Wikipedia talk:WikiProject Physics/Archive 9

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Erroneous placement of c in special relativity articles

There is a problem which appears to afflict most of the articles on Special Relativity. They are not consistent with the International System of Units. Ultimately this is because you-all are using ct (i.e. meters) as the time coordinate rather than t (i.e. seconds). But it results in you having the wrong versions of the Minkowski metric, the momentum 4-vector, the velocity 4-vector, etc.. I cannot fix all of them myself because there are too many such articles and I am sure that I would encounter significant opposition from people who suffer from the mistaken prejudice that every component of a tensor must be in the same units. For a correct understanding of how to assign units to the components of a tensor see E.J.Post, Formal Structure of Electomagnetics: General Covariance and Electromagnetics, Dover Publications Inc. Mineola NY, 1962 reprinted 1997.

Even worse, some people do not seem to realize that one must distinguish between the covariant and contravariant versions of a tensor. JRSpriggs 07:49, 11 September 2006 (UTC)

Could you give an example of an article where the present treatment is erroneous, and what it should have said? --LambiamTalk 10:50, 11 September 2006 (UTC)
Whether c appears in the ct or in the Minkowski metric is merely a convention. If we're actually being consistent in this convention then good for us. — Laura Scudder ☎ 16:09, 11 September 2006 (UTC)

Units are an unnecessary complication in physics. It's simpler to just put c = h-bar = G = 1 and stop arguing about this. If you want to express time in units of seconds then just convert it to seconds. There is no need to put the factor c in formulae just because people might use incompatible units for space and time. Count Iblis 16:40, 11 September 2006 (UTC)

Speaking just for myself, I oppose including c in the metric tensor. As Wheeler is fond of pointing out, it seems silly to measure the components of a single 4-vector like xμ in different units, especially given that they transform into each other upon rotations and boosts (Lorentz transformations/Minkowski rotations). We might as well measure the x-component in furlongs, the y-component in miles and the z-component in Angstroms. One can correct for different units by redefining the metric to include extra unit-conversion constants but, honestly, why bother? The fact that time is measured in seconds and not in meters seems like a historical artifact that does not pertain to the physics.
However, we as a WikiProject should probably be consistent in all of our pages. We could eliminate c altogether by choosing units c=1, but that might be confusing to lay-people. Personally, I favor keeping c in the formulae, and setting x0 = ct and the Minkowski metric diagonal to (-1, 1, 1, 1). What does everyone else think? Perhaps this has been discussed already? Willow 19:16, 11 September 2006 (UTC)
I think that a distinction needs to be made between articles/sections that are intended for the lay person and articles/sections that can really only be read by people with some training in physics. The first should use SI units. The second should state what unit system it is using and use it. Probably we should stick to using either SI units or natural units rather than using SI, natural, cgs, Heaviside, etc..
As a side comment, I don't think anyone sets G to 1. G has natural units of inverse energy squared. The rule everyone around here uses is c = ħ = kB = 1. --Strait 19:59, 11 September 2006 (UTC)
The quantum gravity people usually use Planck units :) Count Iblis 17:02, 13 September 2006 (UTC)

For example, Four-momentum says

P^a := mU^a= m\left( \gamma c , \gamma u_x , \gamma u_y ,\gamma u_z \right) = \left( \gamma m c^2 /c , \gamma m u_x , \gamma m u_y ,\gamma m u_z \right) = \left( {E \over c} , p_x , p_y , p_z \right)

but I contend that it should say

P^a := m U^a = m\left( \gamma , \gamma u_x , \gamma u_y ,\gamma u_z \right) = \left( \gamma m c^2 /c^2 , \gamma m u_x , \gamma m u_y ,\gamma m u_z \right) = \left( {E \over c^2} , p_x , p_y , p_z \right)

and also

P_b := \eta_{ba} P^a = \left( -E , p_x , p_y , p_z \right).

If (as SI units demand) we use t in seconds for time and give the spatial coordinates in meters, then the units of a component of a tensor should be (meter/second)^n times the units of the purely spatial components of the tensor where n is the number of covariant time indices minus the number of contravariant time indices of the component in question.

Is this merely a matter of convention? Yes, but so is the use of SI units. People need to use consistent conventions to avoid being confused and to get the right answers when doing calculations.

Why not use natural units? First, because they are not the standard which is generally used in society (i.e. SI units). Secondly, if c is left out of the equations, then people will have to figure out where to put it in when they convert units. If it is already there, they can just substitute in the appropriate value for the system of units they want to use, whether that value is "299,792,458" or "1" or "186,282.397" or whatever.

Is it merely a silly historical artifact that we use both meters and seconds? Not really. Human activities are conducted almost exclusively at speeds much lower than c. The units we use in everyday life should be such that they yield numerical values which are near one rather than many orders of magnitude off. That requires a different unit for time than for distance.

What you-all are doing currently is building a conversion of units into the process by which you apply your equations. But that makes no sense. Tensors are already designed to handle all such issues. Just let them do it. JRSpriggs 07:52, 12 September 2006 (UTC)

The best argument against your convention is that the elements are different in the covariant versus contravariant vectors. Much easier to keep it straight when they're the same. — Laura Scudder ☎ 15:33, 13 September 2006 (UTC)
I agree with Laura. Also, although you can say that natural units are not the standard used in society it is also the case that relativity theory is not used much by the average person. And those in society who do work with relativity, QM et. on a daily basis, do mostly use natural units. And why not just define t as c times x_0 and work with x_0?
Natural units are the default conventions used by the physics community. In journals many authors don't explain anymore that they are using natural units if they say that e.g. that "the temperature is 10 GeV". From my experience, some students have difficulties working with natural units because they have been wrongly taught about units in high school. They are indoctrinated by "false propaganda" that somehow time, distance, energy, mass, temperature are incompatible quantities that cannot be expressed in the same units. Count Iblis 17:02, 13 September 2006 (UTC)
I merely explained how to determine the units for completeness. However, in practice, for most tensors, you can just ignore the units and translate the 3+1 version of the equations into the 4D tensor form, relying on the consistency of the equations to get the units right. The equations of electromagnetism assume a nice simple form as I would have it -- one in which there are no cs or ε0s or μ0s or 4πs except in the constitutive equations.
Count Iblis makes a point AGAINST natural units by saying "define t as c times x_0 and work with x_0". To convert from x_0 (time in the spatial unit) to t (time as such), you must DIVIDE by c rather than multiply by it. If even the Count cannot figure that out, then we need the c explicitly in the equations somewhere. Also dimensional analysis which relies on the units to help figure out whether an equation is reasonable or not would go out the window with natural units. JRSpriggs 07:43, 14 September 2006 (UTC)
Yes, I made a mistake, you must indeed divide by c :). I don't agree that dimensional analyses can't be used with natural units. Dimensional analyses cannot be used in QM/Relativity the way it is used in classical mechanics anyway. If you have the constants h-bar, c and G avvailable (even if you set these to 1 you can still rescale your time/space and masses, so they reappear as dimensionless constants), you can use them to make any equation dimensionally correct.
E.g. if you use dimensional analyses to derive that the period of a pendulum is proportional to (L/g)^(1/2), what you actually doing is finding a relation between L and T that stays non-singular in the limit c--> infinity, h--> 0 and G --> 0 and simultaneously the mass of Earth --> infinity such that g stays constant. Here c, h and G are interpreted as dimensionless rescaling constants. So, e.g. the equation T = L becomes, under a rescaling of time relative to distance, T = L/c. This becomes singular in the limit c --> infinity.
So, you can indeed derive the same results from dimensional analysis starting from dimensionless physics. Another example are scaling relations in lattice models in statistical mechanics. Everything in the lattice model is dimensionless, but you can eliminate the microscopic variables and fiind relations between macroscopic variables. When you approach the critical point the correlation length diverges and you can have a unique relation between the variables.
The bottom line is that dimensions are a human invention that are no longer useful because we now know that c, h and G are finite. If they were infinite or zero, then you would have incompatible physical quantities. Dimensional analysis when dealing with dimensionless quantities makes sense, it just has to be interpreted as finding the correct scaling limit.

Count Iblis 16:53, 15 September 2006 (UTC)

Units are not really part of the numerical value of a variable. They are flags which are carried along to tell us how to rescale things, if we want to do that. You are saying that we can go ahead and rescale things even if we have deliberately forgotten how to do it. That makes no sense. JRSpriggs 05:17, 24 September 2006 (UTC)
Of course, once you start to rescale you need to keep track of what you are doing. You'll get your (incompatible) units back in the limit of infinite rescaling. The point is that the units you get depend on what you choose to rescale. The flags you are talkng about are not physical properties. They are artefacts of our desire to use incompatible units for length, mass, time etc. Count Iblis 13:27, 25 September 2006 (UTC)

Photon as a Featured Article

Hi everyone,

Photon seems to be getting close to becoming a Featured Article. But we would really appreciate your suggestions on how to improve it before we submit it as an FA candidate. Please take a few minutes to review the article and give us your advice on whether it's ready to be an FA at Talk:Photon. Thanks muchly! :D Willow 19:21, 11 September 2006 (UTC)

Conservation of momentum disproved

Sort of. EmDrive. The keepers are already piling up at Wikipedia:Articles for deletion/EmDrive, so we have another of those pesky pages to look after. --Pjacobi 16:43, 13 September 2006 (UTC)

A recurring theme. I wouldn't be averse to articulating a policy for this kind of stuff. Anyway, I claim its not notable. linas 04:28, 14 September 2006 (UTC)

Newton's Laws of Motion

Newton first published his remarkably concise and simple formalism about Nature in 1687. His three Laws of Motion turned out to be far ahead of their time, more accurate than the accuracy of experimental data available to Newton. More than three centuries later, after Classical Mechanics was taken to its climax, considered a dead science and resurrected once more, they remain the prototype of physical theories and high practical utility. More sophisticated reformulations of classical mechanics, while in many ways outstripping Newton's original formulation which seems almost childishly simple compared to the level of mathematical complexity inherent in these formalisms, still lose to Newton's Laws of Motion in terms of practical usefulness because of their failure to model systems with the dissipation approximation.

It is sad indeed, therefore, to see our article on this remarkable theory of Physics lie neglected. The level of exposition is suited to Children's Learning Library, not a serious encyclopedia. Nothing is mentioned about the significance of inertial reference frames. No reference is made to the interpretation of the first law of motion as a definition, no explanation is given why the first law must be considered independent of and preceding the second law. Detailed discussions are not provided about the validity of the third law in the context of classical electrodynamics. No mention at all of their reformulation without using the concept of force, depending on momentum and energy. Very important topics such as the role of Galilean relativity in Newtonian mechanics and the subsequent need to formulate the theory in terms of fiber bundles is absent.

My grasp of physics is not advanced enough to undertake these tasks without the fear of mistake, therefore I appeal to you to improve this article. The current state of the article, particularly in comparison with our articles on Lagrangian Mechanics, Hamiltonian Mechanics, Hamilton-Jacobi equation etc, gives the distinct impression that the contributors considered NLM to be a theory without any mathematical beauty or elegance behind it, something only children do. This situation must be rectified, most importantly for students just learning the theory who may visit our pages for an extended perspective and academics who may have lost sight of the theories remarkable power when faced with the cacophony of alternative theories. Loom91 11:53, 14 September 2006 (UTC)

Since this article, Newton's laws of motion, is of unusual importance and has been relatively static except for a substantial amount of vandalism, I think that it might be good to restrict the ability of anonimous editors to edit it. Would someone with administrative powers please restrict editing of it to registered users! JRSpriggs 05:40, 18 September 2006 (UTC)
Unfortunately, this is not covered by policy. --Pjacobi 06:33, 18 September 2006 (UTC)

Photon in Peer Review

Hi everyone,

Photon is now in peer review, in preparation for its Featured Article candidacy. Please take a few minutes to review the article and give us your advice on how to prepare it to be Featured — thanks! :D Willow 11:31, 15 September 2006 (UTC)

Physics categories & WP coverage of astronomy?

As per #Automatic adding of project banner to articles in Category:Physics above, I've put together an initial list of physics categories for auto-tagging with the project banner. The list is currently located at User:Mike Peel/Physics categories. I'd appreciate people's help at trimming down the list to only those appropriate to physics (my selection method wasn't that accurate), as well as adding any that I've missed. I'd also like to pose a question: does this Wikiproject also cover astronomy, or should a new wikiproject be established to cover that? Thanks. Mike Peel 18:38, 16 September 2006 (UTC)

Are these the categories which are directly or indirectly subcategories of Category:Physics? If not, then how did you put the list together? JRSpriggs 04:02, 18 September 2006 (UTC)
They're all subcategories of Category:Physics (or sub-subcategories, etc). Mike Peel 12:44, 18 September 2006 (UTC)

Infinite nesting

Someone's theory of everything, "licensed" under the GPL!; this one says we all live inside a hydrogen molecule. The AfD is here...it started quite well, but now the usual accusations of being the people who burnt Giordano Bruno are coming up. Oh dear. Byrgenwulf 11:13, 18 September 2006 (UTC)

Automatic adding of project banner to articles in Category:Physics

I've recently noticed User:Kingbotk's application of the Template:WPBiography template to articles within the living persons category. Would it be worth me approaching him to ask if he could do something similar with the articles in Category:Physics? Additionally, it seems that he can classify articles within the appropriate stubs section as class=stub, which also may be worth doing. The process would not be able to classify the articles by quality or class, excluding the stubs, so although they would appear in Wikipedia:Version 1.0 Editorial Team/Physics articles by quality, they would be marked as unclassified. Mike Peel 13:53, 21 August 2006 (UTC)

I've recently created a new template called {{stubclass}} which I'll be placing onto talk pages when auto-assessing as class=Stub example. I don't know yet how successful this approach will be but I think it's a winner.
Unfortunately, I have 22,000 living person bios still to do (~90,000 done), and a load of songs and albums. That's without even thinking about the biographies of deceased persons. I can't undertake to help any more projects at this time, but there's plenty of bots about and I'm sure someone would be willing to help! :) --kingboyk 18:10, 21 August 2006 (UTC)

Another approach to getting this done would be to make a request at Wikipedia:Bot requests. What do people think - is this worth doing? Mike Peel 22:06, 29 August 2006 (UTC)

Have you any idea how many talk pages currently transclude your template? And, approximately how many still need to be tagged? --kingboyk 12:05, 3 September 2006 (UTC)
The answer to the first is easy: 140 (they all appear on Wikipedia:Version 1.0 Editorial Team/Physics articles by quality). The latter is a bit more difficult. This project page currently says "as of November 2005, there are over 11,000 articles on mathematics and physics", but that's 10 months out of date (and includes the maths articles too). I would guestimate around 5-10,000 physics articles at the moment, but I could be completely wrong. I'm away from tomorrow 'till the 14th; I'll try to come up with a more accurate number after then. Mike Peel 12:39, 3 September 2006 (UTC)
My word, only 140 including unassessed? Well, certainly you need some bot assistance.
  1. I'm in the process of writing an AWB Plugin (see User:Kingbotk/Plugin) which will ease Wikipedia assessments and WikiProject template tagging, either for manual or automated bots. If a project has 10,000 or so articles within scope I'd support it. Looks like you're in that ballpark so if you want me to support your project I'm willing to.
  2. I guess I could tag that number of articles in a couple of days so I'd be willing to do an automated run for you, provided you can wait until I've finished at the very least living persons biographies. To make it easier for me, I'd like to be given either a filtered article list or a list of categories which contains articles suitable for tagging. I don't want to just start at your top level category and tag everything beneath it, since invariably some subcategories shouldn't be there or are outside scope and I don't know enough about your project to make the decisions myself. You can build such a list in AWB and export it, provided you carefully check each subcategory. (A categories list is fine and shorter, I can then expand the list into a list of articles using AWB, but won't include any extra subcategories which come up as I'll assume you've purposefully excluded them). --kingboyk 13:07, 3 September 2006 (UTC)

<-- Me again! My plugin has come on in leaps and bounds (see User:Kingbotk/Plugin) and I think the version I'm testing now ready for release later this evening will interest you.

The plugin can tag talk pages with WikiProject banners. If the template doesn't exist on the page, it creates one; if it exists under a different (redirected) name, it renames it to the "official" name. Existing parameters which are already on the page are retained, and new ones added which have been selected by the operator. If the article is a redlink (it sometimes happens that articles get deleted after the list has been built but before the bot gets there) it skips it. If the talk page template is misconfigured it skips and logs it. The beauty of all this is that it happens transparently - drop the plugin file into the AWB folder, click a few checkboxes, and off you go. A recent version also added support for reviewing and assessing articles manually, but I'm not aware that anybody's used that feature in anger yet.

Until now I've only supported specific, very complex templates ({{WPBiography}}, {{WPMILHIST}} and {{WP Australia}}). The changes I've just been working on allow the plugin to work with the template of any WikiProject, provided it has a class= parameter (which yours does). Ideally, the template should have needs-infobox=, attention= and auto= parameters too (you can steal some code for these from {{WPBiography}}). I call these templates "Generic WikiProject templates".

Anyway! To get to the end of a long story, I've just had my bot tag Category:Australian physicists with 3 templates, WPBIO, WPAUS, and "Physics generic template". Example diff:[1] Example where some templates already existed and only Physics got added: [2]

  • If you're interested in trying this, please keep an eye out for the upload I'll make later today.
  • If you want to get full support from my plugin, implement the 3 missing parameters I mentioned above
  • If you want to go ahead with tagging your articles, I can try to do Category:Physicists for you as it overlaps with WikiProject Biography.
  • Asking another bot operator to do the rest, perhaps at Wikipedia:Bot requests wouldn't be a bad idea, or use my plugin and get your own bot account at Wikipedia:Bots/Requests for approval.

Hope that helps. Any more questions you can ask me here as I'll keep this page watchlisted for a while longer. --kingboyk 18:08, 18 September 2006 (UTC)

Thanks for the information. I've now implemented the three missing parameters you mentioned. I'm currently trying to persuade your plugin to work on my computer (I've got AWB installed, but haven't yet managed to make any edits with it), and will hopefully start tagging articles shortly. Thanks for the offer to tag the Category:Physicists articles with Template:Physics - assuming noone here has any objections, could you go ahead and do that when you're ready, please? Mike Peel 16:18, 19 September 2006 (UTC)
Yes, I have it queued up to do after Politicians. (I need to find out first whether WPBiography are going to have a "scientists workgroup", so I can make sure I add the correct WPBio template at the same time). Any problems with the plugin let me know on the plugin's talk page. I'll remove this page from my watchlist now :) Cheers! --kingboyk 16:25, 19 September 2006 (UTC)
Do we have a better figure for the overall number of physics articles? Anville 01:41, 22 September 2006 (UTC)

Egan's "Plea to Save New Scientist"

John Baez has posted a public letter from Greg Egan about New Scientist magazine at The n-Category Café. Since the issue of this magazine's reliability (and how much "notability" its august aegis actually confers) has come up here a few times, I figured I should post a link. Quoting the first few paragraphs from Egan:

New Scientist is a British-based publication where many thousands of lay people get their information on scientific matters, and (IMHO) it does an excellent job about 70% of the time. But the combination of a sensationalist bent and a lack of basic knowledge by its writers (most obviously in physics) is rendering it unreliable often enough to constitute a real threat to the public understanding of science.
There are many areas in cosmology, fundamental physics and so on where there are controversies over issues that are hotly contested by various competent, highly educated and respected scientists, and I have no quarrel with New Scientist publishing views on various sides of these debates, even when those from the opposing camp would consider the claims to be nonsense.
However, I really was gobsmacked by the level of scientific illiteracy in the article "Fly by Light" in the 9 September 2006 issue, concerning the supposed "electromagnetic drive" of Roger Shawyer.

I like the word gobsmacked. Anville 17:46, 19 September 2006 (UTC)

I read this just now, wrote a comment on the blog and a letter to New Scientist, and I was just coming to post this very link. I urge everyone to go and consider writing to the magazine also. In the meantime perhaps we should reconsider whether they're really a reliable source...? -- SCZenz 23:49, 19 September 2006 (UTC)
The open letter also appeared as a post in the moderated newsgroup sci.physics.research. I emphatically agree with what Egan wrote. In addition to blog postings and individual letters to the editor, perhaps open letters from leading physical societies expressing concern would help. If you use the search engine at newscientist.com, it seems clear that the fringe science fans are not shy about expressing their desire to see more of this stuff in the magazine, so the editors may have concluded that physicists in general just don't care what appears in their mag. ---CH 20:47, 20 September 2006 (UTC)
Geez guys, New Scientist has always been like this! Come on, don't you recall the articles about wormhole transporters, that guy that said every aerodynamisist was wrong and wings really work "this way", or how about the recent "forget the rules" article where a guy put a wire mesh in front of a double slit and declared quantum was dead? I'm sorry, but NS has always been the British version of OMNI, sans the fiction. I still read it and enjoy it, but I've never considered it to either reliable nor anything but an interesting read.
It is worth pointing out, however, that the letter mentioned above seems to suggest all the more that the article in question should be kept -- if only as an introduction to the controversy it causes. Maury 22:33, 20 September 2006 (UTC)
Interestingly, in response to my post on the above blog, I received an email that's apparently from one of the New Scientist editors, asking for clarification of how their content affects us at Wikipedia. I'm not sure the difficulty that they cause Wikipedia should be high on their priority list when compared with the disservice they do to their readers, but it seems as though they want to know about it. -- SCZenz 23:57, 20 September 2006 (UTC)
Give them an ear-full and include links to the relevant discussions here. I guess that they are considering a brief news article on the controversy here. JRSpriggs 05:53, 21 September 2006 (UTC)

couple of questions for the cosmologists

Hey physics guruz, a couple questions have come up in recent editing, and I thought I'd get some expert advice. They both relate in some way to the possibility of physically real infinities. One is whether there is a consensus that the universe (the whole universe, not just the observable universe) has finite mass. The other is about just what "observable universe" means. I'll break them down into subsections for ease of discussion. --Trovatore 07:46, 21 September 2006 (UTC)

This page isn't really intended as a forum for questions; try WP:RD/S. But I admit you are more likely to get misinformation there than here, since it is obvious that not everyone who answers questions there knows very much or takes questioners seriously.
It sounds like your question might be based on a simplified paradigm for possible cosmological models which is some decades old. One relevant point which has been popularized in papers by Cornish and Weeks is that "negatively curved universe" models (this really means an FRW dust model with hyperslices orthogonal to the world lines of the dust particles or a closely related model) might have "spatial geometry" which is a compact quotient space of three dimensional hyperbolic space H3; similarly for "flat universe" models ('E3 hyperslices orthogonal to the world lines of the dust particles). Once you know enough about relativistic cosmology it is obvious from this remark that there couldn't be concensus unless we had good reason to think that possible "periods" in a quotient should be short enough that the quotient structure would in principle be observable. You might look for papers by Cornish and Weeks over at the arXiv if you want to learn more about how one might be able to observe possible quotient structures.---CH 23:51, 21 September 2006 (UTC)

(in)finitude of the physical universe

This discussion came up at infinite monkey theorem. An editor there had made a calculation (a bit OR-ish, but that's not important right now) about how long it would take to get a certain part of Hamlet's famous soliloquy if every atom in the universe were a monkey, or something along those lines. He claimed that this means the whole universe, not just the observable universe.

I doubt that any such thing is known. As I understand it, if the universe is asymptotically flat or negatively curved, then it is infinite in extent. Thus if the universe has a more-or-less uniform density, less than the critical density, then there must exist infinite mass. Is there something wrong with this argument?

The other editor claims that an infinitely massive universe would contradict the big bang. I don't think that's so either; again as I understand it, if you take a hyperbolic universe of uniform density and consistent with known astronomical facts, and run the equations backward in time, you still arrive at a singularity (infinite density) some finite distance into the past. --Trovatore 07:46, 21 September 2006 (UTC)

Unless you know precisely what the inflaton is and how inflation occurred, there is no way to know how many atoms there are in the total universe. There are ways to model both finite and infinite numbers of atoms. Most calculations of atoms in the universe apply only to atoms in the observable universe or atoms that are possible to observe for all time (which is a slightly different thing -- dependent on a different horizon). --ScienceApologist 17:56, 21 September 2006 (UTC)
Trovatore, you wrote "if the universe is asymptotically flat or negatively curved, then it is infinite in extent" which is exactly the local vs. global goof which has been stressed by Cornish and Weeks, as I mentioned in my comment in the preceding section of this talk page. It is true even for possible quotients of these however that they exhibit a Big Bang type curvature singularity if you run back by some finite proper time along one of the world lines of the dust.
However, the main point here is that the claim that "an infinitely massive universe would contradict the big bang" is nonsense. The classical FRW dust solutions with E3 or H3 hyperslices orthogonal to the world lines of the dust particles (or better, the FRW radiation fluid solution with either of those properties) are perfectly legitimate exact solution to the Einstein field equation which exhibit a Big Bang type isotropic curvature singularity.---CH 00:00, 22 September 2006 (UTC)

notion of observable universe

The above discussion led me to observable universe, which had some rather odd claims when I got to it. It appeared to claim that the observable universe was the whole universe. Moreover, it didn't have any reference to the observable universe depending on the observer, which it seems to me it obviously must, just assuming that the universe is a connected 3-manifold. As I understand it, point B may be in point A's observable universe, and point C may be in point B's observable universe, but point C may not be in point A's observable universe. So a photon could get from point C to point B, but by that time, the expansion of the universe would have carried B out of A's observable universe, so the information could not then be passed to A.

But I do have a little difficulty thinking about just how to express it mathematically. Suppose for convenience that the universe is asymptotically flat, so it can be treated as R3. Is it accurate to say, in the above situation, that C is outside A's observable universe because the universal expansion means that it is moving faster than the speed of light, from A's point of view, but that B is moving slower than the speed of light from A's point of view, and C is moving slower than the speed of light from B's point of view? But then what happened to the usual relativistic addition of velocities? Is it just not possible to consider an inertial coordinate system from A's point of view that extends to C? --Trovatore 07:46, 21 September 2006 (UTC)

Think of an "observation (of the universe)" as a point in spacetime: an event, and the observable universe w.r.t. such an observation as the set of events to which the observation is causally connected: the observation is in their "future light cones". Then you get transitivity: if observation B is in the observable universe of observation A, and observation C is in the observable universe of observation B, then C is also in the observable universe of A. This is just a complicated way of saying that the relation of being causally connected is transitive. What muddies this simple picture is that in a popular style of discourse, used in many accounts, the events of "our" observable universe are projected to their respective futures to become as it were "contemporaneous" with "now". From a purist GR point of view this is severely meaningless: it requires a preferred inertial framework always everywhere. This leads to observable events being projected to outside the actually observable universe: in an expanding universe, what "happened" to much of the observable universe is not observable. The resulting confusion may lead to apparent paradoxes. In most discourses on this kind of stuff an observer may be equated with an observation, like they are taking a snapshot, but you can also think of an observer as a worldline of observations, leading to an evolution of the observable universe. Then the non-observable rest is much like a black hole. Another worldline that moves to outside the observable universe (for the observer at some time) cannot move back in (for the same observer at some later time). --LambiamTalk 09:32, 21 September 2006 (UTC)
Well, but I don't think your first remarks are exactly what we're talking about in the context of the notion of "observable universe". After all, two event points could be an inch apart, spatially, and yet not be in each others' timelike cones; they don't have to be 14 billion light-years apart, or whatever the number is supposed to be for the radius of the observable universe.
As for the preferred inertial framework, I don't think that's required. Just pick some maximal connected spacelike 3-manifold embedded in spacetime, and call that the "whole" universe for purposes of discussion. It's true, is it not, that there are pairs of points in that 3-manifold such that a photon sent from one can never get to the other, at least if the universe is hyperbolic? And it's also true that this relation between pairs of points is not transitive, because if it were it would be an equivalence relation, and would partition the universe into disjoint nonempty open sets, contradicting connectedness? --Trovatore 15:19, 21 September 2006 (UTC)
I'm not sure who "we" is in your phrase "what we're talking about". My claim is that the notions as I defined them are precise and clear concepts, while the "usual" popular presentation is unphysical and murky, and leads to conceptual problems. Yes, two events can be spatially close and not in each other's future cones, and so they are then not causally connected one way or another. But if they are events on two worldlines, then presumably events on one worldline are in the observable universe of some observations on the other worldline. So if an observer is equated with a whole worldline of observations, you can take the union of all observable universes w.r.t. the observations of the observer. Since we can't predict the future, we cannot know the extension of our current worldline. To "solve" that problem, you might next take the union over all possible worldlines extending from a worldline ending here-and-now. In doing so, you lose of course transitivity. As time proceeds, the observable universe then shrinks even assuming a cosmology with a static universe. If that is supposed to be the meaning of "observable universe", it should be made clear, but I don't think it conforms to the standard concept.
I don't understand the last part, nor why you wrote it. What do you mean by "spacelike"? My first interpretation is that any two distinct points of the manifold are space-like distinct. So no photon from any point of the manifold can get to any other point. Restricted to the spacelike manifold, this relation is by definition transitive. Outside that manifold it is not. Did anyone suggest such a thing?
What I said about projecting events to their future to make them contemporaneous is not the only possible way of thinking about the observable universe as a contemporaneous blob, but it seems to be the usual way. I've never seen an account based on "picking" a spacelike 3-manifold. It's not clear to me how you go on from there to define the notion of observable universe. Are you claiming that the result of "your" observable universe does not depend on the "whole universe" you pick? Could you present your preferred definition in the form of: "The observable universe is the set of events E such that P(E)", for some predicate P? --LambiamTalk 17:38, 21 September 2006 (UTC)
Haven't really followed the first paragraph above; maybe I'll get back to it once I do. As to the second:
  • When I say the 3-manifold is spacelike, I mean all tangent vectors to it are spacelike. At least I think that's what I mean. It's been a while since I did manifold theory.
  • As to the photons getting from one point to another, what I really mean is, can a photon from point A ever reach an object that is currently (that is, in the spacelike slice) at point B? It's my understanding that, in a hyperbolic universe, there are points A and B such that this is impossible, because universal expansion will always keep the object from point B ahead of the photon from point A, and that this is the fact that delimits the "observable universe".
  • No, I'm not claiming it's independent of the slice you pick. As I'm envisioning it, it's not a set of events at all, but a set of points in 3-space. --Trovatore 17:50, 21 September 2006 (UTC)
Trovatore, I'd reccommend the excellent textbook by D'Inverno, Understanding Einstein's Relativity, which has a good introduction to the basic FRW models (with and without Λ). Should be easy reading for a Ph.D. mathematician, but do ask again if that doesn't help. Since you have earned a Ph.D. I invoke the powers invested in me by WP:IAR :-/ to give you special dispensation to ask your educated peers here on this page, rather than in our forum for the hoi-polloi, WP:RD/S.---CH 00:06, 22 September 2006 (UTC) (Just kidding, of course. Or am I? A Ph.D. ought to be good for something around here!)

You asked "But then what happened to the usual relativistic addition of velocities? Is it just not possible to consider an inertial coordinate system from A's point of view that extends to C?". The notions of "relativistic addition of velocities" and "inertial coordinate system" are part of special relativity and cannot be applied, without modification, to general relativitiy. Imagine a model in which the manifold is R4 with the metric (d\tau)^2 = (dt)^2 - (\exp(t))^2((dx)^2 + (dy)^2 +(dz)^2)\! which corresponds to a universe dominated by the cosmological constant. Then every particle has a horizon surrounding it which asymptotically (exponentially) approaches it as time goes to infinity. If you go far enough into the past, you can see the early history of any other particle. But any two dust particles, no matter how close to each other, will eventually get so far apart that light rays emitted from them heading toward each other cannot ever meet. JRSpriggs 09:17, 22 September 2006 (UTC)

User:Thljcl

Hi everyone,

Thljcl (talk • contribs) has made several edits, which seem questionable to me, to articles such as kinetic energy, E=mc², mass and special relativity. These edits have a theme of removing indications that mass is a form of energy (which is correct, as far as I know). Can anyone have a look and check if they are legitimate? -- Meni Rosenfeld (talk) 06:39, 22 September 2006 (UTC)

I can't figure out what he means by this, and his edits appear to be wrong. I am working on fixing this and adding comments to the talk page discussion of the issue. -- SCZenz 07:20, 22 September 2006 (UTC)
Think this edit, in which he links to this article, is particularly indicative. He clearly has some peculiar POV about special relativity disagrees with the definitions used by modern particle physicists. And we all know what WP:V says about statements you can't cite, and what WP:NPOV says about extremely rare minority viewpoints. -- SCZenz 07:28, 22 September 2006 (UTC)
I've reverted all his physics related edits, for the time being. I suggest we keep an eye on his contribs and on the sort of articles he's edited so far. Special:Contributions/Thljcl. -- SCZenz 07:31, 22 September 2006 (UTC)

User:Thljcl has clarified in Talk:Kinetic energy that he means to say that every form of energy is mass, that is, mass and energy are the same thing. Isn't that a legitimate interpretaion? What should be done about it? -- Meni Rosenfeld (talk) 06:59, 23 September 2006 (UTC)

Unless you are working specifically with natural units in which c is dimensionless, mass and energy have different dimensions. Isn't that enough to make obvious they shouldn't be equated just like that? (Butcher, can I have 18 PJ of pastrami?) --LambiamTalk 11:02, 23 September 2006 (UTC)

Well, they're certainly different as far as calculations are concerned. However, conceptually they describe the same physical reality. 200 g, 18 PJ and 1.961 N (assuming a constant g = 9.805 m/s2) all describe the same amount of pastrami. This, I think, means we should at least give some thought about the merits of said edits. -- Meni Rosenfeld (talk) 11:15, 23 September 2006 (UTC)

You are wrong. Thljcl may have a conceptual system for physics that is self-consistent and useful (i.e. that all energy is mass, rather than vice versa), but that is not the terminology that physicists use. Unless he can cite sources in the field that use his framework, including his alternate point of view violates Wikipedia:No original research. -- SCZenz 20:55, 23 September 2006 (UTC)
It's not quite clear what the issue is. Under the assumption that the equation E = mc2 adequately describes physical reality (after all, it's only part a theory that might be overturned by the next revolution), if you give me m I'll give you E, and if you give me E I'll give you m. In natural units, E = m. I think we all know that. It would therefore make perfect sense to talk about excitation FOO, kinetic FOO, potential FOO and material FOO, where FOO is consistently either "mass" or "energy" (or some newly coined term, like "inertia"). This requires reeducating physicists. Until such time as this reeducation project has borne fruit, I think Wikipedia should conform to the usual terminology. --LambiamTalk 21:13, 23 September 2006 (UTC)

Very well. SCZenz, please note that I did not say we should include his edits (in which case I would probably have been, indeed, wrong), but only that we should take a look and see if they contain anything salvageable - which I'm sure you did, and support your conclusion that there is none. Perhaps it's worth mentioning that the idea that potential energy is manifested as mass is new to me, which is why I've brought this issue up here.-- Meni Rosenfeld (talk) 21:23, 23 September 2006 (UTC)

You're right; I didn't need to be as harsh in my last post as I was, and I apologize. That being said, an idea appearing to be a "new approach" to basic physical concepts with well-established definitions is a point against it, given our policies on original research, especially when the user is citing pages like the one I linked above. Remember that an interpretation being "legitimate," in the sense of functional, is not the same as it appearing in the literature—and that Wikipedia is a secondary source. Anyway, although it's not relevant to whether we include the edits, I don't see how it's sensible to think of potential energy as mass. -- SCZenz 00:00, 24 September 2006 (UTC)

Now I'm confused. See here. -- Meni Rosenfeld (talk) 05:10, 24 September 2006 (UTC)

Energy refers to the time component of linear momentum (more precisely -p0). While mass is the energy of the object in its rest frame divided by c2 (more precisely it is the value determined by the nature of the object to which that quantity tends to be close). These are two different things. The potential energy of an object contributes to its mass, if its rest energy is measured in a global reference frame; but not if measured in a local reference frame where the source of the potential is considered part of the background which is tranformed away. JRSpriggs 05:47, 24 September 2006 (UTC)

Theory of everything

Wortzman (talk · contribs) aka 162.84.136.215  (talk · contribs) has been adding blab on some bollocks called the "Gyroverse" to the Theory of everything article. He has done it 3 times (once under the IP address), and I have reverted all 3 times and warned them, but if I revert again, I am in violation of 3RR whereas he isn't (because of the IP). If anyone has the chance to keep an eye on the article... Byrgenwulf 13:56, 22 September 2006 (UTC)

P.S. It seems that the user above would be Donald Wortzman (website), the inventor of the theory. Byrgenwulf 14:01, 22 September 2006 (UTC)
It's bollocks alright. I've just reverted him again. --Michael C. Price talk 15:01, 22 September 2006 (UTC)
Thanks. I just reported him for 3RR, so let's hope he stops. Byrgenwulf 15:04, 22 September 2006 (UTC)
I only count 3 reverts. The first (anon) edit does not qualify as such. --LambiamTalk 16:08, 22 September 2006 (UTC)
Oh well, he seems to have stopped, and that's the main thing; he appears to be here solely to shill for his personal theory. Byrgenwulf 20:35, 22 September 2006 (UTC)

I was in trim down mood and reduced the other efforts section. And noticing one of these overgrown templates, I've put Template:Theories of gravitation of TfD. --Pjacobi 16:49, 22 September 2006 (UTC)

Scalar field theory

I noticed that the WP pages on scalar field theory were fairly disparate, with no coherent description or even agreement on conventions. So, I've created the new page Scalar field theory, which no longer just redirects to Scalar field. I've also changed the links on a number of physics pages which used to link to Scalar field, so that they now point to the new article (I've been fairly selective when doing this, i.e. linking pages which clearly mean to refer to scalar field theory, rather than the more general concept of the scalar field.)

There are two things I'd appreciate feedback on. First, there's still more work to do on the page, so help would be appreciated. But also, I'd wondered whether it now might now be worth blanking and redirecting this page on scalar field theory and this page on phi^4 theory.

I'm not sure about the latter just yet, because there are a few things on there that are not yet on the new page. However, I believe the parts that do overlap are now more coherently described. Perhaps the phi^4 page could be reserved for more detailed information on that theory, I'm not sure at the moment.

I've left relevant messages on the talk pages, but thought they might not be widely watched. All the best--Jpod2 09:55, 23 September 2006 (UTC)

Whenever you create an article, the FIRST thing you should do is put it in a category so that it does not get lost. Please do that. JRSpriggs 05:58, 24 September 2006 (UTC)
Good point. Looks like someone else has got there first, though there may well be other relevant categories. Thoughts on redirecting the other page(s)? All the best--Jpod2 09:01, 24 September 2006 (UTC)
I do not know enough about the substance to have a strong opinion on that. But as a matter of process, I think that you should not just blank pages without more discussion. Put the merger template on those pages. Consider whether there is material on them that you have not incorporated into your page yet (as there appears to be to me as a non-expert in QFT). Also you need to consider whether the revision histories of those pages will be readily accessible. Perhaps it would be better to just have a pointer to the phi to the fourth page and put your stuff on that into the existing page? JRSpriggs 03:59, 25 September 2006 (UTC)
Hi, thanks. I agree there should be more discussion (which is why I left the messages here and on the relevant talk pages, and have not redirected the pages themselves). However, the template is a good idea, I didn't think of that.
I think there is currently very little on the scalar field (quantum field theory) that is not on the new page. Perhaps only the propagator for the free field, which is introduced somewhat out of context on that page (i.e. without motivation or description), and deserves a much fuller discussion! A discussion I'd like to have on the new page, but haven't gotten around to, yet.
As I think I explained above, there is some additional material on the phi^4 page, but I thought I would initiate the discussion for that page, too, though I do not think it should be redirected imminently. I think the idea of a pointer to the phi^4 page would be inappropriate, mainly because phi^4 is a special case of a scalar field theory, not the other way round. Perhaps I am missing your reasoning, though? Oh, I see I've misunderstood you---you mean merging specifically the new phi^4 stuff with the current page? Perhaps---though I'm not sure if that would be best.
I suppose the revision histories will simply remain in place if they were redirected? I assume that such a situation is far from unprecedented, anyway. I will put up the merger template and await further discussion.--Jpod2 09:41, 25 September 2006 (UTC)

Photon is a Featured Article candidate

Hi everyone,

Photon is now a Featured Article candidate. If you like the article, please leave lots of Support votes there, so that the WikiProject will get another FA. Thanks! :D Willow 10:00, 23 September 2006 (UTC)

Another case of undetected vandalism in a key article

Non existing key experiment added to quantum mechanics in May 2006

Just one edit before, there was some "asdf"-vandalism

Recent changes patroller Beek man removed the "asdf"-vandalism, but considered the key experiment to be legit:

Pjacobi 20:12, 24 September 2006 (UTC)

How depressing. . . but not exactly unexpected. Anville 22:47, 24 September 2006 (UTC)
Should we consider asking recent-changes patrollers not to do reverts when there have been edits they're not sure about, lest they mask changes for people who know what they're talking about? Or at least that they drop a quick message to the relevant wikiproject? -- SCZenz 04:16, 25 September 2006 (UTC)
I found a similar example of edit creep, involving a dubious but superficially plausible paragraph and a Chuck Norris joke, in the uncertainty principle article (I shan't bore anyone with the details).
I think SCZenz's suggestion could work...I also found this proposal thingummy which looks like it could be a help, if it ever gets enacted. I left a brief note of approval on the talk page: we can see what happens. Byrgenwulf 16:01, 25 September 2006 (UTC)
The proposal essentially involves adding a feature to the wiki software, which keeps IP/anon/new users' edits in abeyance (i.e. out of the "visible" article) for some period of time (at the moment, 24hrs), to allow for a form of "light peer review" (approval by more experienced editors) to try to stop nonsense from slipping through. Byrgenwulf 16:04, 25 September 2006 (UTC)
"Chuck Norris can observe an electron so hard that he can measure its position and momentum simultaneously!"
I doubt that SCZenz's suggestion will change the behavior of any Recent Changes patrollers (even though it is a reasonable request pertaining to a real problem). Would you listen to someone telling you not to revert changes like "asdfasdfjimboisaloser" being inserted into loop quantum gravity? Requesting that notice be given at WikiProject Talk pages is a bit more reasonable, although we shouldn't count on all the RC patrollers taking the time to do that. We folks here know that only physics articles matter (har har), but hundreds of thousands of other articles are potentially in the purview of other, relatively specialist WikiProjects: chemistry, history, music, etc. Which vandalism reverts do you not wish reported?
I hate to say it, but the only solution I see offering even partial reliability is increased vigilance over the articles in our domain. We should learn not to trust edit summaries like "rvv", particularly if we cannot recognize the username as belonging to a knowledgeable editor. I have developed the habit of checking at least one edit back in the histories of the pages I have watchlisted; this may be a useful habit to adopt.
On another, partially related front, my grandiose plan for providing an antidote to at least a few of our problems is proceeding forward. I've received (qualified) approval from the bot crowd for the first phase of operations, and this afternoon I'll be speaking to people about server space, domain names and other technical details. Anville 16:23, 25 September 2006 (UTC)

Discouraging people from reverting vandalism would be a mistake. The only solution I see is for more people to do what I usually do -- I look at each individual change in the revision history since the last time I checked that article. Unfortunately, there are some articles (like Golden ratio) which are so active that I do not have enough time to do that. But in those cases, there are usually other people I trust who are watching them more closely. Also there are often changes which I cannot verify because they lie outside the scope of my knowledge. So I just have to hope that errors in such changes will be corrected by someone else. JRSpriggs 04:33, 26 September 2006 (UTC)


Some comments:

  • Recent changes patrol and hidden errors: As most of RCP works with some Javascript wizardry nowadays, and as the articles starts being linked to the matching WikiProject on their talkpage, perhaps a feature requests for our Javascript wizards would do? A button "report to WikiProject" when a patrollers touches an articles but is uneasy about something he can't decide himself?
  • Wikipedia:Timed_article_change_stabilisation_mechanism: I assume this one of the new feature to be tested Real Soon Now on de:. Due to some communication disaster, this wasn't exactly universally applauded to say the least. But I assume some test will be done anyway. I'll report back here.

Pjacobi 07:26, 26 September 2006 (UTC)

Harmonic coordinate condition

I was thinking of creating an article on the Harmonic coordinate condition. See http://mathworld.wolfram.com/HarmonicCoordinates.html You-all do not seem to have any articles or categories which fit exactly. The closest thing I see is Category:Frames of reference. Is that the appropriate category for it? JRSpriggs 06:50, 26 September 2006 (UTC)

An article on popular choices of gauge in a diffeo-invariant theory (i.e. choices of coord system) might well be useful. --Jpod2 13:47, 26 September 2006 (UTC)
Yes. A more general article on how and why to choose a coordinate system might be more appropriate. It could also include A.Einstein's practice of setting \sqrt{-g} = 1. Any other suggestions? JRSpriggs 03:05, 27 September 2006 (UTC)
I have to think a bit more about it. I know a lot of theoretical physicists (including me) think of diffeomorphism invariance as a gauge symmetry---morally speaking because it indicates a redundancy in the description of the system. I can't see any mention of this perspective (or indeed `popular' choices of gauge/coordinate system) in General relativity or General covariance. Gauge symmetry mentions it in passing in this section, but in no detail.
So I guess I am saying it might be possible to include something in one of those articles (or related articles). Or if it's too much material to include there then perhaps a brief section in one or more of them and then link to the new page. What do you think? --Jpod2 08:49, 27 September 2006 (UTC)

I found another category which may be more appropriate, to wit Category:Coordinate charts in general relativity. Yes, General covariance might be a good place to put material on harmonic coordinates and other coordinate choices. It is frequently said that a choice of coordinate system is the analogue for gravity of choosing a gauge in electromagnetism. But I am not sure that that is exactly right. Perhaps it might be more correct to say that the gauge of gravity is a choice of a "background" (non-physical) connection whose Riemann-Christoffel (curvature) tensor is zero everywhere. Then the gravitational force-field is the physical connection minus the background connection (and thus a tensor field). Does that make sense? JRSpriggs 07:59, 28 September 2006 (UTC)

Ah, well found on that category. So I think the conclusion might be to create an article on the harmonic coodinate system, and include some example of where it is useful in GR perhaps. The second conclusion might be that the choices of coordinate system are not adequately linked to GR and general covariance (it looks like the individual articles on coordinate systems are typically linked from a particular solution of GR).
I think it is analogous to choosing a gauge in a gauge theory, as a choice of gauge is in some sense a choice of coordinates on the fiber. It is also analogous in a physical sense because GCI indicates a redundancy in the description of the system (i.e. the number of physical degrees of freedom is fewer than those explicitly in the problem), which is the usual way to think of a gauge symmetry.
I'm not quite sure what you mean by your intepretation of choice of gauge. You want to separate Γ = Γ1 + Γ2, such that R(Γ1) = 0? --Jpod2 09:47, 28 September 2006 (UTC)
1. What do you mean by "GCI"? 2. Although the article in the coordinate chart category mostly deal with particular solutions, I think that it would be OK to put in a more general article on a coordinate condition which can be used in solving many problems (especially for gravitational radiation). 3. One way of stating the equivalence principle is that one cannot distinguish between inertial forces which are fictitious (e.g. centrifugal force and Coriolis force) and gravity, except that fictitious forces can be zeroed globally by a coordinate change and gravity cannot. It is the fictitious forces which are necessarily non-tensor. If gravity is separated from them, then it can be made into a tensor. Of course, the ambiguity remains, but now it is an ambiguity in choosing the fictitious forces rather than in choosing the coordinate system. Notice that the connection acts like a tensor under a globally linear coordinate tranformation. And other fields than gravity are invariant under general curvilinear coordinate tranformations. So that there is not a one-to-one relationship between coordinate transformations and gauge-like changes. JRSpriggs 04:18, 29 September 2006 (UTC)
Hi JR 1. General coordinate invariance, 2. I think a more general article is a good idea, and also more discussion on the GR/GC pages perhaps, 3. I'm not sure what a 1-1 relationship between these things would satisfy :) However, from the reasoning I've given above diffeomorphism invariance is often thought of as analogous to a gauge symmetry, and certainly is somtimes termed as such in physics departments. ANyway, let's not worry too much about the terminology. I think it would be worth creating that article---ah I see you've done it. All the best--Jpod2 08:59, 29 September 2006 (UTC)

Background colour of info tables

Hi, in articles on particles, the background colour of info tables is a dark grey. This isn't too legible, so the photon article has been edited to use "lightgray" instead of "gray". Would it be OK to spread the change to all articles? If yes, I propose we change them all. --Kjoonlee 06:54, 26 September 2006 (UTC)

I boldly went ahead.
These are the articles that I changed. --Kjoonlee 08:24, 26 September 2006 (UTC)


Why Wikipedia sucks (sometimes)

I'm not going to argue and find consensus with Kentforbes (talk · contribs · block log) whether electrolysing water, burning the hydrogen, and having a net energy gain in the process should be considered to be a perpetuum mobile. Nor do I intend to put a humble "cite needed" tag to the claim, that this Water fuel cell powered a car driven across the United States. I will simply revert until someone blocks me for 3RR violation.

If someone is in the mood to resolve the problem by other means, don't hesitate.

Pjacobi 08:46, 26 September 2006 (UTC)

Another reason, why Wikipedia sucks

Do you consider it a sane question, to be asked for in-line cites, for e.g. the statement two events happening in two different locations that occur simultaneously to one observer, may occur at different times to another observer at Special relativity? See Talk:Special relativity#GA Re-Review and In-line citations. --Pjacobi 08:55, 26 September 2006 (UTC)

This seems to be a mass change in the standards we've had the same message on 11 mathematics GA's. I've responded to this at Wikipedia talk:WikiProject Good articles you may like to add your voice there. --Salix alba (talk) 10:51, 26 September 2006 (UTC)
There must be an official policy statement somewhere that generally known and accepted facts, such as "2 × 2 = 4", or "The Sun rises in the East and sets in the West", or "Rome is the capital of Italy", can be stated without requiring a citation of a source. I know I saw this somewhere, but can't find it now. Possibly the frame-dependency of simultaneity is also covered by the applicable clause. --LambiamTalk 13:39, 26 September 2006 (UTC)
The closest thing I can find (though I recall reading a similar statement somewhere in meta-land) is the Common knowledge guideline, which sounds like it was written by people who hadn't even considered the issue now being discussed. "Certain kinds of claims should most definitely not be left to common knowledge without citations," it says, one of which is "Claims that something is a scientific fact." Why? "Acceptable scientific theories are published and peer reviewed." Slightly later in the same list is "Anything where a PhD (or other advanced training) is required in the field to be able to evaluate truth and consistency with the consensus view; for example, quantum mechanics."
Er. Um. Huh?
I have come to feel that our policies leave us caught in a cleft stick. They are workable tools for defending against total crackpottery (although "notability" is being a shrill mosquito of a problem), but those same policies cripple our ability to write good material about uncontested science. Anville 14:55, 26 September 2006 (UTC)
I thought the policy change was very rushed, without any consensus, but it looks like there was *some* talk about the matter. To overturn the decision, please make your voice heard at Wikipedia talk:Good article candidates#Discussion on criteria changes. --Kjoonlee 16:18, 26 September 2006 (UTC)
We also have the option to stop co-operating with the centralised WP:GOOD process and identify A- and B-class articles ourselves by Wikipedia:Version 1.0 Editorial Team/Work via Wikiprojects. --Pjacobi 18:45, 26 September 2006 (UTC)
What I've done on Wikipedia:WikiProject Mathematics/Wikipedia 1.0 is create a B+ rating. This is specifically for articles which are close to GA standard, and includes most failed or delisted nominations, whilst they are not quite up to GA standard, they are some of the better mathematics articles. The criteria are basically: understandable by mear mortals and actual cover the history of the topic. --Salix alba (talk) 23:40, 26 September 2006 (UTC)

Wow, I'm currently embroiled in the GOOD article nonsense that is non-expert Wikipedians saying that articles like Hubble's Law aren't good because they only have two in-line citations. Yuck. I say we start our own Wikipedia project "Good science articles". We can make it part of Wikipedia:Scientific peer review. --ScienceApologist 18:53, 26 September 2006 (UTC)

Pjacobi and ScienceApologist's suggestions are all well and good, but we'd just be stuck with the same problem all over again if we tried to take anything to Featured Articles instead of merely Good Articles. Anville 19:53, 26 September 2006 (UTC)
FAC process is broken. Ignore it. Physics is such a niche theme at Wikipedia, it doesn't make sense to try to make general process match our requirements. --Pjacobi
I disagree. At the very least, it's a good way to draw non-scientist's attention to physics topics, which is always good. While they can be finicky about inline references, that's normally good - and in the case of common knowledge, surely it's easy to point towards a couple of decent textbooks that discuss that bit of knowledge, and say that there's a lot more, which will hopefully satisfy them. Other than that, what else do you think of as "broken" in the FAC process? Mike Peel 20:12, 26 September 2006 (UTC)
But surely we can make a new category of "Featured Physics articles" and impose our own standards for inclusion in this category? Count Iblis 20:18, 26 September 2006 (UTC)

To see what happens when a non-physicist decides that there isn't enough inline references, look no further than the current state of redshift which, I might add, is probably over-inline-cited right now (if you can believe it). If you don't feel like routing through this article, I'll give you an example. An enterprising FA reviewer thought it wise to put a {{fact}} tag on a statement that amounts to the idea that Rayleigh scattering accounts for the sky being blue. --ScienceApologist 20:32, 26 September 2006 (UTC)

FA is intentionally more stringent than the requirements of the WP:V and WP:NOR policies. It's the nature of the beast geared to showcase the "best of wikipedia." Nevertheless, many of those fact tags seem pointless. Even in that FAC, the editor who added all the fact tags was not supported by other reviewers. Gimmetrow 21:22, 26 September 2006 (UTC)

Yes, this is also going on at Talk:String theory. This makes very little sense to me. It is something that I've occasionally tried to bring up on WT:V and elsewhere, and made very little headway. (I can't remember what initially got me worrying about this.) The attitude of the rest of the Wikipedia community is "Well, if it's in so many books, then it should be easy to find a reference." This all originated from legitimate worries that information in Wikipedia wasn't sufficiently verifiable, which is true, but like many policies, some people seem intent on pushing it to its bone-headed extreme.

Part of the problem is that a lot of information that is common knowledge to specialists (or even undergraduates in physics) is hard to tell from genuinely controversial statements. This only reinforces the need for some mechanism by which specialists (or WikiProjects) can bless content. –Joke 20:35, 26 September 2006 (UTC)

We can setup an assessment team to identify "A"-class articles. --Pjacobi 21:05, 26 September 2006 (UTC)

I have made a request regarding this issue here. --ScienceApologist 21:03, 26 September 2006 (UTC)

The problem with saying "it's common knowledge, so it must be easy to find a book" is twofold. First, citing a particular book for something like the postulates of special relativity is essentially spamming for that particular book. Why choose it over all the others — because you used it in college? Second, more importantly, the qualified editors we hope to attract have not been trained to write in that fashion. When was the last time anyone here writing class notes on relativity actually cited Einstein for E = mc2? (I recall an letter several months ago in Physics Today which pointed out that ignoring this issue and accepting citation counts literally leads to the claim that Einstein is more revered for the photoelectric effect than for relativity.) I expect that the average physics person who wants to contribute a physics article thinks of it as writing a short stretch of textbook; what is the footnote density in Griffiths' Introduction to Quantum Mechanics or, taking the extreme case, Feynman's Lectures on Physics? Anville 21:56, 26 September 2006 (UTC)
Well, it's important to remember that WP is a reference work, not a textbook. Keeping that in mind is protection against an overly chatty, "pedagogical" style. But I agree with the point that the footnote thing is overdone. (Maybe a better question: What's the footnote density in Brittanica?) --Trovatore 22:06, 26 September 2006 (UTC)
I can't resist making a silly linguistic remark: doesn't the -pedia in Wikipedia come from the same place as the peda- in pedagogy? [3] [4] Anville 22:22, 26 September 2006 (UTC)
I strongly agree with Anville's remarks, although I don't necessarily believe that we should base our referencing standards on textbooks, Britannica, or even how most editors have been trained to do referencing. We have to establish our own commonsense standard, based on the competing needs for verifiability (which is a particular issue for Wikipedia, because of its anonymous and semi-anonymous editing), clarity and readability, and even editability. I've worked on articles that need extensive referencing (say false vacuum and cosmic microwave background) and some that, at least in my opinion, are better off with very little (say big bang or, as SA points out, redshift). –Joke 00:02, 27 September 2006 (UTC)

My attempt to edit

My attempt to edit the in-line citation criterion to be saner here was immediately knee-jerk reverted because the old version supposedly "had consensus." I believe this is false.

If, as it appears, most of us here agree that my version was more sensible, I propose that we make our voices heard. This being a wiki, a very reasonable course of action is to revert the criterion once each. -- SCZenz 00:21, 27 September 2006 (UTC)

Honestly, as the knee-jerk reverter in question, I think this whole situation has gotten a bit out of hand, several of the articles I saw people actually add warnings too honestly seemed very debateable to me in terms of whether they really fit the inline citation criteria, Mathematics in particular seems pretty well-referenced to me, most of this came from just one user's warnings, and due to the flexible natures of people's reviews, one reviwers standards can deviate somewhat from other reviewers. Which, coincidentally enough, is basically what WP:GA/R is for. Homestarmy 00:25, 27 September 2006 (UTC)
Then the criterion should be clarified so it doesn't cause such problems. It is unacceptable to have guidelines that support the harassment of hardworking experts who volunteer their time. -- SCZenz 00:27, 27 September 2006 (UTC)
I'd hardly call a few advisory notices "harassment"..... Homestarmy 00:29, 27 September 2006 (UTC)
I've tried to explain back on the other page. What would you call writing "Hi, your articles will no longer count as good unless you follow this new rule we made up and never asked you about"...? -- SCZenz 00:32, 27 September 2006 (UTC)
Ok, sure, the notifications wern't exactly reflective of the subjective way "Well-refrenced" can be interpreted, but think of it this way, instead of warning articles, (Many of which I noticed some editors improved in time based on the advisories) we could just do nothing and delist most of them with no warning, and I don't think that would be very fair. Homestarmy 00:37, 27 September 2006 (UTC)
Or maybe you could talk to the people who wrote the articles, who are in fact experts on the subjects of the articles, and ask them if they think the references are sufficient. Then you could listen to what they say and revise your criteria. -- SCZenz 00:41, 27 September 2006 (UTC)
This is not Citizendium, what the "experts" say isn't the final decision on things. Homestarmy 01:39, 27 September 2006 (UTC)
You're right, we don't get the final say, and I didn't mean to imply otherwise. However, you feel no obligation even to listen, or ask our opinion, before declaring consensus finalized. And in that you are mistaken. -- SCZenz 01:46, 27 September 2006 (UTC)
It was an approximatly two week discussion where editors who had never before even shown up on the talk page chipped in, how were we supposed to know when we had "enough" people to actually make a good criteria? Maybe we should of waited for people from a couple History Wikiprojects to wander on over, or Chemistry, and maybe some evolutionary biologists, there's no set-in-stone need to wait for all of Wikipedia to join a discussion to change one criteria in one optional grading system which has only recently gotten a real system in place so to speak and still hasn't even impressed many people as to the purpose of the project. Homestarmy 02:18, 27 September 2006 (UTC)
Well, you putting the "real system" in place seems to be the source of the problem. And yes, Physics and History and Chemistry and all the other areas of serious article-writing should have been contacted before you put new standards in place, rather than imposing them on the articles we wrote afterward. But, since those things are done, here's the new problem... Now that we've had issues with the criteria, and new editors are arriving to make their opinions known, the consensus you had goes away—that's the risk of building a consensus with only certain parties, and without those who may be most affected by the results of that consensus. So now we talk, and stop declaring that the page is finalized because you had a consensus in the past. -- SCZenz 03:38, 27 September 2006 (UTC)
I know this is a complete side issue, but please please please don't say "a criteria". It's horrifically jarring. Frankly, it sounds completely illiterate. The singular is "criterion". --Trovatore 04:53, 27 September 2006 (UTC)

@Homestarmy: This is not Citizendium, what the "experts" say isn't the final decision on things. This is wrong for at least two reason:

  • Experts have the final say in the sense, that they can leave or never enter the project.
  • Several efforts of the WMF aim for attracting experts and experts' annoyance with process wonkery and the like are on the list of Wikimedia's problems.

Pjacobi 07:33, 27 September 2006 (UTC)

Update on inline citation issue

I've agressively tried to get this problem fixed, with some limited success. Now I need to cool off and ignore Wikipedia for a while. If it's really important, I'm sure others here can take up the banner from this point. -- SCZenz 02:12, 27 September 2006 (UTC)

It is important as an indicator, what's going wrong in Wikipedia. But it is of minor importance, as just ignoring WP:GOOD and WP:FAC is a viable option. Besides actually forking we can always use WikiProject driven assessment scales or wait for the results of the de: experiment. Note that in the de: experiment, the labelling as "geprüft" will be done domain experts (real name and academic credentials must given to volunteer as "Prüfer"). --Pjacobi 07:37, 27 September 2006 (UTC)
Ignoring GA and FA is a viable option, except (as mentioned somewhere above) that it cuts down our chances of receiving outside input. Some of those people are, after all, our "target audience" — maybe not for Lie superalgebra, but certainly for Big Bang, Redshift and Trigonometric function. I have always been a fan of David Brin's aphorism, "Criticism is the only known antidote to error." In order to understand how non-experts respond to articles intended at least partially for a non-expert audience, we need input from readers outside our own august circle. We can always hang around and watch the Talk pages, and I can always ask my mother to read articles like Bogdanov Affair, but occasionally a crucible of community criticism can be a good thing.
This presumes, of course, that the process is not completely broken — that FAC reviewers are capable of delivering useful criticism at least some of the time. I think this is true, at least in areas like grammar, overall clarity, picture use and such. Referencing will be a concern we have to address, probably by railroading an article through the system and establishing a precedent we can point to later. Anville 13:03, 27 September 2006 (UTC)

Separate guideline for science article citation

(Originally in reply to Anville's comment at 13:03 27 September.) "Precedence" does not appear to have much weight, unless presented as a "guideline". Can we, by a consensus process, establish a proposal guideline for citations in science and mathematics articles, and then declare them to be a Wikipedia guideline, just as by some mysterious process there are notability guidelines for different kinds of topics? -- --LambiamTalk 21:59, 27 September 2006 (UTC)

I'm not sure it's a good idea to fork the citation guidelines for different subjects; splitting such things is not clearly necessary, adds an extra layer of bureaucracy, and could create some very intense debates. But we could do as you say: write a page addressing issues particular to the sciences, in particular the issue of line-by-line citation of settled science, and link it from WP:CITE. I'm undecided on this. -- SCZenz 22:05, 27 September 2006 (UTC)

Let's just ignore GA

I propose we just ignore the good articles page. GA used to be an extra step between A- and B-class; now that step has moved, from my reading, above A-class. They are not responsive to our concerns over at the GA criteria page.

So let's just use A- and B- and Stub- and Start-, which are criteria internal to our project. I do not think we need a new bureaucracy for identifying A-class articles. Let's just keep rating articles on a volunteer basis and trying to improve them, and discuss it here if an article is badly mis-rated.

We do need outside feedback, and lots of it, but I think the far older and less-rigid Wikipedia:Peer review is a better place to get it. -- SCZenz 14:57, 27 September 2006 (UTC)

So, should we just set the Way Back Machine to 2004 — write an article, get feedback from Peer review and occasionally nominate to FAC? (I am reluctant to abandon FA, though GA can go hang: science on the Main Page is just too juicy to give up.)
Last night, I found the following passage in George Sarton's A History of Science: Hellenistic Science and Culture in the Last Three Centuries B.C. (1959). From page 150, discussing the early days of Alexandria's Library:
The first head of the Library, Zēnodotos of Ephesos [early third century B.C.], was a pupil of Philētas; his scholarly activities were so considerable that the probably devoted to them the whole of his time that was not eaten up by the library administration. It is highly probable, however, that the administration was still rudimentary; this was an age of administrative innocence, truly a golden age. All the chores were shared or divided amicably, without red tape, and done informally and wholeheartedly. The work was immense, for it did not suffice to put the rolls in order; each of them needed a special investigation, and not only that but the texts themselves required editing.
Ah, for the "golden age" of Alexandria. Anville 15:32, 27 September 2006 (UTC)

Ah, that's worthy of a wistful sigh or two. I wrote a few paragraphs about my attitude towards this whole thing at Wikipedia_talk:Good_article_candidates#Can a compromise be found?. The gist of it is:

  1. No doubt, many of the articles whose talk pages received the message could use additional footnotes in places.
  2. But spamming the talk pages in this way was counterproductive.
  3. And this is ridiculous.
  4. Physicists and science editors in general want to be part of the GA process.
  5. But we also think there ought to be a happy medium between referencing every sentence and not having any footnotes at all.
  6. Can't we sometimes be given the benefit of the doubt (within our WikiProject) regarding footnoting?

I'd appreciate any comments. –Joke 16:34, 27 September 2006 (UTC)

Most of what you say is reasonable, but whether it can be worked out depends on the GA people changing their tune. Their response so far as been wholly unacceptable as far as I'm concerned, and focused on claims of "past consensus" rather than an understanding of the new issues we've raised. I have no interest personally in participating in a bureaucracy where non-experts determine whether our articles are "good" by counting the citations; better to ignore it than to argue, I think. -- SCZenz 16:49, 27 September 2006 (UTC)

Back to business: new article Rietdijk-Putnam Argument

Please see Talk:Rietdijk-Putnam Argument. --Pjacobi 09:31, 28 September 2006 (UTC)

I read the article and the talk, however the first words just caught my eye "if special relativity is correct" actually special relativity has been tested in lots of ways.. so probably this should be corrected other than that I still don't see the point of the article at all... And actually I find this even uncorrect under the special relativity postulate, since the two people mentioned when meeting will be simultaneous, and hence their light cones and event horizons will be well defined, and so the paradox wouldn't occur, as it is described at least... maybe I wasn't too clear, but we can discuss about this further Tatonzolo 14:53, 28 September 2006 (UTC)
This is silly. One does not use a reference frame tied to his person (which is constantly accelerating). He uses a reference frame tied to the Earth, or even the Sun. And for astronomical purposes, we use retarded time which does not vary from person to person depending on their velocity. JRSpriggs 04:27, 29 September 2006 (UTC)
Yep that would be the point... it's something like a wrong description of the twin paradox... :-)

Tatonzolo 07:47, 29 September 2006 (UTC)

Is someone here also working at Wikibooks? This article seems to be just a summary from a Wikibooks chapter. --Pjacobi 07:55, 29 September 2006 (UTC)

Heim theory AfD

Heim theory has been proposed for deletion. Comment as you see fit. Anville 13:49, 28 September 2006 (UTC)

More citation nonsense

Look what one editor is doing to science articles. Can we say, anti-science bias perhaps? --ScienceApologist 21:51, 28 September 2006 (UTC)

Dear me. This individual has de-listed redshift from GA. Does anyone actually have the enthusiasm to open a "Good article review" on this, or should I just curse very loudly at the whole GA process? Anville 22:13, 28 September 2006 (UTC)
I'm not surprised
"ClairSamoht - citation adder"
Hahahaahahaa! Count Iblis 23:43, 28 September 2006 (UTC)
Can't we just do an assessment to check whether it is an A- or B-class article? --Pjacobi 08:28, 29 September 2006 (UTC)
Assessment sounds like a better and better idea. I worked on that article enough (during its first FAC go-around) that I should recuse myself from the appraisal, but in my view you could strip out all those {{fact}} tags and give it an A-class stamp. Anville 14:46, 29 September 2006 (UTC)

This is apparently the future of Wikipedia: Lancaster County, Pennsylvania. It'll be a heck of a lot of fun to write for the project then. –Joke 13:07, 29 September 2006 (UTC)

Yes that article is in a terrible shape, full of uncited statements. How the heck is an innocent reader supposed to verify from reliable published sources that "The principal freight operator in the county is Norfolk Southern Railway (NS)", or that "Lancaster County is also home to the amateur football team called the Lancaster Lightning, of whom are members of the North American Football League" without proper citations? This is just the kind of stuff that makes people wary of Wikipedia as a source.  --LambiamTalk 16:03, 29 September 2006 (UTC)
I wonder how you found this page. Did you use some kind of a bot, or there is a special page on the most referenced articles in Wikipedia? I think we need such a page. (Igny 17:46, 29 September 2006 (UTC))

11 references in a stub of three sentences :-) Count Iblis 18:33, 29 September 2006 (UTC)

Citation guideline modification

Let's try to get people at WP:CITE to listen to us. We have a suggestion that this guideline include a statement to the effect that elementary facts should not be cited. I tried to qualify this with a statement of what things I think (and maybe others think) should be cited in science articles and what things should not (and why). Please read, comment, and modify this work here. --ScienceApologist 05:50, 29 September 2006 (UTC)

Every article needs to answer "Says who?" in a clear way that is understandable to every English speaking person. For articles that contain nothing more than the facts available in every standard textbook on the subject, exactly that should be told the reader in the same way that an article that is basicly a copy of the century-or-so old Britannica says that. 4.250.177.242 15:12, 29 September 2006 (UTC) User talk:WAS 4.250
Here is a little exercise for you.
  • Our article Apple pie states: "The fruit for the pie can be fresh, canned, or reconstituted from dried apples."
  • Our article Spain states: "To the west and to the south of Galicia, Spain borders Portugal."
  • Our article Sun states: "The Sun is the star of our solar system."
  • Our article Week states: "A week is a unit of time longer than a day and shorter than a month."
  • Our article Yellow pages states: "In many countries, the Yellow Pages refers to a telephone directory for businesses organized by the category of product or service. As the name suggests, they are usually printed on yellow paper, as opposed to white pages with non-commerical listings, printed on white paper."
For each of these, either come up with a reasonable way of saying "as is common knowledge" that can be inserted into the article as it stands, or find a reliable source that can be used for a reasonable citation.  --LambiamTalk 16:23, 29 September 2006 (UTC)
Also Ho ho ho is the way that many languages write out how Santa Claus laughs. "Ho, ho, ho! Merry Christmas!"  :-) Count Iblis 16:38, 29 September 2006 (UTC)
Specifying the ingredients of an apple pie is not so easy. After all, what did Carl Sagan say: "If you wish to make an apple pie from scratch, you must first invent the Universe." (Cosmos: A Personal Voyage, episode 9). Anville 17:31, 29 September 2006 (UTC)