Wikipedia talk:WikiProject Physics/Archive October 2010

Foerster coupling

FYI, Foerster coupling has been requested to be renamed. 76.66.200.95 (talk) 04:33, 2 October 2010 (UTC)

Intro to QM

Someone may want to take a look at the recent changes in a section title by anonymous IP. ---- Steve Quinn (talk) 03:34, 3 October 2010 (UTC)

See Introduction to quantum mechanics. Is this not one of those British English spelling versus American English spelling controversies? We are not supposed to change the spelling in such cases, but reverting them seems equally pointless. JRSpriggs (talk) 04:34, 4 October 2010 (UTC)

Possible Higgs-related spamming

Moose-32 (talk · contribs) has been very busy adding links to this fluff piece to many Higgs related articles (and to Big Bang). My comment to them here sums up my concerns with the document in question. The reason why I'm bringing it up here is that their larger pattern of edits is also worrying, and I'm going to need help determining the degree of cleanup needed. They've extensively edited C.R. Hagen and 1964 PRL symmetry breaking papers, in ways that might or might not be adding linkcruft or bias, but I don't have the expertise to determine this. If people familiar with the history of the development of the Higgs mechanism could take a look at these, I'd appreciate it. --Christopher Thomas (talk) 19:51, 3 October 2010 (UTC)

Resolve POV Fork: Kendrick Mass and Kendrick Unit

Request comments on proposed merge of Kendrick unit into Kendrick mass and mend a POV fork. In 1963, Kendrick proposed a scale based on the mass of CH₂ = 14.0000.[1] This scale is useful in organic mass spectrometry, particularly in high resolution mass spectrometry of hydrocarbons (see [2]). A Kendrick unit has not been proposed, although a paper published last month uses “Ke” in a manner parallel to the Dalton unit.[3] The basis of the merge is that the Kendrick unit article goes beyond what is stated in the literature and is therefore WP:SYNTHESIS. Kendrick mass is widely accepted and a balanced discussion of a Kendrick unit is appropriate within the Kendrick mass article. Additional discussion on Talk:Kendrick_mass. --Kkmurray (talk) 15:34, 27 September 2010 (UTC)

If you haven't already, also try contacting WP:CHEMISTRY. Pretty sure you'll find lots of people that could help there. Headbomb {talk / contribs / physics / books} 15:40, 27 September 2010 (UTC)

It's posted to WP:CHEMISTRY; still hoping to get some input from WP:PHYSICS. --Kkmurray (talk) 15:26, 4 October 2010 (UTC)

"Finite Probability"

Hello! I have noticed several physics pages using the term "finite probability", which I was told means "nonzero probability". I realize this term must make perfect sense to physicists, but unfortunately causes confusion for other scientists (I'm a mathematician and I find the choice of terminology baffling). Could we create a short article explicitly clearing this term up? Thanks Rschwieb (talk) 20:11, 5 October 2010 (UTC)

I thought that we might have an article on almost never (zero probability, the negation of finite probability). But apparently that redirects to almost surely (probability one) which does not mention "almost never". An event would happen almost never if the measure of the set of events is zero. None the less, such an event could have occurred, but only if it is defined in hindsight. It could never happen again. JRSpriggs (talk) 21:09, 5 October 2010 (UTC)

I agree:

(1) We should replace "finite" with "nonzero" or "positive" when possible and appropriate, especially in articles that non-physicists might read. (This also applies to "finite mass", "finite resistance", etc. etc.)

(2) When that's not possible, "finite" should link to...something, but I'm not sure what. I could make an article Finite (physics terminology), but it would just be one sentence: "'Finite' usually means 'nonzero and non-infinite' in physics." But a one-sentence article seems wrong. Is it possible to link to a certain entry in wiktionary? Any other possibilities? --Steve (talk) 01:55, 6 October 2010 (UTC)

I think the term finite is very common in physics, eventhough (especially for mathematicians) it might be confusing, since it is not very precise. So I would prefer to keep it, since it is quite commonly used and thus I think it will often appear again in many physics related articles. I think a link to the wikitionary would be the best choice, since it is really only a matter of what physisist understand when they use this word. But maybe, there is enough to say for an article Steve mentioned..? RolteVolte (talk) 08:36, 6 October 2010 (UTC)

IIRC, there was some article explaining that "finite" in physicists' lingo means "finite and non-zero". Anyway, I agree that we'd better say "non-zero probability" than "finite probability". A. di M. (talk) 09:28, 6 October 2010 (UTC)

Although physics was part of my first years at university and I had an intuitive grasp for this peculiar unetymological use of "finite", I would never have thought that this is actually considered standard. I agree that (1) if it is standard it should be used to some extent in physics articles, and (2) it needs unobtrusive explanation to minimise confusion. This is similar to the problem of different variants of English. I looked for a glossary of physics terms that could contain that definition, but I only found glossary of classical physics, which is very neglected and doesn't really seem to fit. Hans Adler 11:33, 6 October 2010 (UTC)

In nonstandard analysis "finite" might mean larger than infinitesimal, but smaller than infinite. JRSpriggs (talk) 13:53, 6 October 2010 (UTC)

As Steve already mentioned: In physicists slang finite just means not-infinite and non-zero (or not-${\frac {1}{\infty }}$ ;) ). But since it is just used in spoken language I don't know any reference.. It's just common... RolteVolte (talk) 15:09, 6 October 2010 (UTC)

I saw right now its mentioned here: Finite, so I think there is no need for a new article, maybe it can just be avoided, or if used, then one can link there.. RolteVolte (talk) 15:13, 6 October 2010 (UTC)

There are quite a few differences between terminology in math and physics and also writing style, the requirement that every sentence be unambigous, even if the meaning is clear in the context etc. etc. If you have submitted articles to math journals, you'll be familiar with this these and other similar objections by mathematicians. While the typical referee report you get when submitting to a physics journal looks like: "Wonderful results, well written, I recommend publication", the referee report for a similar article submitted to a math journal will be many pages long, it will start with a sentence like: "Interesting results that should be published, but this manuscript is clearly written by physicists in "physics style" in vague nonrigorous language." And then a few pages detailing every non-rigorous word like "finite" for nonzero, every misplaced comma making some sentence not 100% clear etc. etc. follows. Count Iblis (talk) 15:33, 6 October 2010 (UTC)

The term 'finite' in physics can be used in three separate manners that I think need to be treated separately:

• The good: Non-infinite. We should keep.
• The bad: Non-infinitesimal (or non-zero). We need to replace this use in an encyclopedic setting. I have never seen this use cause troubles with students and I doubt that any half-ways proficient reader will be confused by this use, but it is non-professional. The only problem is that 'non-zero' is too clunky.
• The ugly: Non-infinite and non-zero. We should use our best judgment leaning toward replacing. The use of the word, to me, in this case is similar to the use of few for 3-5. Few doesn't have to be 3-5 but in certain contexts where it is obvious that the speaker would say one if there is one or a couple if there are two or several if there are around 7 or so then few implies 3-5. Finite only says that it is less then infinity, but if it is obvious from the context that the author would say zero if it was zero then the non-zero can be implied. Edit: Fixed the definition in the ugly section.

In terms of a general rules about writing encyclopedia articles, I disagree strongly with the mathematical approach described by Count Iblis above. There is another name for 'vague non-rigorous language'; its called English. The vagueness and non-rigor of language is not a bug but a feature; it focuses the listener on the big picture without swamping them in unneeded detail. Precision is to be applauded, except when it interferes with the main point of the article or sentence. Like including every tree in a forest on a map, precision comes with a cost.

Somehow we need to balance 'encyclopedic' with readable. TStein (talk) 18:56, 6 October 2010 (UTC)

Does anyone work on Wiktionary? Perhaps it just needs some link to a wiktionary entry. And that wouldn't contravene WP:NOTDIC. Be aware, if you've never worked on Wiktionary, that they are not overly friendly, and tend to delete things out of hand, won't explain why things are not copacetic and seemingly hand out 24-hour bans like candy. 76.66.200.95 (talk) 03:41, 7 October 2010 (UTC)

I agree with TStein, except I don't think "non-zero" is that clunky. A. di M. (talk) 15:44, 7 October 2010 (UTC)

What's wrong with "positive"? --Trovatore (talk) 15:47, 7 October 2010 (UTC)

The term "positive" may indeed be the best term for some cases. (My thoughts above are addressed to the general case of the use of 'finite' anywhere and not just in probability). Some care must be taken using the term positive, though, since many people think of zero as being a positive value; even some people who should know better do. I prefer non-zero to positive since it says directly what is meant. TStein (talk) 16:30, 7 October 2010 (UTC)

I endorse "nonzero probability" (with or without the hyphen). --Christopher Thomas (talk) 18:41, 7 October 2010 (UTC)

I think the definition of "positive" that includes 0 is the standard definition in French, and I am sure that explains part of the confusion around that term. (As a mathematician I would obviously prefer "non-zero" because that's how we say it and it sounds natural to me. But I realise that my opinion shouldn't count for much here.) Hans Adler 19:08, 7 October 2010 (UTC)

Even in English, I mentally expand "positive" to "non-negative non-zero", so "positive probability" (expanding to "non-negative non-zero probability") sound weirdly redundant to me as a probability cannot be negative. (Compare with "odd prime number greater than 17", where all prime numbers greater than 2 are odd.) The presence/absence of the hyphen is slightly WP:ENGVAR-related, "non-zero" being about 2.8 times as common as "nonzero" in BrE and "nonzero" being about 3.3 times as common as "non-zero" in AmE (at least in the BNC and the COCA). (A thing which I similarly dislike is when people say "x is real" when their point is not that x can't be complex but that it needn't be rational.) A. di M. (talk) 07:28, 8 October 2010 (UTC)

I don't see the problem with "finite". It universally refers to any larger-than-infinitesimal, smaller-than-infinite value. I don't see what's ambiguous or non-clear about it. Headbomb {talk / contribs / physics / books} 09:56, 8 October 2010 (UTC)

ambiguous or non-clear? Zero is not infinite, therefore it is finite. --Michael C. Price ^talk 10:20, 8 October 2010 (UTC)

Ah yes, the mathematicians... The value is finite in that it is smaller-than-infinite and larger-than-infinitesimal. Compare with the finite element method, which uses elements of finite length/area/volume/etc... Headbomb {talk / contribs / physics / books} 10:07, 8 October 2010 (UTC)

Add "engineers" to your list too, then. I've always treated "finite" as meaning "not infinite" and nothing more, and mentally expanded "finite probability" to "finite, nonzero probability". I reserve judgement as to whether it's worth the bother of revising articles, but I do feel that "nonzero probability" would be a) more correct, and b) closer to what is literally meant (after all, saying a probability value is non-infinite is rather redundant). --Christopher Thomas (talk) 17:16, 8 October 2010 (UTC)

Introduction to atomic structure

FYI, Introduction to atomic structure has been prodded for deletion. 76.66.200.95 (talk) 06:11, 13 October 2010 (UTC)

Additions to Ultimate fate of the universe and elsewhere

User Efficiency1101e (talk · contribs) has just added a couple of stub sections to Ultimate fate of the universe (edit | talk | history | protect | delete | links | watch | logs | views). I'm not in a position to vet the reference at present; more eyes would be appreciated. They've also recently been active at negative index metamaterials, telescope, and mechanics. A quick look there would also be appreciated if anyone has time.

They seem to be acting in good faith; I'm just concerned about well-meaning linkspamming or undue-weight happening (it looked ambiguous to me at first glance). --Christopher Thomas (talk) 05:47, 11 October 2010 (UTC)

The stub sections have been extended by Dermiel (talk · contribs), as that user's only edits. The text looks like a rehashed version of popular-press description, not making much sense as-is. The new sections still need vetting. --Christopher Thomas (talk) 17:12, 12 October 2010 (UTC)

The original editor has added these sections to ultimate fate of the universe again. On one hand, they have slightly more content and a couple of additional links, but on the other hand, they have at least one of the same sources that was pruned last time around. If anyone feels like mentoring them and vetting the additions, go ahead. I have my hands full off-wiki. --Christopher Thomas (talk) 04:29, 20 October 2010 (UTC)

To play devil's advocate, it's entirely possible that the editor is right about a Scientific American write-up existing, despite the editor's difficulty providing useful reference links. That doesn't necessarily make the added content noteworthy, of course. --Christopher Thomas (talk) 23:30, 20 October 2010 (UTC)

There have been a number of ScAm articles about the ultimate fate of the universe. Quite a notable subject, I think, and one that readers find interesting. --Michael C. Price ^talk 00:42, 21 October 2010 (UTC)

To clarify my position, while the topic is notable, and while the existence (if true) of an article in a popular science magazine such as Scientific American is usually a point in favour of a given view or conjecture being notable enough to have mention somewhere on Wikipedia, I don't think the existence of a SciAm article necessarily means that the specific concepts mentioned in that one article are noteworthy enough to warrant inclusion in an article on a larger topic (such as ultimate fate of the universe). That would require an evaluation of the references provided, and of degree of impact on the field, per WP:UNDUE.

I am not in a position to perform this evaluation at present (my first impression is that the sections give undue weight to not-very-significant hypotheses, but it's possible I'm mistaken). Hence, asking if anyone was willing to vet it. The "devil's advocate" note was posted as a response to the "undo as probable hoax" edit summary (an edit which presumably occurred in response to my previous post in this thread).

I apologize for any confusion that my posts in this thread have caused. I'm juggling several off-wiki tasks at the moment, so I might not have been spending sufficient time checking my statements for clarity. --Christopher Thomas (talk) 00:52, 21 October 2010 (UTC)

Well, I agree that the article needs cleaning up. It's not, in places, very encyclopedic, but in general I think this is a worthy topic to cover. --Michael C. Price ^talk 00:58, 21 October 2010 (UTC)

Rotating black hole

Hi and sorry for my bad english :)

I'm an it.wiki contributor, looking for source for our article it:Ergosfera I look at the interwiki, that link Rotating black hole: here i found the same lack of inline citation of the italian version, but also a very "strange" section Rotating_black_hole#The_possibility_of_time_travel, also completely unsourced. I see that this section was added by an IP this summer, and similar teories appear also in the es.wiki es:Ergosfera and ca.wiki ca:Ergosfera, but, for what a read here and vaguely understand in the spanish language article, these explanations contradict what is written on the it.wiki article. Can someone take a look to this section? Yoggysot (talk) 01:32, 20 October 2010 (UTC)

I've put a "multiple issues" cleanup tag on the section, as an interim measure.

It seems to be confusing two (valid, published) ideas. One is that the singularity of a rotating black hole, being ring-shaped, can be passed through. Where you end up is rather vague, if I understand correctly, but the conjecture I've seen quoted most often is a universe not otherwise connected to our own. The second idea is that the singularity of a rotating black hole ends up causing frame dragging with a speed exceeding that of light as far as an external observer is concerned. If you have an extremal black hole where the singularity isn't within the event horizon, you can hitch a ride and end up at your starting point before you left, given appropriate choices of reference frame. Similar closed timelike curves exist in other rotating solutions that don't involve black holes, but they tend to be unphysical (things like one of the rotating dust solutions where angular velocity is proportional to radius, out to infinite radius, for instance).

Long story short, a coherent, well-referenced section about something not too dissimilar to the anon's concept could probably be written, but as-is it's a rambling essay without much redeeming content. --Christopher Thomas (talk) 04:41, 20 October 2010 (UTC)

My Italian is close to non-existent, but shouldn't the interwiki of it:ergosfera point to ergosphere?TimothyRias (talk) 05:14, 20 October 2010 (UTC)

Yes, the interwiki are wrong, i correct some of them. For what i see in the history, they was putted in the article when ergosphere was only a redirect to Rotating black hole, so they link the main article ([4] [5])--Yoggysot (talk) 23:30, 20 October 2010 (UTC)

Earth's shadow article to be an upcoming DYK

Hi Project members, Earth's shadow is a new article that will soon be a DYK. It's specifically about the sky phenomenon which is visible from the Earth's surface. Would someone please take a look through the article and see if it seems OK as it is? I mean that it has no glaring errors of physics? Thanks, Invertzoo (talk) 17:18, 20 October 2010 (UTC)

ADS bibcode on articles about journals

Over at Template_talk:Infobox_journal#ADS_bibcode, we are considering adding the bibcode to {{Infobox journal}}. However we have a few options for where the link should take the clicker. Ideas welcome.. John Vandenberg ^(chat) 05:25, 21 October 2010 (UTC)

Length contraction

Based on the German version, I completely rewrote the article, and included sections on Experimental verifications, Derivation, Methods of Measurements, Reality of contraction etc. (all of this was completely missing in the former version. But it contained three (!) sections mainly related to historical developments, which are now replaced by a single History section.) Opinions? --D.H (talk) 21:24, 7 October 2010 (UTC)

If some of your new text was the result of translating from the German Wikipedia, then you should say so in your edit summaries to comply with the attribution requirements of our CC-BY-SA license. JRSpriggs (talk) 08:26, 8 October 2010 (UTC)

In fact, also the German version was written by me so it's not really a "translation" of a foreign text (although the German text was created by me before the English one). --D.H (talk) 18:29, 8 October 2010 (UTC)

I guess we could give you a special dispensation not to have to credit yourself. :) JRSpriggs (talk) 22:12, 8 October 2010 (UTC)

Looks good to me, except one should explain somewhere (probably with pictures) how and why electrostatic fields are deformed in motion. That's important because all intermolecular forces are of electrostatic origin. Lorentz ether theory might also benefit from this.Biophys (talk) 15:17, 23 October 2010 (UTC)

Specific gravity and relative density

Specific gravity and relative density as they stand are covering the same material. They either need to be made distinct from each other or merged. A merge was tried (without much discussion that I could find) but it was de-merged shortly later without fixing the problem in my opinion. It would be nice if we can get more eyes and a discussion going so that we can fix this the right way one way or the other. Also, I would appreciated it if someone could contact other projects that might be interested. Relative density only has a physics tag now and specific gravity has none. TStein (talk) 17:40, 22 October 2010 (UTC)

Beyond the Standard Model

Extra pairs of eyes would be nice here. An editor has recently given a much-needed expansion of the article, however a lot of it seems to be based on preprints, and (to me at least) seems to be a tad bit too enthusiastic in embracing string theory as the ultimate truth. I toned down the article, but I'm woefully unequipped to tackle the subtleties. Headbomb {talk / contribs / physics / books} 08:56, 25 October 2010 (UTC)

Lithium burning - exact reaction formula needed

See Talk:Lithium burning#Dubious: Lithium burning is mentioned on a couple of pages and various different formulae are provided. It seems to me they can't all be correct but I am not educated enough in this area to find out the correct formula and a proper reference for the information. If somebody could provide this information on the Lithium burning page, I'd be much obliged! Once we get the facts straight on the main page, I'll see about updating the various pages that also refer to it incorrectly at the moment.     — SkyLined (talk) 08:44, 22 October 2010 (UTC)

The Wikipedia entry, "nuclear fusion," has the relevant equations for lithium burning. See equations (7i)- (9).

Lee Hively, Oak Ridge National Laboratory, Oak Ridge, TN (hivelylmornl.gov). —Preceding unsigned comment added by 128.219.49.9 (talk) 19:38, 27 October 2010 (UTC)

I've added notes regarding this to Talk:Lithium burning#Disputed. It also might be a good idea to register an account with Wikipedia; that'd give other users a way to unambiguously contact you without you having to put your real name, workplace, and email address in public view (which can be risky). --Christopher Thomas (talk) 20:47, 27 October 2010 (UTC)

Using modern sources to re-write history

I noticed today at the speed of light article that an editor has recorded in the history section the false fact that Maxwell's 1861 and 1864 theories involved the propagation of light in empty space. And interestingly this bizarre assertion was backed up by three in-line sources mid sentence. These three sources are all very modern, dated 1992, 2005, and 2009. They are secondary sources, exactly as is preferred by wikipedia's rules, and I checked them out, and they do actually try to assert that Maxwell's theory involved the propagation of light in empty space. Now we all know that that is wrong and it would be very easy to produce secondary sources that would refute these three sources. This therefore seems to illustrate the importance of unambiguous primary sources, otherwise we will soon see the entire history of physics re-written to the extent that 20th century physics was always there. The history section at 'speed of light' now contains a distorted view of Maxwell's 1861 paper, a modern interpretation of Weber and Kohlrausch's 1856 experiment, and a statement about the precision of modern instrumentation for the purpose of measuring the speed of light. And yet it still ends with the conclusion that the aether was abandoned post-1905 with the advent of Einstein's theory of relativity, even though it seems to have been abandoned throughout the entire history section. It would seem that more care needs to be taken not to confuse the past with the present when writing physics articles. David Tombe (talk) 18:57, 25 October 2010 (UTC)

If you have a careful look at the sources, you will notice that they acknowledge the fact that the thing that Maxwell called a "luminiferous medium", or "ether", or whatever, is nowadays called "empty space". DVdm (talk) 19:57, 25 October 2010 (UTC)

Dvdm, That's exactly what I said above. I acknowledged that your sources backed up the point which you are making. But it's known as 'revisionism'. It's pushing it beyond the bounds of reason to try and argue that Maxwell's sea of molecular vortices is nowadays called 'empty space'. Maxwell's sea of molecular vortices has been abandoned and forms no part of modern physics. That doesn't make it retrospectively become equivalent to 'empty space'. David Tombe (talk) 20:07, 25 October 2010 (UTC)

I don't think it is known as 'revisionism', but as 'citing sources' which say that nowadays that "luminiferous medium" is called "empty space". DVdm (talk) 21:13, 25 October 2010 (UTC)

For once, I agree with David here. In modern physics, Maxwell's equations describe the propagation of light in empty space, but that wasn't what Maxwell thought they meant in the 1860's. "Luminiferous aether, non-existence thereof" was an important result in the history of science, but it came later - to quote the Giordano reference, "eventually (around 1900) the existence of the ether was disproved". None of the three sources given above claim that the aether is now called empty space - they all make clear that the aether is a disproved theory.

In the context of the current discussion, though, surely the problem is solved simply by removing the words "in empty space"? The sentence doesn't need them, they are anachronistic, and the whole aether issue is perfectly clearly covered in the subsequent paragraph. Djr32 (talk) 22:18, 25 October 2010 (UTC)

I've removed "in empty space", per this suggestion. --Christopher Thomas (talk) 22:35, 25 October 2010 (UTC)

I disagree that the use of the qualification "in empty space" is anachronistic this is supported by Kirchoff reference from 1857 which uses the same qualification for velocity measured by Fizeau (and its apparent equality to the quantity measured by Weber and Kohlrausch) Since Maxwell was comparing to the same measurement, he apparently also considered his result to be "in empty space". He (and his contemporaries) had very different idea about the physical nature of empty space, but they stilled called it "empty space".

I also disagree that the qualification "in empty space" is unnecessary, since with out it it is unclear how Maxwell's result distinguished itself from Kirchoff's mentioned in the preceding sentence.TimothyRias (talk) 05:54, 26 October 2010 (UTC)

I think that writing "in empty space" gives modern readers a misleading impression, as they'll tend to interpret that as "aether-free vacuum". If you can see a good way of putting it back in while keeping that point clear, though, by all means go ahead. --Christopher Thomas (talk) 06:04, 26 October 2010 (UTC)

Well, literally the next sentence explains that, at the time, there was a different understanding of "empty space". I also think that most modern readers would actually just get the most down to Earth interpretation of "empty space", i.e. space which is free of physical objects.TimothyRias (talk) 07:29, 26 October 2010 (UTC)

Timothy, You'll find that Wilhelm Eduard Weber's theory of electrodynamics does not utilize an aether, although I have read that he believed in it nevertheless and that it comprised of some kind of dual particles. And as regards Kirchhoff's use of the terminology 'empty space', I cannot account for that. Kirchhoff's paper clearly does say that, as you say. But The section about Maxwell is not deferring to the Kirchhoff reference. There are plenty of references, primary, secondary, and tertiary, which make it quite clear that Maxwell's EM theory was definitely not in empty space, and one such reference appears to have been removed by yourself. The aether was a big factor in nineteenth century physics, and there is an important chronology of events in which Maxwell's role is central along with the 1856 Weber/Kohlrausch experiment. Yet the history section at speed of light does not even deal with the Lorentz contraction, which is the significant step between the 1887 Michelson-Morley experiment and Einstein's special relativity in 1905, and the eventual abandoning of the aether. Even then, the abandoning of the aether wasn't just as abrupt as has been made out in the article. The 1937 Encyclopaedia Britannica still gives details of the 'existing' theory of the propagation of light through a sea of tiny vortices. That may or may not have been Tesla's theory. I don't know because it doesn't specify the architect.

The point is that we know that you personally don't believe in the aether. And we know that modern physics doesn't believe in the aether. But it gets quite silly when people start to amend history sections in order to bring them into line with modern thinking. This is actually a very silly argument and I'm sorry that it has had to take place at all. As Christopher Thomas says, by all means go back and re-insert the reference to 'empty space'. But if you do so, stand back and have a look at how the whole history paragraph reads and ask yourself these questions,.

(1) Does the history section correctly portray the sequence of events? Or is it confusing and misleading the reader into believing that Maxwell never believed in the aether?

(2) Does it correctly inform the reader that Maxwell's 1861 theory involved the propagation of light in a sea of molecular vortices which was also an elastic solid, and which was made partly of aether and partly of ordinary matter? And does it portray the fact that in his 1864 paper, although less specific about the details, that nevertheless he was clearly talking about an medium which was dielectric?

(3)Does it let the readers know that the Michelson-Morley experiment was designed to try and establish the motion of the Earth through what they were then referring to as 'Maxwell's aether'.

(4) Does it neatly summarize Lorentz's length contraction hypothesis in the wake of the Michelson-Morley experiment and the fact that Einstein's theories followed on from Lorentz's theories?

(5) If somebody is confident that there is no aether, do they need to tamper with history sections to mislead readers into thinking that there was never an aether?

The bottom line is that we cannot start re-writing history because modern textbooks, and especially very modern textbooks, start to claim that the likes of Maxwell was wrong. That gets us into the realms of a disproportionate and bureaucratic application of all the literature that is available. David Tombe (talk) 07:47, 26 October 2010 (UTC)

David, I would quickly stop with rampantly accusing other users of "historical revisionism". That is a blatant violation of WP:AGF, and in your case likely to get you a permaban. (This is meant as a piece of friendly advise, rather than a threat. I believe you have made great progress in amending your ways, and currently deserve the benefit of the doubt.)

To respond to your questions: (reading the section as if the "in empty space" qualification is restored:

(1)Yes, although brief, it portrays the right sequence of events. And "No" it does not suggest that Maxwell did not believe in the ether. To make this more explicit the start of the second paragraph could be changed to: "Maxwell, like most of his contemporaries, thought that empty space was filled with a medium called the aether in which the electromagnetic field existed." Or something like it.

(2)No, it does neither of those. But, it say both those facts are beyond the level of detail of that section.

(3)Yes. (Although, it doesn't specifically attribute the idea of an ether to Maxwell, probably rightly so, because the idea was not specific to Maxwell.)

(4) Again, this is beyond the level of detail in that section. Note that this article is about the constant called the speed of light. The relevant historical events from the 19th century are: 1) the measurements made by Fizeau and Foucault 2)the connection made between the electromagnetic constants and light. (experimentally by Weber and Kohlrausch and theoretically by Maxwell by postulating that light was an EM wave) 3)Postulation of the observer invariance of this constant at the start of the 20th century by Einstein.

Some mention of the ether is necessary to relate the last point since the failed search for experimental evidence for the ether was part of Einstein's motivation. Since this article is not a history of the ether or a history of special relativity, I don't see much reason for mentioning Lorentz contractions.

(5)No, and I extremely resent the implications you are making. (See my piece of advice at the top of this post.)

TimothyRias (talk) 09:07, 26 October 2010 (UTC)

This issue of whether empty space is really empty persists even to this day. See Vacuum energy and Virtual particle. JRSpriggs (talk) 09:22, 26 October 2010 (UTC)

Of course, which is why don't see the problem with using the phrase "empty space" for something that neither now or then was thought to be completely empty. The me (and I think most people now and then) the phrase simply means, space as devoid of matter as possible. If people feel more at easy with the term vacuum (a term that Maxwell also uses in the introduction of his 1964 paper, when noting that his idea of EM fields can exist in what is known as a vacuum), I'd be Okay with it as well. Although, that term has some other connotations.TimothyRias (talk) 09:38, 26 October 2010 (UTC)

Yeah, vacuum seems like a good way to mean "space containing aether and/or vacuum energy and/or other stuff thought to be found throughout the universe, but containing no other matter such as water or glass". A. di M. (talk) 10:01, 26 October 2010 (UTC)

Vacuum has two distinguishing characteristics: (1) it is as symmetrical as can be, and (2) it has the lowest energy per unit volume of any bulk substance. The first implies that vacuum does not resist the movement of other things through it or into it. JRSpriggs (talk) 10:20, 26 October 2010 (UTC)

The vacuum is not necessarily symmetric, although there is no complelling evidence for any unsymmetry. So I would go with (2) alone. --Michael C. Price ^talk 10:50, 26 October 2010 (UTC)

Let's not have a discussion about the definition of vacuum. (off-topic: The standard model assumes that the vacuum is not completely symmetric, i.e. it breaks electroweak symmetry.)TimothyRias (talk) 11:13, 26 October 2010 (UTC)

And I'm not sure the "as empty as possible" definition works, because IIUC the space between two plates attracting each other due to the Casimir effect is emptier than vacuum. A. di M. (talk) 18:24, 26 October 2010 (UTC)

Good point. --Michael C. Price ^talk 22:17, 26 October 2010 (UTC)

Instead of aether, nowadays we have virtual particles...  Cs32en Talk to me  23:09, 27 October 2010 (UTC)

After weighing the objections, I've restored "in empty space" and made a wording tweak along the lines of that proposed by Timothy. For what it's worth, I'd be hesitant to use the word "vacuum", because it implies modern concepts even more strongly than "empty space" does. --Christopher Thomas (talk) 18:22, 26 October 2010 (UTC)

Timothy, I would agree that we shouldn't start a discussion on the vacuum, because such discussions tend to degenerate into prolonged debates about absolutely nothing at all. But in answer to A. di M. it should be pointed out that Maxwell's luminiferous medium was not just pure aether. It contained some ordinary matter a well. There was his electric particles which acted as idle wheels. So he was not exactly dealing in empty space. Maybe we don't need to elaborate too much for the purposes of the article, but why go to the opposite extreme and claim that he was dealing in empty space when we all know that that was not true. David Tombe (talk) 11:53, 26 October 2010 (UTC)

Because he was dealing with empty space in the common sense of the word, i.e. space that is empty like he would expect to encounter outside of the Earth's atmosphere or in a glass tube devoid of air. Whatever Maxwell's specific idea's were about the physical nature of such a "medium", such a medium can sensibly called "empty space" or "vacuum". The problem with writing that Maxwell derived the speed of EM waves in some luminerifuous medium, is that a general reader is not going to understand this as applying to outer space. (Although Maxwell and his contemporaries would have.)TimothyRias (talk) 14:14, 26 October 2010 (UTC)

No Timothy, You go and write whatever you like in the article. Maxwell was dealing in an elastic solid with hard balls. That is not 'empty space', and I'm not prepared to engage in the necessary doublethink that would be required to think of it in terms of being empty space. In my view, you have inserted wrong information into the article. I have brought the matter to attention and I am glad that you have concluded that I deserve the benefit of the doubt as regards whether or not I should be permanently banned from editing physics articles. If that's the way it works, then so be it. You write what you like at speed of light and I will not be showing up. David Tombe (talk) 14:28, 26 October 2010 (UTC)

So you think that Maxwell did not think that his calculations applied to outer space or a vacuum tube? Interesting.TimothyRias (talk) 14:53, 26 October 2010 (UTC)

For what it's worth, I agree with Tim. From reading things, it seems like the "elastic solid with hard balls" was either a hypothesis with regards to the nature of vacuum, or a toy model, but Maxwell most definitely was talking of a classical vacuum [i.e. what you have when you suck all the air out of a vacuum tube]. Headbomb {talk / contribs / physics / books} 15:11, 26 October 2010 (UTC)

I think it is more important to emphasize that in the 19th century, the laws of physics were thought to be invariant under Galilean transformations instead of Lorentz transformations. Maxwell and his colleagues could thus never have dealt with empty space as we know it as they had to somehow impose Galilean invariance, one way or the other. Count Iblis (talk) 15:29, 26 October 2010 (UTC)

Just as a point of information, the word vacuum comes from the Latin for 'empty space'. Empty means empty. If space is filled with an elastic solid with hard balls, then it is not empty. Maxwell's theory was about the propagation of waves in an elastic solid of hard balls, and so it is wrong to write in a history section that Maxwell dealt in the propagation of EM waves in 'empty space' or in the vacuum. For Maxwell, space was not empty. There was an elastic solid filling the space between us and the distant stars, and that elastic solid didn't get in the way of the motion of the planets. David Tombe (talk) 15:59, 26 October 2010 (UTC)

"Empty means empty". Sure. If I say that the bottle I've just finished drinking is empty I'm a liar, as it's actually full of air. :-) A. di M. (talk) 18:24, 26 October 2010 (UTC)

Shortly before his death, Maxwell wrote (around 1878) the article s:Encyclopædia Britannica Ninth Edition/Ether. He stated: "Whatever difficulties we may have in forming a consistent idea of the constitution of the aether, there can be no doubt that the interplanetary and interstellar spaces are not empty, but are occupied by a material substance or body, which is certainly the largest, and probably the most uniform body of which we have any knowledge." --D.H (talk) 17:31, 26 October 2010 (UTC)

Modern quantum gravitists often interpret the aether to mean the (quantum) geometry of space-time. See Bryce DeWitt's chapter in "General Relativity: An Einstein Centenary Survey" 14.2 The quantum ether. --Michael C. Price ^talk 22:17, 26 October 2010 (UTC)

TfD:Electromagnetic Field Theory

Some feedback would be welcomed there. Headbomb {talk / contribs / physics / books} 18:47, 28 October 2010 (UTC)

Possible content forks

Status of special relativity: This article appears to be at best a content fork of some sort. Also, I can't see anything in the article that describes the topic it is purpored to discuss. Also the title itself may just be someone's original idea, or a neologism. Mostly all I see is a rehash of an amalgam of facts already in other Wikipedia physics articles (that's why I say content fork). In any case, I was going to PROD it, but AfD appears to be more appropriate. Does anyone else think AfD is the way to go here? ---- Steve Quinn (talk) 03:31, 26 October 2010 (UTC)

Closely related: This article Timeline of gravitational physics and relativity appears to be a dissatisfied version of this History of general relativity. I hate to use the word content fork twice in one hour, but... Also, the first may also pertain to WP:NOTREPOSITORY, and does not conform to WP:MOS. ---- Steve Quinn (talk) 03:59, 26 October 2010 (UTC)

I've consolidated these threads, as I suspect we'll get a fair bit of commentary that applies to both. Regarding Status of special relativity (edit | talk | history | protect | delete | links | watch | logs | views), its edit history indicates that it was explicitly started as a "fork" in 2005, though whether that was intended to mean "content fork" is unclear (it might just have been an article split to move an overly-detailed section to its own page). If we have a better article that addresses the topic, a merge might be the best approach, especially since this one seems to be an orphan.

Regarding Timeline of gravitational physics and relativity (edit | talk | history | protect | delete | links | watch | logs | views), it seems to be little more than a bulletted list, so a merge would again be my suggestion. There are a handful of articles that link to it (along with a few talk pages), and it was started in 2002, so I suspect it was developed in parallel with history of general relativity in good faith (without either page's editors aware of the other).

Regarding putting the pages up for AfD, that would be a low-risk and fairly prompt way of getting more opinions on what to do with the pages (WT:PHYS isn't a cabal, after all). On the other hand, if the logical thing to do is merge/redirect, the AfD will just be closed with a statement that we should do that ourselves, so it arguably doesn't really serve a point. The other option is to stick "mergeto" and "mergefrom" templates on appropriate pages with pointers to centralized discussion threads (probably on the more popular pages). I'd be willing to do this if people think merging is the way to go. --Christopher Thomas (talk) 04:20, 26 October 2010 (UTC)

• Thanks Christopher. We can see what the consensus is here, which is sensible. ---- Steve Quinn (talk) 05:33, 26 October 2010 (UTC)
• Also, you might be interested that I just merged content into History of general relativity from an article which consisted of someone's POV commentary, and a timeline. You can read about in the edit histories. I had to request speedy delete for the resulting redirect because it appears to be synthesis of some sort. I might need to leave a comment on the History of GR's talk page. ---- Steve Quinn (talk) 05:39, 26 October 2010 (UTC)

WRT Status of Special Relativity. This article is currently "summarized" in the Special relativity article (in the section with the same name). In itself this is the way that forks should be done per WP:SUMMARYSTYLE. The article currently has sever issues though, starting with a complete lack of references. No valid reason for deletion though.TimothyRias (talk) 09:50, 26 October 2010 (UTC)

Special relativity is already big enough without Status of special relativity being merged into it, and the material in the latter does deserve a place in Wikipedia, though maybe a better title could be found. A. di M. (talk) 20:08, 31 October 2010 (UTC)

Newtonian motivations for general relativity

This article does not actually appear to describe the topic title. Also, it starts off sounding like a text book. Actually, I am not sure what is the point of the article as related to its title. Someone may want to look at this and assess. There is definitely some good information here. It looks like a good article, but may need to be renamed and copy edited (imho). ---- Steve Quinn (talk) 06:32, 26 October 2010 (UTC)

How about "Comparison of Newtonian and Einsteinian gravity"? JRSpriggs (talk) 09:17, 26 October 2010 (UTC)

Theoretical motivation for general relativity seems to be related to this article.  Cs32en Talk to me  21:07, 31 October 2010 (UTC)

Coandă-1910 thrust comparison

Hi all. I posed a question on the Coandă-1910 talk page which as yet has not been answered and thought that maybe someone here might be able to help. Basically, the Coandă-1910 was an aircraft built to test an experimental propulsion system comprising a rotary fan driven by a 50 hp conventional piston engine, argued as being the first jet engine (but that's another matter). This propulsion system was claimed to have generated approximately 485 lbf thrust with the piston engine running at 1,000 rpm, but it's not known whether this figure was achieved during static tests or while using a test bed at the front of a moving railway locomotive. Considering this was 1910 and that aircraft were typically reaching speeds of around 50 mph, my question is what thrust figure might be generated by a typical aircraft propeller of the day driven by the same 50 hp engine? There might be many variables to consider, and assumptions made to answer the question, but I'd just like to get an idea of how significant (or not) this propulsion system would have been had it not been destroyed in a crash.--TransientVoyager (talk) 19:28, 30 October 2010 (UTC)

Perhaps Wikipedia talk:WikiProject Engineering or Wikipedia talk:WikiProject Aircraft would be more appropriate for this issue. JRSpriggs (talk) 15:10, 31 October 2010 (UTC)

Thanks; I'll give them a buzz.--TransientVoyager (talk) 17:08, 31 October 2010 (UTC)