View source for Wikipedia talk:WikiProject Physics/Taskforces/Relativity/Archive 1

{{Talk archive}}

== Intro unnecessarily slanted towards overly simplistic (textbook) POV ==

First of all, good project initiative! But I have immediately a suggestion about the presentation: 

In view of the article [[http://en.wikipedia.org/wiki/Priority_disputes_about_Einstein_and_the_relativity_theories]], stating this project as being about "Albert Einstein's theories of special and general relativity" could suggest a kind of tunnelvision or partisan approach as well as taking a stand (POV) in an issue that --if I understand it well-- is not the scope of this project (right?). 

Thus I advise to instead put it as it's commonly put: "The theories of special and general relativity". 

That would also avoid the suggestion that this project intends to promote exclusively a single person's idea's and interpretations (philosophies) concerning those theories of physics.

It's certainly a detail, but nevertheless an important one IMHO. 

Cheers, [[User:Harald88|Harald88]] 13:48, 29 October 2006 (UTC)

:That's a good point. I'll fix that once I get the chance. [[User:MathPhys|MP]]  [[User_talk:MathPhys | (talk)]] 16:58, 29 October 2006 (UTC)
:: Fine but... it only takes 10 sec. to fix it. Perhaps you were you in a hurry? I'll do that now. [[User:Harald88|Harald88]] 19:25, 30 October 2006 (UTC)

:::Yes, I was in a hurry. Thanks for fixing it. [[User:MathPhys|MP]]  [[User_talk:MathPhys | (talk)]] 22:25, 1 November 2006 (UTC)

== Got a doozy for you ==

We've got a weird situation over at GA Review - we have someone who is claiming that his math proves Einstein's theory of [[WP:GA/R#Special_relativity|special relativity is false]] and so should lose its GA rating and he won't go away until someone checks his math :-P We're not mathematicians, etc., so was going to see if someone here might be able to put this to rest? --[[User:Plange|plange]] 15:40, 29 October 2006 (UTC)

: Hmm... I'm afraid that the question is wrong: his/her math is ''irrelevant'' for Wikipedia -- see [[WP:NOR]]+[[WP:V]]. BTW, usenet has a long experience with people who claim that a well verified theory is "wrong": it's rarely possible to make them change their mind with logical (mathematical) arguments. 
:But what needs to be accurate for a "good" article is the article's description of the subject. Wikipedia specifically refuses to decide for the reader what is "true". [[User:Harald88|Harald88]] 20:14, 29 October 2006 (UTC)
::Yep, thanks for posting to the review page too! We tried arguing about OR and V until we were blue in the face. Seems like a crank to me and we keep telling him to go and publish that we were not the publisher of last resort but he's hinging his whole argument on the fact that since the WikiProject Mathematics project tag has GA on it, it means they checked the math and he says its wrong. Sigh. I will close it... --[[User:Plange|plange]] 20:35, 29 October 2006 (UTC)

== Recommended general relativity sources ==

Hi MPatel,

I would like to recommend the following scholars as sources: [http://www.tc.umn.edu/~janss011/ Michel Janssen] and [http://www.pitt.edu/~jdnorton/jdnorton.html John Norton] Generally, I would like to recommend the writings of the scholars who are involved in [http://www.einstein.caltech.edu/ the Einstein Papers project] such as [http://www.bu.edu/philo/faculty/stachel.html John Stachel], [http://www.jhu.edu/~phil/faculty/rynasiewicz.html Robert Rynasiewicz] Jürgen Renn and other staff members of the Einstein papers project.  

These scholars are physicists who in the course of their career have shifted to the history of science/physics and the philosophy of physics. The writing of these scholars is focused on critical examination of underlying concepts of physics theories. The following two articles by [http://www.pitt.edu/~jdnorton/jdnorton.html John Norton] were very important sources of information for me.

''[http://www.pitt.edu/~jdnorton/papers/ProfE_re-set.pdf What was Einstein's principle of equivalence?]'' (PDF-document, 376 KB, viewable with Acrobat Reader 6 or higher.) John Norton discusses that the version of the Equivalence principle that is commonly offered in expositions of general relativity fundamentally differs in content from the principle that Einstein presented in his papers. Norton judges Einstein's version to be superior.

''[http://www.pitt.edu/~jdnorton/papers/decades_re-set.pdf General Covariance and the Foundations of General Relativity: Eight Decades of Dispute]'' (PDF-document, 460 KB, viewable with Acrobat Reader 6 or higher.) For as long as the general theory of relativity has been around there has been dispute about the question whether there is any physical content in a concept of a "principle of general covariance". At the end of this painstaking monograph, Norton arrives at the conclusion that the concept of a "principle of general covariance" is indeed physically vacuous. (Of course, this has no consequences for GTR, which does not need a "principle of general covariance".) At the same time, Norton argues how it can be seen that the diffeomorphism invariance of GTR does have physical significance. 

I have a [[User:Cleonis/Time_dilation|user subpage article about special relativity]]. There are several animation in that article (manufactured by me; Creative Commons license). 

I also have a [http://www.cleonis.nl website of my own with physics articles], including an article about the general theory of relativity. Check it out.

Large parts of the wikipedia [[Sagnac effect]] article were written by me. I watch the Sagnac effect article, and will discuss any changes to it. --[[User:Cleonis|Cleonis]] | [[User talk:Cleonis|Talk]] 19:03, 29 October 2006 (UTC)
:Any theory can be written in a generally covariant form (as Misner-Thorne-Wheeler point out). So general covariance is not, in itself, a physical constraint on a theory. However, the mathematical simplicity and asthetic beauty of a theory has long been recognized as a heuristic criterion for preferring some theories over others. And the significance of general covariance is that that criterion should be applied to the generally covariant forms of the competing theories (rather than a form which assumes a particular type of reference frame or coordinate system). Why? Because we believe that coordinate systems are a human creation rather than part of the natural world. [[User:JRSpriggs|JRSpriggs]] 06:50, 31 October 2006 (UTC)

::Naturally I endorse the point of view that coordinate systems are a human creation. However, in my opinion (adopted from John Norton), that is unrelated to the physical significance of diffeomorphism invariance. 
::What is not a human creation, in my opinion, is that it is possible in the first place to map spacetime. We can define a unit of length, say a meter, with this unit of a meter defined as the distance that light travels in a particular amount of time. With that unit of spatial distance and that unit of time we can map a region of spacetime. The sheer possibility of mapping spacetime is what gives rise to the sheer possibility of formulating laws of motion. In the case of newtonian space and time and in the case of Minkowski spacetime, an immutable background is assumed, and motion is mapped with respect to that background structure. 
::Pre-GTR theories assert that when spacetime is thus mapped, the mapping will be found to be linear. There is an equivalence class of spacetime mappings, related by transformation rules. Pre-GTR theories assert that inertial mass couples to spacetime, giving rise to the phenomenon of inertia. In pre-GTR theories the coupling is assumed to be uni-directional: spacetime is acting upon inertial mass.
::GTR of course asserts that the coupling of inertial mass to spacetime is '''bi'''-directional. Spacetime is acting upon inertial mass (inertia), and inertial mass is acting upon spacetime, with the corresponding curvature of spacetime acting as the mediator of gravitational interaction.
::In pre-GTR theories, setting ap an equation in dynamics has the immutable background as a constant factor. In GTR, in setting up the Einstien Field equations, the very background, spacetime itself, is a dynamical factor in the equations. 
::This, argues Norton, is why GTR finds its natural formulation in a form with diffeomorphism invariance. The problem that Einstein was up against was how to formulate a theory of motion when the very background, spacetime, is a dynamic variable, acting upon inertial mass and being acted upon by inertial mass. Since finding the future shape of spacetime is what the Einstein Field Equations are set up for, the equations find their natural formulation in a form that is uncommitted to any choice of mapping spacetime.
::Summarizing: coordinate systems are a human creation but the fact that spacetime can be mapped at all is what makes is possible at all to formulate laws of motion. (More generally 'laws of motion' can be taken as 'laws that govern how processes develop over time'). The diffeomorphism invariance provides the necessary freedom to handle the fact that the structure of spacetime is a dynamic variable. --[[User:Cleonis|Cleonis]] | [[User talk:Cleonis|Talk]] 11:36, 31 October 2006 (UTC)

== Should this be made a sub project of Wikipedia Project Physcis? ==

See [[Wikipedia:WikiProject_Physics]] and SCZenz's comments under [http://en.wikipedia.org/enwiki/w/index.php?title=Wikipedia:WikiProject/List_of_proposed_projects&curid=3110326&diff=84640057&oldid=84628383#Relativity]

He argues that it's better to include this inside the physics project, and I think that he has a good point. 
However, how would that work out in practice? Are there existing exmples of other projects with sub projects? [[User:Harald88|Harald88]] 19:33, 30 October 2006 (UTC)
:Yes, there are several, the most notable being [[WP:BIOGRAPHY]] and [[WP:MILHIST]] which have "work groups" and "task forces" respectively to handle sub-projects --[[User:Plange|plange]] 19:36, 30 October 2006 (UTC)
:: Looks OK to me. [[User:Harald88|Harald88]] 19:46, 30 October 2006 (UTC)
::Sure there are, but I don't think relativity will have enough activity to warrant a separate project ''or'' a subproject.  That is to say, the activity on physics is light enough that everybody can keep track of it without difficulty; I'd support sub-projects only if the main physics activity got too heavy. -- [[User:SCZenz|SCZenz]] 01:58, 1 November 2006 (UTC)

== How to improve relativity-related articles ==

Above I have pointed out the community of editors of the  [http://www.einstein.caltech.edu/ Einstein Papers project] as a major source of information. Among them, [http://www.pitt.edu/~jdnorton/jdnorton.html John Norton] and [http://www.tc.umn.edu/~janss011/ Michel Janssen] have made many of their papers available for download as PDF-file. Since their articles are so available, I take them as main references.

Underlying in any presentation of special and general relativity should be the notion that relativistic physics is a field theory. It should be emphasized that The Einstein Field equations are in fact field equations.

The natural terminology of presenting a field theory is to express physics taking place in terms of particles coupling to the described field. (Another matter of terminology: there is the name 'Minkowski spacetime' for a manifold with a (-,&nbsp;+,&nbsp;+,&nbsp;+) signature metric, but the spacetime of GTR, Riemannian manifold with a (-,&nbsp;+,&nbsp;+,&nbsp;+) signature metric, does not have a specific name. I will call the spacetime as described by the Einstein field equations: 'Einstein spacetime'.)

GTR is a theory that describes interaction of inertial mass with a ''field'': inertial mass ''couples'' to Einstein spacetime. Spacetime is acting upon inertial mass, and inertial mass is acting upon Einstein spacetime, inducing spacetime curvature.

This offers a perspective on the question why special relativity is unsatisfactory. GTR describes that spacetime is acting upon inertial mass, giving rise to the phenomenon of inertia. In retrospect, special relativity looks odd in the sense that it describes a uni-directional field-coupling. Spacetime is acting upon inertial mass, but Minkowski spacetime itself is assumed to be immutable. As we all know, GTR resolves that tension.

'''The number one stumbling block for novices'''<br>
For novices, the problem that arises most frequently is that they are sometimes led to expect that relativistic physics is a theory that asserts that spacetime does nothing at all. Sometimes, they are led to a line of reasoning that goes as follows: "Einstein showed he didn't need an Lorentzian ether, this shows that spacetime is just ''emptyness'' and not involved at all." That erroneous pattern of expectation then blocks understanding of relativistic physics. What needs to be emphasized is that according to relativistic physics Minkowski spacetime and Einstein spacetime are participants in the physics taking place. 

The concept of Lorentzian ether and the concept of Minkowski spacetime have in common that they both are physical entities, participating in the physica taking place. The one distinction that needs to be emphasized is that in the context of special relativity velocity with respect to Minkowski spacetime does not enter the theory as a matter of principle. --[[User:Cleonis|Cleonis]] | [[User talk:Cleonis|Talk]] 09:53, 5 November 2006 (UTC)

: Just as a reminder, it's not a good idea to bias Wikipedia towards one or two easily available sources, and relativity theory is certainly not limited to Einstein's papers. But indeed, Einstein's papers are of course important and I also find Janssens's papers a very useful and illuminating background source; their easy availability is a plus. [[User:Harald88|Harald88]] 12:40, 5 November 2006 (UTC)

:::I suppose I should have emphasized Norton's and Janssen's accomplishments in the philosophy of physics, rather than mentioning that they have served as editors in the Einstein papers project. (I assume that the people that are invited to serve as editor on the Einstein papers project are chosen for their understanding of the philosophy of physics and specific historical knowledge of relativistic physics.) 
:::About Einstein's papers: <br> Einstein was a trailblazer, and while he was ultimately successful, many of his choices along the way turned out to be dead ends. Because of that, I think Einstein's own views (varying wildly until settling on his mature views in the mid 1920's) are not particularly helpful in education. Einstein's writings are studied by historians of science for the sake of reconstructing the developments in Einstein's thinking. For the purpose of elucidating GTR itself as much as possible, Einsteins writings can only play a minor part. 
:::Norton's article [http://www.pitt.edu/~jdnorton/papers/decades_re-set.pdf 'Eight decades of dispute'] is for the most part a painstaking survey of expositions of GTR. As far as I can tell, Norton has acquired all textbook expositions of GTR, stretching from 1921 to the early 90's, and he compares the views of the authors, documenting the extend of disagreement about what consitutes the foundations of GTR. In being a survey, the aim of 'eight decades of dispute' is to present an overview that is as unbiased as the possible, just like an encyclopic article.  

:::: Your emphasis about philosophy is useful and at the same time it should serve as a warning: philosophy of physics is not physics but physics-related philosophy. Where such philosophy enters physics articles, readers should be warned that it's philosophy and not hard science. 
:::: Norton's overview of criticism sounds very useful for GRT. [[User:Harald88|Harald88]] 23:59, 6 November 2006 (UTC)
::::: Unfortunately, the word 'philosophy' has for many people negative connotations. I did not have any of those in mind. I am '''not''' referring to physics-related philosophy, I am referring to theoretical physics. Examination of (assumptions underlying) the theoretical framework itself is part of the endeavour of theoretical physics. This is key to science education. An introduction to relativistic physics for novices must concentrate on the barest essentials. For an encyclopedic article, the task of identifying barest essentials is everything. --[[User:Cleonis|Cleonis]] | [[User talk:Cleonis|Talk]] 12:12, 7 November 2006 (UTC)

:::::: Assumptions that underlie a theoretical framework cannot be tested and quite often, incompatible assumptions result in the same theory of physics. They are part of natural philosophy. But I'm not against philosophy at all and philosophy of physics does include philosophy (surprise?). For example, Janssen also gave his opinion about the "neo-Lorentzian interpretation" of relativity which according to the philosopher Mauro Dorato[http://209.85.135.104/search?q=cache:8y4WAENsu2gJ:philsci-archive.pitt.edu/archive/00000902/00/SRTbre.rtf+%22neo-lorentzian+interpretation%22&hl=en&ct=clnk&cd=4].  was motivated for "the rescue of a mind-independent becoming" . [[User:Harald88|Harald88]] 20:29, 7 November 2006 (UTC)

::Einstein showed that the principle that a particle (which is not affected by forces other than gravity) follows a geodesic thru space-time is a consequence of his field equations, i.e. it is the only way that the metric of the surrounding vacuum can be matched to the [[Schwarzschild metric]] generated by the particle. So the action of mass upon the geometry ''produces'' the reaction of geometry upon mass. (This leads me to the conclusion that electromagnetic forces act on charges via changing the geometry -- the charge is deflected, not directly by the electric field, but by the gravitational effect of the cross-term in the stress-energy tensor between the particle's field and the ambient field.) [[User:JRSpriggs|JRSpriggs]] 05:05, 6 November 2006 (UTC)

== New category for Relativists ==

I created a new category [[:Category:Relativists]] to replace the category "Contributers to general relativity" which was deleted (CFD-ed). This one includes people involved in special relativity as well as general relativity. Please add or delete people as appropriate. [[User:JRSpriggs|JRSpriggs]] 05:58, 23 February 2007 (UTC)

== Mass in SR ==

There is currently some discussion (verging on an edit war) concerning [[mass in special relativity]].  That page looks like it needs some work. Also, the separate page on [[invariant mass]] seems to me to be unnecessary.  Are you editors able to become involved in this? [[User:Timb66|Timb66]] 12:03, 29 May 2007 (UTC)

== Userbox ==

A userboxe is the center of any wikiproject. Well, maybe not, but I made one anyway. [[User:Beast of traal|<span style="color:gray">Beast of traal</span>]] [[User talk:Beast of traal|<span style="color:gray">T</span>]] [[Special:Contributions/Beast of traal |<span style="color:gray">C</span>]] [[User:Beast of traal/the_hidden_button |<span style="color: white">_</span>]] 21:41, 2 November 2007 (UTC)Beast of traal


Oh, and the color matches the color of the heading of the project page. [[User:Beast of traal|<span style="color:gray">Beast of traal</span>]] [[User talk:Beast of traal|<span style="color:gray">T</span>]] [[Special:Contributions/Beast of traal |<span style="color:gray">C</span>]] [[User:Beast of traal/the_hidden_button |<span style="color: white">_</span>]] 21:42, 2 November 2007 (UTC)Beast of traal

{{Template:User_WikiProject_Relativity}}
{{-}}

== Missing articles ==

I noticed that some missing articles are still red-links even when there is a comment saying that it "exists as" another article. In this case, why have you not changed the red-link into a redirect? -- [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 21:08, 16 November 2007 (UTC)

: Because I have more important things to do in my life. [[User:Mpatel|MP]] <sup>([[User_talk:Mpatel|talk]]•[[Special:Contributions/Mpatel|contribs]])</sup> 19:10, 17 November 2007 (UTC)

::It only takes about a minute to create a redirect. I would do it myself, if I was sure that there was no affirmative reason why they were not created. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 07:27, 18 November 2007 (UTC)

:::Done. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 21:42, 18 November 2007 (UTC)

== Rationale for redirecting some red links ==

Some redlinks have comments stating that the topic under consideration already exists in another article (e.g. [[Einstein static universe]] exists as part of [[Static universe]]). Sometimes it's better to have a separate article with more details. If more details can't be included yet, then a new article probably should not be created. But then again, a stub article can encourage more editors to contribute. I suppose it's a matter of individual judgement. In the [[Einstein static universe]] case, I would like to see a separate article with more details. [[User:Mpatel|MP]] <sup>([[User_talk:Mpatel|talk]]•[[Special:Contributions/Mpatel|contribs]])</sup> 13:43, 18 November 2007 (UTC)

== Recruiting editors for [[Black hole]] ==

I am currently trying to improve the quality of the [[Black hole]] article. (which has devolved in quite terrible state.) I thought some of the GR specialists here might want to help contribute to it. I especially need help find references/identifying statements that probably need referencing. Any help would be kindly appreciated. ([[User:TimothyRias|TimothyRias]] ([[User talk:TimothyRias|talk]]) 14:59, 13 May 2008 (UTC))

== Agreeing on a consistent metric for SR ==
I am not quite sure if this is the appropriate place to suggest this.  But, is there any way that the Relativity working group can decide on a consistent metric for SR.  Right now I am seeing at least three different metrics: -+++ (most common) , +--- [[spacetime]] and [[four-vector]], and -c^2+++ [[Special relativity]] and [[four-momentum]].  As a physicist who deals with similar stuff it is a small irritant that won't go away.  For anyone without experience with different conventions and trying to understand relativity, it must be a major stumbling block.  For what it is worth, I have expressed my preference on the [[Special relativity]] page.  [[User:TStein|TStein]] ([[User talk:TStein|talk]]) 15:34, 19 June 2008 (UTC)
:There is no global standard for selecting -+++ (Misner, Wheeler, Thorne) over +--- (some editions of Landau-Lifshitz) (although my preference is for -+++, which seems to be the wiki standard), but the use of -c^2+++ is horrendous and, AFAIK, completely unsupported by the literature (see the refs I've added at four vector); where C is explicit (i.e. not set to 1) it is attached to the four vector, not the metric. Unfortunately one rather determined editor has been inserting the ugly and original researched factor of c^2 everywhere attached to the metric (e.g. see [[Talk:Stress-energy_tensor#Dimension_problem.]], in addition to the dialogue at [[Special relativity]] page that TStein mentioned). --[[User:MichaelCPrice|Michael C. Price]] <sup>[[User talk:MichaelCPrice|talk]]</sup> 17:28, 13 September 2008 (UTC)
::As the editor whom MichaelCPrice is criticizing, I request the privilege of replying.
::Most importantly, what I am doing in this case is not original research. It is based on "Post, E.J., ''Formal Structure of Electromagnetics: General Covariance and Electromagnetics'', Dover Publications Inc. Mineola NY, 1962 reprinted 1997.". In chapter 2, "Transformation behavior and dimensional properties of physical fields", he explains the correct method of assigning dimensions to the components of tensors as it was developed by Dorgelo and Schouten.
:::"Their considerations led them to distinguish an invariant factor in the dimensional characterization of physical quantities, called the absolute dimension. The actual dimensions of the components of a physical quantity are then determined by this absolute dimension times a multiplicative contribution which solely determined by the transformation behavior of the physical quantity." (page 23)
:::"However, the common dimensional identification of position and time coordinates is acceptable only as an expedient. It facilitates the exploration of the basic physical relations in four-dimensional garb, but it is unacceptable as a lasting feature, because it eliminates the undeniable differences in dimensional individuality of time and space coordinates. The tacit assumption of dimensional homogeneity is bound to lead to obstacles because it ignores a fundamental principle, the principle of causality." (page 24)
:::"For a linear frame in E<sub>1+3</sub> the relative dimensions of the components of a tensor field can be found by adding to the absolute dimension a factor l or t for every contravariant index, a factor of l<sup>-1</sup> or t<sup>-1</sup> for every covariant index, depending on whether the index is a space label or a time label. A density of weight + k obtains in addition a common factor t<sup>-k</sup>l<sup>-3k</sup>." (page 29)
:::"The line element with a length dimension implies that the fundamental tensor ''g''<sub>ab</sub> should carry an absolute dimension of [l<sup>-2</sup>] as stipulated by Dorgelo and Schouten." (page 34)
::Thus I am merely following their directions, not performing original research.
::Also, let me point out that tensors are very flexible and one could associate a separate unit of one's choice with each of the four principal directions. However, using the [[SI units]] (seconds, meters, meters, meters) seems the most practical to me, and most consistent with non-relativistic equations. Remember that tensor equations are really just arrays of ordinary equations; and tensors are just arrays of ordinary real-valued physical variables.
::I am just saying, let us group the appropriate ''unaltered'' equations together rather than doing an unnecessary conversion of units every time one processes a quantity associated with time.
::The speed of light is a feature of the metric in fact. Without the metric, one could not even say what that speed was. So why do some people want to divorce it from the metric? Only because they have been misled by the myth that all components of a tensor must have the same units. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 21:21, 13 September 2008 (UTC)
:::A number of points 
:::1) Even the quotation from a rather obscure E.J.Post admits that this is a minority viewpoint when he/she refers to the "dimensionless-metric" stance as the "the '''common''' dimensional identification of position and time coordinates".  IOW the author is arguing for a position ''that even in 1962'' was already a minority position.
:::2) If we attach dimensions to the metric, as E.J.Post suggests, then not only does an arbitrary tensor <math>T_{\mu \nu} \,</math> have different dimensions from <math>T_{\mu}^{\nu}\,</math> and <math>T^{\mu \nu} \,</math> but even <math>T^{0j}\,</math> differs from <math>T^{ij}\,</math>.  Dimensional analysis, instead of being a useful and easy sort of checksum becomes a complete nightmare.  By contrast, with the modern, conventional standard of making the all metric components dimensionless all the components (time, space, or mixed) of a tensor have the same dimension, whether covariant, contravariant or mixed.
:::3) Most textbooks sidestep the problem by setting c=1 ''before'' they define the lorentz coordinates; all the textbooks I've found which are explicit on the issue set <math>x^0 = ct</math>, not <math>x^0 = t</math>.  This includes the rather definitive Misner, Wheeler, Thorne tome, Gravitation. 
:::So, in summary, there is no reason to adopt such a confusing standard.  It is not supported by the modern literature, and for good reason. --[[User:MichaelCPrice|Michael C. Price]] <sup>[[User talk:MichaelCPrice|talk]]</sup> 08:25, 14 September 2008 (UTC)

:Regarding dimensional analysis as a sort of checksum:
:To convert a tensor component from my convention to your convention, you can simply multiply it by ''c''<sup>i-j-k</sup> where ''i'' is the number of contravariant time indices, ''j'' is the number of covariant time indices, and ''k'' is the weight of the tensor density (which is zero for ordinary tensors). If you have made sure that the indices are properly balanced in your tensor equation (which you should do anyway), then these factors of ''c'' will cancel out. Thus you can do your dimensional analysis in the same way as you usually do, if you just apply it consistently to the purely spatial components.
:So there is no "nightmare". If you bother to really understand my convention, then you will see that it is just as simple as yours. And it avoids a lot of unnecessary factors of ''c'' in the conversion between tensors and the non-relativistic equivalents. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 07:45, 17 September 2008 (UTC)
:::I guess the contradiction in the statement ''If you bother to really understand my convention, then you will see that it is just as simple as yours.'' is lost on you? And please don't assume I don't understand "your" convention; I do, but it is not supported by the literature, as I have previously explained. So it is just your OR. --[[User:MichaelCPrice|Michael C. Price]] <sup>[[User talk:MichaelCPrice|talk]]</sup> 07:17, 22 September 2008 (UTC)
::On a side issue, ideally we should not be using a variety of versions of a tensor with the indices raised or lowered (unless that is unavoidable for historical reasons). If one does use them, then one is hiding copies of the metric tensor. This is contrary to the spirit of general covariance which is to make '''everything''' explicit. So as far as possible, we should define a tensor to have one form with each index specified as contravariant or as covariant and with a specified weight. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 15:08, 17 September 2008 (UTC)
:::Requiring that each tensor be specified with some precise contravariant/ covariant mix is an unfortunate effect of JRSpriggs's standard...... Need I say more? --[[User:MichaelCPrice|Michael C. Price]] <sup>[[User talk:MichaelCPrice|talk]]</sup> 07:17, 22 September 2008 (UTC)

==Exact Solutions Template==

I propose to create a new template, something which incorporates important features of an exact solution. Such features could include things like: Petrov Type, Segre Type and Energy-Momentum tensor type (e.g. perfect fluid). Global properties such as possible singularities and geodesics (timelike, null) could also be incorporated. Local as well as global symmetry vector fields may be mentioned where important (the global ones are probably the most important, though). I'd like some ideas about this please. Thanks. :) [[User:Mpatel|MP]] <sup>([[User_talk:Mpatel|talk]]•[[Special:Contributions/Mpatel|contribs]])</sup> 15:24, 3 August 2008 (UTC)

== Intro to General theory ==

[[Introduction to general relativity]] has been nominated for a [[Wikipedia:Featured_article_review|featured article review]]. Articles are typically reviewed for two weeks. Please leave your comments and help us to return the article to [[Wikipedia:What is a featured article?|featured quality]]. If concerns are not addressed during the review period, articles are moved onto the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Remove" the article from featured status. The instructions for the review process are [[Wikipedia:Featured_article_review|here]]. Reviewers' concerns are [[Wikipedia:Featured_article_review/{{#if:|{{{2}}}|Introduction to general relativity}}|here]]. [[User:DrKiernan|DrKiernan]] ([[User talk:DrKiernan|talk]]) 11:19, 8 September 2008 (UTC)

== Taskforce ==

I noticed that [[Wikipedia:WikiProject Relativity|WP Relativity]], [[Wikipedia:WikiProject Fluid dynamics|WP Fluid dynamics]] and [[Wikipedia:WikiProject Acoustics|WP Acoustics]] all have low level of participation, if any. I would propose making them taskforces of [[Wikipedia:WikiProject Physics|WP Physics]] rather than WikiProjects due to the relatively low number of articles under their wings. I think participation in them would increase if they were made taskforces, as well as make it easier to coordinate efforts. Any thoughts? 

<small>I'm also posting this on the relavant WP talk pages.</small>[[User:Headbomb|Headbomb]] {<sup>[[User talk:Headbomb|ταλκ]]</sup><sub style="margin-left:-3.5ex;">[[Special:Contributions/Headbomb|κοντριβς]]</sub> – [[WP:PHYS|WP Physics]]} 22:20, 10 November 2008 (UTC)

==Does your WikiProject care about talk pages of redirects?==
Does your project care about what happens to the talk pages of articles that have been replaced with redirects?  If so, please provide your input at [[User:Mikaey/Request for Input/ListasBot 3]].  Thanks, [[User:Mikaey|Matt]] ([[User talk:Mikaey|talk]]) 01:50, 12 May 2009 (UTC)

== [[Albert Einstein]] ==

...is at [[Wikipedia:Peer review/Albert Einstein/archive1|peer review]]. Help get it back to FA. [[User:Casliber|Casliber]] ([[User talk:Casliber|talk]] '''·''' [[Special:Contributions/Casliber|contribs]]) 11:34, 17 June 2009 (UTC)

== GA Reassessment of [[Special relativity]] ==

I have done a GA Reassessment of the [[Special relativity]] article as part of the GA Sweeps project.  I have found the article to need quite a bit of referencing.  I have placed the article on hold for a week pending work.  I am notifying all interested projects of this review which can be found [[Talk:Special relativity/GA1|here]].  If there are any questions please contact me on my talk page.  [[User:H1nkles|H1nkles]] ([[User talk:H1nkles|talk]]) 18:00, 19 June 2009 (UTC)

== Changes to popular pages lists ==

There are a few important changes to the popular pages system. A quick summary:
* The "importance" ranking (for projects that use it) will be included in the lists along with assessment.
* The default list size has been lowered to 500 entries (from 1000)
* I've set up a project on the Toolserver for the popular pages - [[tools:~alexz/pop/]].
** This includes a page to view the results for projects, including the in-progress results from the current month. Currently this can only show the results from a single project in one month. Features to see multiple projects or multiple months may be added later.
** This includes a new interface for making requests to add a new project to the list.
** There is also a form to request a change to the configuration for a project. Currently the configurable options are the size of the on-wiki list and the project subpage used for the list.
* The on-wiki list should be generated and posted in a more timely and consistent manner than before.
* The data is now retained indefinitely.
* The script used to generate the pages has changed. The output ''should'' be the same. Please report any apparent inconsistencies (see below).
* Bugs and feature requests should be reported using the Toolserver's bug tracker for "alexz's tools" - [https://jira.toolserver.org/browse/alexz]
-- <span style="font-family:Broadway">[[User:Mr.Z-man|Mr.]][[User talk:Mr.Z-man|'''''Z-'''man'']]</span> 00:31, 12 July 2009 (UTC)

== Disentangling General Relativity ==

I've been trying to learn General Relativity by reading Wikipedia articles.
In doing so, I've become aware of several serious problems.

The first is the entanglement of the mathematics of GR's pseudo-Riemannian manifold with the mathematics of Riemannian manifolds.
This leads to awkward discussion of GR within articles that are really about mathematics of Riemannian manifolds.
Spacetime in GR is NOT a Riemannian manifold.  
It is a pseudo-Riemannian manifold because it has a pseudo-metric, not a metric.

The second is that links often are to articles that define a concept in much more generality than is needed for a discussion of GR.

A third is an apparent missing link between the fundamental principles on which GR is based and the Einstein-Hilbert action that is the customary starting point for the derivation of the field equations.
I looked in vain for it and finally stumbled on the article "Theoretical Motivations for General Relativity", which has numerous severe problems and doesn't seem to be exactly what is wanted anyway.

Fourth, sometimes notations and terms are used that do not have obvious meanings yet lack any link to explanatory material.  

Anyway, when I feel energetic enough, I'll try to get back to this topic and see if I can lay out a structure for GR articles that will cover the subject adequately and will disentangle it from confusion with metric spaces and articles on mathematics of much greater generality than is needed for GR.

I also agree with others here that there need to be some standards developed for notations and conventions to be used on all the GR pages.
[[User:Thinkor|Thinkor]] ([[User talk:Thinkor|talk]]) 23:48, 24 December 2009 (UTC)

:I was not aware of the article [[Theoretical motivation for general relativity]] until you mentioned it here. I disagree with the approach used in that article because it is not generally covariant.
:Wikipedia is not the best place from which to learn a complicated subject such as general relativity. Articles in wikipedia may contain serious errors or vandalism, and they are not organized by a unifying intelligence because they have many rather than a single author. It would be better to read [[Gravitation (book)|Misner, Thorne, and Wheeler]] or any of many other textbooks on general relativity.
:Outside wikipedia, I have not seen a firm distinction made between [[Riemannian manifold]]s and [[pseudo-Riemannian manifold]]s. For practical purposes the mathematics is almost identical in so far as it applies to general relativity. However, wikipedia must serve a community which is interested in applications of Riemannian manifolds to other things than just general relativity, so the articles must compromise (another reason wikipedia is not the place to study GTR).
:Indeed, [[general covariance]] and the [[equivalence principle]] are not sufficient to derive GTR since they cannot distinguish it from some other [[alternatives to general relativity]] such as [[f(R) gravity]]. The cosmological term in the [[Hilbert action]] represents the "surface tension" (minimization of hyper-volume) of space-time while the ''R'' term represents the "stiffness" (resistance to bending) of space-time.
:Einstein noted that it is unnecessary (and wrong) to have a separate rule (e.g. [[geodesic]] motion) for the path of a particle since that is determined by matching the solution for a single particle ([[black hole]]) to the back-ground metric. See my comment at [[#How to improve relativity-related articles]]. [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 14:37, 27 December 2009 (UTC)

== WP 1.0 bot announcement ==

This message is being sent to each WikiProject that participates in the [[Wikipedia:Version 1.0 Editorial Team/Assessment|WP 1.0 assessment system]]. On '''Saturday, January 23, 2010''', the [[User:WP 1.0 bot|WP 1.0 bot]] will be upgraded. Your project does not need to take any action, but the appearance of your project's [[Wikipedia:Version 1.0 Editorial Team/Relativity articles by quality statistics|summary table]] will change. The upgrade will make many new, optional features available to all WikiProjects. Additional information is available at the [[Wikipedia talk:Version 1.0 Editorial Team/Index|WP 1.0 project homepage]]. &mdash;&nbsp;Carl <small>([[User:CBM|CBM]]&nbsp;·&nbsp;[[User talk:CBM|talk]])</small> 03:50, 22 January 2010 (UTC)

== Einsteins Nobel Prize ==

We are in need of the help of an expert at the [[Nobel Prize]] page. A source has been found that says the Photoelectric Effect was one proof of the Theory of Relativity. A few editors are questioning the accuracy of that statement. The help of someone who understands Einsteins Theory better than me would be appreciated. Regards [[User:Aircorn|AIRcorn]] ([[User talk:Aircorn|talk]]) 01:30, 19 February 2010 (UTC)
:Thank you to Paradoctor and Michael C Price for responding. We have sorted out the problem. [[User:Aircorn|AIR<span style="color:green;">'''''corn'''''</span>]]&nbsp;[[User talk:Aircorn|(talk)]] 01:42, 24 February 2010 (UTC)

== [[Wikipedia talk:WikiProject Physics#RfC on coordinators|RfC on WP Physics coordinators]] ==

Please take a look and feel free to comment (or not). [[User:Headbomb|Headbomb]]&nbsp;{<sup>[[User talk:Headbomb|ταλκ]]</sup><sub style="margin-left:-4.0ex;">[[Special:Contributions/Headbomb|κοντριβς]]</sub>&nbsp;&ndash;&nbsp;[[WP:PHYS|WP Physics]]} 23:41, 23 February 2010 (UTC)

==Unreferenced living people articles bot== 

{{User:DASHBot/Wikiprojects/welcome/first}} [[User:Okip |Okip ]]  02:50, 28 March 2010 (UTC)
==[[Heim theory]]==
I need help with improving this article--<span style="background:saddlebrown; color:red;font-size:small;;font-family:Arial;">[[User:Terra Novus|Novus]]</span><span style="background:darkgreen; color:white;font-size:small;;font-family:Arial;"> [[User talk:Terra Novus|Orator]]</span>  08:11, 18 September 2010 (UTC)

:Is this fringe theory actually notable enough to be covered by Wikipedia? [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 11:27, 18 September 2010 (UTC)
::Would anyone on this taskforce be willing add their [[Talk:Heim theory#Template|input]] on including a relevant template in the article?--<span style="background:burlywood; color:red;font-size:small;;font-family:Arial;">[[User:Terra Novus|Novus]]</span><span style="background:yellowgreen; color:white;font-size:small;;font-family:Arial;"> [[User talk:Terra Novus|Orator]]</span>  14:01, 6 November 2010 (UTC)
:::Can someone follow this [http://www.physforum.com/index.php?showtopic=4385&st=2715 link] (to a relevant discussion on the Physics forum) to see if they can get an expert on [[Heim theory]] to work on the article?--<span style="background:burlywood; color:red;font-size:small;;font-family:Arial;">[[User:Terra Novus|Novus]]</span><span style="background:yellowgreen; color:white;font-size:small;;font-family:Arial;"> [[User talk:Terra Novus|Orator]]</span>  06:44, 12 December 2010 (UTC)
::::To Terra Novus: Would you not be the best person to do that? [[User:JRSpriggs|JRSpriggs]] ([[User talk:JRSpriggs|talk]]) 08:38, 12 December 2010 (UTC)

:::::I would be, but I  had a long and problematic conflict with other editors who disagreed on the focus of this article; in which I finally agreed not to personally get involved with the actual article, just to cool things down a little. I hoped that by leaving this link someone will be able to pick up the baton since I can't.--<span style="background:burlywood; color:red;font-size:small;;font-family:Arial;">[[User:Terra Novus|Novus]]</span><span style="background:yellowgreen; color:white;font-size:small;;font-family:Arial;"> [[User talk:Terra Novus|Orator]]</span>  04:27, 13 December 2010 (UTC)

== Relativity articles have been selected for the Wikipedia 0.8 release ==

Version 0.8 is a collection of Wikipedia articles selected by the [[Wikipedia:Version_1.0_Editorial_Team|Wikipedia 1.0 team]] for offline release on USB key, DVD and mobile phone.  Articles were [[Wikipedia:Version 1.0 Editorial Team/Article selection|selected based on their assessed  importance and quality]], then article ''versions'' (revisionIDs) were chosen for trustworthiness (freedom from vandalism) using an adaptation of the [[WikiTrust]] algorithm.

We would like to ask you to review the [http://toolserver.org/~enwp10/bin/list2.fcgi?run=yes&namespace=0&pagename=&quality=&importance=&score=&limit=100&offset=1&sorta=Importance&sortb=Quality&filterRelease=on&reviewFilter=0&releaseFilter=1&projecta=Relativity Relativity articles and revisionIDs we have chosen]. Selected articles are marked with a diamond symbol (&diams;) to the right of each article, and this symbol links to the selected version of each article. If you believe we have included or excluded articles inappropriately, please contact us at '''[[Wikipedia talk:Version 0.8]]''' with the details.  You may wish to look at your WikiProject's [http://toolserver.org/~cbm/cgi-bin/problems.cgi articles with cleanup tags] and try to improve any that need work; if you do, please give us the new revisionID at [[Wikipedia talk:Version 0.8]]. We would like to complete this consultation period by midnight UTC on Monday, October 11th.

We have greatly streamlined the process since the Version 0.7 release, so we aim to have the collection ready for distribution by the end of October, 2010.  As a result, we are planning to distribute the collection much more widely, while continuing to work with groups such as [[One Laptop per Child]] and [http://schools-wikipedia.org/ Wikipedia for Schools] to extend the reach of Wikipedia worldwide.  Please help us, with [[Wikipedia_talk:Version_0.8|your WikiProject's feedback]]! 

For the Wikipedia 1.0 editorial team, [[User:SelectionBot|SelectionBot]] 23:32, 19 September 2010 (UTC)

==[[Template talk:Citation#Implementation|Citation templates now support more identifiers]]==

[[Template talk:Citation#Implementation|Recent changes were made to citations templates]] (such as {{tl|citation}}, {{tl|cite journal}}, {{tl|cite web}}...). In addition to what was previously supported (bibcode, doi, jstor, isbn, ...), templates now support arXiv, ASIN, JFM, LCCN, MR, OL, OSTI, RFC, SSRN and Zbl. Before, you needed to place {{para|id|{{tlx|arxiv|0123.4567}}}} (or worse {{para|url|http://arxiv.org/abs/0123.4567}}), now you can simply use {{para|arxiv|0123.4567}}, likewise for {{para|id|{{tlx|JSTOR|0123456789}}}} and {{para|url|http://www.jstor.org/stable/0123456789}} &rarr; {{para|jstor|0123456789}}.

The full list of supported identifiers is given here (with dummy values):

*<nowiki>{{cite journal
 |author=John Smith
 |year=2000
 |title=How to Put Things into Other Things
 |journal=Journal of Foobar
 |volume=1 |issue=2 |pages=3–4
 |arxiv=0123456789
 |asin=0123456789
 |bibcode=0123456789
 |doi=0123456789
 |jfm=0123456789
 |jstor=0123456789
 |lccn=0123456789
 |isbn=0123456789
 |issn=0123456789
 |mr=0123456789
 |oclc=0123456789
 |ol=0123456789
 |osti=0123456789
 |rfc=0123456789
 |pmc=0123456789
 |pmid=0123456789
 |ssrn=0123456789
 |zbl=0123456789
 |id={{para|id|____}}
}}</nowiki>

Obviously not all citations needs all parameters, but this streamlines the most popular ones and gives both better metadata and better appearances when printed. <span style="font-variant:small-caps; whitespace:nowrap;">[[User:Headbomb|Headbomb]] {[[User talk:Headbomb|talk]] / [[Special:Contributions/Headbomb|contribs]] / [[WP:PHYS|physics]] / [[WP:WBOOKS|books]]}</span> 03:16, 8 March 2011 (UTC)

== [[Wikipedia:Bot requests/Archive 41#Bibcode bot]] ==

I've made a request for a bot to try and guess bibcodes for the most popular astronomy journals / journals with the biggest presence in the ADSABS database. Feedback is welcome. <span style="font-variant:small-caps; whitespace:nowrap;">[[User:Headbomb|Headbomb]] {[[User talk:Headbomb|talk]] / [[Special:Contributions/Headbomb|contribs]] / [[WP:PHYS|physics]] / [[WP:WBOOKS|books]]}</span> 04:04, 16 March 2011 (UTC)

== Inconsistencies in special relativity articles and categories ==

I have taken note of the following issues in the organization of special relativity articles and categories. There may be good reasons for these issues, but they should be examined for improvement in clarity and organization. I will participate in correcting these issues, but correcting these requires community collaboration.
# [[General relativity]] has a subarticle [[Tests of general relativity]] that is linked in the main article.
# [[Tests of general relativity]] also has a corresponding category: http://en.wikipedia.org/wiki/Category:Tests_of_general_relativity.
# [[Special relativity]] does not have a corresponding test article [[Tests of special relativity]]. There is an article that looks as if it might perform the same function: [[Status of special relativity]]. This should be examined for consistency and either corrected or explained.
# There does not appear to be a category for special relativity tests: http://en.wikipedia.org/wiki/Category:Tests_of_special_relativity which would be useful in the same way that http://en.wikipedia.org/wiki/Category:Tests_of_general_relativity is useful.
# There is additionally another article, [[Test theories of special relativity]]. There are multiple problems with this article: it is not clear where it fits into the group of articles on special relativity, the article is of generally poor quality and should probably be considered for a deletion or merge, it is not linked anywhere in the [[Special relativity]] article, it links confusingly to [[Tests of general relativity]].
# [[Tests of general relativity]] contains editor's notes in comments that make absolutely no sense and should be resolved in favor of making changes easier.
That about does it for my list of observations, thank you for your consideration.[[User:Jarhed|Jarhed]] ([[User talk:Jarhed|talk]]) 16:04, 26 April 2011 (UTC)
::[[Tests of special relativity]] are described in a couple of different articles (see [[Template:Tests of special relativity]]). The article [[Test theories of special relativity]] is about an important framework to evaluate experimental outcomes concerning special relativity. --[[User:D.H|D.H]] ([[User talk:D.H|talk]]) 08:32, 27 April 2011 (UTC)
:::That template is good, but I looked everywhere I could think to look for a list that corresponds to Category:Tests_of_general_relativity and I couldn't find one. It would be helpful for all of these resources to be more obviously available to a reader. If [[Test theories of special relativity]] is indeed a good and useful article, its purpose in the article mix needs to be clarified and it needs to be made more available to the reader.[[User:Jarhed|Jarhed]] ([[User talk:Jarhed|talk]]) 19:32, 27 April 2011 (UTC)

== Imaginary relativity ==

I am suspicious of the article [[Imaginary relativity]], that either this is a hoax, or just an article by "Mehran Rezaei, Bachelor of Electronic Engineer, Esfahan Azad University, Shahinshahr, Isfahan, Iran" to promote a completely non-notable theory. See the second paragraph:

<nowiki>
This idea first was published “[[Journal WSEAS TRANSACTIONS on COMMUNICATIONS, Volume 9 Issue 2, February 2010]]” <ref> [http://www.wseas.us/e-library/transactions/communications/2010/89-404.pdf Imaginary Relativity], Journal WSEAS TRANSACTIONS on COMMUNICATIONS, Volume 9 Issue 2, February 2010</ref> by Mehran Rezaei.
</nowiki>.

Assistance with this article by someone who knows physics would be appreciated. --[[User:Dthomsen8|DThomsen8]] ([[User talk:Dthomsen8|talk]]) 14:45, 16 June 2012 (UTC)

:This whole article seems to be based on a single non-notable paper published in a journal that isn't widely read by physicists (I'd never heard about the journal before). It seems as though the page may have been created by the author of that paper, and the article also contains text copy-and-pasted from the paper. I had a quick look at the paper and wasn't very impressed, it is unlikely to be correct or even interesting. The page is a good candidate for deletion. [[User:CodeTheorist|CodeTheorist]] ([[User talk:CodeTheorist|talk]]) 15:42, 16 June 2012 (UTC)

:I've flagged the page for deletion, here is the discussion page: [[Wikipedia:Articles for deletion/Imaginary relativity]]. [[User:CodeTheorist|CodeTheorist]] ([[User talk:CodeTheorist|talk]]) 08:45, 17 June 2012 (UTC)