Talk:General relativity/Archive 5

message: In this subsection, the first sentence talks about alternative classical theories of gravitation; however, there is mention of a Fierz-Pauli spin-two theory, which is decidedly described as a quantum theory. Should this theory be mentioned here ? Maybe it's better to mention it in the QM section. MP   (talk) 09:10, 29 December 2005 (UTC)
thread_title:  Alternative theories 

message: The history I was taught says that Einstein added Lambda because gravity would have caused the universe to collapse in on itself. He was later embarrassed about this because it seemed an unnecessary addition to the theory, but Hubble's work showed that a "lambda-like" factor was at work.
216.207.89.51 14:52, 3 February 2006 (UTC)
replies: text: No, it didn't. This arose much later (1998) with the discovery of dark energy. –Joke 14:56, 3 February 2006 (UTC)

text: Three things have happened to change these issues: (I) Hubble found that the Universe is expanding, after which Einstein said that sticking in a positive value for Lambda had been a mistake. He may have gone farther to say that even bringing the constant into the theory was a mistake, but we all know that constants of integration are best not ignored, but are best used to fit boundary conditions.   (II) With the Universe expanding, cosmologists at first tried solutions with various values of Lambda and found that they could get away with zero within the available accuracies of the data.   Next the new distance determinations using supernovae appear to demonstrate that Lambda must be positive and of significant value - i.e. it does affect the dynamics.  Why it has a value that would start being important at redshift 3 or wherever in that vicinity would be a mystery.  Finally (III) elementary particle physicists have come to regard Lambda not as a constant of integration, but as a manifestation of poorly understood cosmic field representing some undiscovered particle or other source.  Then, they are free to assume that Lambda varies, and have set up an exponent "w" do describe that, with w=-1 returning one to the case of a constant.   If w is not equal to -1 there is a research area into what kind of field and particle is involved, what equations it obeys, and possible a connection to dark matter research.Carrionluggage 18:19, 3 February 2006 (UTC)
thread_title:  History Section Appears to be Erroneous. 

message: May want to take a look at this. MP   (talk) 11:35, 12 February 2006 (UTC)
replies: text: That is interesting, but I fail to see how it directly impacts this artcile.  The article in its current form lists "fundamental principles", not outright axioms.  That spacetime as a Lorentzian manifold may not be a necesary axiom is intriguing, but even if that Arxiv article should pan out the concept of Lorentzian spacetime is still something that has to be explicitly mentioned.  In the meantime, I would point out that the Arxiv has not yet been published in a journal.  --EMS | Talk 06:26, 13 February 2006 (UTC)
thread_title:  Axioms of GR - is one of them redundant (!!!!) ? 

message: User:Garthbarber has added a link to self creation cosmology to the alternate theories part of the article.  I for one have not heard of this myself, but the self creation cosmology article seems to have passed some basic sanity tests based on its talk page.  It is also to be noted that Garthbarber is apparently one of the authors associated with the creation of this theory  (which is not a good sign but does not automatically impeach it either).  I see a need to a read on this:  Either it gets bounced (and maybe the article AfD-ed), or we bring that page into :category:theories of gravitation.  Thoughts?  --EMS | Talk 06:15, 13 February 2006 (UTC)
replies: text: This article made a very interesting read. It certainly _looks_ like real science, now that the initial objections have been addressed. If the citations at the bottom of the SCC article can be vetted as being reputable, it would seen to me that this is as valid to present as any other alternative model. I am not an astrophysicist, so I can't vet this myself. --Christopher Thomas 07:04, 13 February 2006 (UTC)
replies: text:  That pretty much is my read on it.  As best I can tell, the real issue is one of whether it is sufficiently encyclopedic to warrant mention in Wikipedia.  I suspect that there are more theories of a similar ilk out there, and it is a legitimate issue as to whether they should be covered and if so how. --EMS | Talk 18:22, 13 February 2006 (UTC)

text: Yeah, I marked this with OR for a while and discussed it with WMC a little bit. Of course, it is not exactly encouraged to write about your own work on Wikipedia, but it is not forbidden if the work is verifiable and notable, which this page meets the criteria for. However, perhaps this indicates that the time is ripe to bring some organization to the alternative theories section of this page. –Joke 18:37, 13 February 2006 (UTC)
replies: text: FWIW, I have to agree with Joke that self creation cosmology is notable, but I too am concerned by the potential for abuse, so this bears monitoring.---CH 03:55, 21 April 2006 (UTC)
replies: text:  I see the "notability" line as currently being placed somewhere on the odder side of "odd".  I am dealing for now with issues involving the speed of gravity and Le Sage's theory of gravitation as a result instead of taking the "easy road" and bouncing the non-standard stuff outright.  I will not say that this is the wrong place for the line to be, but do caution that some questionable material gets in under the current setting.  My advice is to monitor this line and how it shifts over time.  If left to its own devices, this line will move over so far that the original research policy will become ineffective.  However, I also expect the notability line to be reset long before that happens.  --EMS | Talk 03:02, 22 April 2006 (UTC)
thread_title:  self creation cosmology 

message: An article called Einstein's theory of gravitation has appeared, and I wish to endorse it. It seems to be an excellent bridge between the new gravitation page and this one, providing a breif and fairly non-technical explanation of what general relativity achieves.  I advise watching it to ensure that it is not either vandalized, given inappropriate duplicate content, or redirected here.  That page may also bear some editting and expansion.  (For example, no mention is made of the cosmological implications of general relativity.)  However, it is most important that the "Einstein's theory ..." article be maintained as a non-technical bridge article.  That is it's value.  That is why I want it kept. --EMS | Talk 17:10, 14 March 2006 (UTC)
thread_title:  New article 

message: The article Einstein's theory of gravitation delas with the same thing as this article, therefore it should be merged into this article. As for it being a non-technical introduction, such an example of a trampoline aricle exists for Special relativity, but that's because the trampoline article is very well written and does provide some insights into the theory that can be grasped by the layman who is not very confident with hgigh-school math. This is not the case with the article Einstein's theory of gravitation, it does not say anything. Unless someone pledges to do some drastic improvements to that page in a few days, it should be merged (there is little to merge anyway). Comment. Loom91 17:43, 15 March 2006 (UTC)
replies: text: BTW, Loom91, your markup in the gravitation article was failing in Firefox, so I have reverted it for now. You may wish to revise your edit so that it renders adequately. --Ancheta Wis 11:15, 16 March 2006 (UTC)

text: No, I advocate deleting [Einstein's theory of gravitation], which means that I oppose merging it with anything (since merge implies that text is retained, rather than tossed). ---CH 02:33, 6 April 2006 (UTC)
thread_title:  Proposed Merge 

message: Under the "Acceleration effects" header, it lists only gravitational effects. I realize that those effects are equivalent, but I've been told that gravitational effects happen quite separately from acceleration. For example, if one was in the middle of two large masses with no net force on them, that person would experience time dilation when compared to someone infinitely far away from those masses (ie also with no net force on them). Also, if someone were in a void with no masses around, accelleration would cause time dilation when compared to an observer in a different accelerative frame. It seems to me that these effects happen very separately, and I wonder why they're treated like the same thing. Fresheneesz 21:51, 23 April 2006 (UTC)
replies: text: Good question.  See the equivalence principle.  (Simple answer:  The acceleration of a freefalling object is due to our being the ones in an accelerated frame of reference.  So gravitational fields are due to our being accelerated.  In the case of the person between point masses: He may not be accelerated with respect to a distant observer, but between himself and the distant position there is a gravitational field where such accelerations do occur.)  BTW - You need to remember that gravitational time dilation is due to gravitational potential, not due to acceleration alone. --EMS | Talk 00:04, 24 April 2006 (UTC)
thread_title:  accelerative effects or gravitational? 

message: I haven't had a chance to examine these, but they seem to constitute a description of the hole argument and its resolution.  If so, if they are basically correct, they can probably be incorporated into an article which is currently a stub.  I was (am?) planning my own article on this, which is currently a stub.  
If Ian moves the sections he added to here, I can refer to what he wrote while writing my own version and possibly incorporate some or all it.  (I planned to give a much more explicit discussion than anything I've seen in the literature, while referring to papers by Norton). ---CH 23:51, 24 April 2006 (UTC)
replies: text: I agree and have asked much the same of Ian on his talk page.  I just want to give him a day to clean up his own mess.  After that I am all for doing it for him. --EMS | Talk 02:33, 25 April 2006 (UTC)
thread_title: Suggestion for where to move Ian B's additions

message: The only thing that I have heard from Ian was an anon (which apparently was Ian) removing the "please don't revert" notice and adding more text to that section.  So since the day I gave him was up, I moved the section to Chris' suggested location.  
This may be a case where we will do an edit war until Ian hits the "discussion" tab and finds this discussion of his work.  However, I am hopeful that we can work with him.  He seems knowledgable, but needs to learn how to edit here. --EMS | Talk 04:12, 26 April 2006 (UTC)
thread_title:  section removed