Talk:Gravitomagnetism

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[edit] Frame-dragging

As I know, frame-dragging is not a gravitomagmetic, but stand-alone effect.--Nixer 09:04, 17 October 2005 (UTC)

• I think that as we get to deeper theories (like GR) the degee of overlap between effects gets greater, and the same effects can often end up being calculated and classified in lots of different ways. You can derive the existence of rotational frame dragging "uncontroversially" as a result of the principle that rotation is relative, or you can calculate it much more controversially as the effect of hypothetical (and probably disputed) velocity-dependent gravitomagnetic terms (the receding part of a rotating star has a stronger pull than the approaching side - don't use this in a homework answer, it doesn't sit well with SR). There's probably lots of other ways of getting to the same final result. Wheeler's (listed) two-page essay on "Gravity's next prize: Gravitomagnetism" is certainly all about about rotational frame-dragging and the Gravity Probe B experiment. Cheers, ErkDemon 03:02, 19 October 2005 (UTC)
  • Yes, for example electric field can be described as magnetic field and vice versa depending on observer. Though this is improper to say "electricity is a magnetic effect" or "magnetism is an electric effect".--Nixer 20:55, 8 February 2006 (UTC)

I am working off-line on preparing a new set of articles on weak-field gravity, multipoles, far fields, gravitoelectromagnetism which should clarify all of this! Short story is that anything which involves only the magnetogravitic tensor field in the Bel decomposition (this closely related to but more general than the most common formulation of gravitomagnetic vector field) can be called a gravitomagnetic effect. Contrast effects involving only the electrogravitic tensor field or tidal tensor. The Lense-Thirring effect should probably be reserved for effects inside a rotating thin spherical shell (or something like that), while Schiff precession (often called Lense-Thirring precession) of the spin axis of an orbiting gyroscope (additional to other precession effects) was introduced as another gravitomagnetic effect which is easier to check experimentally. In addition to these there are certain clock effects and spin-spin forces. In my articles I hope to contrast these with related tidal effects such as de Sitter precession, tidal stresses on a rotating asymmetric object in an ambient gravitational field, etc. I also hope to clarify the analogies between EM and gtr, and to answer the question of why GEM (mainstream) is not at all to be confused with cranky ideas sometimes called electrogravity.---CH 02:15, 14 February 2006 (UTC)

[edit] Electromagnetic and gravitational fields

Whoever added the external links

• [1] on interconversion of EM and gravitational fields
• [2] on "gravity shielding"

please note well: these topics are not related to GEM. Even worse, GEM is mainstream physics, whereas "gravity shielding" is protoscience at best. In principle, some interconversion of electric and gravitational fields should occur if you hit a charged black hole with a gravitational wave (for example), and is also exhibited by some CPW models, which are mainstream. However, the first Pop Sci article you linked to is discussing a much more controversial claim. ---CH 04:51, 2 February 2006 (UTC)

It would be nice if the article also mentioned the fringe science field of "electrogravitics" which attempts to exploit higher order interactions between gravity and electromagnetism to interconvert between the two. Gravitoelectromagnetism and electrogravitics are sufficiently similar terms that it would be reasonable to cover them both in a single article.Hermitian 02:38, 8 February 2006 (UTC)

I'm not sure what all of the above is about, but it has been pointed out by legit researchers that QED in a weak gravitational field takes the form of

where hopefully you immediately recognize the standard Dirac Lagrangian with an extra funny term gH_μ. I don't remember how to construct gH_μ but it can be derived from the local space-time metric; it is some gravito-electric type field. I believe the same term also appears in the theory of gravitational waves interacting with a SQUID. There are two problems with this equation: first, its derivation requires a bit of the usual physics hand-waving; i.e. its not clear its entirely correct from first principles, although the argument seems mostly healthy. The second problem is that it seems to predict an effect that can't be measured in the lab: one might think that one should be able to bounce microwaves off a superconductor, and get microwave-frequency gravity waves. (and vice-versa). This has been actually tried and is not seen in the lab.

The derivation of the microwave-to-gravity-wave coupling in the superconductor depends critically on the superconductor skin depth (Landau depth ??) and some other tricky arguments, possibly hinging on Type I vs Type II superconductors. An important part of the argument is "what is the efficiency of conversion from one to the other", and the derivation I saw argued that it was (amazingly) close to 1. (i.e. more than 0.01 i.e. more than infinitessimal.). The upshot is that this actually has not been completely tested in the lab (its a little too fringe for respectable researchers). On the other hand, no one has a good theoretical argument on why the above Lagrangian term is wrong, so the over-all status is cloudy. There's a good paper on this, I lost the reference, but google can surely find it. I think I saw it on some crank-science website, actually. linas 05:07, 8 February 2006 (UTC)

And no, its not about Plodnekov, although, ahem, cough, it sure does make one wonder. Nobel prize if someone could make it actually work. linas 05:13, 8 February 2006 (UTC)

I've been following this gravity beams from superconductors thing for a few years now. Various people have claimed to be on the verge of producing an apparatus which demonstrates the effect to the scientific community, and NASA even funded one of them for $600k. But years have now passed, and not a peep has been heard from them. So their devices either didn't work, or the government has classified their work, and they are now forbidden to talk to the press. I also wouldn't leap to the conclusion that if you align all the ions in a type II superconductor, and jerk them around at petahertz frequencies, you get a pure beam of gravitational radiation. You might also be getting chromodynamic radiation, and it would be interesting to see to what extent the beam has its effect on baryonic matter, versus all matter. Enough people have published on the physics of such devices at this point that there's probably some sort of effect going on. I think the major hurdle is writing computer codes to model the physics so that you can engineer useful devices without the prototyping trial and error process which takes forever on anything complicated. eg Fusion reactors. Hermitian 22:13, 11 February 2006 (UTC)

If it can't be done in the lab, then are there theoretical papers that explain why the naive calculation is faulty/incorrect? linas 18:33, 13 February 2006 (UTC)

Hold your horses, all. I think I can clarify all these questions, but it will take some work. GEM is perfectly mainstream, and the notion that a passing gravitational wave can wiggle charges and cause some EM radiation is perfectly mainstream, and there are very close formal analogies as suggested by the GEM field equations, but it seems there is no review which sorts out the approximations involved or which discusses ways in which EM and gravitation are not alike, or which presents an adequate number of specific examples to understand how to do computations to see for yourself whether or not gtr really agrees with claims some cranky "researchers" have made about it! The true story, as often happens, is much more interesting that the many crank claims, which are based upon numerous misunderstandings.---CH 02:23, 14 February 2006 (UTC)

One of the nuances here is that GEM isn't all of general relativity, because unlike the electromagnetic field, the gravitational field is self-interacting. You couldn't, for instance, cancel a non-time-varying electric or magnetic field by shining a light on it. With very high frequency gravitational radiation, however, the self-interaction contributes non-trivially to the physics, and can conceivably yield attractive and repulsive gravitostatic fields which affect objects in the path of the beam. One of the big problems here is that GR, while an elegant theory, is not particularly well suited for doing engineering calculations of complex scenarios. Hermitian 08:15, 14 February 2006 (UTC)

Yes. I note that at microwave frequencies, the wavelength is of the same order as the size of the superconductor, so long-wavelength limits aren't appropriate.linas 22:34, 14 February 2006 (UTC)

[edit] More fringe physics?

Maybe Heim Theory should be added in the fringe physics section, especially considering its proposed connection between gravity and electromagnetism.

(unsigned comment by User:Hslayer)

No. This article is not about fringe physics. This article is about a specific formulation of the gravitational field equations. linas 05:14, 9 February 2006 (UTC)

Please sign future comments, Hslayer. And of course Linas is correct: GEM is perfectly mainstream (Gravity Probe B, currently in final stages of data analysis, is a mainstream satellite test of an important GEM effect). Don't confuse GEM with various crank "theories" which sometimes have similar names.---CH 02:28, 14 February 2006 (UTC)

[edit] Gravitoelectromagnetism vs gravitomagnetism.

Compare 13900 hits for gravitomagnetism with 295 hits for gravitoelectromagnetism. Please bring the article back to the proper place.--Nixer 18:12, 9 February 2006 (UTC)

well, i'm glad that you're talking about it rather than just acting unilaterally. would you care to list English language research papers (this is the English Wikipedia) that use the term "gravitomagnetism" outside of any larger context of "gravitoelectromagnetism"? it won't be Mashhoon et. al., that's for sure. r b-j 18:19, 9 February 2006 (UTC)

For example, this term uses NASA. I suppose there can exist both terms to determine different things. Since the article itially was for gravitomagnetism, dont rename it. If you wish, write a new article on Gravitoelectromagnetism.--Nixer 22:16, 11 February 2006 (UTC)

Give me a chance to write the articles, Nixer! It is true that there should be a redirect page from GEM and gravitomagnetism to this article, so you can create that if you like. Please let the name change stand, though. When I've written the articles I plan, you'll see why Gravitoelectromagnetism is the best name for this article. TIA ---CH 02:32, 14 February 2006 (UTC)

true, you get more hits with popular web pages when searching for "gravitomagnetism" exclusive of "gravitoelectromagnetism" [3] and when you reverse the roles, you get hits with arXiv and IOP published papers [4].

it's not hard to see what the prevalent use is in the scientific lit, even if it is not in the popular webspace. the subject is about analogous behavior of gravitation to E&M (under certain conditions). there are 4 GEM equations, 2 are for gravitomagnetic behavior and 2 for gravitoelectric (or what i would call "gravitostatic"). the Lorentz force equations covers the force due to both phenomena, gravitoelectric and gravitomagnetic. the term that covers both is "gravitoelectromagnetic" or "GEM" as those are the key terms in the lit. r b-j 02:39, 12 February 2006 (UTC)

There are two different things - gravitomagnetism (a field, analogious to magnetism) and "gravitoelectromagnetism" which is used rerely to describe analogy between electromagnetism and gravity (?). So if you want to create a new article, please do not move the already existing valid article.--Nixer 12:34, 12 February 2006 (UTC)

please explain the difference. you say that gravitomagnetism is a field analogious to magnetism. the (electro)magnetic force is one in which, in the classical sense, the movement of electric charge generates additional forces upon other moving charges that is in addition to the electrostatic force that would be exerted on the charges. is gravitomagnetism a force that is generated by a moving mass that exerts a force on other moving masses that is in addition to the Newtonian gravitational force? if the answer is "yes" (and i am certain it is) we are talking about the same thing. r b-j 17:53, 12 February 2006 (UTC)

Please, answer first, electromagnetism and magnetism are the same things? GEM is simply another name for gravity, i.e. all gravity forces (except may be, frame-dragging). By the way, the number of scientific publications with "gravitomagnetism" is more than with "gravitoelectromagnetism":[5] --Nixer 18:50, 12 February 2006 (UTC)

magnetic effects are simply those of electrostatic effects when (Special) Relativity are taken into consideration. but from the POV of classical physics magnetic action is a different force from electrostatic that acts on charges that move. now, answer my question. r b-j 21:21, 12 February 2006 (UTC)

So do you think magnetism should be merged with electromagnetism in a single article?--Nixer 22:50, 12 February 2006 (UTC)

so do you think that i should continue to answer your questions when you do not answer mine at all? you shrink from the challenge. you say that gravitomagnetism and gravitoelectromagnetism are about "two different things" and i said "please explain the difference" and you continue to put that off and to distract. i have played along with it for one round but will not continue to. the onus is on you to explain what is the salient difference between the two subjects. r b-j 06:51, 13 February 2006 (UTC)

If they different things, it should be two articles. If they one thing it should be one article "gravitomagnetism" because it is more spread term - in popular as long as in scientific context. Gravitoelectromagnetism is really too rare word, I never faced it before you.--Nixer 07:06, 13 February 2006 (UTC)

you're still not answering the question. now you believe you can make your point by assuming your premise is true. i am asking you to prove the premise by explaining what is the salient difference between the two subjects. that you have not come across "gravitoelectromagnetism" or "GEM" is only because you don't look at the physics lit (arXiv and IOP) in English. don't expect me to account for why you haven't come across the term before. it's your problem. r b-j 07:16, 13 February 2006 (UTC)

User:Nixer, please see the recent reviews by Mashhoon on the arXiv. See also the reviews by Jantzen et al. Note these are the two authors who have authored or coauthored many of the research articles whose title includes gravitomagnetism or some cognate, as you can easily verify! ---CH 02:35, 14 February 2006 (UTC)

r b-j, gravitomagneism is much more spread word. I will revert you unless you prove other.--Nixer 02:54, 14 February 2006 (UTC)

i had already proven that the term used in the lit (arXiv and IOP) is "Gravitoelectromagnetism" and "GEM" (where does the "E" come from?) as well as by the recognized authors in the field (Mashhoon, Clark). you were previously basing your case that Gravitoelectromagnetism and Gravitomagnetism are "different things", to which the onus was on you to explain what the difference is. the fact that you repeatedly attempted to change that argument to which i held you to is evidence that, in fact, you Nixer cannot explain the difference. (attempting) changing subject to avoid having to prove the case does not prove the case. r b-j 04:16, 14 February 2006 (UTC)

User:Nixer, please get a hold of yourself! I just said that I am going to completely rewrite this article and add some new articles which will clarify all this. Please take the time to read the review by Mashhoon (see the citation in the article) to see why the name change should stand. TIA ---CH 03:00, 14 February 2006 (UTC)

It is a good idea - to add new articles. But do not delete the existing ones.--Nixer 03:02, 14 February 2006 (UTC)

User:Nixer obviously feels very strongly about this. I think Nixer might like what I eventually come up with, but for the moment it might save unneccessary grief if we let this stand: two articles which are currently almost identical. I will completely rewrite this one when I have a chance, and then make minimal changes to gravitomagnetism to clarify relation to the new article. ---CH 03:16, 14 February 2006 (UTC)

Good idea. Thank you.--Nixer 03:23, 14 February 2006 (UTC)

i defer to Chris's expertise. i think we all know that, even with the rewrite, it's about the same subject. if Nixer does not create an article that shows it is clearly about something other than GEM, i will redirect it to GEM in the future. in fact, Nixer did nothing to support his position (even after repeated inquiry by me for him to explain the difference), but i will defer to CH's judgement here. r b-j 04:16, 14 February 2006 (UTC)

Not I but you moved the article from gravitimagnetism to gravitoelectromagnetism, which is a very rare word. So not I, but you shoud prove that this is more spread term.--Nixer 11:58, 15 February 2006 (UTC)

I think we need to let CH be the reigning expert here. In particular, I abhor the idea that we have two identical articles, and that one is not a redirect to the other. linas 22:30, 14 February 2006 (UTC)

It's an interesting debate. The most commonly used word is "gravitomagnetism," because gravitoelectric fields are ordinary gravity and combining both as "gravitoelectromagnetism" really doesn't involve the addition of any new information. I would suggest more people are going to look up gravitomagnetism than gravitoelectromagnetism on Wikipedia, but there's really nothing wrong with letting GEM be the article, and GM be a redirect to it. If you look at the similar terminological situation with the strong force, Chromoelectric and chromomagnetic are all over the literature, but so far no one has seen fit to start calling QCD "chromoelectromagnetism." I think any way of resolving this argument is fine, as long as it doesn't result in two distinct but substantially similar articles. Hermitian 04:00, 15 February 2006 (UTC)

well, it appears that is exactly what we will get. "Gravitomagnetism" may be the more popular word in the popular web, but "GEM" is what is used in the scientific lit unless they specifically mean only the additional gravitational action (over the static gravitation) from the movement of masses on other moving masses. but if you're talking about the quasi-analogous behavior of this inverse-square action that propagates at the speed of c with this other inverse-square action that propagates at the speed of c and to reflect that with equations that look like:

... then "gravitomagnetic" is not sufficient to name it. indeed the first equation is not about anything gravitomagnetic, yet it is about this analogy which is what the subject is about. moreover, we are having this discussion here not at Talk:Gravitomagnetism. r b-j 04:19, 15 February 2006 (UTC)

In scientific word the term gravitomagnetism is also more popular. Please stop pushing your POV and move the article to the original location.--Nixer 12:06, 15 February 2006 (UTC)

Nixer, please stop arguing. Read what Hermitian wrote, for example. You appear to be in the minority; the article title seems perfectly adequate to me; there seems to be nothing wrong with a redirect, and the intro already defines "gravitomagnetism" in an entirely adquate way. I fail to see the point of getting so heated and worked up over this issue. linas 23:26, 15 February 2006 (UTC)

rbj, actually I anticipate a substantially different article, which I hope will be much more useful. It might be a week or more before I can start writing it, though, so despite the awkwardness of temporarily having two almost identical articles, it will save me some effort if we just let this stand until I have a chance to write the article I have in mind (probably from scratch). Once I've done that I will link from gravitomagnetism to this article and we can reopen the discussion of whether to merge the two. I would probably advocate giving Nixer time to study the new article. I think he might like it, which should help us all stay calm in discussing the future of gravitomagnetism. ---CH 01:11, 17 February 2006 (UTC)

[edit] Opposite Gravitic Charges

"Meanwhile, the gravitomagnetic force repels when gravitomagnetic polarities (or equidirectional fluids of mass) differ, and attract when those polarities (or opposite-directional fluids of mass) are similar"

What exactly does that mean? I thought all mass charges were "positive", thus, of equal polarity. Can matter really have negative mass? --Peter Farago 19:00, 24 March 2006 (UTC)

This is not about charges, but polarities: note its not gravitoelectric, but gravitomagnetic force, which occures only in case of moving mass.--Nixer 17:51, 3 May 2006 (UTC)

We define empty space as having zero mass, but it is a churning froth of virtual particle-antiparticle pairs. If we exclude some of these modes from empty spacetime, we can get spacetime with a negative energy density compared to regular space. Such a negative energy density would curve spacetime negatively, just as ordinary matter curves it positively. Both Warp and Traversable Wormholes require this kind of "exotic" matter to produce. We do not presently know how to engineer negative energy or matter in meaningful quantities, although the concept of negative energy density can be demonstrated by the Casimir Effect, in which closely spaced parallel plates are forced together because virtual photons of wavelength greater than their separation are excluded, resulting in greater pressure from the outside than the inside.

In other news, scientists at ESA have announced a repeatable experiment which demonstrates that rotating superconductors generate a gravitomagnetic field, and devised an accurate mathematical model of the physics. 66.235.54.29 22:18, 24 March 2006 (UTC)

[edit] GEM

I am trying to get the duplicate article Gravitoelectromagnetism deleted. You may remember that I had complained about confusion between mainstream stuff (GEM), cranky stuff (Anti-gravity, Eugene Podkletnov) and offered to rewrite the article, then foolishly agreed to a plan I now regret. Briefly, by some foulup, we had one talk page for two articles with almost identical names, Gravitoelectromagnetism and Gravitomagnetism, but there should only be one article on a given topic and there is only one topic here.

I am adding citations to some mainstream review articles on GEM but others will have to sort out this article. ---CH 00:29, 25 March 2006 (UTC)

[edit] Citations

To ensure uniform appearance and for other reasons, in future please use citation templates. Please bear in mind that this is an encyclopedia article, not a review article in RMP. Don't attempt to list every paper which has ever appeared. Don't list your own papers (very bad form!). Don't list paper A if there is a better paper B, particularly if B cites A. Do list review good papers like Mashhoon 2003. Do think carefully and try to keep the list to a half dozen primary sources. For example, do consider removing A and B if review R cites them. TIA ---CH 01:03, 27 March 2006 (UTC)

[edit] From SI to Planck: Question

The last 2 paragraphs of section 1.1 may be wrong. The fourth Maxwell equation in SI units is:

In Planck units:

Planck and CGS units normalize the Coulomb force constant, (4πε₀)^-1, to 1. The above equation in Planck units makes sense if such units normalize μ₀ to 4π, a normalization I cannot confirm. Do CGS units normalize μ₀ to 1? How can 4π be eliminated from Maxwell's equations? If you can answer these perplexities, don't reply here; instead, please edit the last 2 paras of section 1.1.202.36.179.65 17:52, 29 March 2006 (UTC)

even though Planck units are a neat topic that i have interest in, i am not sure of the pedgagical advantage in putting all that in this article. we should just point out, in comparison to E&M, that charge is replaced by mass, charge density by mass density and . true, if you use rationalized Planck units (same as Planck units except is normalized to one instead of ), then the GEM equations look just like Maxwell's Eqs. except for a minus sign where there is charge or charge density. Rbj 21:56, 29 March 2006 (UTC)

[edit] Justification of move from Gravitomagnetism

Since the title of the subject in the very first line is "Gravitoelectromagnetism", since the topic as a whole is "Gravitoelectromagnetism" (Gravitomagnetism refers to only the magnetic aspect, additional (pseudo)forces when masses are moving), since the name given this area of research by the physicists doing it (Mashhoon, et al.) is "Gravitoelectromagnetism", since the common acronym is "GEM", the primary article should be "Gravitoelectromagnetism" and Gravitomagnetism can redirect to it. I manually moved the contents over since the page move was not working. Rbj 21:49, 29 March 2006 (UTC)

I reverted your manual edits. You should always use move to rename an article. As both articles already exist, a simple move is no longer possible. You must ask an administrator for assistance.

I do not oppose the renaming. The issue should however be discussed here first or we will once again end up with a rename war, or worse yet, two duplicate articles. Petri Krohn 23:35, 29 March 2006 (UTC)

Thanks to User:Locke Cole for saving these changes from Talk:Gravitoelectromagnetism. Manual moves are total mess. Moving talk pages is even worse! :-( Petri Krohn 00:02, 30 March 2006 (UTC)

(I moved these comments fom my talk page: Petri Krohn 00:02, 30 March 2006 (UTC))

it's been discussed multiple times and the only objector was User:Nixer who got his way only because he was stubborn. User:Hillman (a.k.a. Chris Hillman, well known physicist) had asked for that changed long ago (it was on the Todo: list) and i did it for him which started a move/revert war with Nixer. i made my explanation in the Talk page, you should have read it. please talk to people before reverting something like this (a reform). Rbj 23:48, 29 March 2006 (UTC)

For the record, User:Hillman (that's me) is a mathematician by training, not a physicist.---CH 04:09, 30 March 2006 (UTC)

Edit and naming wars on this article have already once caused great havoc on this article. I spent several hours restoring edits from a duplicate version and merging the article. I would not like to do it again. So, pleace this time follow the correct procedure. Petri Krohn 00:07, 30 March 2006 (UTC)

Rbj, I opposed you not because I am stubborn, but because the term "gravitoelectromagnetism" is not widespread unlike "gravitomagnetism".--Nixer 10:04, 30 March 2006 (UTC)

[edit] Move request

Standard "Requested move" voting/discussion now at top of page, following my finding User:Rbj's posting at WP:RM. David Kernow 00:17, 30 March 2006 (UTC)

I reverted Rbj's copy-paste move because it is a bad procedure. In principle I had nothing against the name Gravitoelectromagnetism. Now I have changed my mind and oppose also on substantive grounds.

I made a search in Google and found 39 300 hits for "Gravitomagnetism". A search for "Gravitoelectromagnetism" produces only 634 hits, 145 of these are mirrors of Wikipedia, 245 also contain the word "Mashhoon". Non-Mashhoon, non-wikipedia hits are only 292.

It seems that the word Gravitoelectromagnetism is only used by one researcher, Bahram Mashhoon. On the other hand Gravitomagnetism is a part of main stream general relativity. I do not think this article should be about Bahram Mashhoons any more than about Eugene Podkletnovs. Giving a non standard name has the danger of associating the article with pseudoscience. There is no need for that, this is solid science. Petri Krohn 01:59, 30 March 2006 (UTC)

Wow, what a mess. First, this whole kerfluffle started because I promised to write my own version from scratch, to be called Gravitoelectromagnetism. (Petri, look harder; the term GEM (gravitoelectromagnetism) is not used only by Mashhoon.) Ideally, it would be appropriate to have an article called gravitoelectromagnetism with a redirect from gravitomagnetism to this article. However, due to messed up page moves, we need to wait for an admin to fix the current redirect mess before taking any action. Even after that happens, I am disenaging from article space at WP so won't be writing the new version after all. That being the case, I think leaving the article with current title is best for now. BTW, if there is any question, I would urge anyone moving a page to do it correctly. That includes moving the talk page and fixing any double redirects. ---CH 02:51, 30 March 2006 (UTC)

Can somebody please do a count at arXiv.org? My provider is blocked there since two days ;-( http://scholar.google.com is moderately in favour of GEM. --Pjacobi 09:05, 3 April 2006 (UTC)

I think some of these comments may be missing the point. GEM and gravitomagnetism are not "competing" terms! Rather, gravitomagnetism is part of GEM. See the review articles I cited, please. I tend to feel that you guys should keep gravitomagnetism until such time as someone rewrites this article to cover in detail aspects of GEM in addition to gravitomagetism, but if you choose to stick with gravitomagnetism, please do so for a good reason, not because of some mistaken idea that gravitoelectromagnetism is a non-standard term. ---CH 02:42, 6 April 2006 (UTC)

Chris, i wish that you and other folks that hang around sci.physics.research might exert some authority here (since i am an electrical engineer, not a physicist) to essentially declare what this "formal analogy" is called in the physics literature. this formal analogy contains both "gravito-static" and "gravito-magnetic" effects. Gravitomagnetism is the term for only the effects of additional gravitational forces ("force" from a classical POV) due to the movement of gravitational "charges" (or "mass charge"). GEM contains both static effects (analogy to the electrostatic force in E&M) and gravitomagnetic effects (analogy to the electromagnetic force in E&M). since the article is about this analogy (and other editors have made that even more clear since i added the GEM equations, from the Mashoon and Clark papers equations, long ago), the article is clearly mistitled. Nixer and Petri Krohn are acting as dilettantes by insisting on the wrong name just because they find more occurances of it on Google. there are more occuraces of the word "magic" than "gravitomagnetism", why don't they change the name of the article to that? Chris and Linas, will you please find a sufficient number of real physicists to come here to correct this. since the WP admins do not know the difference between experts and dilettantes, i guess that will be necessary. Rbj 20:28, 11 April 2006 (UTC)

Er,

1. For the record, I have no "authority" (if that means something like extraordinary WP powers),
2. I still can't understand what all the fuss is about (I must confess the move proposal discussion looks like unpleasant reading, so I didn't read all of it),
3. I have pretty much given up on editing WP articles myself and do not expect to try to rewrite the article as I think it should be written.

I can offer some advice to everyone participating in this discussion: it seems to me that what really matters is improving the content of WP. I believe that WP should include a well-written, well-organized, balanced (wrt various formulations of gravitoelectromagnetism, bearing in mind considerations of audience, available background articles, length) article discussing gravitoelectromagnetism, at a level ranging from nontechnical (introduction) to the level of Mashhoon's recent review (body of article). This article could be named gravitoelectromagnetism with a redirect from gravitomagnetism, or it could be named gravitomagnetism with a redirect from gravitoelectromagnetism. As long as the material is available at WP it doesn't matter very much what the article is called, one simply has to change the introduction slightly. It is true that gravitomagnetism is part of gravitoelectromagnetism, and anyone capable of following Mashhoon's and other papers will no doubt know this and explain this in the introduction. As far as I can tell, no-one has been disputing either this assertion or the notability of the subject, which is good. HTH ---CH 20:35, 20 April 2006 (UTC)

[edit] GM field of Earth

Instead of citing a source, couldn't we simply show a calculation on the page from well-known quantities? I believe B_g = 2G/c² * L/r³ , where L is the angular momentum and r is the distance to the center of mass. -User: Nightvid

[edit] Random correction

"if two wheels are spun on a common axis": same sense or opposite sense? ---CH 08:28, 29 April 2006 (UTC)

[edit] What does this article need now?

Why does this entry still have a flag asking for expert assistance, when Chris Hillman is here? As far as I'm concerned, he's an expert on general relativity. What needs to be done to eliminate this flag?

If the main issue is whether this page should be called "gravitomagnetism" or "gravitoelectromagnetism", I don't think it's worth getting into a snit about this. Far more important is that the article be clear. I'm worried that certain crucial simple points aren't being made in simple enough language.

There's a lot of confusion out there about the relation between gravity and magnetism, thanks to the claims of Podkletnov, the NASA antigravity research program, and the recent ESA experiment. In fact, I'm confused myself - does anyone know if the ESA experiment has any chance of giving the observed result if 1) GR is true and 2) they didn't screw up???

So, 90% of the people turning to this article will be asking themselves, "is there any weird relationship between gravity and electromagnetism that allows spinning magnets or something like that to have some funny gravitational effect... maybe antigravity?"

So, I think it's important to say very clearly that this article is not about that. It's just about a useful mathematical analogy between Einstein's theory of gravity and Maxwell's theory of gravity.

I know the first sentence of the article says this. But, I would find it clearer to come right out in the first paragraph and say that gravitoelectromagnetism, or gravitomagnetism, is not a name for some special interaction between the electromagnetic field and gravity. (Is there some rule against saying what a term does not mean?)

And later there's a paragraph that begins, "According to GEM..." - which gives the impression that GEM is a kind of theory, perhaps a competitor to GR. A better way to start this paragraph would be "According to general relativity..."

What do people think? —The preceding unsigned comment was added by John Baez (talk • contribs) .

I will repeat my question: what if anything need be done to remove this flag asking for expert assistance? I'm an expert, and so is Chris Hillman - this page doesn't need any more assistance. I just made the changes I suggested above, and a couple more small ones.

I also think we should eliminate the word "mantissa" in this article - few people will know what it means, and it's really quite irrelevant to the physics of the gravitoelectromagnetism. If any explanation of the 4π is called for (doubtful - this isn't a page on units!), all most people need is a short reminder that this is the area of the unit sphere. That's why it's there. John Baez 23:07, 23 May 2006 (UTC)

Hi, John, good to see you speaking up here! And thanks for the kudos :-)

I have been reluctant to start revising this because I fear an edit war with some WP editors whose enthusiasm for wild "new technology" schemes exceeds (in my view) their knowledge of physics. Many Teslamaniacs, advocates of "over-unity" (as in perpetual motion) "new energy" schemes, "energy from the vacuum schemes", Podkletnov fans, Hutchison fans and others have rushed to see in the Tajmar/Matos eprint "vindication" of their claims, despite the authors's attempts to disavow a connection with some of these fairly notorious topics, and they are not happy at attempts to disabuse them of this hope.

Anyway, I could always use more help in monitoring this article and helping add authoriative voice to my attempts to improve it. I did try a few months ago and more or less go drowned out by others. Currently, WP tends to treat all editors as equally knowledgeable, and unfortunately this particular topic has attracted a host of fruitflies as well as well-intentioned editors who are misled by the similarity of terms such as gravitoelectromagnetism to electromagnetism. So simply having more registered users who are willing to let me write a new a version without interferrence would be very helpful.

I added the expert flag and wrote the original todo list and similar todo lists in other articles basically as a way to remind myself of needed improvements. I see that recently an anon, 82.66.77.139 (talk • contribs), aka the fbx.proxad.net anon (apparently associated with ONLINE-BMN-ORG in Paris) overwrote my list with a spam promoting a website which is registered to one Joseph Nduriri in Lille, France. This was inappropriate and I just reverted it to my original todo list. ---CH 02:07, 24 May 2006 (UTC)

I agree with you about the name, of course. Someone tried to involve me in a dispute which raged on without me about whether or not the name should be changed (see the archived discussion above). In the course of this acrimonious dispute the much more substantial issue of long-standing and serious problems with the article itself were overlooked. If I can gather a group of supporters I would like try again to rewrite the article to more accurately describe what gravitomagnetism is all about.---CH 02:18, 24 May 2006 (UTC)

[edit] Help us promptly revert gravitomagnetism.com linkspam

Distinctive linkspam to this website registered to one Joseph Nduriri of Lille has recently been added (sometimes blanking previous version of the article) by:

• the fbx.proxad.net anon (Online-BMN-org; geolocated near Paris)

1. 82.66.77.139 (talk • contribs)
   1. 6 May 2006 replaces entire article with " think the best thing is to read www.gravitomagnetism.com, you will get all the information you wish about gravitomagnetism"

• the abo.wanadoo.fr anon (Wanadoo France; geolocated near Paris)

1. 82.127.9.234 (talk • contribs)
   1. 9 Jun 2006 edit warring
   2. 9 Jun 2006 replaces entire article with essay and link
   3. 4 May 2006 replaces entire article with "I think the best thing is to read www.gravitomagnetism.com, you will get all the information you wish about gravitomagnetism"
   4. 31 May 2006 replaces NPOV dispute with "www.gravitomagnetism.com"

---CH 13:45, 10 June 2006 (UTC)

[edit] Todo list and students beware

This article concerns a topic dear to my heart, but which unfortunately

1. attracts many cranks interested in notionswhich mainstream scientists regard as outright pseudoscience, such as
   • Electrogravity
   • Anti-gravity
   • Podkletnov "effect" (sic)
   • Dean drive
   • Hutchison effect
   • any of dozens of "low to no cost energy from the vacuum" schemes, and other "over-unity" schemes which would violate the laws of thermodynamics and constitute perpetual motion machines
2. may attract fringe physicists working on topics such as
   • Polarizable vacuum
   • Stochastic electrodyamics
   • Felber "effect" (sic; actually a coordinate effect, not a physical effect)
   • Plasma cosmology

For the record, GEM (gravitoelectromagnetism) as described in mainstream textbook such as Wald, General relativity, does constitute mainstream theoretical physics, but this topic is easily confused by laypersons with a variety of highly cranky topics and with more or less dubious fringe science proposals. I feel I could have explained this, but during my year as a Wikipedian, I was dissuaded from making the attempt by the discouraging frequency of bad edits (or well intentioned but seriously misinformed edits) to this article.

While I never had the heart to try to improve it, or even to monitor it, I did write the todo list and from time to time suggested improvements in this talk page. Sadly, I am now abandoning this article to its fate. I emphatically do not vouch for anything you might see in more recent versions. Given the above list and the past history of this article, IMO I have good reason to believe that at least some future versions of this article are highly likely to present slanted information, misinformation, or disinformation. Beware also of external links to websites which may be cranky, and may attempt to portray pseudoscience or dubious fringe science speculations as belonging to the canon of accepted mainstream scientific belief, which would be highly misleading.

As a courtesy, I have removed the todo list. I am leaving WP and doubt anyone else will know how to implement the suggested improvements since this was mostly a note to myself.

Good luck to all students in your search for information, regardless!---CH 00:34, 1 July 2006 (UTC)

this is what you guys get when you insist that you know better than experts like Chris Hillman, John Baez, and User:linas. User:Nixer, your insistance on the wrong principle name for the article (and your ability to get popular support of this wrong primary name), in controversion of what the published experts say, sets you apart (as a non-expert). it's a perfect example of a non-expert unable to understand what it is that he/she doesn't know and insisting on canonizing his/her ignorance. (at the turn of the century, the legislature of the state of Indiana attempted to pass legislation defining π as precisely 22/7.) popular idea, makes the concept simpler for the non-experts. but it's wrong.

too bad that they (John, Chris, Linas) gave up and abandoned the article to its fate. Nixer can take credit for its slide into irrelevancy and inaccuracy. r b-j 04:36, 17 July 2006 (UTC)