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Discussion about html formatted style for simple tex formatted equations

The many people who have the (I believe default) setting for equation rendering as using html for simple equations, have been seeing the equations as being too small relative to the ping equivalents. This is fairly simple to fix in the style file; although it may cause other problems, in particular with inline math equations. (Those should be removed in general principle anyway.)

I started a discussion about changing the font size for the span.texhtml element that is used for the html rendered equations at MediaWiki talk:Common.css about this issue.

• Current rendering of a simple equation: ${\displaystyle e^{i\pi }+1=0}$.
• Forced to render with png using \,: ${\displaystyle e^{i\pi }+1=0\,}$.
• One proposed solution changing style: ${\displaystyle e^{i\pi }+1=0}$.

I probably should have discussed it here and in WP:math or in WP:village pump (technical) but I got a little ahead of myself I am afraid. In any case I think it is worth discussing and hope to get your input.

Stuff that is missing in a lot of physics articles

As I've been reading a lot of the articles about physics, I have noticed that a lot of basic information is missing, or is hard to find without reading through the entire article. For example, in articles about physical quantities, I think some of the most important things are that it should be easy to find: 1. which sign (letter) is usually used for that physical quantity, 2. the unit of that physical quantity, 3. how to calculate its value as a function of other physical quantities (if possible) and 4. as many ways as possible that the physical quantity is commonly used in. Often when you open an article about a physical quantity, you are only looking to find one of the two or three first of these things. However, it is not always that easy to find, if even present in the article. Often it is hidden somewhere in the text.

What really should be done is that, for example, in every article about a physical quantity, it should be made sure that at least the first three of these things are easy to find.

To help making this a reality, we should make more use of physics infoboxes. There is already a proposed infobox for units, which is great; it should be approved and then it should be made sure it comes to use. We also need an infobox for physical quantities, similar to that one.

What can be done about this? What is done about this today? Is this anything WikiProject Physics deals with or can deal with? If not, is there any other Misplaced Pages project which has this aim today? Otherwise one should be started. A lot of physics articles need this type of maintenance. But it is worth it, I promise.

--Kri (talk) 12:35, 24 July 2009 (UTC)

My experience is that most articles on units and quantities have not been worked on much and could use a lot of work. Having some good standardized infoboxes for these articles may provide some backbone for these articles. I'll try to whip up a {{Infobox Unit}} later today following that 3 year old proposal.

Moreover, many of these article tend to fall in between projects. WikiProject Meaurement may also be a good place to bring this up. (TimothyRias (talk) 13:03, 24 July 2009 (UTC))

OK, how about something like this? Most of the parameters are optional so the last few items do not need to be included in tautological cases like this one. Any suggestions for other items? (TimothyRias (talk) 13:46, 24 July 2009 (UTC))

Definitely a good start. I was thinking it might also be useful to add the Geometric Unit System , Am I right? Harharvoxels (talk) 02:12, 1 September 2009 (UTC)

How many electrons are in -1 Coulomb? JRSpriggs (talk) 16:39, 24 July 2009 (UTC)

The charge on an electron is considered to be the elementary charge (ie none smaller can be detected - despite quarks having 1/3 or 2/3 of that charge). This elementary charge e is ~ 1.602 x 10^-19 C. Protons have a charge of the same magnitude. Abtract (talk) 21:08, 24 July 2009 (UTC)

That seems really good! We could use a similar one for physical quantities (which we can put in the electric charge article!), I shall make a proposal for one later. What we really need is an organized attempt to improve every article in this way – just put in one of those infoboxes in every article which needs one. Later on when we see that it works some other criterias for maintaining good physics articles can be added as well. Probably a new wikiproject would be the best for this reason, anyone who knows how to start one? --Kri (talk) 21:24, 24 July 2009 (UTC)

Ok, I have now created an Infobox Physical quantity, it is a little bit small compared to that one for units, but what more is needed? Anything more you can come to think of? Couldn't come up with anything more. It has now been proposed on the proposal page.

By the way, now when the infobox templates are finished, do they even need approval, isn't it just to use them? --Kri (talk) 00:27, 25 July 2009 (UTC)

You're in the clear. Nothing special needed to use them. Also the relevant project would probably be WP:MEASURE.Headbomb {_{κοντριβς} – WP Physics} 00:38, 25 July 2009 (UTC)

I guess the issue raised by JRSpriggs is that there may be other common nonstandard units in which a unit may be commonly expressed. That is a good point. I could simply add an "other units" parameter. A more sophisticated approach would be to add "otherunit=" and "inotherunit=" parameters allowing custom defined units. How many of these should I add? 2 or 3 probably would suffice, and with them in place more can easily be added as needed without breaking the template for article already using it.

I could also replace all the inXXXunits options with pairs "unit1=" and "inunit1=", what would be preferable? (TimothyRias (talk) 15:14, 25 July 2009 (UTC))

So -1 C = 6.242×10 electrons. Which fact should be included in the table. JRSpriggs (talk) 15:28, 25 July 2009 (UTC)

I have used the last option to make the template more flexible. See template documentation for details. (TimothyRias (talk) 08:25, 27 July 2009 (UTC))

Well, now we have created two infobox templates, that is great. Currently no articles are using them, so, what is needed to get these templates to use? Is it possible to start a new project, or a subproject, which aims to make every physics article have certain information easily accessible, and which puts some requirements on every article (depending on what type of physics article it is)? How should we make these templates come to use? I shall start myself (so long) to implement these wherever I feel they are needed. --Kri (talk) 20:33, 25 July 2009 (UTC)

By the way, do you think some of the names of the arguments should be changed? For example, "derivations" in the Infobox Physical quantity, I don't know if that is the best name for that variable. Probably the names should be changed as fast as possible if they need to be changed. Anyway, I'm starting to use the templates, we will just have to find all implementations later and change in them at the time. --Kri (talk) 20:44, 25 July 2009 (UTC)

I don't know why you are talking about creating a project or subproject just to add a few infoboxes to a few pages. That would be very unusual, a waste of resources, and unlikely to succeed. The way to do it is to do it. (I am not going to do it, though, as I am busy with other things.) Hans Adler 20:59, 25 July 2009 (UTC)

Here is what you need to do:

1. Extract list of physical quantities and units from List of physical quantities see also the category:physical quantities
2. Copy these into 2 lists on your user page (one for quantities; the other for units)
3. Post the link here and invite others to go through list scratching off <s></s> ones they have done
4. Optional: get Misplaced Pages:AutoWikiBrowser if you can to help speed the process up
5. Check the results and make changes. there is a template:done template

TStein (talk) 17:57, 27 July 2009 (UTC)

We also have to be careful with incompatible units, e.g. the CGS unit of charge is not dimensionally compatible with the SI unit of charge. The conversion factor in the table is thus not useful (because CGS doesn't mean that we can only use centimeters, grams and seconds). It is better to say that q_{si}/sqrt(4 pi epsilon_0) -----> q_{cgs}. Count Iblis (talk) 19:08, 27 July 2009 (UTC)

I agree with Count Iblis...for example, the template above ("Coulomb") should say "2997924580 statC × sqrt(4pi epsilon_0)".

Also, maybe conversions should be in the table? Or a separate/add-on template? For example, the left column could say conversions and the right column could say

1 atm = 101325 Pa

1 bar = 100000 Pa

1 torr = 133.322 Pa

1 psi = 6.894×10 Pa

Obviously for pressure, there's too many units to list every pair...But even just conversions into SI would be nice. But come to think of it, maybe every pair could be included by using show/hide boxes or something along those lines. (i.e., you select "Pa" to see all units expressed in Pa like above, or instead you select "atm" to see all units expressed in atm, and so on.) That would be really nice if it could be done in an elegant and unobtrusive way...wiki-syntax challenge anyone? :-) --Steve (talk) 00:48, 28 July 2009 (UTC)

You don't have to include every pair. On the Pascal page it is not relevant how to express an atm in a psi, just how to express Pa in atm and psi etc. (TimothyRias (talk) 08:04, 28 July 2009 (UTC))

Personally, I think having conversions and/or expressing the unit in other system is too complicated. I would prefer to have just the units with a link to the relevant article. For example:

Name: Pascal

Abreviation: Pa

Unit of: Pressure

Named after: Blaise Pascal

Type: SI derived unit

1 Pa = 1 N/m

Common units of pressure:

pascal, Torr, psi, atmosphere, bar

Description: A small unit of pressure. Atmospheric pressure is around 100,000 Pa

I added the description category here as well just to see how it would work and as an idea to allow both for simplicity and for flexibility. TStein (talk) 18:33, 28 July 2009 (UTC)

A lot of your proposals seem nice! I am on a vacation right now. Maybe I will create a page on my user listing articles that still need infoboxes when I get back from the vacation, if not anybody else has done it before. There are some things that may be good to discuss, for example, are the infoboxes finished enough for starting to put them in a lot of articles, or do we have to change something in them before? In that case I guess it is just to start using them. --Kri (talk) 20:21, 29 July 2009 (UTC)

Hello, I'm back from the vacation now. The reason I wanted to start a project (because it really is a big project) was that I wanted something to happen, quickly. So that something big could be organized that would improve all physics articles that needed to be improved. If you look at which pages that link to the physical quantity infobox, and pager that link to the unit infobox, you see that it is not especially many (basically just the pages I have put them on). And I am not going to do it myself, because it is a lot of articles, a lot of articles that would benefit from this service. So, what I wanted was basically help putting up something that could do a lot of work (i.e. putting these templates in all the proper articles, and maybe other stuff like administration too); maybe if I'm lucky the measurement project can take care of it. What needed to be done was to standardize these articles, and create certain minimum demands for them. That would really improve them a lot.

However, my interest has cooled down. This project is yours now; if some other people feel like taking over, that would be great. Or maybe it should be left like this, I mean, it hasn't happened especially much. What I asked for before has not been returned. I asked for a project, but apparently it wasn't worth spending that much attention on it. We at least have two working (I guess) infobox templates now, and hopefully they could also start to be used eventually if people think they will do any good. --Kri (talk) 10:16, 10 August 2009 (UTC)

Oh, and if anybody wants me something, he can contact me on my talk page. I'm removing this page from my watch list now. --Kri (talk) 10:20, 10 August 2009 (UTC)

Sorry, didn't mean to sound ungrateful, what I meant was just that I had a little bit to high expectations on this. Maybe I was a little bit to unpatient. And then I became disappointed when I realized it wasn't going to work. But what do I know, Rome wasn't built in one day. :) Should we try, just as a test, and see how many articles use the templates in one month from today? Currently, 6 articles are using the physical quantity infobox (Electric charge, Force, Shear stress, Shear modulus, Shear strain and Viscosity), and 3 pages are using the unit infobox (Kilogram, Coulomb and Pascal (unit)). Today it is the 12:th of August, so, let's check again the 12:th of September. --Kri (talk) 12:06, 12 August 2009 (UTC)

(undo indent) Someone with AWB privileges can probably do this really quickly. Once we get a template settled. TStein (talk) 17:46, 12 August 2009 (UTC)

Dry ice

Spotlight An article covered by this WikiProject, Dry ice, is currently under the Spotlight. If you wish to help, please join the editors in #wikipedia-spotlight on the freenode IRC network where the project is coordinated. (See the IRC tutorial for help with IRC)

IP creating questionable articles

See Selfconsistent electromagnetic constants. Seems like definite OR in places, but I can't make much sense of it. Maybe there's good material in there somewhere?? Anyone else have an opinion? --Steve (talk) 19:18, 4 August 2009 (UTC)

I looked at it and I agree with both not being able to make much sense of it and that places seemed like OR. On the other hand, this would not be the first article that does not make sense to me. The main contributor is an anonymous IP with an interesting history. From a very cursory look, some of the other articles seem to be skirting OR as well. TStein (talk) 21:12, 4 August 2009 (UTC)

I agree with TStein on this. I never heard of "self-consistent constants", nor is "self-consistent" ever defined (at least clearly). I say let's send it to AfD on grounds of WP:OR/WP:Neologism and we can give it bigger scrutinity then. Headbomb {_{κοντριβς} – WP Physics} 22:00, 4 August 2009 (UTC)

Seconded (you actually beat me to it, as I was about to make a post about this IP contributor). Long story short, 195.47.212.108 (talk · contribs · WHOIS) has been making a very large number of minor edits to selected physics articles (mostly good-faith equation formatting tweaks, as far as I can tell). They've also been creating a large number of rather dubious articles and linking to them. As near as I can tell, their behaviour pattern has been to submit requests at "articles for creation", wait until they're rubber-stamped, and fill in the resulting blank articles. --Christopher Thomas (talk) 04:46, 5 August 2009 (UTC)

Articles created in this manner, that could use a review by experts in the field:

• Gravitational characteristic impedance of free space (edit | talk | history | protect | delete | links | watch | logs | views)
• Maxwell-like gravitational equations (edit | talk | history | protect | delete | links | watch | logs | views)
• Selfconsistent gravidynamic constants (edit | talk | history | protect | delete | links | watch | logs | views)
• Selfconsistent electromagnetic constants (edit | talk | history | protect | delete | links | watch | logs | views)
• Quantum Hall composite resonator (edit | talk | history | protect | delete | links | watch | logs | views)
• Quantum electromagnetic resonator (edit | talk | history | protect | delete | links | watch | logs | views)
• Quantum inductance (edit | talk | history | protect | delete | links | watch | logs | views)
• Quantum capacitance (edit | talk | history | protect | delete | links | watch | logs | views)

The vast majority of this user's edits have been to these articles, not to existing articles in Misplaced Pages. Also of interest are the following articles:

• Quantum LC Circuit (edit | talk | history | protect | delete | links | watch | logs | views)
• Semicircular potential well (edit | talk | history | protect | delete | links | watch | logs | views)
• Anti-symmetric operator (edit | talk | history | protect | delete | links | watch | logs | views)

These were created by Dahnamics (talk · contribs), who stopped editing on the same day the IP user started, and by Liphe (talk · contribs), who stopped editing roughly when Dahnamics (talk · contribs) started. My guess is that they're the same person who just forgot their passwords or discarded their accounts.

I'm not accusing this editor of malicious intent. However, they seem to be very industriously building a "walled garden", may not be adequately sourcing (per comments by TStein and Headbomb), and in at least one case (noted at User talk:Liphe) were flagged as duplicating material already covered in another article.

If anyone wants to try to talk to this user to explain to them how to work with existing material, by all means do so. I'm in deadline season again, so the best I can do is bring it to your attention. --Christopher Thomas (talk) 23:38, 6 August 2009 (UTC)

This IP has become active again, and is now adding a lot of material to articles like Planck charge, linking to their "quantum electromagnetic resonator" article. A review of the changes to Planck units articles, and of the new articles listed above, is probably in order at some point. I'm still not in a position to do this. --Christopher Thomas (talk) 08:06, 21 August 2009 (UTC)

Is this valid or BS?

I have no idea whether stealth technology as a pliable electromagnetic envelope is a valid article or not, so I'd like someone here to take a look. It's probably perfectly fine, just needs some cleanup, but better safe than sorry. --NE2 00:57, 7 August 2009 (UTC)

This is a way of looking at metamaterial-based "cloaking devices" that's commonly used in literature. I don't usually hear stealth technology described this way, though. That's generally more about absorbing or deflecting radar. I also usually see the metamaterial stuff described in terms of "constructing a coordinate system where paths do not intersect the hidden object" rather than as a "pliable envelope", but that's a fixable issue (and it's possible that this term has come into vogue and I just missed it). --Christopher Thomas (talk) 01:57, 7 August 2009 (UTC)

The core of the article is derived from peer reviewed journals. Content related to current stealth technology was gleaned from books, magazines, and a good Washington Post newspaper article. Ti-30X (talk) 16:00, 7 August 2009 (UTC)

My point is that while the stealth technologies described in the article are properly sourced, describing them as a "pliable electromagnetic envelope" might not be. I've never heard that term used for them before, and I've followed metamaterial research off and on for a while (labmate is doing his thesis on it, so I get a fair bit of exposure). I'll vet the article if I have time, but I should be working on my own thesis :). First impression was that it looked like a peculiar duplication of stealth technology. --Christopher Thomas (talk) 16:53, 7 August 2009 (UTC)

Christopher - OK, I see what you are geting at. The "pliable envelope" part would be controlling responsive electromagnetic fields. It's kind of a metaphor. The envelope would also be in enveloping the object in the electromagnetic fields. It's a two word description of a mature future technology, perhaps sometime in the 2040's, 2050's, or 2060's. I have no problem in letting that go from the title, at this time. It sounds too glitzy, anyway. To provide further clarity - I am not refering to current stealth technology as a pliable electromagnetic envelope. Current stealth is about the physcial materials used. It is actually used as a contrast, in the article. So the sourced material on current stealth technology, is about current stealth (today). Thank you for your input. Ti-30X (talk) 01:06, 8 August 2009 (UTC)

My concern is that it looks like you're making a content fork of material from Stealth technology and of Metamaterial#Cloaking_devices. I agree that this could use a better treatment, and that focusing on the idea of using a deformed coordinate system as the basis for constructing metamaterial cloaking systems is worthwhile. I'd just feel more comfortable if there was less duplication between your article and existing articles, and if your article's terms were tied more closely to terms verifiably used in literature about metamaterial-based stealth and cloaking. I'm not trying to attack your efforts - I'm just trying to avoid forking or the appearance of OR. --Christopher Thomas (talk) 05:48, 8 August 2009 (UTC)

Christopher, I understand your concern. I was concerned about the same thing, when I started to write it. The science of the theory of negative refractive index is much more in depth than any other article. Also, perhaps, I have a more in depth description of the properties of Metamaterials. Furthermore, the view of stealth technology is unique, in that I point out metamaterials (along with electromagnetic concealment) is a solution, to the current problems expeienced to today. There is no other Misplaced Pages article that has listed the limitations of cureent stealth with sourced references. I have managed to do this. Another article or two summarizes limitations, but most of those summarizations lack sources. They are just there without citations. Also, the limitations that I have discussed are not the same as their's because of sourcing and citations.

If you don't mind, one more thing. I would like you to come and work on the article with us. Right now, I have a team of four or five editors starting to dig in on the article. With your knowledge of this science you would be an incredible asset. I know that you are working on your thesis. But, if you could put in some time, any amount of time, that would be great. BTW, the article has been renamed to a more appropriate title. But even a new title is being discussed, as a possibility. Anyway - come on in, the water is fine. (It might look like mayhem on the talk page though). Ti-30X (talk) 18:40, 8 August 2009 (UTC)

I might have time to take a look at this on Monday (undetermined). Based on a cursory skim of the talk page, I'd vote that the stealth material be moved back into stealth technology, some of the metamaterial material be moved back to metamaterial, and the article renamed to something like "metamaterial invisibility cloak" (a term which, while corny, was used in at least a couple of places; I'll check more thoroughly before formally suggesting it). The existing short section on cloaking in metamaterial and in cloaking device would have "main article: metamaterial invisibility cloak" in this scenario. I realize that the techniques you've described in the article have applications more general than just cloaking, but so far the lion's share of papers (that I'm aware of; an incomplete set) apply coordinate transformations to construct metamaterials that implement cloaks. Again, I'll do a more thorough literature search before formally suggesting anything. --Christopher Thomas (talk) 05:22, 9 August 2009 (UTC)

Thanks. Ti-30X (talk) 15:57, 9 August 2009 (UTC)

Still no time to pursue this, so I'm shelving any intention to look at it (I really should still be on wiki-sabbatical, but it's almost as bad as tvtropes.org for addictiveness). I'll post a link to this thread on the article talk page. --Christopher Thomas (talk) 22:24, 12 August 2009 (UTC)

Problems at entropy

A new editor ( User Quantumechanic), who does not understand the very basics of thermodynamics, insists on making substantial edits to the entropy page. This is very problematic. The article had been rewritten by someone else giving it an information theoretical introduction, but needed more work. I can do some work starting from that version.

In principle, I would have no problems putting my own POV on how entropy should be defined (information theoretical or phenomenological using heat/work/temperature) aside and let someone else have his/her prefered version.

So, I gave this new user the benefit of the doubt, letting him do the writing and I would just comment, suggest improvements. But that process failed today as it is clear that he is either a kook or he is an expert who deliberately tries to edit in nonsense (e.g. you can imagine that a Professor at some unversity has made a bet with a colleague that he can turn a wiki article on physics topic into complete nonsense such that the nonsensical verion will stick).

I first edited in corrections still consistent with his preferred version (phenomenological definition), but then I spotted a completely nonsensical edit to another section, that I missed previously. A question about that on the talk page which he wasn't able to answer proved, beyond a reasonable doubt, that he shouldn't be editing this article (apart from correcting typos or grammar). Count Iblis (talk) 20:36, 9 August 2009 (UTC)

User:Quantumechanic and User:Subversive.sound are very likely the same individual. They also are redolent of Scibaby, though that's a little more speculative. Short Brigade Harvester Boris (talk) 20:03, 10 August 2009 (UTC)

I am willing to help but will be mostly out of contact for the next week, and will probably need to do some review of the material. Awickert (talk) 03:36, 11 August 2009 (UTC)

Heim theory

Ixfd64 (talk · contribs) has recently added links to Heim theory to the Alcubierre drive (edit | talk | history | protect | delete | links | watch | logs | views) and Faster-than-light (edit | talk | history | protect | delete | links | watch | logs | views). My understanding was that Heim theory was fringe enough to not deserve mention in these articles, but it's not my field, so I'd like second opinions before rolling back those additions. --Christopher Thomas (talk) 17:28, 10 August 2009 (UTC)

I agree with removing Heim theory from these articles. The fact that Heim theory is allowed to be represented at all here on wikipedia is a result of a compromize. It survived VFD but there was a consensus that thre article should not promote a pro-Heim theory POV. So, promoting Heim theory on other pages is completely out of the question. Count Iblis (talk) 18:28, 10 August 2009 (UTC)

I've removed it from Alcubierre drive, but so far I've left it in the FTL article. I really hate to say this, but getting a long write-up in New Scientist may be enough to justify the (short) mention it gets, given all of the other handwaving in the Faster-than-light article. --Christopher Thomas (talk) 22:15, 17 August 2009 (UTC)

Headbomb's administrator candidacy

Physics project member Headbomb is currently a candidate to receive access to administrative tools. Project members, and others, who have an opinion of Headbomb's fitness to receive these tools are invited to comment on Misplaced Pages:Requests for adminship/Headbomb 3. -- Crowsnest (talk) 15:22, 11 August 2009 (UTC)

Wave-icle

Feedback on this? Seems like a WP:Neologism to me. A user on the talk page also pointed that that Wavicle redirects to Wave-particle duality, and I don't think it's all that inappropriate. Headbomb {_{κοντριβς} – WP Physics} 02:41, 13 August 2009 (UTC)

Based on the extreme sparsity in books, it looks like a neologism that didn't catch on. Make it a redirect. Dicklyon (talk) 03:03, 13 August 2009 (UTC)

Done.Headbomb {_{κοντριβς} – WP Physics} 03:16, 13 August 2009 (UTC)

Someone who typed "wave-icle" or "wavicle" might be looking for Wavelet rather than wave-particle duality. JRSpriggs (talk) 10:40, 14 August 2009 (UTC)

"Wave-icle" is surely just a mis-spelling of "wavicle", which is a reasonably well known term (though, I agree, one that is better redirected to Wave-particle duality than given an article of its own). I can't see any reason that someone interested in wavelets would search for either "wavicle" or "wave-icle". Djr32 (talk) 11:50, 14 August 2009 (UTC)

New behavioral guideline: Misplaced Pages:Editing scientific articles

Based on my experience on wikipedia so far, I think this is necessary. Usually editors stick to what I wrote, because of their experience or they intuitively understand that this is the correct way to behave, and you don't get problems. Often, when problems do happen that's because we intitially don't stick to these rules. But usually, as soon as we see problems arise, we stick to these rules and then the problems get solved.

In rare cases, you can have editors who do not have any idea that one should stick to these rules. This then very often leads to problems. If the editor goes unopposed, you are at big risk of getting a flawed article. I have seen the examples of the flawed articles on thermodynamics which I corrected last year. This was a systematic issue because many articles were affected. The editors of these articles (some of whom were experts), simply failed to be sceptical about the validity of their own edits. I think this inherent scepticism is necessary, so I included that in the guidline.

When in rare cases we get into a dispute with an editor who doesn't stick to these rules, we typically get severe problems. To our frustration the existing wiki rules are not really helpful and can even be used against you. I had such an experience a few days ago, see the above section about the problmes in the entropy page and also the discussion about my conduct here.

Also some here my remember the problems we had with editor Ed Gerck who had flawed understanding of special relativity. It took a lot of time to refute him. He was constantly claiming that he was right because he could directly quote some (out of context) text from a book that seemed to support his point, while the reason why he was wrong required some working knowledge of special relativity and you could not really produce a direct counter quote to refute him. So, detailed discusons were necessary and as soon as he was willng to engage in such discussions, problems started to be solved, although he bailed out in the end. His insistance on sticking to the wiki rules was part of the problem, not part of the solution. Count Iblis (talk) 14:48, 13 August 2009 (UTC)

I'll give feedback soon. I'm not super confortable with the wording, especially #2. Headbomb {_{κοντριβς} – WP Physics} 15:30, 13 August 2009 (UTC)

Lots of scientific articles are lousy and full of incorrect information. We all know that. The solution is to have competent and knowledgeable people edit them and make them better. If someone is knowledgeable and motivated, they will write a by-and-large good and accurate article, with or without reading Count Iblis's essay. If there is no one knowledgeable (or at all) trying to fix up a lousy article, it won't get fixed, with or without Count Iblis's essay.

Count Iblis, inevitable in how Misplaced Pages works is that there will be a lot of lousy and incorrect articles. Writing essays and petitioning for rule-changes within wikipedia will not change that, in my opinion. If you want to change that, you need to change the whole model, and go to Encyclopedia Brittanica, or maybe Citizendium or something. If you want Misplaced Pages articles to be better, make them better yourself, and tell your scientific friends to do the same. And meanwhile, keep telling everyone you know not to trust a Misplaced Pages article to be correct. I do. :-) --Steve (talk) 18:57, 13 August 2009 (UTC)

I think that the totality of the wiki rules and the guidlines that currently exist put experts too much on the defensive. E.g., Instead of me spending a lot of time in these sorts of arguments, I could simply point to some guidlines that make the same point. Count Iblis (talk) 16:25, 14 August 2009 (UTC)

Sorry Steve, I must agree with Count Iblis on this. I've just wasted a chunk of time removing some excerable rubbish -- less defensive guidelines would be very welcome and greatly assist the job. I found quoting chapter and verse of some existing guidelines very helpful; more science-friendly guidelines would make the job much easier. We are not talking about root-and-branch reforms, just a few carefully crafted reforms here and there.--Michael C. Price 17:55, 14 August 2009 (UTC)

I am not quite sure what policies you are trying to implement here. Is this what you are trying to say?

Scientific quotations, particularly from textbooks, are more vulnerable to be taken out of context because the necessary conditions for their validity are explained many pages even chapters earlier. Further, unlike many other disciplines, the validity of a scientific statement is NOT based on authority, but on how well it agrees with experiment and well established theories. Therefore:

1. Editors must include the necessary conditions of validity for all non-trivial statements that are not always true. It is the editors responsibility to check and double check this.
2. When resolving conflicts, authoritative sources are not sufficient by themselves; they must be supported by proof that their range of validity coincides with the conflicting statement. In some cases both statements may be true under different circumstances.
3. Conflicts should be resolved primarily through agreement with well established first principles and not authoritative quotations. Discussing topics from well established first principles is not original research.

TStein (talk) 20:00, 14 August 2009 (UTC)

I am not saying that I agree or disagree with these statements. I need to think about it before committing one way or the other. I am only trying to make sense of what you are saying first. If I am wrong please correct it. TStein (talk) 20:00, 14 August 2009 (UTC)

I'm not sure what I think yet, either, but your encapsulation above looks pretty good. #1 is merely a wish, although a good one at that, albeit unenforceable. Points 2 & 3 are the meat.

I've made a few more comments over at the essay's talk page.--Michael C. Price 20:45, 14 August 2009 (UTC)

Yes, this is a more neatly formulated version of my points :) Count Iblis (talk) 22:50, 14 August 2009 (UTC)

I don't really like the text of the current proposal – although I support the idea behind it – as it seems to insist on editors having common sense. We cannot legislate (i.e. force upon third parties) common sense, which is not that common after all… French Misplaced Pages has come up with the idea of a "Charter" (maybe better translated as a "Code of Practice") to which editors can sign up: perhaps we could try something similar here. I'm willing to translate the French if there is an interest. Physchim62 (talk) 23:27, 14 August 2009 (UTC)

Surely the point about common sense is the other way around. The guideline does not require common sense, it is encapsulating it. That's the function of the guidelines.

I'm sure the French charter has some good ideas, so please do translate it. --Michael C. Price 06:47, 15 August 2009 (UTC)

I don't think the "scientific" field in wikipedia is as special as Count Iblis thinks. Editing is basically flaky everywhere, and we just have to do the best we can to improve the quality, fight off the nonsense, and not piss off too many people in the process. Our luck varies, and depends on our patience and style. What baffles me is how this opinion of his is to be reconciled with his defense of Brews ohare's editing in the discussions above. Dicklyon (talk) 02:41, 15 August 2009 (UTC)

I agree with Count Iblis' sentiment, and is in fact the route that I have generally used in the past. I think it is nice to have something like this up, especially when dealing with "authority", as pseudoscience can so easily be infused with a few sources. I also do see how it can work to help editors understand one another by discussion instead of just by quoting sources. My primary concern is of its effectiveness: how many truly effective editors do not already follow the basics of cross-checking their work and making necessary discussion and clarification? It will certainly be useful to help instruct those who want to be good editors, but how big is the group of those who want to be good editors and don't already have an intuition of how to do that? Awickert (talk) 04:02, 15 August 2009 (UTC)

To answer Awickert's last point, I would say that the group of editors in need of legislative support is quite large. Frequently I experience, and have seen, attempts to argue (on talk pages) from first principles, to clarify a techinical matter, dismissed as WP:OR by editors who really need the help, to the detriment of article development.--Michael C. Price 06:47, 15 August 2009 (UTC)

(EC) Ah, I've only had that problem while removing pseudoscience. But as that's your experience, I agree with its intent and effectiveness. Awickert (talk) 15:07, 15 August 2009 (UTC)

Diclyon wrote:

What baffles me is how this opinion of his is to be reconciled with his defense of Brews ohare's editing in the discussions above.

In case of the disputes with Brews, I think having discussions on the talk page based on the fundamentals would be helpful. I don't think that's happening right now. Also, the disputes with Brews are centered mostly around definitions, not on real physics. If you were to follow my guidelines for discussions, you would more quicly arrive at the heart of the matter and then you can reach an agrement. It will either be the case that the way Brews wants to define a concept is not consistent with the way sources define it or it is, but to find out you may need to go beyond simply quoting from sources.

E.g. on the wiki page on apparent weight, SBHarris claimed that the article is edundant as we already ahve an article on G-force. But I countered that the two concepts are not exactly the same, giving the example of frogs floating in a magnetic field. Although the discussion will still go on as SBHarris wants to make ad hoc exceptions, it is still very helpful to use these sorts of arguments based on real physics. It is better than simply quote definitions from sources and then having to argue why your source is of higher quality than the source of your opponent. These sorts of arguments are often besides the point. Count Iblis (talk) 15:06, 15 August 2009 (UTC)

What we really need is an answer to WP:MEDRS - those silly medical so-called "doctors" are getting ahead of us! Reminds me of Misplaced Pages:Scientific standards. - 2/0 (cont.) 18:12, 20 August 2009 (UTC)

Which connection I notice has already been made - good on you. - 2/0 (cont.) 18:26, 20 August 2009 (UTC)

I'd like to add to the guidelines some advice about debate over meanings of terms. My own experience on centrifugal force and its related articles, and on electromotive force, has been the unfortunate usage in published sources of different meanings for the same exact wording. That would not be a problem if we just listed the meanings with their sources, and then presented the matter. But instead there is a tendency for participants to divide in support of their favorite definition and call the opposing forces bad names. Once that mode sets in, there seems to be no short way out of the problem. Brews ohare (talk) 23:38, 24 August 2009 (UTC)

Another guideline I'd like to see added has to do with the selection of material and the evolution of articles over time. There are those among us that think WP is for grades 5 - 8 and anything more complex or detailed is inappropriate. There are others with the view that if you cannot understand the article, then the whole topic is beyond you, so forget it. My view is that every article should have an understandable intro with links to related topics so the reader can identify the range of the topic and the resources available on WP. The remainder of the article may include complexity, and as the article grows, these complex issues may be spun off to independent more technical articles. However, I object to a requirement that every article be completely understandable to anyone, which seems to me to be too restrictive. I have had very extended wars with Dicklyon and others who, simply based upon their own judgment, exclude technical material because they feel that simplicity is king, or perhaps simply do not understand the relevance of the more technical topics. Brews ohare (talk) 23:51, 24 August 2009 (UTC)

You had me up until "Dicklyon". All sounds very sensible. I do write a lot of technical stuff, and I don't think I have ever excluded material for being too technical; you just don't listen to feedback very well. Dicklyon (talk)

Brews, I think that's a straw horse; everyone agrees that articles should include relevant technical material (after the intro) put into its proper context, and not include irrelevant and/or out-of-context technical material anywhere. The disagreements I've seen you have with Dicklyon at wavelength, with Martin Hogbin, myself, and others at speed of light, with Steven G. Johnson at Maxwell's equations, etc. have all been about putting that into practice, rather than the principles themselves, as far as I could tell.

That said, it wouldn't hurt to set it down within Count Iblis's guideline.

If I were writing this, I would mention something about being aware of the audience. For example, an "accessible introduction" for an article like Lindblad equation isn't the same thing as an "accessible introduction" for an article like electron. Likewise, every article has an implicit threshold for how long and technical some section should be before it gets spun off into a separate article; the threshold for an article like Lindblad equation should be much higher than the threshold for an article like electron. I think we all know this, but maybe it should be there anyway. :-) --Steve (talk) 08:06, 25 August 2009 (UTC)

Well Steve, I have had disagreements over subject material and what you call "being aware of the audience", but what I would call "arbitrary dismissal of certain topics" justified by arguments like yours, and arguments about "bloat" and so forth, that are equally interpretable as highly individual criteria for exclusion, not based upon sources, lack of rigor, relevance etc. but simply an unsourced difference of opinion. I'd like some guideline that would break that deadlock based upon a wider and more objective view of relevance to the article. In support, I note that a major reason readers turn to WP is for exactly such a wider view of a subject, a reason for consulting WP that I have heard from others outweighs a common perception that WP is not authoritative and that WP is full of crackpot ideas. The scoping out of a topic is one unequivocal asset of WP. Brews ohare (talk) 11:01, 25 August 2009 (UTC)

Yikes. I can understand the frustration that all of you have but can we keep this on topic please. (WP:Goodfaith and all that jazz.)

Brews: you state that we should have guidelines with 'some advice about debate over meanings of terms'. Can you give us some concrete guidelines for this? I think we can all agree that this can be a problem. I am not quite sure if there is a solution to it. Nor am I convinced that it happens enough that we need to establish a guideline for it. I would love to see your ideas, though.

Your second paragraph above about how to organize WP articles is already established WP policy. (See WP:TPA for instance. I am sure there is something clearer, but I can't find it now.) I suppose we can have a short description and link to that policy, though. TStein (talk) 13:54, 25 August 2009 (UTC)

Here is a possible wording of a guideline:

Draft guideline concerning debate over meanings

Authors may embroil themselves in unnecessary debate by assuming their usage of a technical term like "fictitious force" (for example) has a single meaning in the technical literature. When a definition or usage is contested, the best way to approach the matter is not a defensive pose and a battery of sources supporting your usage. That tends to result in protracted skirmish. Instead, it is prudent to search for alternative meanings, rare as they may be, and present all the possibilities. That way one hopes editors will agree that alternatives exist and some discussion over how to present the alternatives can replace a battle over "who is right". It should be borne in mind that this is not a situation where only the predominant usage should be presented, as many readers will be familiar with other usages. So several, maybe all, usages should be introduced, though perhaps not dwelt upon equally. Where widely varying usages appear, a disambiguation page may be indicated, leading to separate articles. An example is centrifugal force, where this term is commonly used in several ways, and a separate article has been written for each of the common usages. (Although the final result is sensible in this case, its Talk pages are not an example of following this guideline, but a cautionary example of how not to go about such resolution.) Brews ohare (talk) 14:55, 25 August 2009 (UTC)

any experts willing to work on Gauge theory and Nontechnical introduction to gauge theory?

It would be wonderful if someone with expertise could help out with these two articles. We actually have some people already working on the articles who consider themselves to have the relevant expertise (including me and user Bakken), but have not been able to reach a good consensus on a variety of issues. The Gauge theory article has a long history of intractable disputes relating to accessibility to the general reader, and is currently extremely disorganized. It would be great to have someone with relevant expertise who could come in and help to break the logjam, having no ego preinvested in these two articles.--76.167.77.165 (talk) 20:44, 13 August 2009 (UTC)

Electrical material

Freshly created disambiguation page. Expand and prettify at will. Headbomb {_{κοντριβς} – WP Physics} 23:28, 14 August 2009 (UTC)

Experimental determination of the electric permittivity

There is a well known experiment which appears in the literature in relation to determining the numerical value of the electric permittivity. It involves an electric capacitor circuit with a vibrating reed switch, and it operates in conjunction with the equation C = Q/V = εA/d. We can determine ε from this experiment since all the other parameters in the equation can be directly measured. This experiment is closely related to the famous experiment of 1856 by Wilhelm Eduard Weber and Rudolf Kohlrausch in which they used a Leyden jar and linked the electrostatic/electromagnetic ratio to the speed of light. The modern conclusion of this experiment is the equation,

c^2 = 1/(εμ)

The modern version of this experiment is (or was) prolific in the advanced physics textbooks, and it has generally been accepted (at least until recently) that the electric permittivity can never be accurately determined because it is subject to experimental accuracy.

It seems however, that this experiment has recently been sacrificed in order to preserve the new 1983 definition of the metre. The 1983 definition of the metre in terms of the speed of light has resulted in the speed of light now being defined in terms of itself, along with an arbitrarily assigned number. This fact has been the cause of prolonged confusion and discussions at the speed of light article.

However, the matter gets alot worse. With the sacrificing of the above mentioned experiment, one might have thought that the resulting equation c^2 = 1/(εμ) should have also been sacrificed as a matter of course, since it is an integral part of the same package. But this does not appear to have happened. The equation c^2 = 1/(εμ) has been inexplicably retained without any rationale, and it is being used in reverse, in conjunction with the new post-1983 speed of light in order to define an exact value for the electric permittivity.

I now need to clarify whether or not I am correct in suspecting that the above mentioned experiment has been sacrificed. Do we have evidence of a large scale purging of this experiment from the literature in the years following 1983? Does anybody have an advanced level physics book printed after 1983 in order to see if the above experiment has been removed? The experiment certainly appears in the 1979 version of 'Nelkon & Parker' "Advanced Level Physics", but then that was before the 1983 SI unit conference.

This matter needs to be confirmed one way or the other as a matter of importance, because the present introduction to vacuum permittivity contains new physics that simply wasn't heard of until very recently. We need to confirm its authenticity. We need to know if it's really true that they are teaching that electric permittivity is a defined quantity that is all tied up with the SI units system, and that any physical significance that this quantity was believed to possess in the past is now being officially denied. David Tombe (talk) 22:33, 16 August 2009 (UTC)

The constant ε0 only relates charge and voltage to the mechanical units. That is why "electrical constant" is a better name than "permittivity of free space" etcetera; this is defining the unit system, it is not a materials property. /Pieter Kuiper (talk) 23:45, 16 August 2009 (UTC)

Pieter, we're not discussing that here. I'm asking whether or not the experiment mentioned above involving the capacitor and the vibrating reed switch has been purged from the textbooks since 1983. David Tombe (talk) 00:18, 17 August 2009 (UTC)

You can open any electronics or even electromagnetism textbook and learn how to experimentally measure the capacitance of a capacitor. (Hint: Use a current source, a voltmeter, and a stopwatch!) So, I don't know about the historical experiment, but I can confirm that in post-1983 textbooks it's still made clear that capacitances are measureable electronically. And yes, you can make a parallel-plate capacitor in vacuum and use it to "measure" ε0. Try it at home! If your current source and voltmeter and stopwatch were calibrated correctly at the factory, and your parallel-plate capacitor is good enough (negligible fringing fields, etc.), you'll get the true value of ε0. :-) --Steve (talk) 02:57, 17 August 2009 (UTC)

c_0, μ_0 and ε_0 are all defined units. If you "measure" one of them, you are not in fact measuring these quantities but rather are calibrating your rulers, charge meters, etc... In the example given by Steve, assuming you are able to realize the perfect version of this, you are not measuring the separation of the plates, but rather are making sure that your ruler is calibrated. In practice this may be called "measuring the value of ε_0", but only because rulers are common and "trust" them, and we are used to measure speeds by taking a ruler and comparing against time. Here, the speed of light, combined with the definition of the second, decides what a meter is. We chose an arbitrary value for it that coincided with the accuracy of the old definitions at the time. We could have chosen the speed of light to be 1 m/s, and have long meters and short seconds (relative to now) but we chose to have short meters and long seconds. c is the equivalent of hbar. We choose big joules and long seconds, so the energy contained by a photon oscillating at 1 Hz is ridiculously low. Headbomb {_{κοντριβς} – WP Physics} 07:45, 17 August 2009 (UTC)

Steve and Headbomb, Thanks for your answers. That's the very experiment that I was talking about. Thanks for confirming that it still exists in post-1983 textbooks. Headbomb obviously missed the entire point that the equation c^2 = 1/(εμ) follows from that experiment.

So Steve takes my view that the experiment in question is still officially valid, whereas Headbomb is adopting the viewpoint that the equation c^2 = 1/(εμ) which follows from that experiment is merely a calibration, and that the experiment no longer measures ε. So under Headbomb's viewpoint, where did the equation c^2 = 1/(εμ) come from in the first place? David Tombe (talk) 10:59, 17 August 2009 (UTC)

c^2 = 1/(εμ) is the relation between the strength of magnetic and electric components of an EM wave. You know, ${\displaystyle \nabla \times \mathbf {B} =\mu _{0}\varepsilon _{0}{\frac {\partial \mathbf {E} }{\partial t}}}$ (or differently, ${\displaystyle \nabla \times \mathbf {B} ={\frac {1}{c^{2}}}{\frac {\partial \mathbf {E} }{\partial t}}}$) and all that. Headbomb {_{κοντριβς} – WP Physics} 13:29, 17 August 2009 (UTC)

Headbomb, We know that. But you didn't tell us how Maxwell discovered the connection to the speed of light. It was through the experiments of Weber and Kohlrausch in 1856 using a Leyden jar. David Tombe (talk) 19:42, 17 August 2009 (UTC)

Give a reference that clearly states that it is possible (even in principle) to measure the permittivity of vacuum and look for discrepancies compared to ε₀ (in the current SI units), otherwise this discussion is pointless. (And no, general descriptions of measurements of permittivities don't count: you can measure velocities, too, but you can't measure the speed of light in vacuum in the current system of units because the yardstick is defined by c. This is not a statement about the "validity" of experiments, but rather it is about what the experiments are measuring.) We're not here to debate our own interpretations of physics. — Steven G. Johnson (talk) 17:13, 17 August 2009 (UTC)

Stevenj, you keep saying that this discussion is pointless. But it obviously isn't pointless because we have already had conflicting responses. You haven't explained what has changed since 1983 with respect to the above mentioned experiment, that means that we are no longer measuring the ε in C = εA/d. We can measure d directly even though Headbomb says that we can't. If Headbomb is correct, which I know he isn't, then there is something seriously wrong with the 1983 definition of the metre if it means that we can no longer put a ruler across the plates of a capacitor and measure the separation distance. And with the separation distance 'd' measured, then all we have to do is substitute the other values and hence determine ε experimentally. Without an experimental determination of ε, we could never have had the equation c^2 = 1/(εμ) in the first place. That equation is rooted in experimental measurements.

It strikes me that you are trying too hard to defend what cannot be defended. Once I hear people telling me that when you measure the distance across the plates of a capacitor with a ruler that, to quote from above you are not measuring the separation of the plates, but rather are making sure that your ruler is calibrated then I know that they have lost the argument. Nobody engaged in serious scientific debate ever says something like that.

Think about it Stevenj. It makes no sense to try and make sense out that from which sense cannot be made. David Tombe (talk) 18:53, 17 August 2009 (UTC)

David - you seem to have confused the BIPM with George Orwell's MiniTrue. The definition of the metre was changed, nothing has been "purged". The problem you identify was always there. Pre-1983 it wasn't possible to put a ruler across the international prototype metre and measure the distance between the marks --- the distance was (by definition) 1 metre, and so what you were doing was not measuring the separation between the marks, but making sure your ruler was calibrated. Djr32 (talk) 20:36, 17 August 2009 (UTC)

Djr32, The problem that I have identified wasn't there pre-1983. Prior to 1983, the capacitor (or the older Leyden jar) experiment in question appeared in the textbooks, and the formula C = εA/d contained quantities that could be measured. And from this equation we were able to determine ε experimentally, and hence conclude the existence of the equation c^2 = 1/(εμ). As far as I am concerned, nothing has changed today regarding that experiment. I am waiting to hear whether or not it has been purged from the textbooks. What has changed since 1983 is that they have forgotten the experimental origins of the equation c^2 = 1/(εμ), and they are using this equation in reverse, without questioning where it came from, in order to produce a defined value of ε from a defined value of c. Meanwhile, based on Headbomb's statement above, it seems that we have now moved into some kind of Alice in Wonderland world in which rather than measure a distance with a ruler, the distance in question actually calibrates our ruler. There also seems to be a prevailing ignorance which claims that the linkage of c^2 = 1/(εμ) to the speed of light follows directly from Maxwell's theoretical work, without any involvement of the experimental works of Weber and Kohlrausch in 1856. My guess is that the delegates at the 1983 conference got carried away with themselves because they were so drunk on relativity. David Tombe (talk) 00:05, 18 August 2009 (UTC)

To clarify my previous statement: the problem that was always there is that there is some physical "thing" that you can hold a ruler up to, and not be able to "measure" because its length is a defined quantity. In Maxwell's day, that "thing" was the distance between two marks on a particular metal bar; nowadays it's the distance between the parallel plates of this capacitor in a hypothetical perfect experimental setup. Djr32 (talk) 22:20, 18 August 2009 (UTC)

I think that people are confusing a pedagogical measurement with a cutting edge research measurement. I have my students measure c and εo all the time. Any difference between their measured value and the true value is rightly attributed to the precision of their equipment. Their calculated c says more about the measuring apparatus and the measuring technique then it does about the actual speed of light. If on the other hand someone needs c to further precision then normal they look it up and use the exact for extremely precise measurements.

Let say you were trying to measure the speed of light, with the most precise equipment possible, though. Eventually you would need to use the most precise 1983 definition for determining the distance. Once you start doing that (by say using a clock to determine the distance that light travels in 1/2998.....s then you are not measuring c anymore. The same is true for εo, the charge is set by mu_o and the distance is set by ct so that any direct measure of εo is impossible using precise measurements.

As far as whether textbooks dropped the experiment where εo is measured. I don't know. Most of my textbooks are theoretically bases and don't have any interest in these type of examples. Books like, Griffith's and Jackeon focus on using the experiment to calculate the capacitance, rather than the permittivity in free space. More experimentally oriented books may focus more on calculating εo (as a pedagogical exercise), I don't know. Even if textbooks don't include that experiment it probably doesn't mean anything though. It could be that textbooks dropped it for any other number of reasons such as not being trendy at this moment.TStein (talk) 22:00, 17 August 2009 (UTC)

Tstein, You're probably correct when you say that the experiment was dropped because it was no longer trendy. Physics certainly appears to have its trends. But the actual reasons why this experiment is no longer trendy is what I am interested in. Has it been sacrificed to preserve a foolish mistake which took place at a conference in 1983? People keep forgetting the fact that the equation c^2 = 1/(εμ) only exists because of the experimental determination of ε. We have seen cases above of editors believing that this equation just happens to exist as a matter of course, and that we are free to use it in reverse to determine ε theoretically. When pressed on the matter and forced to think a little, they then seem to think that it was initially wheeled in with Maxwell's equations, forgetting of course about the crucial role of the predecessor experiment in 1856 by Wilhelm Eduard Weber and Rudolf Kohlrausch.

As far as I am concerned, the experiment still holds, as does the equation C = εA/d. And if I measure d with a ruler, then I can obtain a value for ε. But they are actually trying to tell me above, that since 1983, I can no longer measure the distance between the plates of a capacitor. They are trying to tell me that if I try to do so, I will merely be calibrating the ruler, and the equation c^2 = 1/(εμ) is the calibration factor. And they seriously expect me to swallow all these absurdities. David Tombe (talk) 00:26, 18 August 2009 (UTC)

Your opinion of what is absurd is irrelevant to Misplaced Pages. You are simply wasting everyone's time by this unreferenced postulation; see WP:V and WP:NOR. — Steven G. Johnson (talk) 00:43, 18 August 2009 (UTC)

David, are you denying that the equation c^2 = 1/(εμ) for the propagation speed of EM waves can directly be derived from Maxwell's equations? (Because, if you are. We are done, any undergrad can show you how to get the wave equation from Maxwell's equations (hint: take the double curl), and read of the propagation speed as sqrt(1/(εμ)).

That Maxwell required the equation as input for deriving his theory is completely irrelevant. Since Maxwell's time there have appeared much more elegant derivations of his equations based on more fundemental physical concepts. (Like U(1) gauge symmetry and the action principle). It is a very simple physical fact that the equation c^2 = 1/(εμ) now follows from current theory. (If you think that it doesn't follow from Maxwell's theory you'll just have to accept that it does follow from QED.) So, fixing to of the quantities by definition of our units for length and current also fixes the third quantity. Plain and simple. (TimothyRias (talk) 10:36, 18 August 2009 (UTC))

Stevenj, We're trying to establish whether or not the experiment in question was purged from the literature subsequent to 1983. You are the one who said that I have got no sources. There are plenty of sources pre-1983. We need to know what happened to those sources after 1983. David Tombe (talk) 00:53, 18 August 2009 (UTC)

Then we are in Wonderland, since the definition of one meter is the distance light travels in vacuum in a time of 1⁄299792458 of one second. And one second is "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom." If you want to know how big is the seperation between two plates, you need to check against a caesium clock, and a pulse of lightbeam travelling in vacuum. Otherwise you are relying on something that was calibrated against a caesium clock and a pulse of lightbeam travelling in vacuum.

In the time of Maxwell, the definition of what a meter (or any units of distance) was different. You would say "this stick is one unit of distance", and "one second is 1/84600th of the duration of the rotation of the Earth against the stars", and would express speed in terms of that. Then you could measure the speed of light, since the definitions of relevant units were how big a stick was and how fast Earth rotated. You could only measure the speed of light up to your knowledge of the stick's length. In 1983, people decided it was more convenient to decide how long the sticks should be, because we need to build lots of sticks, and the speed of light is vacuum is constant. And it is convenient, because a stick can be damaged, bent, stolen, and we'd look pretty foolish if we suddenly stopped knowing how big a meter is because someone thought it made a good prying bar.

So yes, if you could somehow build a perfect plane capacitor with negligible edge effects, you would not be measuring the distance between the plates, but rather making sure your ruler's ticks are at the right place. What happens in undergraduate experiments is that you have a clock, calibrated against a caesium clock, and a stick, calibrated against a pulse of light travelling for 1⁄299792458 seconds. Forgetting experimental factors, if you do not get 299792458 for answer, either your clock is off, or your ruler's ticks are off, or both. Headbomb {_{κοντριβς} – WP Physics} 00:50, 18 August 2009 (UTC)

Headbomb, If you are happy enough with that Alice in Wonderland arrangement in which the act of measuring a length becomes an act of calibration of the measuring instrument, then so be it. But you also need to address that other important issue. Further up the page, you wheeled in Maxwell's equations (Ampère's circuital law to be precise), and you thought that you had solved the mystery of where the equation c^2 = 1/(εμ) comes from. But you overlooked the fact that even Maxwell had to resort to the experimental results of Wilhelm Eduard Weber and Rudolf Kohlrausch in order to obtain the linkage to the numerical value of the speed of light. Nothing has changed today. The capacitor experiment in question is simply a modern day variation of the Leyden jar experiment performed by Weber and Kohlrausch in 1856. Without these experiments, there is no equation c^2 = 1/(εμ). That equation is not the calibration device that you seem to think that it is. You have got this entire aspect of electromagnetism upside down. David Tombe (talk) 01:04, 18 August 2009 (UTC)

David is clearly willing to waste everyone's time by arguing ad infinitum, hoping to somehow sway by the force of his logic despite his lack of sources and despite Misplaced Pages policy on unsourced material. Don't feed the troll, don't bother to explain (unless you enjoy debating to no purpose). It suffices to point out he has no reputable sources. — Steven G. Johnson (talk) 02:19, 18 August 2009 (UTC)

Stevenj, What lack of sources are you talking about? The whole point of this section was to try and establish what exactly the sources are saying. You are the one who told me that I don't have any post-1983 sources for the point that I was trying to make at vacuum permittivity. Correct. But I do have pre-1983 sources, and the evidence is the the experiment in question is widely known in physics circles. So it is a matter of importance for everybody to know whether or not this very important experiment has been purged from the literature, beginning 1984. So far, we have had two replies. Steve Byrnes tells us that this experiment is still easily found in the literature. Tstein tells us that he hasn't seen it much in the post-1983 in relation to ε, although he has seen it in relation to capacitance (as also have I), and that it has probably been dropped because it is no longer trendy. To say that is of course somewhat of a euphemism. We need to know the facts here. You are not correct in stating that this thread is a waste of time. There is clearly a case to be answered. Your statement that I have got no reputable sources is a gross misrepresentation of the facts. David Tombe (talk) 12:06, 18 August 2009 (UTC)

What part of WP:V and WP:NOR don't you understand?

Debating without unambiguous post-1983 sources describing (or at least proposing) measurements of the vacuum permittivity, clearly stating the possibility of measuring discrepancies against ε₀ (as opposed to simply calibrating instrument error) is pointless.

Without clear sources, debating our interpretation has no relevance for Misplaced Pages. Since no clear sources have been provided, this discussion can go nowhere. — Steven G. Johnson (talk) 14:44, 18 August 2009 (UTC)

Stevenj, This is a situation in which the onus is clearly on you to show that the experiment in question was purged from the literature in the years following 1983. The lead in the vacuum permittivity article is far too presumptious. Physics doesn't change as drastically as that, just because of a decision in 1983 to re-define the metre. Three measured quantities can't suddenly become a single definition and a calibration factor. I opened this section as an inquiry regarding the issue of to what degree the physics literature has been altered as a consequence of the 1983 conference. You are now instructing everybody not to reply to this request. And the lack of replies so far indicates that the literature has not been substantially altered since 1983. David Tombe (talk) 18:20, 18 August 2009 (UTC)

Just in case Hanlon's razor applied there: that Maxwell didn't himself derive the speed of light before the experiments of Weber and Kohlrausch is irrelevant. The speed of electromagnetic waves can be derived theoretically from the Maxwell-Hertz equations as 1/√ε₀μ₀ without recourse to experiment (and this is what pushed Einstein to introduce special relativity). That no-one had done that before 1856 is totally irrelevant. --___A. di M. 15:51, 18 August 2009 (UTC)

A. di M. The equations which you have just mentioned link to the speed of light, exclusively because of the 1856 experiment by Weber and Kohlruasch. If that is not true, then can you please tell me exactly how that linkage was established. You can't seriously be trying to tell me that the numbers fell out of the theoretical derivation of the equations, without any experimental input. David Tombe (talk) 18:24, 18 August 2009 (UTC)

Nope, the onus is not on me. Numerous textbooks and standards documents are already referenced stating that the permittivity of vacuum is ε₀ and that ε₀ has a defined (i.e. not measured) value in SI units. No one is discussing a "purge" of anything, just a reinterpretation of what precisely is being measured. For example, the new system of units and why certain quantities are now defined rather than measured (and the pitfalls of the previous definitions) is discussed in detail in the appendix of Jackson's Classical Electrodynamics, an reputable source if there ever was one.

The onus is on you to provide unambiguous post-1983 sources describing (or at least proposing) measurements of the vacuum permittivity, clearly stating the possibility of measuring discrepancies against ε₀ (as opposed to simply calibrating instrument error). You have not done so. Ergo, this discussion is pointless. — Steven G. Johnson (talk) 18:56, 18 August 2009 (UTC)

Steven, This post asks a question. I don't need sources to ask a question. I am asking whether or not thre has been a large scale purging from the textbooks of the experiment that uses a capacitor and a vibrating reed switch to determine electric permittivity experimentally. I have a pre-1983 textbook with this experiment, and I taught it myself. We are now trying to get a definitive answer as to whether or not this experiment has been sacrificed in order to preserve this new physics in which three previously measured physical quantities have now all been consumed in a definition. If it can be established that it has been sacrificed, then that will settle the issue. And if we establish that it is still taught, but in the new Alice in wonderland context such that measuring the distance between the plates of a capacitor really means that we are calibrating the ruler, then that will also settle the issue, and we will all know where we stand as regards modern physics. David Tombe (talk) 19:56, 18 August 2009 (UTC)

(edit conflict) In free space (ρ = J = 0) the Maxwell equations say that ${\displaystyle \nabla \cdot \mathbf {E} =0,\nabla \cdot \mathbf {B} =0,\nabla \times \mathbf {E} =-{\frac {\partial \mathbf {B} }{\partial t}},\nabla \times \mathbf {B} =\mu _{0}\epsilon _{0}{\frac {\partial \mathbf {E} }{\partial t}}.}$ Take the curl of the last: ${\displaystyle \nabla \times \nabla \times \mathbf {B} =\mu _{0}\epsilon _{0}\nabla \times {\frac {\partial \mathbf {E} }{\partial t}}.}$ Symmetry of second derivatives says you can swap ${\displaystyle \nabla \times }$ with ${\displaystyle {\frac {\partial }{\partial t}}}$ and by substituting the third equation in it you get ${\displaystyle \nabla \times \nabla \times \mathbf {B} =\mu _{0}\epsilon _{0}{\frac {\partial ^{2}\mathbf {B} }{\partial t^{2}}}.}$ Now, apply Vector calculus identities#Curl of the curl, substitute in the second equation and you'll get ${\displaystyle \nabla ^{2}\mathbf {B} =\mu _{0}\epsilon _{0}{\frac {\partial \mathbf {B} ^{2}}{\partial t^{2}}}.}$. Ta-dah! That's D'Alembert's equation with 1/c = μ₀ε₀. Finding the same equation for E is left as an exercise. --___A. di M. 19:05, 18 August 2009 (UTC)

A. di M., I've known about that derivation for nearly thirty years. It's a standard textbook derivation that is taught on second year undergraduate courses. But you haven't explained how it was established that the product εμ is numerically equal to 1/c^2. That is the crucial part that requires the experiment. David Tombe (talk) 19:42, 18 August 2009 (UTC)

Ah, I get it now. From a 19th-century perspective, if you had measured ε₀, μ₀, and c, and that you found that that relation didn't hold, then it could have meant that Maxwell's equations are wrong. Since then, Maxwell's equations have been verified in many, many, many more other ways; so if you measured ε₀ by the method you describe and found any other value than ${\displaystyle {\frac {1}{\mu _{0}c^{2}}},}$ that'd be far, far, far more likely to mean that your measurement was inaccurate than that you were the first to discover that Maxwell's equations are wrong in more than a century. --___A. di M. 20:14, 18 August 2009 (UTC)

(Well, Galilean relativity was shown to be wrong after over two centuries, but before Fizeau's experiment and the Michelson-Morley one no-one had tested it to any speed anywhere near that of light; OTOH Maxwell's equations have been verified in an enormous variety of temporal and spatial scales, so if there's a violation of them you're unlikely to discover them with an experiment you can perform in a classroom. --___A. di M. 20:21, 18 August 2009 (UTC))

A. di M., I'm not doubting Maxwell's equations. But the linkage of ε and μ to the speed of light is an experimental fact. There was never any way of linking εμ to the speed of light, other than by experiment. Maxwell himself used the 1856 experiment of Weber and Kohlrausch. You seem to think that the equation c^2 = 1/(εμ) was handed to Maxwell on a plate as a result of his theoretical manipulations. David Tombe (talk) 20:42, 18 August 2009 (UTC)

That's where you are wrong. c^2 = 1/(εμ) is not merely an empirical fact,or happenstance. The relation has a reason behind it, and that reason is that the E and B fields are coupled through ${\displaystyle \nabla \times \mathbf {B} ={\frac {1}{c^{2}}}{\frac {\partial \mathbf {E} }{\partial t}}}$. See A. di M.'s comments above, or pick up Jackson (grad-level) or Good (undergrad-level), or any other textbook on the subject if you need a refresher. Headbomb {_{κοντριβς} – WP Physics} 22:33, 18 August 2009 (UTC)

Headbomb, You've just repeated what A. di M. has said, and you have made the exact same mistake. You have forgotten that the numerical linkage of ε and μ to the speed of light in Maxwell's equations is a purely experimental observation. The numerical relationship c^2 = 1/(εμ) does not follow from any theory. Maxwell's theoretical work linked ε and μ to Newton's equation for the speed of sound. But it took the experimental results of Weber and Kohlrausch in order to produce a value close to the speed of light from Newton's equation. David Tombe (talk) 00:01, 19 August 2009 (UTC)

But A. di M. just derived it right in front of you! So stop claiming that you can't derived c^2 = 1/(εμ) from Maxwell's equation and that we "fail to realize" that c^2 = 1/(εμ), because that's insulting beyond belief. Go write a blog about it if you want, redefine physics in any way you like, or complain at the BIPM, but realize that Misplaced Pages is not your soapbox. The speed of light is by definition 299,792,458 m/s, exactly. The second is defined as a fixed number of the transition between the hyperfine structure of a caesium-133 at 0K, in its ground state, at rest, exactly. The meter is defined as the distance light in vacuum in 1/299,792,458 of a second, exactly. You don't have to like it, but this is how science is done today. Now please stop being disruptive. Headbomb {_{κοντριβς} – WP Physics} 02:24, 19 August 2009 (UTC)

Headbomb, The issue is whether or not we can still measure the distance between the plates of a capacitor subsequent to the 1983 definition of the metre. See my response further down the page. If you knew what you were talking about, you wouldn't be making allegations of disruptive behaviour. David Tombe (talk) 11:39, 19 August 2009 (UTC)

Perhaps David means that the fact that light is an electromagnetic wave could not be directly verified at the time. So, Maxwell using his equations predicts the existence of electromagnetic waves, the speed of which is close to the speed of light. That leads to the idea that light is the predicted electromagnetic wave. Count Iblis (talk) 23:46, 18 August 2009 (UTC)

Headbomb, I think I can understand David Tombe's point. It is akin to saying: "According to those who defined the metre in terms of the speed of light, you cannot experimentally verify special relativity, as the speed of light is constant in any inertial frame of reference because the metre is defined that way without reference to any frame, and couldn't possibly depend on a choice of frame. This is absurd." (Now replace "special relativity" with "Maxwell's equations", add "and ampere" after "metre", add "and magnetic permeability" after "speed of light", etc.) That would only be a valid point if special relativity hadn't been verified zillions of times in zillions of circumstances before the metre was redefined. (BTW, I've fixed the indent in his post.) --___A. di M. 11:54, 19 August 2009 (UTC)

Count Ibliss, If it was a prediction, the prediction came from the linkage to the speed of light through the 1856 experiment of Weber and Kohlrausch. Maxwell used those results in Newton's equation for the speed of sound in order to predict that light was a wave. But Headbomb and A. di M. have overlooked this. They know about how textbooks present Maxwell's equations and that the equation c^2 = 1/(εμ) comes with the package. But they have both failed to realize that c^2 = 1/(εμ), although used by Maxwell in his equations, is in fact an experimental result which he looked up in London in 1861. There seems to be a prevailing misunderstanding about this, and many people seem to think that c^2 = 1/(εμ) was a built in part of the theoretical package that Maxwell derived.

This most important chapter of scientific history has now degenerated into the abominable post-1983 new physics that is summed up in the lead to the vacuum permittivity article. What was once three independent measurable physical quantities, (1) the speed of light, (2) density (μ), and (3) transverse elasticity (1/ε), that all related to each other through Newton's equation for the speed of sound, has now been reduced to a calibration factor with no physical significance whatsoever.

The question now is, what happened to the physics books from 1984 onwards? Where they all revised in order to remove references to the experiment for determining the value of ε ? This shouldn't be a hard question to answer. Has anybody got a copy of Nelkon & Parker "Advanced Level Physics" that has been printed since 1984 so that we can compare its contents in this respect with the contents of my 1979 edition. David Tombe (talk) 00:20, 19 August 2009 (UTC)

I don't understand what you mean by "many people seem to think that c^2 = 1/(εμ) was a built in part of the theoretical package that Maxwell derived". As I shown above and you said you have known for thirty years, that relationship can be shown theoretically from Maxwell's equations, so if the speed of light were anything else than 1/√εμ, that'd mean 1) that Maxwell's equations are wrong, or 2) that light isn't an electromagnetic radiation. (Indeed, my high school textbook claims that Maxwell predicted the speed of electromagnetic waves to be 1/√εμ, observed that that value was within experimental errors of the measured speed of light, and thence hypothesised light to be an electromagnetic radiation. I was not 100% sure that's an accurate account, but Count Iblis seems to have heard this story too.) And I don't understand why choosing a set of measurement units such that fundamental constants have exact values is "abominable physics". If the coulomb was defined as "the electric charge equal to exactly 6,241,509,647,120,417,390 elementary charges", then the value of the elementary charge in coulombs would no longer be measurable and would be reduced to a calibration factor with no physical significance whatsoever. What would be abominable in that? BTW, that is exactly what is done in natural units, except that values such as "1" rather than "299,792,458" are used. And in CGS units, ε equals 1/(4π) by definition, and that was long before 1984. --___A. di M. 01:01, 19 August 2009 (UTC)

A. di M., All Maxwell's predictions in this regard were based on the experimental results of Weber and Kohlrausch. Why not look at the paper itself. Go to page 49 of the pdf file in this link . Equation (132) is the equation c^2 = 1/(εμ) with ε being the inverse of the transverse elasticity and μ being the density. Maxwell linked these quanitities in the equations (80) through to (105). Note however that in order to get the numerical linkage to the speed of light how he mentions the experimental results of Weber and Kohlrausch just before equation (130) and just after equation (137).

Hence, this equation comes from an experimental determination of ε and μ. It is not theoretically derived. Hence we cannot use it in reverse to obtain a defined value of ε. To do so would be a tautology. The modern experiment involving the capacitor and the vibrating reed switch was still taught in recent times and it is in my 1979 Nelkon & Parker. Has this experiment been purged from the literature since 1984? David Tombe (talk) 01:30, 19 August 2009 (UTC)

Misplaced Pages is not here to cater to David's whims, answer his questions, or to debate his interpretations of physics. There is no obligation to argue with him.

The onus is on him to provide unambiguous post-1983 sources describing (or at least proposing) measurements of the vacuum permittivity, clearly stating the possibility of measuring discrepancies against ε₀ (as opposed to simply calibrating instrument error). He has not done so. Ergo, this discussion is pointless. — Steven G. Johnson (talk) 02:15, 19 August 2009 (UTC)

Stevenj, The onus is on you to show sources which explicitly state that the 1983 definition of the metre means that I can no longer put a ruler to something and measure a distance. David Tombe (talk) 11:41, 19 August 2009 (UTC)

Headbomb, We need to get one thing quite straight. A. di M. did not derive what you have claimed he derived. A.di M. copied a well known derivation of the EM wave equation out of the textbooks. That EM wave equation relates to the speed of light because we know that the product εμ is equal to 1/c^2. The reason we know that c^2 = 1/(εμ) is because Maxwell substituted the experimental results of Weber and Kohlrausch into Newton's equation for the speed of sound. You can check it out for yourself at page 49 of the pdf file at this link . The situation has not changed to this day. An experiment can still be performed to measure ε. The experiment is in the physics textbooks. It involves an electric circuit with a capacitor being discharged using a vibrating reed switch. The equation C = εA/d is then invoked. In my world of physics, we can measure d using a ruler. The delegates at the 1983 conference assured us all that the new definition of the metre would leave everything equivalent. So I am not prepared to accept your argument that we can no longer measure the distance across the plates of a capacitor. David Tombe (talk) 11:35, 19 August 2009 (UTC)

David, the EM wave equation as derived from Maxwell's equation (as shown by A. di M. above) tells us that EM waves travel with a speed sqrt(1/(εμ)). This is a simple mathematical fact. The fact that this speed closely agreed with the speed of light, was reason for Maxwell to suggest that light is, in fact, an EM wave (as can be read on the page you keep telling everybody to read). Hence his conclusion that this close agreement must in fact be exact. Since Maxwell's time a ton of different ways have come up that confirm Maxwell's hypothesis that light is an EM wave. This clearly hasn't changed since 1983, so even after the redefinition of the meter in terms of lightseconds, the conclusion that the equation c^2 = 1/(εμ) is exact still holds.

As for your experiment with a capacitor. Ever since the SI definition of the Ampere fixed the value of μ, this experminent has just been an alternative way to determine c. After 1983, you can still preform this measurement to determine ε, but any deviation from the exact defined value is due purely due to calibration errors in your measuring devices. Similarly, you can still measure the speed of light with a ruler calibrated in lightseconds and a stopwatch measuring seconds, but any deviation from 1 lightsecond per second will be pure measurement error. (I know it is not very practical to measure the speed of light with a ruler and a stopwatch, but any experiment that does at somepoint will use a ruler and a stopwatch of some sort. So you get the gist.) (TimothyRias (talk) 12:16, 19 August 2009 (UTC))

No Tim, David won't get the gist. Nice try, though. --Michael C. Price 12:21, 19 August 2009 (UTC)

No, unfortunately he doesn't. (TimothyRias (talk) 13:30, 19 August 2009 (UTC))

Timothy, I'm glad that you have confirmed that we can still do the experiment subsequent to the re-definition of the metre. On your other point, Maxwell only ever became aware of the fact that electromagnetism was numerically related to the speed of like because of the 1856 experiment of Weber and Kohlrausch. That is a well known fact. What is not so well known are the details of how Maxwell first became aware, because the sources about this matter are conflicting. There are a number of stories circulating around. One is that Weber and Kohlrausch were not explicitly aware of their result because it was masked by a factor of root2, and that Weber simply talked about a factor C that became referred to as the Weber constant. Another source says that they were most excited about their discovery of the link to the speed of light. Another source says that when Maxwell heard about it he knew that he then had to work towards a wave equation. As you know, in 1855, prior to Weber and Kohlrausch's experiment, Maxwell had already done a substantial part of his theoretical work in a paper entitled 'On Faraday's Lines of Force'. Another source says that while writing his 1861 paper, Maxwell travelled from Galloway, Scotland, to London to look up the experimental results of Weber and Kohlrausch. He then put them in a suitable form for substitution into Newton's equation for the speed of sound and hence obtained the linkage to the speed of light. You can read the final conclusion at page 49 of the pdf link at .

And nothing has changed to this day. The speed of light can be measured directly, or it can be obtained by experimental measurements of ε. These are two independent experimental approaches which converge, and that is the full significance of Maxwell's work. But this convergence does not fall out of Maxwell's equations alone. It falls out of the experimental results of Weber and Kohlrausch as applied to Newton's equation for the speed of sound as then applied to Maxwell's EM wave equation.

We are seeing a string of people above who are reciting Maxwell's equations from the textbooks and who have no idea how the linkage between the product εμ and the speed of light comes about. David Tombe (talk) 12:50, 19 August 2009 (UTC)

David, you seem to be only person here that doesn't understand how that comes about. (TimothyRias (talk) 13:30, 19 August 2009 (UTC))

We all understand that experiments drive theory, and theory drives experiments, and it's all a nice little ecosystem. What we don't understand is why one test of Maxwell's equations (or if you like, one piece of evidence that led Maxwell to formulate them) is so sacrosanct, nor why it being so means you can't define the quantities it measured. But as Steven G. Johnson has pointed out, it doesn't matter much in the grand scheme of things if we're just arguing about our understand without source. --Falcorian  14:30, 19 August 2009 (UTC)

The equation c^2 = 1/(εμ) is a purely experimental result that was incorporated into Maxwell's equations, originally by Maxwell himself. We cannot then cite Maxwell's equations as being the justification of this numerical relationship. And nothing has changed since the time of Maxwell in this respect. There is no other way, apart from by experiment, to determine the relationship c^2 = 1/(εμ). It is pointless to keep copying Maxwell's equations from the textbooks as if this constitutes a theoretical proof of c^2 = 1/(εμ). And the modern experiment, which is in the textbooks, uses the equation C = εA/d. It is nonsense to deny that experiment on the grounds that we can no longer measure the distance between the plates of a capacitor because of the new 1983 definition of the metre. Of course we can measure that distance. If the separation distance is 1 centimetre, then I will know that by putting a ruler across the plates, irrespective of the 1983 definition of the metre, and I will obtain a measured value of ε. And that measured value of ε will confirm the equation c^2 = 1/(εμ). David Tombe (talk) 15:25, 19 August 2009 (UTC)

Alright David, at this point you're just wasting out time. We went over this several times now. If you have a problem with the definition of the speed of light, write the BIPM and contact us when they have changed it. Or alternatively, pick up any modern EM book on the topic. If you want one at the graduate level, see Jackson, and if you want something more accessible, see Good. Until then, please stop beating the horse. Headbomb {_{κοντριβς} – WP Physics} 15:54, 19 August 2009 (UTC)

Headbomb, You are mixing up two disputes. This is about the fact that the equation c^2 = 1/(εμ) arises from an experiment which can still be performed, and that it can arise on no other basis. The modern definition of the speed of light is a side issue. The speed of light, whether pre-1983, or post 1983, cannot however be reversed into the above equation in order to determine ε theoretically. David Tombe (talk) 16:23, 19 August 2009 (UTC)

Which is simply not true. You are basically saying that all literature on the matter that concludes that ε has become a defined quantity since the 1983 fixing of the speed of light is wrong. Well, you better have a hell of source to back-up that rather strong claim. Since you don't, why don't you just get a life? (TimothyRias (talk) 16:59, 19 August 2009 (UTC))

Timothy, What I'm saying is that the equation c^2 = 1/(εμ) has only ever been justified on the basis of experimental measurement of the right hand side. You and a number of others have been showing me Maxwell's equations, as if I hadn't ever seen them before, and then claiming that this equation falls out of Maxwell's equations. You have all been overlooking the fact that Maxwell himself used an experimental result in order to incorporate this equation into his equations. This is clearly a part of the 'history of physics' regarding which most modern physicists appear to be somewhat rusty.

The consequence of defining c at the 1983 conference has been that they are now reversing c into this equation in order to define ε theoretically. This is known as cooking the books. The next step is of course to ban the experiment that measures ε. And this is what the current controversy is about. That experiment is in my Nelkon & Parker (1979). The question being asked here is whether or not this experiment has been removed from the more recent textbooks. It's a very simple question, but so far the responses have been mixed. David Tombe (talk) 18:07, 19 August 2009 (UTC)

How Maxwell came by his equations is irrelevant. We now have much better (more fundamental) ways of deriving those equations. Maybe Maxwell needed experimental input to derive his equations, we no longer do. U(1) Yang-Mills theory (aka Maxwell Theory) is essentially unique and completely determined by the U(1) gauge symmetry. You clearly don't understand this, but that is just your lack of knowledge. (TimothyRias (talk) 19:43, 19 August 2009 (UTC))

Timothy, It doesn't matter what theory we use. The actual numerical relationship c^2 = 1/(εμ) can only be deduced from experiment. Yang-Mills did not work out that numerical relationship theoretically. Neither Maxwell, nor anybody since Maxwell, has ever worked out that equation, other than by experimental determination of the numerical value of the right hand side. David Tombe (talk) 19:50, 19 August 2009 (UTC)

David, that's just another of your strawman arguments. Which units are derived/defined and which are "free" makes no difference to the empirical basis of c. --Michael C. Price 20:04, 19 August 2009 (UTC)

Michael, You are confusing two things,

(1) The direct experimental determination of the speed of light. And,

(2) The direct experimental determination of electric permittivity which results in the equation c^2 = 1/(με)

The point of interest to physicists is that these electric and magnetic constants are closely related to the speed of light as is indicated by the above two converging experimental results.

There is no way, other than by experimental measure, to determine the numerical relationship c^2 = 1/(εμ). This equation cannot be worked out theoretically.

This fundamental fact has been overlooked by alot of people, and it is the realization of this oversight that has resulted in the cries for a topic ban and the malicious allegations of crankery at ANI, admittedly not from yourself. David Tombe (talk) 20:22, 19 August 2009 (UTC)

There is no way, other than by experimental measure, to determine the numerical relationship c^2 = 1/(εμ). That's odd because that's precisely what we derived in my school physics class (High School for you Yanks, Sixth Form for us Brits). --Michael C. Price 20:36, 19 August 2009 (UTC)

Well Michael, can you then show us this theoretical determination that doesn't use experimenatl values of ε and μ. I'd be really interested to see it. David Tombe (talk) 21:41, 19 August 2009 (UTC)

That's called moving the goalposts. I addressed what you said, not what you now claim you said. --Michael C. Price 22:47, 19 August 2009 (UTC)

David, I think you're overlooking something. Pretend, for a moment, that there's a constant "c" that has nothing to do with the phenomenon we call "light". This constant shows up in the equations governing electricity and magnetism, and is related to other parameters as a direct consequence of the way the equations are derived, via any of several methods. This produces the "c^2 = 1/(εμ)" relation. If one assumes that the equations governing EM are a correct description of electromagnetism, then one must assume the above relation (because otherwise the equations are inconsistent).

Your argument appears to boil down to a statement that we need experimental evidence linking the measured speed of light with this magical constant "c" that shows up in Maxwell's equations, or QED, or whatever model we're choosing to use for EM. That's fine and dandy, but it doesn't change the fact that we can relate c, ε, and μ without recourse to experiment. --Christopher Thomas (talk) 20:37, 19 August 2009 (UTC)

Christopher, In your above example, how would you ever know that 1/(εμ) was numerically equal to the square of the speed of light unless you had numerical values of ε and μ to substitute into the expression? The equation itself, without the involvement of numbers, appears at equation (132) in Maxwell's 1861 paper. I have provided the link on a few occasions, further up the page (see page 49 in the pdf file in the link). The equation is essentially Newton's equation for the speed of sound. Maxwell theoretically linked permittivity to transverse elasticity, and he theoretically linked permeability to density. He then used the numerical results of the 1856 experiment of Weber and Kohlrausch in order to reveal the numerical value of the speed of light. Weber and Kohlrausch's experiment gave a numerical value for 1/(εμ). You cannot escape the fact that c^2 = 1/(εμ) is an experimental result. David Tombe (talk) 21:31, 19 August 2009 (UTC)

You miss my point. You can easily prove, as multiple people have shown you above, that 1/(εμ) is equal to the square of the magic constant called "c" in Maxwell's equations. What takes experimental evidence, is showing that the constant called "c" is equal to the speed of light. This was a big result, back in the day (showing that light could be treated as being a Hertzian wave). --Christopher Thomas (talk) 21:41, 19 August 2009 (UTC)

Christopher, You said, "What takes experimental evidence, is showing that the constant called "c" is equal to the speed of light". That's what I've been saying too. So why are you arguing with me? The numerical relationship c^2 = 1/(εμ) is an experimental result. If the variables are undetermined, we merely have equation (132) in Maxwell's 1861 paper without the numbers. But it is the numbers, and hence the linkage to the speed of light that are the important thing. Without the numbers in equation (132), it is simply Newton's equation for the speed of a wave in an elastic solid. But without the numbers in the modern day c^2 = 1/(εμ), it is just a meaningless equation because the linkage to Newton's wave speed equation is no longer recognized today. David Tombe (talk) 23:35, 19 August 2009 (UTC)

No it is not a meaningless equation because we now have many other lines of evidence that say light is a Hertzian wave. Hence we can now derive cεμ = 1. --Michael C. Price 23:53, 19 August 2009 (UTC)

Michael, Read what I said. The equation is meaningless unless there are numbers involved. Those numbers come from experiment only. I'm still waiting to see how you derive those numbers theoretically. David Tombe (talk) 00:15, 20 August 2009 (UTC)

The reason that few people have answered you is twofold. First it is difficult to do a full literature search. Second, most people don't think it is important. In the end, it is an argument by authority and one vulnerable to many problems such as a dependency on the motivation of the authors to do so. I wish I can help you more with that but I only have theoretically oriented textbooks such as Griffiths and Jackson.

Just as important is that it seems to bother you and others (I am not just singling you out here) that defining something such as c precludes measuring it. I can see why you think this is 'cooking the books' or 'tautology' but it is far less worse then you think. For example, for a time, the hour was defined as 1/24 of the mean solar day. With that definition, of course, it is impossible to measure the mean solar day. (It is defined as being 24 hours.) That did not stop scientists from figuring out that the mean solar day was not a constant. (It may even be possible that it helped scientist figure out that fact since testing standards for consistency is a vital part of metrology.) Defining c to be a certain value is exactly the same. It precludes one from 'measuring' a value of c, but does not preclude determining how valid the definition (d=ct) is. TStein (talk) 21:01, 19 August 2009 (UTC)

Tstein, The issue about the defined speed of light itself is a side issue. My concern here is about the defined value of electric permittivity. My point is that the equation c^2 = 1/(εμ) is an experimental result based on numerical values of ε and μ. Most people here have totally failed to realize that fact. They think that it automatically comes with Maxwell's equations as a theoretical result. And because they have forgotten this important fact, they are using the equation in reverse, in conjunction with the new defined value of the speed of light, in order to produce a defined value for electric permittivity. And they are then further saying that we can no longer do the experiment to ascertain the numerical value for the electric permittivity. They have turned physics totally upside down. David Tombe (talk) 21:38, 19 August 2009 (UTC)

David, you are the one who keeps on missing the point. Take TStein's example of the day. You can measure the length of a day against some standard "hour", or you can define the day to be 24 hours and then when you measure the day length you are actually measuring ("calibrating") how long an hour is. It makes absolutely no difference whatsoever which you opt for. Same with the speed light and the meter and all the other constants. Get it? --Michael C. Price 23:01, 19 August 2009 (UTC)

Right Michael, That's enough. I don't know what you're talking about. I'll make my point one more time. I can't keep repeating it for everybody who decides to come into the ring without reading what I have already repeated quite a few times above.

The well known numerical relationship c^2 = 1/(εμ) is a purely experimental result. It links measured values of electric permittivity to the speed of light. This equation has got nothing to do with any direct measurements of the speed of light, never mind the post-1983 defined speed of light. The equation in question has its origins in Newton's equation for the speed of a wave in an elastic solid in conjunction with an experiment with a Leyden jar that was performed by Wilhelm Eduard Weber and Rudolf Kohlrausch in the year 1856. Maxwell used those experimental results in the derivation of his famous equations (Maxwell's equations) in 1861. The modern experiment is done with a discharging capacitor and a vibrating reed switch in conjunction with the well known equation C = εA/d. This experiment appears in recent textbooks, and despite what some people say, the separation distance d across the plates of the capacitor can still be measured despite the new definition of the metre. I don't expect anybody to come here and agree with what I have said, because that is not in the nature of things. But you all know fine well that what I have said is true. You must all realize by now that this equation cannot be used in reverse to define the very measured quantities that are the cause of its existence in the first place. I'm not going to answer anymore questions on the this issue. You can all go away and have a long and hard think about the matter. This page is here for the purposes of increasing the knowledge of those who edit on physics articles. I hope that this thread has increased that knowledge considerably. David Tombe (talk) 00:00, 20 August 2009 (UTC)

I have learnt something important here: cranks can't analogise. Thank you. --Michael C. Price 00:59, 20 August 2009 (UTC)

The only issue I can see that hasn't been raised yet is that in practice we never have a perfect vacuum. So, you have an epsilon that differs from the vacuum value and this also depends on frequency. If you measure epsilon using capacitors you perform a measurement at zero frequency, while if you measure the speed of light you're doing a measurement at very high frequency.

You can also assume a perfect vacuum and consider exotic theories, e.g. a massive photon described by the Proca Lagrangian or theories in which Lorentz invariance is broken. But I think it would be a good thing if David himself would point out how and why c would not be given in terms of epsilon derived from experiments with capacitors. So, basically, David has to stick to what I wrote in WP:ESCA about arguing from first principles. :). Count Iblis (talk) 23:48, 19 August 2009 (UTC)

Count Ibliss, c IS given in terms of epsilon derived from experiments with capacitors. That's what I've just said above. We don't need to involve the frequency of a light wave because we are not directly measuring the speed of any light wave. David Tombe (talk) 00:19, 20 August 2009 (UTC)

Comments at AN/I

I realize everyone's likely sick of this discussion, but over the last week there's been a substantial amount of traffic at the AN/I thread regarding Mr. Tombe's editing. Further comments (edit: at the AN/I thread) from all involved parties would likely help clarify matters for the administrators assessing the thread. --Christopher Thomas (talk) 04:56, 24 August 2009 (UTC)

I've checked at the science library. I found only one book, post-1983, which dealt with the experiment described above. It was the 1995 (seventh edition) of Nelkon & Parker 'Advanced Level Physics'. The experiment was described on page 247 just as it appeared in the fourth edition of 1979. The rest of the modern books that I checked did not deal with this experiment. They treated electric permittivity as a defined quantity that is obtained by substituting the defined speed of light into the equation c^2 = 1/(εμ). The balance of sources would therefore confirm the position adopted by Steven G. Johnson regarding the introduction at vacuum permittivity, as far as the issue of what the sources are saying is concerned. The 1995 Nelkon & Parker however contradicts Steven G. Johnson's bold assertion that this discussion is pointless. This discussion has revealed that since the 1983 re-definition of the metre, a significant historical experiment has been side-lined and the associated equation has been reversed from a right hand reading to a left hand reading equation. Hardly a basis for allegations of disruptive behaviour at AN/I and talk about sanctions. David Tombe (talk) 17:33, 24 August 2009 (UTC)

Endless repetition on the speed of light talk page - Search for the words, 'equation', 'tautology', '1983'. Allusions to 'wrongness' of special relativity.

Compare with

• profile at NPA and what NPA stands for: "The central theme that concerns nearly all members, both because of its highly honored position in current dogma and because its rather simple mathematics makes it comparatively easy to deal with, is special relativity (SR). A very large majority in the NPA believe it is seriously flawed, and a clear majority believe it is totally invalid. I earnestly subscribe to the latter view: SR has no validity whatsoever. I agree with most of my NPA colleagues that SR never was valid, never will be valid, and in fact cannot possibly be valid."
• publications at babin and babin purpose: "The original and continued purpose of these pages is to present an assessment of special relativity".

DVdm (talk) 21:14, 24 August 2009 (UTC)

I probably should have clarified: Further comments at the AN/I thread would probably be useful. Apologies for the confusion. --Christopher Thomas (talk) 21:39, 24 August 2009 (UTC)

I disagree with adding to the thread at the drama board known as AN/I. The issue has been noted by several admins and non-admins, and there is no benefit in belaboring it there. While admins make plenty of mistakes, the vast majority of them are not in general dumber than a box of rocks. Tombe's behavior there, here, on King Jimbo's page, and elsewhere has not gone unnoticed. If anything, it would be better to directly addresss one of the admins on their talk pages, especially the one who initiated the page ban. Tim Shuba (talk) 22:30, 24 August 2009 (UTC)

Wikibreak.

I'm moving out soon and I will have limited access to the internet for the new few weeks (should be back in early September). I will check-in and take messages on a semi-regular basis. Luckily the Article Alerts are working again, and the New Article feed from AlexNewArtBot is up and running as usual, so there shouldn't be too much problems for the Physics project. Please keep an eye on these two things while I'm gone (I'll go through all the new articles once I'm back from my wikibreak, but it would be nice if you could keep an eye out for crank/POV-pushing/spammy content).

Headbomb out, see you in 2-3 weeks. Headbomb {_{κοντριβς} – WP Physics} 14:11, 17 August 2009 (UTC)

Kazuhiko Nishijima

I've significantly expanded the article based on his obituary from Yoichiro Nambu, and a hefty dose of google searches. If you have more to add, or feedback to give, go right ahead. Headbomb {_{κοντριβς} – WP Physics} 22:27, 18 August 2009 (UTC)

Poincare better than Einstein edits by Schlafly?

FYI and FWIW, user Schlafly (talk) seems to be pushing some kind of agenda at , , , , , , . I undid some of the edits and made some changes. DVdm (talk) 09:02, 25 August 2009 (UTC)

Schlafly is doing this since July.... --D.H (talk) 14:07, 25 August 2009 (UTC)

To commit the association fallacy by way of explanation, Schlafly's brother's site Conservapedia has a long history of linking relativity with moral relativism, and thus evil to be defeated. It could be a family thing. AlmostReadytoFly (talk) 09:15, 26 August 2009 (UTC)

Good grief. DVdm (talk) 09:23, 26 August 2009 (UTC)

limit of super-heavy elements

At Extension_of_the_periodic_table_beyond_the_seventh_period#End_of_the_periodic_table, we say that the limit of neutral atoms is around Z = 176, and of nuclei at Z = 210. At untriseptium we state that 137 is the limit. Both require up-to-date referencing, and review by s.o. who knows what they're talking about (assuming that anyone knows what they're talking about on this subject). kwami (talk) 20:53, 27 August 2009 (UTC)

Okay, this has been partially straightened out, but it needs to be reviewed, and hopefully we can come up with a better citation for the Z = 210 limit than the Encyclopedia Britannica! kwami (talk) 05:45, 28 August 2009 (UTC)

Request third opinion

To prevent a potential edit war on the article Solid, I am asking the project members to vote here. Thank you. Materialscientist (talk) 01:20, 28 August 2009 (UTC)

Category:Markov chains and Category:Markov models

There is a naming dispute considering the correct name for the category for the main article Markov chain and related articles, see WP:CFD. 76.66.192.144 (talk) 03:22, 28 August 2009 (UTC)

Confinement articles are tangled

• Quark–gluon plasma is a medium-sized article
  • Its redirects include Deconfining phase
• Color confinement is a short article
  • Its redirects include Quark deconfinement
• Deconfinement is a stub with no redirects
• Onset of deconfinement is a stub with no redirects

It seems to me that there are at most two articles here, and the redirects don't make a great deal of sense. I'm not sure what exactly is the best solution. Melchoir (talk) 03:36, 28 August 2009 (UTC)

Deletion discussion for Introduction to Dirac's constant

Misplaced Pages:Articles for deletion/Introduction to Dirac's constant. Please read the history of the debate and voice your opinions there. - 2/0 (cont.) 17:20, 29 August 2009 (UTC)

Still need help with the 'Speed of light' article.

One editor has been pushing his idiosyncratic views on the 1983 definition of the speed of light for some months now. I have had enough edit warring, sometimes with little support from other physicists active on the page. His edits on the subject are sometimes blatant nonsense and other times more subtle but a concerted effort is needed to ensure the standard mainstream view of the subject is presented in this article.

Please help. Martin Hogbin (talk) 18:48, 2 September 2009 (UTC)

I think it would be helpful to discuss this with Brews again (he asked me to get involved on my talk page a few days ago, but I was too busy then), but this time with one new rule: Citing from sources is not allowed. So, we have to discuss from first principles and explain everything when challenged from first principles. This removes the freedom to interpret what some source says in some arbitrary way. Because most contributors are experts in physics, this can work. If someone is not an expert and makes mistakes he/she will be disqualified more easily (precisely because you can't hide behind sources). Count Iblis (talk) 20:33, 2 September 2009 (UTC)

Arguing from first principles has no place in wikipedia; we're about reliable sources. What's not OK is for Brews to push an interpretation that he has no source for; he has sources for bits and pieces of info, all of which is acceptable content, I think, but not for his idiosyncratic synthesis from those sources. This is just business as usual for Brews, as the history of discussions of him on this project talk page amply demonstrates. I have been pushing Martin to not remove things that are backed up by sources, and Brews to not add stuff without explicit support in sources, and if they would both comply I think the problem would sort itself out. There are still lots of other details that people will fight over, but it will be easier without these two dominating it the article and talk page. Dicklyon (talk) 03:23, 3 September 2009 (UTC)

I defy Dicklyon (or anyone else) to come up with a single piece of "idiosyncratic synthesis" from the presentation at User:Brews ohare/Speed of light (Example). It is very simple textbook logic based upon the basic BIPM definitions, on the level of grade school geometry. Dicklyon's characterization is pure yellow journalism unless supported by some factual example that could be discussed. This kind of harangue and band leading appears contrived only to shut down any exchange. Brews ohare (talk) 06:28, 3 September 2009 (UTC)

No, Brews what you write there is just a logical fallacy based on your incorrect preconceptions and lack of understanding of modern physics most notably general relativity. The physical interpretation of your example is simply that the spacetime metric has changed between the first and second measurements. (Our that the first measurement was inaccurate due to inaccuracies in our knowledge of the actual length of the meter.) Any change in the 'actual speed of light' is always physically equivalent to change in the metric. And a change in the metric is the only known possible physical cause of a change in the 'actual' speed of light. One thing that is completely clear from GR is that logically speaking the units for space and time should be identical. In such units the actual speed of light is always exactly 1 (which is the result of the signature of the metric, which cannot vary continuously since it is a discrete property.) The 1983 decision just complied with this physical reality and added a numerical factor between the units to make them backwards compatible with the previous definition. In the end your argument just goes to show your lack of physical sophistication. (TimothyRias (talk) 09:59, 3 September 2009 (UTC))

TimothyRias: The argument presented does not depend in any way upon GR. There is nothing in the hypothetical nature of an improved time measurement that requires a change in the spacetime metric. The actual physical speed of light is not hypothesized to change in any way. Please read User:Brews ohare/Speed of light (Example) again. If you see anything in there that requires GR, please point it out by some direct quote. Brews ohare (talk) 14:56, 3 September 2009 (UTC)

Sorry, I indeed slightly misread what you comparing to what. The gist stays the same though. The correct physical conclusion of your hypothetical experimental outcome is that (in SI units) the wavelength of the atomic transition you used to define the "actual distance between A&B" must have changed between the experiments. (or alternatively that the previous determination of this wave length was inaccurate, but I'm assuming that that possibility is excluded by the precision of the measurements.)

As an exercise for you, replace every occurrence of metre in your example with lightsecond and every occurance of the number 299 792 458 by 1. It is not hard to see that you must come to the same conclusion as I have with the original, namely that the wavelength of the atomic transition expressed in lightseconds has changed. (TimothyRias (talk) 15:39, 3 September 2009 (UTC))

Hi TimothyRias: It seems to me that you are trying to come up with a mechanism that might lead to a changed measurement of the time-of-transit. That might be a useful exercise: I believe many of the discussions with Einstein took this kind of turn - answering a question like "could that hypothetical actually arise". However, I'm just focusing upon improvement in measurement technique without going into how that might happen. My take is that an improvement in measurement technique could occur, and its exact origin is not a concern for the purposes of the argument.

The argument in short form is this: suppose the separation of A&B is measured in wavelengths and the time-of-transit is measured in seconds. Then the speed of light is # of wavelengths/ transit time. If the measured time is measured more carefully, a different, more accurate, speed is found. However, regardless of any of this, the speed of light in SI units is still the defined exact value 299 792 458 m/s. Inasmuch as one speed changes with the measurement improvement, and the other does not change, the two items are not the same thing. One is an approximate measurement of the real speed of light c and the other is only a convention, a defined exact conversion factor c₀ = 299 792 458 m/s. Consequently, a statement like "the fundamental speed of light is a constant of nature with the exact value of 299 792 458 m/s" is, simply, nonsense. In some sense the number 299 792 458 m/s is a charade, because you know how many metres it is per sec but you don't know what the metre is without knowing the real speed of light (it's a tautology). It is a bit much to present a reader with a tautology without explanation in the Intro and pass it off as though it had objective content ("the exact value of this fundamental constant of nature is 299 792 458 m/s"). Do you agree?

I have placed an argument at User:Brews ohare/Speed of light (Example). It does have sources, but I believe they can be ignored for the purposes of this discussion, because all that is needed is velocity = distance/time. If there is a sourced point that requires some first-principles support, that certainly can be looked at. That discussion page can be used to present comments. Brews ohare (talk) 20:48, 2 September 2009 (UTC)

I understand your point, but that's not specific to that definition of c: it applies to any way of defining any unit of measurement. When the second was defined as 1/86,400 of the mean solar day, the length of the mean solar day was 86,400 seconds both in 1900 and in 1956, despite the real length of it being greater in 1956 than in 1900, because the seconds had become larger, too, as a consequence of the definition; a precise measurement of some duration which had remained exactly the same would have yielded a smaller number of seconds in 1956 than in 1900. The mass of the International Prototype Kilogram is 1000 grams both now and one century ago, despite its real mass is (believed to) be greater now than one century ago, because the grams have become larger, too, as a consequence of the definition; yadda yadda yadda. Now, of course, to solve these problems it makes sense to choose as a standard something which varies as little as possible, so we have chosen something for which there's damn strong evidence that it cannot change—namely the speed of light. --___A. di M. 23:51, 2 September 2009 (UTC)

A. di M.: So, if I understand you, since this is my point, which you say is universally true, you agree with the point that the real speed of light is logically and not simply numerically different (perhaps numerically different because of measurement errors or some such) from the SI conversion factor?? So, in this instance of the SI units we are in agreement that the real speed of light is logically different from the SI units conversion factor?? Because, if you do agree, then one cannot say (as was said in speed of light in some versions) that the real speed of light is defined to be exactly 299,792,458 m/s inasmuch as they are two different things, and only the conversion factor is exactly defined. Brews ohare (talk) 03:04, 3 September 2009 (UTC)

That point has been explained to Brews repeatedly—at Talk:Speed of light, on my talk page, at User talk:Dicklyon (under several headings; Brews started 6 discussion topics on Dick's talk page)—but he either can't or won't get it. While speculation on someone else's state of mind is, well, speculation, I think that Brews can't get around the apparent (but not real) logical tautology of the value of c being expressed in terms of a metre that is defined by the speed of light itself. It would be a real tautology, or arbitrary, if the time it took light to get from A to B varied, and the metre fluctuated accordingly. But, as you point out, the constancy of the speed of light is a principal reason that it became the yardstick metre-stick—Finell (Talk) 02:31, 3 September 2009 (UTC)

Finell: Several points have been made by A. di M; which point specifically do you agree with? Are you saying you agree with A. di M that the real speed of light is logically and not just numerically different from the SI units conversion factor?? BTW whatever the validity of using the speed of light as a reference, the reasons for that validity are not the discussion here. The discussion here is whether the real speed of light is logically and not just numerically different (due some accident of measurement say) from the SI units conversion factor. Brews ohare (talk) 03:04, 3 September 2009 (UTC)

Please do not feed the troll; this argument can never end. The only way it matters is if Brews can show a reliable source that make a distinction between the "conversion factor" and the "real physical speed of light". So far, he hasn't shown us one. Dicklyon (talk) 03:26, 3 September 2009 (UTC)

Dicklyon: I'd like a brief answer to these questions:

1. Is it your position that you don't care one way or another whether the argument at User:Brews ohare/Speed of light (Example) is correct?
2. Or, is it your position that the argument at User:Brews ohare/Speed of light (Example) is invalid. If that is your view I'd appreciate being shown the error involved, as the argument seems very simple and unlikely to have any hidden missteps. I assure you that if the argument is wrong, I'll go away with apologies.
3. And, is it your view that the argument at User:Brews ohare/Speed of light (Example) (whatever its validity) exhibits so complex a sequence of reasoning that a normal individual would require a source for reassurance about the conclusion?
4. Or do you simply want the subject to go away? If so, why? In particular, is it simply because of the pack of hounds baying over this subject? Personally, I think you can handle it. Brews ohare (talk) 06:08, 3 September 2009 (UTC)

I didn't state anything like that. It'd be like stating that the mass of the International Prototipe Kilogram "is logically and not just numerically different from" one kilogram, or as if someone in the 1950s had stated that the length of the mean solar day "is logically and not just numerically different from" 86,400 seconds; the only difference is that these two do change, whereas the speed of light doesn't. Please don't misquote me, at least. --___A. di M. 11:01, 3 September 2009 (UTC)

A. di M.: I wasn't aiming to misquote you, I just couldn't understand you. Maybe now I do. I agree that the real speed of light doesn't change and the physical kg does. However, the distinction between the concept of kg and the realization of the kg is not the same kind of distinction made in User:Brews ohare/Speed of light (Example) between the SI units defined conversion factor c₀ = 299 792 458 m/s and the real speed of light. The conversion factor is used to change length measurement to be equivalent to a time-of-transit measurement, thereby eliminating an independent length from the SI units. Consequently, any length measurement in SI units is really a time measurement. So my point could be said this way: a measured speed of light requires both a length and a time measurement and thus is fundamentally different from the defined exact SI conversion factor c₀ = 299 792 458 m/s. The constancy and exactitude of this conversion factor is not a reflection of the underlying constancy of the real speed of light; it is a logical mathematical consequence of using a defined conversion factor that places measurement of the speed of light outside the scope of the SI units by converting all length measurements to comparisons of transit times with 1/299 792 458 s. Brews ohare (talk) 15:45, 3 September 2009 (UTC)

Brews: Since you aren't even trying to learn, I'll stop trying to teach you. The misunderstanding is yours. —Finell (Talk) 04:47, 3 September 2009 (UTC)

Finell, I am afraid that you have not sorted out what the issues are, nevermind understanding the arguments. Your comments so far are on matters peripheral to the discussion. So pack up your attitude. Brews ohare (talk) 06:08, 3 September 2009 (UTC)

Oh, please, not from you! Where do you get the chutzpah to condend that everyone who disagrees with you (which is almost everyone on this subject), including real physicists, is wrong, and that you have managed to discern a fundamental flaw in the foundations of physics that has eluded the best minds in physics for 26 years (actually longer, because the redefinition of the metre was in the works for years before 1983). Instead of impugning everyone else's motives and comprehension level, please try some self-examination for a change. —Finell (Talk) 13:07, 3 September 2009 (UTC)

Finell, I do not impugn your motives or ability to comprehend; I say only that you have not yet comprehended User:Brews ohare/Speed of light (Example). Please quote any remark there that discusses or employs a "fundamental flaw in the foundations of physics". Or, any point in User:Brews ohare/Speed of light (Example) where I "contend real physicists are wrong". Nothing remotely like that is in the article. Brews ohare (talk) 14:59, 3 September 2009 (UTC)

Just to sum up my comment above: Brews, the logically fallacy you are committing in your example is the assumption that the distance between A and B doesn't change overtime. The modern physical paradigm is that distances between points are constantly changing. From that point of view, the physical conclusion of you hypothetical experimental outcome is that indeed the distance between A and B has changed. (TimothyRias (talk) 10:07, 3 September 2009 (UTC))

TimothyRias: I wonder if you are reading reading User:Brews ohare/Speed of light (Example) or something else. There is no "logical fallacy" in assuming two points A & B are a fixed distance apart for the sake of discussion. No part of an improved time measurement requires GR and spacetime variation. It is only about man's abilities to measure. I think we got off on the wrong foot here. Brews ohare (talk) 15:02, 3 September 2009 (UTC)

Tim, your point is true, but Brews' error is more fundamental and exists even if we assume that the distance is constant. The original measurement of the distance is, by the SI definitions, logically dependent on the speed of light. The 2nd measurement -- the one where the light is actually fired across the gap -- amounts to just a recalibration of the original yardstick used to measure the distance. Tombe could never get his head around this, and it seems Brews can't either. --Michael C. Price 11:40, 3 September 2009 (UTC)

Michael C. Price: Tim's point does not bear upon User:Brews ohare/Speed of light (Example) at all. Your understanding of the set up is partly correct. Yes, recalibration of the metre occurs. That is not only accepted but part of the discussion. The other part of the discussion is an interferometric measurement of the length, which does not depend upon the definition of the metre. If improvement in clocks occur (which has happened over and over again historically), then the metre recalibrates as it must so the "speed of light" used in the SI units will stay the same: c₀ = 299 792 458 m/s. On the other hand, the separation of A&B in wavelengths does not change, so the speed of light determine by dividing the spacing in wavelengths by the newly measured time will lead to a newly measured speed of light in wavelengths/s. Do you have a problem with that?? Brews ohare (talk) 15:03, 3 September 2009 (UTC)

Yes, I have a problem with The ... measurement of the length, which does not depend upon the definition of the metre. I'm afraid it does depend on the definition of the metre. Unless you choose to record the result in non-SI units, in which case you merely postpone the moment until convert to metric, which you have to do because you are trying to measure light speed in metres/second. It's as simple and inevitable and as inescapable as that. Your two measurements are measuring the same thing twice. --Michael C. Price 16:54, 3 September 2009 (UTC)

Michael C. Price : We are at cross-purposes here. One measurement uses wavelenghts/s, and is completely separate from the metre. It is not necessary to convert this measurement to m/s because it need not be compared with the measurement in m/s. All that is needed is a comparison of the earlier and the later speeds, both in wavelenghts/s to see that a change has occurred. On the other hand, in the SI units no change occurs: the speed is always c₀ = 299 792 458 m/s. That difference in behavior is the focus here. It means that the speed in wavelengths/s is an actual measurement of the fundamental speed of light c, while the other is simply an arbitrary conversion factor with a defined exact value beyond measurement's ability to alter. Brews ohare (talk) 17:22, 3 September 2009 (UTC)

in the SI units no change occurs Wrong. If c changed then the metre would change. --Michael C. Price 20:03, 3 September 2009 (UTC)

Michael C. Price: Hey, cut me some slack here. What is meant is: in SI units no change occurs in the speed, which is always c₀ = 299 792 458 m/s. That should be clear from context, I hope. Take another look. That I'm aware that the metre changes also is very clearly stated in User:Brews ohare/Speed of light (Example). And just to be clear, it isn't c that changes, its the measured value of transit time. Brews ohare (talk) 21:20, 3 September 2009 (UTC)

You emphasized no in "no change". If now you decide you don't mean it, fair enough. --Michael C. Price 22:17, 3 September 2009 (UTC)

I think implicit in Brews argument is that both measurements are done with high enough precision, to be able to conclude that the two measurements give a different result. Interpreting the measurement as a recalibration of the yardstick, implies that it must have changed in length. If you assume that it didn't, recalibration doesn't make any sense. In essence the two mistakes are the same. I was hoping that my explanation over was more appealing to Brews' physical intuition. (TimothyRias (talk) 11:59, 3 September 2009 (UTC))

Yes, one has to assume measurements of adequate precision. The term recalibration here must be understood in the context of the BIPM definition: c₀ = 299 792 458 m/s must remain constant despite any change in measurement technique; hence, changes in measurement technique affect the metre, not c₀ = 299 792 458 m/s. Do we agree on that point? Brews ohare (talk) 15:05, 3 September 2009 (UTC)

And the discussion goes on below

I am pretty certain that you guys know a lot more about physics than I do but it strikes me that some are being a tad unfair to ohare. I hope good faith can be assumed ... ohare clearly believes there is a problem with the wording of the SoL article and are doing their utmost to gain support for changes in order to help readers (bolding to emphasis that ohare is not on an ego trip but seeks what we all seek ... a better article). Those who do not assume good faith can stop reading now.

Unfortunately for ohare (and maybe us all) support is not forthcoming but they won't give up, indeed the level of verbosity grows by the day ... having said that, Hogbin can be fairly verbose and obdurate as well so it is not all one-sided. What worries me is that the debate is becoming an arguement and a slightly unseemly one at that.

I also have a difficulty with some of the wording of the SoL article. In earlier discussions I have called it the 'circularity difficulty'. In a nutshell it is this: The metre is defined in relation to the SoL and the second. Therefore to state that the speed of light is an exact 299.. m/s is a tautology, it is a circular argument because it is true only in a self-defining way. Saying that the speed of light is exactly 299.. m/s doesn't actually tell us anything about the SoL unless we add into the equation some other definition of the metre, unrelated to the SoL, to give us a scale reference. I am not a stupid person and if I think like this there will be others who do also ... I am thinking of readers, for whom wp is designed (not for editors). I may be wrong, but I think this circularity is at the heart of ohare's point. However, if I am right it should be possible to attack the problem calmly together and work out a form of words that clarifies the article for the reader rather than fighting corners in a macho way.

I hope I have made my points clearly ... I would be interested in hearing other views. Abtract (talk) 12:24, 3 September 2009 (UTC)

Abtract: Thank you for your tone and comments. Yes, the tautology underlies my concern. User:Brews ohare/Speed of light (Example) is aimed only at showing that the speed of light as measured in units with an independent length and the SI units "speed of light" c₀ = 299 792 458 m/s are different concepts. The first is indeed a measured speed and the second is a defined "conversion factor". Consequently statements like the "the real fundamental speed of light has a defined exact value of 299 792 458 m/s" is pure baloney. Brews ohare (talk) 15:08, 3 September 2009 (UTC)

I'm a sympathetic to the confusion this tautology can cause. I've made a minor edit to the lead to stress that c taking a fixed value is a peculiarity of the SI system of units. The tautology itself should not be hard to understand. The definition of units will always have to take some physical value as a reference, with as a result that the value of that quantity becoming fixed. In some cases this is more intuative then in others. Nobody is surprised by the fact that measuring charge in elementary charges leads to the charge of the electron being exactly -1 e. Similarly, if we were to adopt the lightsecond as our official measure of length very few people would be surprised that the speed of light is then exactly 1 lightsecond per second, that would be tautologically true. The 1983 decision to redefine the metre as ~1/299,792,458 lightsecond, of course, has exactly the same effect, but it is less intuitive since 299,792,458 is such an odd number. (TimothyRias (talk) 13:04, 3 September 2009 (UTC))

I take it that these remarks do not bear upon User:Brews ohare/Speed of light (Example) , but are intended as a response to Abtract. Brews ohare (talk) 15:08, 3 September 2009 (UTC)

I think many people are contributing to the problem by talking about seconds getting longer and lengths changing and moving to "better" units of measurement that "don't change as much" (those are scare quotes, not quoting quotes). These are unfortunate linguistic choices that are just going to deepen Brews ohare's confusion.

When we measure continuous quantities we're always measuring the ratio of one to another. It's usually more convenient if one of the two quantities is a standard yardstick of some kind, for roughly the same reason that a cash economy functions better than a barter economy, but the standard yardsticks are defined by a ratio with some measurable quantity, so when you measure with respect to a standard yardstick you're ultimately measuring a ratio of two physical quantities by proxy. What does it mean if the ratio changes? You might say "it means one or both of the quantities has changed but we don't know which", but that would be wrong, because changed with respect to what? You're implicitly comparing to an absolute, true and mathematical unit that doesn't exist. Only the ratios are real. You can measure the speed of light in wavelengths of some atomic spectral line per periods of some other spectral line, as Brews ohare wants to do in his essay, but if that changes it doesn't mean that the speed of light has changed, it means that the ratio formed from those three quantities has changed. Which of the three is responsible? Again, meaningless. So how do we decide to call some units more fundamental than others? By looking at lots of ratios. The international prototype kilogram is a good example. The mass ratio of the IPK to various nations' copies has deviated noticeably from 1 since the copies were made, but the ratios between the national copies have varied relatively little. Occam's razor suggests that we would be better off assuming that other masses have varied less with respect to some weighted average of the national kilograms than with respect to the international kilogram, making the national kilograms a better unit standard. Officially the IPK is right by definition and the national kilograms are wrong, but people are not blind to the implications of these ratios. Nor would they be blind to a systematic variation in many measured quantities that disappeared when a different definition of the meter was adopted. They would adopt that new definition, and if the ratio formed from the speed of light, the second, and the new meter was found to vary then they would probably describe that as variation in the speed of light (though it's debatable whether they should). The current standard meter was chosen because it correlates well with other empirical yardsticks and it's measurable to high precision. If at some point another yardstick satisfies those criteria better then the definition will be changed again. It's not the final definition, just the current one.

"The Nature of Time" by Julian Barbour is a good read on this subject. -- BenRG (talk) 14:09, 3 September 2009 (UTC)

BenRG: Your comment is more an essay than a soundbite, so I may miss some points. In broad outline you are concerned with the general nature of standards, how they are used, and why they are adopted. However, I am unclear how your remarks apply to the article User:Brews ohare/Speed of light (Example). Perhaps you mean to say that general confusion over standards has infected the discussion of this article? Brews ohare (talk) 15:28, 3 September 2009 (UTC)

Abtract, that's true of any way of defining any unit. When the litre was defined as the volume occupied by one kilogram of water at standard pressure and at the temperature at which it has the greatest density, “aying that the” density of water was “exactly” one kilogram per litre didn't “actually tell us anything about the” density of water “unless we add into the equation some other definition of the” litre, “unrelated to the” density of water, “to give us a scale reference.” (The litre has since been re-defined as exactly one cubic decimetre.) --___A. di M. 14:47, 3 September 2009 (UTC)

I am going to suggest something heretical. There are way more then enough editors on speed of light and has been for over a month. It hasn't worked. Why do you think that adding more editors, if they even exist, will work any better?

Maybe it is time for a tactical retreat. There are a number of stalled articles that with a little attention can be greatly improved with far less hassle. Wouldn't it be great to be able to edit articles and have people appreciate your edit again? Just as important, Brews is smart enough to figure out the problem on his own but is stubborn enough that he won't as long as there are people pushing back against him.

Let it be for a little. It wouldn't be the first article with silliness; nor is it even the worst problem with that article. (To me it does not separate c from v enough for the average reader and even implies in some places that the space-time constant depends on v.) TStein (talk) 15:04, 3 September 2009 (UTC)

Thanks for the complement TStein. I don't think, however, that my thoughts are clouded by the need to reply to others here. I do think that the simple discussion at User:Brews ohare/Speed of light (Example) is amazing in its ability to provoke wild response to things that actually are not said there or even discussed there. Many imagine what it says, but not many read what it says.

It would be desirable if editors would quote items from User:Brews ohare/Speed of light (Example) verbatim that they disagree with, and then make their point, rather than gaining some broad view of the article (quite possibly jumping to conclusions) and arguing about things that are not said.

Nonetheless, your advice may be wise. Brews ohare (talk) 15:13, 3 September 2009 (UTC)

Ok, so the point you make is that if nothing really physically changes (e.g. no exotic physics changes, like e.g. the photon gaining a mass in vacuum etc.) except that we would be able to measure time more accurately, we could find that the time it takes for light to move from one fixed point to another fixed point could have changed. It could become less. But this would lead us assigning a smaller distance in meters between the two fixed points, simply because the way we define the meter.

My reply is that before we made the more accurate measurement, the intended definition of the meter would be what we later would have found. So, we would later correct the distance between the two points in terms of meters and that would be due to a recalibration of the meter due to a more accurate measurements of the length standard. Count Iblis (talk) 15:44, 3 September 2009 (UTC)

Count Iblis: The first paragraph I understand and agree with. The second paragraph? Could you rephrase that please? What is the "intended definition"? Are you agreeing or disagreeing, and with what? Maybe the BIPM definition helps here: “length is obtained from the measured time t, using the relation ℓ = c_o·t and the value of the speed of light in vacuum c₀ = 299 792 458 m/s” . Brews ohare (talk) 16:01, 3 September 2009 (UTC)

I don't think there is any real disagreement here either. You have a situation where the speed of light was wrongly measured to be lower than it actually is and that will lead to a recalibration of the meter, because one uses the speed of light to define the length standard. Count Iblis (talk) 17:19, 3 September 2009 (UTC)

I'm happy that there is not disagreement at this point, but that leaves open whether you agree with the view that a measurement of the fundamental speed of light c using units like wavelengths/s that can and does change with experiment is to be distinguished from an exactly defined conversion factor c₀ = 299 792 458 m/s that measurement cannot change. As I said to Tim above: In some sense the number 299 792 458 m/s is a charade, because you know how many metres it is per sec but you don't know what the metre is without knowing the real speed of light (it's a tautology). It is a bit much to present a reader with a tautology without explanation in the Intro and pass it off as though it had objective content ("the exact value of this fundamental constant of nature is 299 792 458 m/s"). Do you agree?Brews ohare (talk) 17:32, 3 September 2009 (UTC)

How do you propose we state the speed of light? "The speed of light is roughly 299792458 times 1650763.73 wavelengths of this spectral line of Kr-86 divided by 9192631770 periods of this spectral line of Cs-133"? Multiplying those numbers together, that simplifies to "The speed of light is roughly 53835 times the wavelength of this spectral line divided by the period of that spectral line". 53835 is the ratio of the frequencies of the spectral lines in question. How is that not circular? How is it "real"? (That's the point I was trying to make in my essay.) -- BenRG (talk) 18:04, 3 September 2009 (UTC)

Not that anyone will listen to what I suggest, eh? I think I'm happy so long as no weird statements are made to the effect that c = 299 792 458 m/s is an exact value for a fundamental constant of nature. Brews ohare (talk) 18:13, 3 September 2009 (UTC)

Sorry, but since that statement is true (and reliably sourced) we would be remiss not to include it.--Michael C. Price 19:57, 3 September 2009 (UTC)

We could say that the the meter is defined such that the speed of light is exactly 299 792 458 meters per second. If we want to say something about the speed of light that does not depend on this arbitrary choice, we could write that that light travels a long a null geodesic. If you choose arbitrary units for space and time, then given the geometry of space time expressed in these units, along the space-time trajectory of a photon, we have that ds^2 = 0. Count Iblis (talk) 20:39, 3 September 2009 (UTC)

I don't know what the mystique is about having an exact speed for the speed of light in the lead. We all know that no property of nature is known exactly, and that includes the real physical speed of light. All that happens in the SI units is that the error bar has been buried in the units instead of in the nine figure number. A normal person will be unaware of the buried error bar, and would take the nine figure number as somehow all there was to it. The whole mess of unraveling this business of burying the error bar can't go into the intro.

So the only justification for introducing true but misleading info in the lead is if you subscribe to the superstition that exact values for measurable entities is OK. Another approach is to follow Abstract in some measure and say something like "In 1972 the speed of light was established as c = 299 792 458 ± 1.4 m/s. In 1983 the definition of the metre was changed from a length to a time-of-flight and the conversion factor was chosen to be c_o = 299 792 458 m/s." The simplest approach, however, is to drop the word "exact" and defer the subject to the later section "Speed of light by definition". Brews ohare (talk) 20:56, 3 September 2009 (UTC)

You wrote: "We all know that no property of nature is known exactly, and that includes the real physical speed of light." and I disagree here. We know that the ratio between the circumference and the diameter of a perfect circle is exactly pi. Of course, such statements comes with some assumptions in small print, in this case that the geometry is exactly Euclidean. Another example: The temperature of water/ice/vapor at the triple point is exactly 273.16 K. Of course, this statement defines the Kelvin scale.

In case of the speed of light, if you look at how it appears in the fundamental laws of physics, then you see that it is a trivial scaling constant that can be set to 1. The fact that it is considered to be a constant of Nature is only for historical reasons. We could measure the speed of light before we had the relevant theories like relativity.

In general, we can always play this game. Take some undisputed exact equation of physics, say, dU = dq - dW, and then replace the invisible factors of 1 by constants. If we do this only for dq, we get dU = r dq - dW. Then assign to heat the new dimension "heat" (do we really know that heat energy is the same as energy in the form of work? Let's be agnostic about that). I can then define the constant r to be exactly 4.184 Joule/Heat. In practice this means that the "Heat" can be identified with the thermochemical calorie.

So far this is all theory. But now, suppose that for metrological reasons it is more convenient (or more accurate) to have separate standard to measure heat. Then, the constant r would no longer have an exact value, but it would be an empirical dimensionful constant constant with an error bar. If later it would be more convenient to measure heat in another way, one could define r to have some fixed value. And theorists would, of course, always prefer to use natural units in which r = 1. Count Iblis (talk) 23:28, 3 September 2009 (UTC)

Count Iblis: First, the "no known property of nature is known exactly." Let's put this in context. For example, we know the fine structure constant is :

${\displaystyle \alpha =\ {\frac {e^{2}}{\hbar c\ 4\pi \varepsilon _{0}}}\ }$

exactly, but we don't know its value exactly because it is made up of measurable parameters that can only be observed with error bars. The speed of light is in that category: it cannot be deduced from logic as can π or e. That is what I meant: we all know that c cannot be known exactly. It has to be measured, and in 1972 or thereabouts it was measured as 299 792 458 ± 1.4 m/s using the pre-1983 metre. That error bar did not "go away" simply because of a change in the definition of units. Rather, we buried the error bar in the uncertainty of the metre. Do you agree? Brews ohare (talk) 00:27, 4 September 2009 (UTC)

I would say that in your expression for alpha, from a purely theoretical physics point of view, you can consider hbar and c and the epsilon_0 to be irrelevant scaling constants. The square of the electric charge in these natural units is the coupling strength of electrons to photons and this is the fine structure constant alpha, which can indeed be measured directly by measuring the magnetic moment of the electron and comparing the measured value to the QED prediction. The reason why, say, hbar is not a defined constant is purely for metrological technical reasons, not because of fundamental physics reasons.

If you have some physical artifacts representing time intervals ad lengths that cannot be computed from first principles, and you take them to be your length and time standard, then in those units the speed of light will have error bars. That was the situation before 1983. In 1983 we decided to do away with the ad hoc physical artifact for length and instead define the speed of light to have some fixed value. Count Iblis (talk) 01:06, 4 September 2009 (UTC)

Count Iblis: I take it that you do still maintain the SI units conversion factor 299...m/s is an exact constant of nature, analogous somehow to mathematical constants like π & e, and not as Jespersen, and Wheeler, and Sydenham say,"a conversion factor whose value is fixed and arbitrary"? (my italics). I guess we can say "what's in a name", but this approach buries the error bar of measurement in the metre, instead of displaying it explicitly, e.g. as 299...± 1.4 m/s as was done pre-1983. So today we have 299 ... m/s as an "exact" speed of light, but we don't know what the metre is exactly. Do you agree? Brews ohare (talk) 05:46, 4 September 2009 (UTC)

Brews, I read your little page and I agree except in using the term "conversion factor". When you use a term like "conversion factor" you're invoking in people's minds a set of ideas and examples, and these are mostly sorta different and misleading. Just replace the term "SI conversion factor speed of light" with "numerical value of the speed of light in meters per second" and I totally agree with what you wrote. Yes, the constancy of the speed of light is different from the constancy of "the numerical value of the speed of light in meters per second".

I don't know whether there's some rigorous and universal and exact definition of the term "conversion factor", and whether what you're saying qualifies, but whether or not it's accurate to call it a conversion factor I definitely think it's unhelpful to call it a conversion factor in this aspect.

--Steve (talk) 21:26, 3 September 2009 (UTC)

Hi Steve. Thanks. Good points. I also noticed that the use of "conversion factor" occurs in special relativity, where it makes sense. I am not clear what the connotations of "conversion factor" are in the context of converting a transit time to a length. The term is used in this context by Jespersen, by Wheeler and by Sydenham. That makes it easy to find sources for the idea that use exactly the same words, a sine qua non for the likes of Dicklyon. I am afraid that your term "numerical value of the speed of light in meters per second" isn't sufficiently different from what might result from a measurement, where here we are dealing with a defined convention. Any more thoughts?? Brews ohare (talk) 21:37, 3 September 2009 (UTC)

Brews asked that we respond to his article User:Brews ohare/Speed of light (Example). That seems fair enough. The problem is with the first paragraphs:

Take two points A & B. Suppose they are some fixed distance apart. (The actual distance between A & B can be measured, for example, using interferometry to determine the separation in units of wavelengths of some atomic transition). Suppose (hypothetically) measurement skills increase and the transit time of light between points A & B is measured to be a time t_AB that is a slightly shorter time than previously measured with older technique.

In that case the real speed of light as determined from the relation real speed = (actual distance between A & B)/ t_AB will be measured as larger, because points A & B have not changed position, and the time-of-transit t_AB has shortened.

The problem is that the statement:

(The actual distance between A & B can be measured, for example, using interferometry to determine the separation in units of wavelengths of some atomic transition)

is false. You are assuming a measurement of the 'actual distance' A to B that is more precise then ct. If we had a way to do that we would be using it instead. There is no measurement technique that can measure this 'actual distance' in meters other then ct or something that is calibrated to ct. Trying to measure the actual distance in any way separate from ct results in a number with a slightly different unit then the actual meter = ct_1m; ie the number will have meaning only to the precision that your personal definition of the meter agrees with ct_1m. Measuring a more precise value for t_AB does not give a more precise value of c; rather it gives a more precise value of the actual distance (in meters).

Prove to me that 'the actual distance between A & B can be measured' (in meters) any method independent of ct_1m and I will join you in this fight.TStein (talk) 21:53, 3 September 2009 (UTC)

TStein: You are right, if we could measure distances more accurately, we would do that. The switch to times-of-transit was predicated upon the greater accuracy of time measurements vis-à-vis length measurements. But this discussion is not about metrology decisions and available technology.

For the purpose of this discussion we may assume hypothetically that the distance measurement using interferometry or some as yet to be discovered technique is super-accurate, because this is a thought experiment, not related to what technology can do today. All we need for the discussion is to establish that length measurements independent of time measurements are doable, that is measurements like counting fringes that do not depend upon c t. And of course, the pre-1983 measurements of c that led to 299 792 458 ± 1.4 m/s are an existence proof that such independent measurements of length are possible, because that is where this number came from. It also is not necessary that this length be measured in metres. In fact the argument is based upon two measurements, one in metres, and one in units defined independent of c such as wavelengths of an atomic transition, determined e.g. by counting fringes.Brews ohare (talk) 00:12, 4 September 2009 (UTC)

Martin started this discussion item to ask for help from knowledgable physicists at Speed of light. He did not do it to open a new front to recreate the battle bewteen Brews ohare and his intransagent arguments in favor of his own untennable thesis against (almost) everoyne else giving the same responses that others have already given, in addition to the 8 or so other talk pages where this same battle has been fought, always resulting in a consensus of almost everyone that Brews' thesis if fundamentally incorrect (not merely flawed in particulars) and that Brews' sources do not support his position. This has been going on for most of 2009, but with increasing intensity for the past 2 or 3 months. The fact the Brews, in good faith, genuinely believes that he is right, and that everyone else, including the physics cabal, is wrong, is not sufficient to justify the commotion that Brews causes, the time of other editors that he takes up, or the frustration that he has caused at Speed of light and the resulting beakdown of collaborative editing and discussion there. He has had more than a full hearing of his ideas, many times over, but refuses to accept the consensus of editors who are better informed than the is. To quote Dicklyon, it is time to stop feeding this troll. —Finell (Talk) 00:46, 4 September 2009 (UTC)

Finell: I thought the discussion here was progressing and matters were becoming clearer. Certainly this is not a forum for your incorrect progress report, intemperate language, and uninvited advice. Brews ohare (talk) 05:30, 4 September 2009 (UTC)

moot point

The reason the meter-poorly-defined crowd is wrong is simple: WP:CRYSTAL. The consensus is, right now, that the speed of light is a constant in all reference frames and that is why the meter can be defined in terms of it and some arbitrary definition of time (it doesn't matter if the standard for the second changes because shorter or longer standard seconds just correspond to proportionally shorter or longer standard meters). If the speed of light is not a constant, then modifications to our definitions will have to be made. However, this has not happened, and it is not Misplaced Pages's place to point out this.

ScienceApologist (talk) 00:49, 4 September 2009 (UTC)

Yes, if the speed of light changes the metre will change. However, its definition will remain the same. The number c₀ = 299 792 458 m/s will remain the same. That is why I don't find it helpful to call the unchangeable numerical quantity 299 792 458 m/s the "exact speed of light" because it doesn't change when the real speed of light changes. However, this number 299 792 458 m/s represents a different speed when the speed of light changes because the metre changes. Brews ohare (talk) 05:57, 4 September 2009 (UTC)

He is saying that you are wrong about this, Brews, as has everyone else who, unlike you, understands the subject. You see a problem that the value of c "doesn't change when the real speed of light changes". However, as you have acknowledged, the real speed of light doesn't change, but is constant, for you to say otherwise in contrary to physics and to all experimental observation. So the problem that you imagine does not exist. Please stop spewing this pseudo-scientific nonsense all over Misplaced Pages. Please stop acting like the common crank. Please stick to subjects that you actually understand, like (presumably) electronic circuits and devices and making beautiful circuit diagrams and graphs, and stay away from theoretical physics. If nothing else, consider WP:SNOWBALL and just give up your futile crusade. Isn't it terribly frustrating for you not to be able to persuade other Wikipedians that what you keep saying, over and over, makes any sense? Wouldn't you be happier in a community that would be more receptive to your speculations, like Crankopedia or the web cite where David Tombe, retired science teacher, self-publishes his pseudo-science essays? —Finell (Talk) 09:14, 4 September 2009 (UTC)

Note now that Brews has finally "got it", he insists that he merely wants to clear up the "misleading" language. He'll never admit that he was just plain wrong.--Michael C. Price 10:51, 4 September 2009 (UTC)

It seems to me that Finnel should be blocked for his insulting comments here. Where are the wikipedia police? I think you guys are wrong, wrong, wrong, and being nasty doesn't make you right. Misplaced Pages needs to ban some of you for being insulting uncivil and just plain mean. The word crank should never be used here or in any other discssion to describe anothers persons viewpoint. It is a value judgement and reveals that the person using it has no valid argument to offer. So instead of being uncivil and nasty why dont you simply realise that Brews is right in what he is saying. I doubt you guys are informed enough to edit any physics articles from what I read here.72.64.63.140 (talk) 13:16, 4 September 2009 (UTC)

Particle in a box

Hi everyone,

I've started a rewrite of the particle in a box/infinite quantum well article. I've tried to make the text more readable for the layperson, I've added some new images and I've been working on the references. I'd appreciate it if other editors could look over the article too. Have I messed anything up? Should any additional topics be covered (e.g. comparison with classical results, comparison with finite quantum wells, comparison with free particles, optical absorption, symmetry selection rules etc...)? Should anything be cut out? Should there be more (or less) mathematical formality? Can anything be explained better? Would any other illustrations be useful? This should be quite a straightforward article and it would be great if we could push it to GA/FA. Papa November (talk) 19:01, 3 September 2009 (UTC)

More dubious references being added.

Remember this thread that spawned this RFC? Well, it seems at least one of the socks is active again. Casimir9999 (talk · contribs) has recently added references to Spinor, Light cone, Femtotechnology, Carbon nanofoam, Carbon nanobud, White hole, and Zero-point energy. If the reference added to Femtotechnology is any guide, these could use third-party vetting ASAP.

The other known socks seem to be inactive. I'm not claiming bad faith; just stating that the references are unlikely to be of uniformly good quality, and so should be checked. --Christopher Thomas (talk) 04:50, 4 September 2009 (UTC)

• Project-Class physics pages
• NA-importance physics pages
• Project-Class physics articles of NA-importance