) may be exhausted. But I think (except for things like volcanic bombs and splashed molten metal, clearly not sparks) the core phenomenon ordinarily does involve oxidation or some similar chemical support. I agree that electrical sparks are something else, though even then there may be a combination, where the initial energy is electrical, then sustained by chemistry. I just added a sentence to the lead to underline the issue. The disabig page does distinguish between electrical and chemical sparks, though not very well. Wwheaton (talk) 21:34, 25 February 2011 (UTC)

Are you sure that they're very commonly fire? Most often they're a small piece of ember, and I'm sure you won't argue that ember is the same as fire. Often times they're a small piece of metal. Regardless of whether they stay heated or incandescent, it doesn't necessarily mean fire is involved.--Yaksar (let's chat) 23:22, 25 February 2011 (UTC)

Ember is indeed fire. A hot coal or ember is material (often but not necessarily carbonaceous) that remains red hot largely because it is slowly being oxidized, which is combustion, which is fire. A speck of hot iron that glows red is also being oxidized. (Steel wool will actually burn continuously in pure oxygen.) The chemical/physical process is the same as for flame (which is fire with luminous gaseous products), although for an ember the reaction is between a solid and gaseous oxygen, with little or no luminous flame. I am sure that glowing sparks are almost always sustained by energy producing oxidation to some extent. I also think their persistence (lifetime before cooling below red heat) is typically dominated by energy from oxidation, though I cannot quantify how common or important that may be. Wwheaton (talk) 07:32, 26 February 2011 (UTC)

I think you're getting some of your facts mixed up. There is a difference between rapid combustion, which is fire, and other types of combustion, such as smoldering. But regardless, even if you want to argue that technically embers are types of fire, they are never considered to be that way. Hell, most definitions of ember specify that they often occur after fires.--Yaksar (let's chat) 07:44, 26 February 2011 (UTC)

We are not getting anywhere with this. You asked for input from someone "more knowledgeable on science". I am a PhD physicist, a retired staff astronomer from a reputable university, for whatever that may be worth. I believe I speak correctly about the science, and also about the meaning of "fire", both as a physical phenomenon, and as an occurrence ("a fire"). Sparks are fire, even if they are not ordinarily called "a fire". If you can get consensus otherwise, I will yield. Best, Wwheaton (talk) 09:31, 26 February 2011 (UTC)

I recommend that anyone here look in at the situation on Talk:Spark (fire) before investing much time on this. Wwheaton (talk) 15:38, 26 February 2011 (UTC)

Isn't that, ermm, somewhat obvious? I don't know if you're trying to discourage people from participating in the discussion or what, but it doesn't seem necessary or fitting.--Yaksar (let's chat) 20:09, 26 February 2011 (UTC)

Electron-positron theory

I recently raised a point at the Robert Oppenheimer featured article discussion over whether electron-positron theory should have its own article. I suggested that the closest we have at the moment is Dirac sea. Currently there are few references to it on Wikipedia, but search engines give a fair number of hits for the phrase + Dirac. See also Dirac's Nobel lecture. Would those reading this be able to say whether electron-positron theory should have its own article, or maybe a redirect to a suitable article? Carcharoth (talk) 15:17, 26 February 2011 (UTC)

What specifically do you mean by "electron-positron theory"? In the case of the Oppenheimer article seems to simply refer to the prediction of the positron/the interpretation of negative energy electron states as positrons. In that case it should just link to positron.TR 15:51, 26 February 2011 (UTC)

I agree, but does the article on the positron give details or not? I went looking for the phrase "electron-positron theory", and I found examples such as Spin-Dependence in the Electron-Positron Theory of Nuclear Forces (1939), and Considers the Dirac equation ... gives a careful formulation of the Stuckelberg-Feynman interpretation. This electron-positron theory may be applied whenever electron and positron states can be separated..., and An Alternative Covariant Formulation of the Electron-Positron Theory (1951). There are many more examples. The point being that the work of Dirac and others (including Oppenheimer) seems to have led to the establishment of a "theory" of this name. It is also, I believe, called "Dirac formalism", presumably the Dirac equation Also, from a 1967 interview with Wheeler, there is As a matter of fact, the work with Breit on pair physics convinced me that the great white hope of theoretical physics was the electron-positron theory. I suspect that the theories relating to nuclear forces came later, but I'm hoping for some clarity on this. The bit about Oppenheimer is best summarised here: "In 1934, with Furry, he developed a field theory of the Dirac equation, treating electrons and positrons as of equal status. This paper contains essentially the modern form of the electron-positron theory." But that may all be too detailed for Wikipedia. Carcharoth (talk) 16:38, 26 February 2011 (UTC)

Should certainly be part of the positron article, there's no difference between "positron theory" and "electron-positron theory". (Electrons are always part of positron theory!) The theoretical-history section in positron is good but if it's missing things than it could certainly be expanded. :-) --Steve (talk) 20:06, 26 February 2011 (UTC)

The positron page was better than I had realised. I do wish there was a source somewhere (there probably is, I just haven't found it yet) that carefully traced the development of theory from Dirac onwards. As far as I can tell, Dirac developed his equation to predict the properties of particles using quantum mechanics, and I suspect that when I am looking for a description of what people mean when they talk about Dirac's electron-positron theory, they simply mean his use of the Dirac equation to describe the properties of the electron, and from that predict the existence of the positron. As for the history, I suppose I will have to wait for someone to flesh out History of quantum field theory. For now, I can use the 'Suggested reading' section of that article. Carcharoth (talk) 00:52, 27 February 2011 (UTC)

The historical development of the prediction of the positron by Dirac is not quite as great man theory exciting as we make it out to be in most discussions of the subject. Although Dirac clearly predicted the positron in 1931, it isn't clear he fully understood the implications of his predictions in the sense of particular observables (what attributes it was supposed to share with the electron and which attributes would be different were still being ironed out). This part of theoretical particle physics was pretty muddled at the time, and when the community had come to terms with Anderson's discovery in 1932, there was something of a minor scramble to figure out exactly who had provenance. A more complete description of the full developments of anti-matter's role in the standard model is to be had from the way Feynman organized and simplified the linearized parts of QFT to distill the most important aspects of positrons. Wheeler's off-the-cuff proposal that positrons are electrons traveling backwards in time lead to the most complete understanding of the subject in terms of symmetries and the conserved Noether currents which demand anti-matter as a conserved partner to matter and also, ultimately, the Sakharov conditions are needed to explain the normal: why the world is not matter/antimatter balanced. Electron-positron symmetry as a manifestation of a greater matter-antimatter symmetry is directly derivable from the Dirac equation, but its implications go far beyond the prediction of a new particle. IvoryMeerkat (talk) 06:05, 27 February 2011 (UTC)

{{Proton decay experiments}}

Just created this earlier. If you know of any other experiments, feel free to add them to the template. Headbomb {talk / contribs / physics / books} 08:58, 27 February 2011 (UTC)

Meaning of "isotherm"

Isotherm is currently a disambiguation page. Please help to answer a question I posed on its talk page.  --Lambiam 16:00, 27 February 2011 (UTC)