Wikipedia talk:WikiProject Relativity

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[edit] 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 [[1]], 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, Harald88 13:48, 29 October 2006 (UTC)

That's a good point. I'll fix that once I get the chance. MP (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. Harald88 19:25, 30 October 2006 (UTC)
Yes, I was in a hurry. Thanks for fixing it. MP (talk) 22:25, 1 November 2006 (UTC)

[edit] 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 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? --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". 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... --plange 20:35, 29 October 2006 (UTC)

[edit] Recommended general relativity sources

Hi MPatel,

I would like to recommend the following scholars as sources: Michel Janssen and John Norton Generally, I would like to recommend the writings of the scholars who are involved in the Einstein Papers project such as John Stachel, 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 John Norton were very important sources of information for me.

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.

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 subpage article about special relativity. There are several animation in that article (manufactured by me; Creative Commons license).

I also have a 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. --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. 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. --Cleonis | Talk 11:36, 31 October 2006 (UTC)

[edit] Should this be made a sub project of Wikipedia Project Physcis?

See Wikipedia:WikiProject_Physics and SCZenz's comments under [2]

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? 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 --plange 19:36, 30 October 2006 (UTC)
Looks OK to me. 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. -- SCZenz 01:58, 1 November 2006 (UTC)

[edit] How to improve relativity-related articles

Above I have pointed out the community of editors of the Einstein Papers project as a major source of information. Among them, John Norton and 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 (-, +, +, +) signature metric, but the spacetime of GTR, Riemannian manifold with a (-, +, +, +) 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
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. --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. 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:
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 '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. 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. --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[3]. was motivated for "the rescue of a mind-independent becoming" . 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.) JRSpriggs 05:05, 6 November 2006 (UTC)

[edit] 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. JRSpriggs 05:58, 23 February 2007 (UTC)

[edit] 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? Timb66 12:03, 29 May 2007 (UTC)

[edit] Userbox

A userboxe is the center of any wikiproject. Well, maybe not, but I made one anyway. Beast of traal T C _ 21:41, 2 November 2007 (UTC)Beast of traal


Oh, and the color matches the color of the heading of the project page. Beast of traal T C _ 21:42, 2 November 2007 (UTC)Beast of traal


[edit] 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? -- JRSpriggs (talk) 21:08, 16 November 2007 (UTC)

Because I have more important things to do in my life. MP (talk•contribs) 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. JRSpriggs (talk) 07:27, 18 November 2007 (UTC)
Done. JRSpriggs (talk) 21:42, 18 November 2007 (UTC)

[edit] 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. MP (talk•contribs) 13:43, 18 November 2007 (UTC)

[edit] 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. (TimothyRias (talk) 14:59, 13 May 2008 (UTC))