Wikipedia talk:Arbitration/Requests/Case/Speed of light/Evidence

Comment on evidence presented by Tim Shuba

I am not a physicist so feel free to discount what I say accordingly. I have not edited any of the articles in question. However, I have had a few opportunities in the past to engage in conversation on-Wiki with Tim Shuba, and I can report that in my opinion he is a cautious, circumspect and helpful editor, who shows no trace of arrogance or condescension to lay people and is pleased to volunteer helpful information. Arbitrators may want to take my comments into account as they consider criticism launched at Shuba by Tombe and Brews. --Goodmorningworld (talk) 17:49, 9 September 2009 (UTC)

The following also might be taken into account as indicative of a grave acceptance of responsibility:

“Primarily, I use wikipedia for enjoyment rather than attempt to edit seriously. Since I am aware of how and why so much blatantly bogus information gets into articles, and why a large number of articles are highly unreliable, it doesn't affect me adversely as a user. Therefore, whether the speed of light article gets better or gets worse isn't too important to me.″ Tim Shuba

Brews ohare (talk) 00:20, 10 September 2009 (UTC)

Goodmorningworld, You seem to be totally overlooking the fact that Tim Shuba is the one who launched the criticism at Myself and Brews. The only thing that I have written that might be interpreted as criticism of Tim Shuba was my reference to the fact that he deleted a large and very important sub-section from the history section of the speed of light article on 29th August, hence leaving an inexplicable gap in the chronology. I wasn't the one who actually put in that sub-section on the luminiferous aether, however, I made substantial modifications to the paragraph regarding Maxwell's role in that part of the history of the speed of light. I challenged Tim Shuba on his talk page as to why he had removed that sub-section, and he replied with double irony disguised as humour. It's all very nice that you can come here as a non-physicist and give a character reference for Tim Shuba, but eventually the merits of Tim Shuba's removal of that section will have to be judged by somebody with a knowledge about electromagnetism. David Tombe (talk) 08:46, 10 September 2009 (UTC)

What is really going on with David Tombe (moved from Evidence page)

In part of a longish rant to Jimbo Wales' talk page, Dave Tombe wrote, "I have therefore attempted to introduce specialized knowledge back into wikipedia in areas that I have done alot of research in."

As regarding physics articles, this statement refers to nineteenth century theories. In particular, the period of "the old real physics", before "the new nonsense physics" of Einstein's theory of relativity. Most of David Tombe's contributions to physics article have this extreme fringiest of the fringe motivation (since the word crank can be incivil, I will endeavor to use euphemisms, though I admit to having used it freely when I first commented about David Tombe). Here are some examples of the kind of "specialized knowledge" we can expect to be introduced.

• "It is likley that Einstein misunderstood Maxwell's equations."
• "Einstein on the other hand appears to have totally failed to grasp anything that Maxwell said at all."

Please arbitrators and other uninvolved interested parties, find an acquaintance who is conversant in physics and ask about these quotes. They are utterly preposterous, show no expertise whatsoever, and bode ill for anything but the attempted introduction of disruption and pseudoscience into the encyclopedia. Many of the recent arguments in the speed of light article center around this 1983 definition, and this undoubtedly leaves outsiders bemused. Well, the theoretical reasoning (there are other reasons) for this definition is solidly based on Einstein's theory of relativity. As such, it is antithetical to David Tombe's extreme minority point of view. In his words, "[t]his 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."

David Tombe's participation in physics articles is the epitome of what needs to be addressed within the context of the intent of the arbcom pseudoscience decision. Tim Shuba (talk) 04:18, 10 September 2009 (UTC)

Statement transferred from Evidence Page

Despite all that Tim Shuba has said above, I have not been putting original research into the articles. My major contribution to the speed of light article was in the history section. It passed the consensus and remained there for a few weeks until Tim Shuba deleted it. Here is the content material in question [1] as removed by Tim Shuba. I wrote most of the middle paragraph beginning with Wilhelm Eduard Weber and Rudolf Kohlrausch in 1856, down to Maxwell's 1865 paper. With the exception of a few modifications relating to Maxwell's 1865 paper that were made by Martin Hogbin, that paragraph is essentially mine. So why did Tim Shuba remove it? That is perhaps the most crucial aspect in the entire history of the speed of light. It relates to how James Clerk-Maxwell showed the linkage between the measured speed of light and the electic and magnetic constants (nowadays referred to as the electric permittivity and the magnetic permeability). I have expanded on this issue in a series of articles that are published in an on-line journal entitled 'The General Science Journal'. There was actually a wikipedia article page about that journal until Tim Shuba had it deleted about a week ago.

Until last month, I knew absolutely nothing about the decision to re-define the metre in 1983 in terms of the speed of light. When I investigated the matter, I discovered that Brews was absolutely correct. The metre is now defined as the distance that light travels in a specified fraction of a second. That means that in SI units, the speed of light is then defined in terms of itself, and so it immediately loses the connection with the physical speed of light and becomes a mere definition with an arbitraily assigned number. It means that in SI units, the speed of light is beyond measurement and it is therefore important that the article introduction clearly makes a distinction between the new SI speed of light on the one hand, and the physical speed of light as is expressed in other systems of units and which can be measured. My involvement in the main article in relation to that issue was minimal and I was not involved in the edit war. Instead, I went to investigate the knock-on effect that this new definition would have on the electric permittivity, and how Maxwell's discovery in 1861 would be written up in the textbooks in the context of the new 1983 definition. The experiment in question was still in my 1979 edition of 'Nelkon & Parker'. I brought up the subject at WT:PHYS. An editor Headbomb tried to tell me that since 1983 we can no longer put a ruler across the plates of a capacitor and measure the distance. He told me that instead we will be in fact merely calibrating the ruler. I considered this to be total nonsense and I made my opinions about it clear on the speed of light talk page. An editor called Physchim62 then ran to AN/I to complain that I was engaging in disruptive editing, and I got promptly page banned without any apparent investigation into the truth of the allegation. Meanwhile, Christopher Thomas, who was the only one who seems to have understood my argument at WT:PHYS came along and maliciously presented the WT:PHYS thread as evidence of disruptive behaviour. Since then, I have been to the science library and confirmed my suspicions, that since 1983, the capacitor experiment that links the electric permittivity to the speed of light has disappeared from the textbooks. I did find one exception, and that was the 1995 (seventh edition) of 'Nelkon & Parker'. This then goes full circle to the bit in the history section that Tim Shuba deleted. The main question that needs to be asked at this hearing is, 'Why did Tim Shuba remove that edit? In doing so, he removed a vital chunk from the chronology in the history section. I questioned him about it on his talk page and all I got in return was double irony disguised as humour. And whatever the answer is, you'll find that it is the exact same reason why he and certain others don't want Brews to elaborate on the significance of the 1983 definition of the metre. That's why I've suggested that the article be handed over to Steve Byrnes and semi-protected for six months, with a voluntary withdrawal of all the disputing parties. David Tombe (talk) 08:07, 10 September 2009 (UTC)

Comment on Physchim62's allegations

Physchim62 has just made a statement on the evidence board to the extent that he believes that I believe that I own the speed of light article. He then asks whether or not he must present evidence that I don't believe it. The answer is that he doesn't have to. But he must present evidence that I do believe it, and so far, he has presented none. And he would have a very hard job presenting any such evidence in view of my minimal involvement in the article. Ultimately it was Physchim62 that started all this. He started it when he went to AN/I to report me for disruptive behaviour without presenting any evidence of what disruption was actually caused. It is because of that singular action on the part of Physchim62 that this whole arbitration hearing has come about. Therefore it might be a good idea if the hearing begins with Physchim62 presenting evidence of the actual disruption that was caused by my edits. If he can't present evidence of any actual disruption, then questions need to be asked by the higher authorities. David Tombe (talk) 13:45, 10 September 2009 (UTC)

Several uninvolved administrators decided that your behaviour at Talk:Speed of light was sufficiently disruptive to merit a topic ban from such articles. If you continue such an editing style on these pages, it will hardly do much for your case. The single talk page section [2], quoted in my evidence section, shows your desire to have editing at Speed of light "handed over" (that was your term in the title of the talkpage section) because "[e]verybody else tried to sweep that experiment under the carpet because it isn't compatible with the new unmeasurable speed of light"; [3] that is, so that (you hope) your absolutely fringe view of physics will continue to be promoted on Wikipedia. I think that justifies any accusations against WP:OWN although it is not, of course, my decision to make at this venue. Physchim62 (talk) 14:10, 10 September 2009 (UTC)

Physchim62, An experiment in physics disappeared from the textbooks because of a new system of units. There are plenty of sources on the library shelves to prove that. Practically any modern physics textbook proves it. Do you want to subordinate real physics to a system of units? Bringing that issue to attention at WT:PHYS is not disruptive behaviour, and the term 'fringe physics' has got nothing to do with it. You need to learn to start actually debating these issues rather than running off to noticeboards trying to get your opponents disqualified. The issue here is, "do we report the physical speed of light and the defined speed of light as two distinct topics, or do we only report the defined speed of light and sweep the physical speed of light under the carpet? Do we sacrifice the physical speed of light to the SI system?". David Tombe (talk) 14:28, 10 September 2009 (UTC)

We do none of the above. We simply report that the speed of light is defined in terms of metres/second. Measuring the speed of light is the same as measuring the length of the metre. Only Brews and you have a problem with that. I don't have to measure the number of inches in a foot to know that it is 12 inches per foot. But that doesn't tell me how long an inch is. Only Brews and you can't see the analogy.--Michael C. Price ^talk 15:13, 11 September 2009 (UTC)

Michael, That of course is the big problem. You want to limit the article to reporting about a defined speed of light in metres/second that is beyond measurement. Brews on the other hand additionally wants to report about the physical speed of light as is expressed in other systems of units, and which can be measured. David Tombe (talk) 15:52, 11 September 2009 (UTC)

David, Brews is mistaken, as are you. See below. Your objection to the speed of light being defined in metres/second is as fundamentally pointless as objecting to the foot being defined as 12 inches. --Michael C. Price ^talk 04:48, 12 September 2009 (UTC)

Michael C. Price: Your remark: "Measuring the speed of light is the same as measuring the length of the metre." is untrue, at least if you stay within the SI units. In the SI units the "speed of light" is a defined numerical value of 299,792,458 m/s “a defined constant, not to be measured again″. The metre is defined as (BIPM SI Units brochure, § 2.1.1.1, p. 112) the distance light travels in 1/299,792,458 s, regardless of whatever the true value of the real speed of light might be, so ipso facto the SI units' "speed of light" is 299,792,458 m/s, period. Of course, one can go outside the SI units and measure the metre in (say) wavelengths, and then the actual speed of light can be measured in units of wavelengths per second. That measurement is entirely unrelated to the number 299,792,458 m/s. Perhaps that is what you mean, although I have no evidence that other editors on Speed of light such as Martin Hogbin, TimothyRias or Finell share that opinion. Brews ohare (talk) 18:25, 11 September 2009 (UTC)

My statement as quoted is true, regardless of any qualification about SI, since the metre is defined via SI. None of your following statements change this. And this is understood by the other editors. As we saw when this was queried by you, no one dissented. --Michael C. Price ^talk 04:48, 12 September 2009 (UTC)

"regardless of what the true value of the speed of light may be…" That is absolutely classic Brews. "The Truth Is Out There", "Trust No One", "I Want to Believe". The speed of light measured as the product of a wavelength and a frequency and the speed of light which is defined as 299,792,458 m/s are exactly the same physical constant. As far as we can tell, this is also the same physical constant which appears in E = mc² and in the Lorentz transformations used in Special Relativity, although if someone were to show that the two are very slightly different then it would hardly be the end of modern physics. All the time that Brews and David cannot accept this, they will be spouting pseudoscience. Physchim62 (talk) 09:40, 12 September 2009 (UTC)

A typically polite commentary by Physchim62, whose main interest is the irritating insult. Brews ohare (talk) 04:45, 14 September 2009 (UTC)

Here again we see Michael Price and Physchim62 attempting to misrepresent the argument and invoking sensational terms such as 'pseudoscience'. The facts are that the speed of light in SI units is a defined quantity that is beyond measurement, whereas the physical speed of light is a measured quantity. Hence we have two different concepts. If the best argument that Michael Price can come up with is to state that his opponents are wrong, then he doesn't have much of an argument. As regards the point made by Physchim62, the c in the equation E = mc² follows from the measured value of E/m. Based on Maxwell's equation (132) in his 1861 paper, this is the electromagnetic/electrostatic ratio as determined experimentally using a discharging capacitor. Maxwell uses the density and the transverse elasticity of the medium that light is propagating in. Hence E/m is equivalent to 1/(εμ), where μ is the density and where ε is related to the inverse of the transverse elasticity. In other words, E refers to the energy in the medium. In 1908, Gilbert N. Lewis derived E = mc² from Maxwell's radiation pressure equation, although I've read that he probably derived it as early as 1903. From all of this, it is clear that we cannot use the SI defined speed of light in the equation E = mc². David Tombe (talk) 10:50, 12 September 2009 (UTC)

The argument is simple and has been given many times before. "the speed of light in SI units is a defined quantity that is beyond measurement, whereas the physical speed of light is a measured quantity. Hence we have two different concepts." They are not different concepts; by measuring the speed of light you are, by definition, measuring the metre. It doesn't matter how many times you state they are different, they are the same by definition. --Michael C. Price ^talk 11:13, 12 September 2009 (UTC)

Michael, If I measure the speed of light, I measure the speed of light. If in this new system you claim that I am measuring the metre, then we are talking about two completely different concepts. No definition can make a measured quantity the same thing as a defined quantity. I hope that the arbitrators examine your statement above very very carefully, because this is the very kind of thing that I have been strongly objecting to. Your statement above, and the fact that you believe in it, is the very epitome of what needs to be investigated here. This statement constitutes pure confusion. It is the kind of confusion that has been used on an ongoing basis to spam out rational argument in relation to this controversy. It is on Michael Price's statement above that I rest my case, and I will engage no further in this matter here. I will leave it for the arbitrators to decide. David Tombe (talk) 11:23, 12 September 2009 (UTC)

I think you've made the case against you very well. You believe that you are right and everybody else (that is, the BIPM, NIST, pretty much the whole of physics since 1983) is wrong. You are willing to say so repeatedly, but you are unwilling to accept that it might be you who are wrong and the rest of the world that is right. I really don't think you have any place on an encyclopedic project. Physchim62 (talk) 13:01, 12 September 2009 (UTC)

Just for the record, David's error lies in his statement

No definition can make a measured quantity the same thing as a defined quantity.

No amount of reasoning will ever budge David from this belief, nor will he cease from spamming Wikipedia with his views, which are pure nonsense. Physics has moved on from 1903 or 1905, David has not. I concur with Physchim62 that he is incapable of making any encyclopedic contribution. --Michael C. Price ^talk 03:28, 13 September 2009 (UTC)

Thing is that if one were to discuss this again with David, the issue would be settled quite fast if we temporarily discuss this without any sources or any appeal to BIPM, NIST, 1983 definition, what Maxwell wrote or didn't write etc. etc. Because, as far as the physics is concerned, this is all completely irrelevant. Electromagnetic fields and light behave as they do, because the laws of physics are the way they are, not because of "BIPM, NIST, 1983 definition, what Maxwell wrote or didn't write".

Then, this adds a constraint to how David can present his argument. E.g., no more citations from the 1861 paper are allowed. We don't care about what Maxwell said. David has to present his argument from A to Z (i.e. derive everything from Maxwell equations himself). Now, if David is wrong, then that means that either he'll make an error somewhere in his self contained logical argument or he'll make an assumption that is not true from which he argues. Either way, it is easy to point out where he goes wrong. And when that happens, he'll at least have to temporarily concede. He may say that he thinks he is still correct, but siunce he can't appeal to any authority from sources, the ball will remain in his court. Count Iblis (talk) 15:39, 12 September 2009 (UTC)

This was tried repeatedly in the WT:PHYS thread (cited in my evidence post), to no effect. That's the main difference I've seen between discussion with User:David Tombe and User:Brews ohare (Brews will understand and respond to points others make). --Christopher Thomas (talk) 16:21, 12 September 2009 (UTC)

But not with the extra rule that would ban anything other than first principles arguments. What happened was that we merely decided to argue also on the basis of first principles (usually we don't do that and simply make short statements while giving some source).

If you only allow first principles arguments (temporarily to settle that particular issue) then when David would not be able to defend his position, it would be over. Until that time that David would be able to reply, the issue would remain closed. He could not keep the issue open simply because of his claim about old sources. And closing an ongoing discussion in which one editor is refusing to concede is precisely what the main issue seems to be to the people who complain about David and Brews.

This also has the advantage for this particular discussion, because you can formulate everything in cgs units and you can also put c = 1. There is no epsilon, mu or c anymore. Then, this immediately makes clear that the issue is purely about units. So, we introduce the Coulomb and then you need an epsilon in your equations to compensate for the freedom to express charge in the new unit. Count Iblis (talk) 17:20, 12 September 2009 (UTC)

Christopher, What are you talking about here? Are you talking about the distinction between the physical speed of light and the defined speed of light? Or are you talking about the subject that I raised at WT:PHYS. If you are talking about the latter, I seem to remember that you agreed with me on that issue, but that you worded your replies as if you were disagreeing with me. The second sentence in your second reply indicates that you agreed with me. You know that an experiment with a discharging capacitor is needed in order to introduce the numerical linkage to the speed of light into Maxwell's equations. Your first reply reads as follows,

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)

But then you contradicted yourself in your second reply and you stated,

What takes experimental evidence, is showing that the constant called "c" is equal to the speed of light.

Which had been my point all along. Then you took the thread to AN/I and presented it as evidence of disruptive behaviour, knowing that I would know that this wasn't disruptive behaviour, but hoping that the non-physics readers would believe you. David Tombe (talk) 16:27, 12 September 2009 (UTC)

Count Iblis arguments may apply well to some other topics of dispute, but they don't apply readily in the particular case brought up by Michael C. Price. Here the subject is the BIPM definition of the metre. Hence, that source must appear. The discussion also requires the BIPM definition of how length is to be found using transit times via the formula ℓ = c₀t with c₀ = 299,792,458 m/s, so that also must be sourced. I don't think that is an important exception from Count Iblis paradigm, because no-one is debating what these definitions are. Given these two points, a strictly logical first principles outline of the subject is presented at User:Brews ohare/Speed of light (Example), which follows the rules proposed by Count Iblis; if anything, this contribution should be dismissed as so patently obvious as to be completely unnecessary in the article Speed of light. However, discussion of this outline was an eye-opener. Possibly because of the heated atmosphere, or possibly because of strongly held preconceptions, this discussion in most cases was a discussion without relation to the article! And yet, participants thought they were discussing the article! For this reason, I believe Count Iblis proposal for first principles argument can work only in conjunction with strict enforcement of rules that (i) prevent escalation of tempers, and (ii) mandate discussion of the presented material by forcing what is actually said to be dealt with, not imaginary constructions triggered in editors' imaginings. The first is accomplished by enforcement of WP:Talk and WP:NPA and disallowing inflammatory one-word descriptions like "nonsense", "crackpot", "pseudoscience", and so forth.. The second is accomplished by restricting the nature of discussion to explicitly handle verbatim quotes from the material and by requiring sources be dealt with and not dismissed cavalierly. The use of WP:OR, WP:FRINGE, WP:POV must be restricted to use only in conjunction with specifics, no idle flag-waving allowed.

This situation still may not be resolved in this manner. If that is so, WP will simply have to live with the fact that a majority of editors will have their opinion presented in WP articles regardless of the merits, because no mechanism exists to create an atmosphere that encourages an engagement of minds. In extreme cases like the Speed of light in its present circumstances, WP becomes a different embodiment of the Jerry Springer Show in which some editors are the stage stooges, and other editors are the booing hoard in the audience. Brews ohare (talk) 16:53, 12 September 2009 (UTC)

Brews, I agee with Count Iblis's argument in general. We should be allowed to argue from first principles on a talk page. My argument at WT:PHYS was to say that experimental results are needed to link the electric and magnetic constants to the speed of light. Christopher Thomas agreed with me on that point, but then he went to AN/I to report me for disruptive behaviour. When he agreed with me he was trying to word his agreement in a manner as if to suggest that he was actually disagreeing with me. At AN/I, he claimed that he had been trying to coach me, but to no avail. The rest of them disagreed with me, yet at AN/I Christopher Thomas tried to give the impression that he had been part of a united front of many who had been trying to coach me, even though Christopher Thomas had actually been in disagreement with the rest of them, and in agreement with me. David Tombe (talk) 17:01, 12 September 2009 (UTC)

Comment on Totientdragooned's proposals at the workshop

This section was moved to Wikipedia talk:Arbitration/Requests/Case/Speed of light/Workshop#Comment on Totientdragooned's proposals at the workshop. Hersfold ^(t/a/c) 16:22, 12 September 2009 (UTC)

Comment on Steve Byrnes's evidence

Once again we see a series of allegations relating to my off-wiki activities. But not a single shred of evidence has been presented as regards inserting original research into main articles. I began my dealings with Steve Byrnes before I started using my proper username. The issue in question was Faraday's law. Steve Byrnes believed that he had detected two Faraday's laws in electromagnetism, and he wanted to amend the Faraday's law article to that end. I tried and succeeded in holding him back from doing so, while explaining to him that in fact there is only one Faraday's law, but that it contains two aspects, and that only one of those aspects is catered for in the modern version of Maxwell's equations, which is why we have to supplement those equations with the Lorentz force. Steve finally realized the inter-relationships after I had demonstrated them to him. There was somewhat of a hitch over the issue of the fact that I was using Maxwell's original papers, and that Maxwell's idea of 'electromotive force' does not correspond exactly with the modern notion of the concept. I was using the term E for F/q in the equation F = qvXB. Hence I was writing E = vXB which is a format that is not used nowadays. But that is the format that is needed in order to show the inter-relationship between the two aspects of Faraday's law. I then had a debate with Steve about the Biot-Savart law and how to reconcile its singularities with its solenoidalness. That steered me into having to divulge the fact that I believe that the Biot-Savart law, just like the centrifugal force, has to obey the inverse cube law, and not the inverse square law as is commonly believed. But I never wrote that in the main article. Others have tried to do that, but I never have.

In my dealings with Steve, I found him to be very knowledgeable in physics, and competent in mathematics, but there were certain patterns which he clearly hadn't seen until I drew his attention to them. In a few other exchanges he has proved to have taken a very balanced approach, which is why I recommended him to be a neutral arbitrator in this dispute. I'm sorry that he has refused the olive branch, and I'm sorry that he has now misrepresented my position in this current speed of light dispute. I didn't say that the BIPM definition was impossible. It is quite possible, but I do believe that it was a mistake. Having said that, I have never once attempted to write my opinions on that matter into the main article. I have attempted to explain on the talk page why the BIPM definition of the metre means that the ensuing speed of light is a definition that is beyond measurement, and hence why it is a different concept than the physical speed of light, that can be measured. I entered the dispute on the talk page to help out Brews who was being rounded on by a crowd, who in my opinion were wrong, and who were trying to hush up this important 'sourced' fact.

I have already suggested that Steve Byrnes should now be allowed a free hand to write the article himself, which should then be semi-protected for six months. I still think that that would be a good idea. Steve has made it clear that he is no ally of mine, and so that should dispel any doubts that he would be biased towards my point of view on the matter. He knows his stuff. Somebody has to write the article coherently. At the moment it is just a pie throwing contest and something needs to be done. I know that Steve will write the article in a balanced fashion, irrespective of his prejudices towards me. If you ban me, as Steve has proposed, it's hardly going to make much difference. I haven't edited the main aticle since 12th August and I have made minimal edits to the talk page in recent weeks. I am not the source of the trouble at that article, and I don't believe that Brews is either. The source of the ongoing trouble at the speed of light article is the confusion that has been sewn by the 1983 BIPM definition.

So I say to Steve, put your bitterness about the Faraday's law argument behind you and move forward. David Tombe (talk) 13:29, 11 September 2009 (UTC)

Comment on Martin Hogbin's evidence

Martin Hogbin has now decided to parrot what Tim Shuba and Steve Byrnes have said. My dealings with Martin Hogbin relate to the history section in the speed of light aticle. Martin, attempted to do exactly what Tim Shuba did after I had been banned. Martin tried to remove all mention of Maxwell's 1861 paper in relation to how Maxwell linked the speed of light to the electric and magnetic constants. Ironically, Martin was happy enough to reinsert this material, but in relation to Maxwell's later approach in his 1865 paper. The difference with the 1865 paper that made it more acceptable to Martin was the fact that it didn't involve any explicit references to Maxwell's sea of molecular vortices. In the end, both the 1861 paper and the 1865 paper were treated in the history section, even though I was of the opinion that the latter was superfluous to requirements. At any rate, both of them dealt equally with the importance of Weber and Kohlrausch's experimental result that linked the electric and magnetic constants to the measured speed of light.

When Martin first removed the material about Maxwell's 1861 paper, he wrote in the caption "Remove Crackpot Physics". Martin has no qualms about referring to his opponents as crackpots even when that opponent is James Clerk-Maxwell. Once again today, he is referring to crackpot physics that I have been inserting into wikipedia. Can we all please see some examples of this crackpot physics. I suggest that the arbitrators cross-examine Martin Hogbin on two issues. (1) Why did Martin Hogbin remove the material on Maxwell's 1861 paper from the history section? and (2) Why does Martin Hogbin think that the physical speed of light should be ignored in the article to the exclusion of the defined speed of light as per the 1983 BIPM metre? Martin argues that the SI system is the official system and that as such only the SI speed of light should be mentioned. The SI system may well be the official system of units, but we cannot sacrifice the physical speed of light for a system of units. If we ever have to measure the actual speed of light, we have to use another system of units, and that needs to be made clear in the article. David Tombe (talk) 13:54, 11 September 2009 (UTC)

Response to Dicklyon's comments at the workshop

Dicklyon asks increduously

Can anyone really believe that there are editors among us with a hidden motivation to hide the truth about the speed of light? or about Maxwell's aether vortex theory? Dicklyon (talk) 04:38, 10 September 2009 (UTC)

Tim Shuba removed the material on Maxwell's aether vortex theory from the history section at speed of light on 29th August [4]. When challenged on the matter on his own talk page, he gave his answer very clearly in double irony disguised as humour.

Martin Hogbin attempted to remove the same material from the history section a few weeks earlier citing "No crackpot physics". [5]

And Dicklyon himself removed all references to Maxwell's vortex aether theory from the history section at centrifugal force claiming that there was no consensus to mention it. He did it in a very crafty manner. On 17th of August 2009, he removed this material [6] from the main centrifugal force article, ostensibly on the grounds that it was being moved to a special history section. As you can see, there is a paragraph about Maxwell's 1861 paper in the removed material. However, when it arrived in the special history section, the material on Maxwell had mysteriously disappeared. Then later in the same day, he removed the similar material in relation to Johann II Bernoulli, [7], leaving in a misrepresetation of the views of Daniel Bernoulli as expressed in a modern source.

Steve Byrnes tried to deny that centrifugal force was real, and in order to make his point, he reduced the argument to the base level of a children's video that showed a dummy getting thrown out the door of a swerving car. The point of course was that the dummy was supposed to fly off at a tangent. But the demonstration was so poor that the driver of the car even had a hard job trying to make his point, because friction stopped the dummy from going very far. At any rate, we should have all seen that the dummy flew off both radially and tangentially, and that the centrifugal force is the radial effect. This effect becomes very important in the context of Maxwell's vortex sea, because it is the centrifugal pressure between the vortices that leads to the radiation pressure in light, and which accounts for the speed of light.

This of course is no longer pat of the current orthodoxy. But we can clearly see that Tim Shuba, Martin Hogbin, and Dicklyon don't even like to have in mentioned in history sections, presumably because it is too plausible.

My very first block on wikipedia was at centrifugal force, and it was for trying to insert this material on Maxwell. Administrator SCZenz blocked me during the course of a revert war with himself, on this very material. That was the beginning of the culture of blocking me which led to my block record. The later blocks were for trying to insert the radial planetary orbital equation which contains a centrifugal force term. David Tombe (talk) 11:52, 12 September 2009 (UTC)

I was questioning your conspiracy theory, not the fact that people have removed stuff on Maxwell's aether vortex theory from the speed of light article. If you want to include such material in a history section, that needs to be backed up by at least one secondary source that connects Maxwell's aether vortex theory to the topic of the speed of light. I think that so far you've only had primary sourcing to Maxwell and your own interpretation of relevance. Dicklyon (talk) 00:10, 14 September 2009 (UTC)

Dick, As regards the history section at speed of light, I provided a primary source, a secondary source, and a tertiary source. You were happy enough with it at the time. The connection to the topic of the speed of light was overwhelming. It dealt with how Maxwell converged the meaured speed of light, as measured by Fizeau, with the electromagnetic/electrostatic ratio as measured by Weber and Kohlrausch. David Tombe (talk) 05:01, 14 September 2009 (UTC)

That sounds like subject matter that I could be happy with; but only if it's done from the POV of a secondary source. If you show me a version that I approved of, I can put it in and get you off the hook for it. Dicklyon (talk) 18:43, 16 September 2009 (UTC)

Comments from Dicklyon

No other editor supports Brews ohare's idiosyncratic points of view

OK, Count Iblis and David Tombe sometimes do, but other than that, the evidence is overwhelming that Brews's points of view are idiosyncratic. He can't often find a source that shows anything like his POV, so he cites multiple sources and lengthy arguments that amount to WP:SYNTH. Many editors push back, and none support him, except that Count Iblis came along with his theory that we should ignore sources are argue from first principles instead. Obviously this is completely contrary to WP:V. Dicklyon (talk) 06:18, 10 September 2009 (UTC)

Dicklyon says my "point of view" cannot be supported by sources, but requires lengthy argument. He has not actually identified what "my point of view" is, which leaves me the latitude to state what "my point of view is". (It's pretty common for Dicklyon to attribute views to me based upon other editors' remarks, because he doesn't read what I say for himself; so who knows what he is really talking about?) First some facts:

the number 299 792 458 m/s before 1983 was a speed of light in the usual sense of the words, and was a measurement expressed more carefully as 299 792 458±1.2 m/s. The number 299 792 458 m/s after the 1983 adoption of transit time definition of length is a defined value that follows by simple logic from the definition of the meter as the distance traveled by light in 1/299 792 458 s.

Those are, I believe facts we all can agree upon, and stem from the 1983 BIPM statement. Here is my unbelievable, unsupportable POV requiring WP:SYNTH:

The number 299 792 458 m/s before 1983 was an approximate measurement, and the number 299 792 458 m/s after 1983 was a committee definition. The measurement established the physical speed of light in the pre-1983 units; the definition was arbitrary, could have been any real number, but was selected to minimize any dislocation in adopting the new definition of the metre. In all of these changes in definition, the goal was not only to improve the precision of the definition, but also to change its actual length as little as possible..

In fact, all these statements are in the article already, and so the the real issue here is that Dicklyon, Finell, Physchim62, MartinHogbin and the entire crowd simply have either not read or not understood the content of this section (written by myself) and recently mistitled by an anonymous editor to be a contradiction of its contents, a change supported at length by TimothyRias.

It might be pointed out that the brouhaha on Project Physics covers the same ground.

In short, all the ideas combated with invective, distortion, incivility, and fury already are in the article, the noise makers have not read or understood what they are talking about, and this entire case is of interest only in demonstrating how a page can get completely out of hand because of a bunch of Pavlovian responses that short-circuit all thinking and civilized behavior. Brews ohare (talk) 18:12, 18 September 2009 (UTC)

The stuff that's sourced and in the article is pretty much OK. What's not OK is when you push further to assert that "speed of light" has two different meanings, and when you push to put the subtle definitional complexity into the lead sentence, against the consensus of all the other editors. I've already stipulated that there are no substantial disagreements on the physics. Dicklyon (talk) 18:38, 18 September 2009 (UTC)

I have absolutely not pushed anything into the lead, but have supported your own draft of the lead repeatedly, and also that of Abtract, both of which avoid the word "exact", which I felt was contrary to WP:Astonish, and have supported the lead of NotAnIP83:149:66:11, which explains the word "exact". Moreover, as pointed out in my above remarks, there are indeed two definitions involved here: the concept of "speed of light" as a measurable quantity that led to the result 299 792 458±1.2 m/s, and the defined value 299 792 458 m/s, which is not a measurement but a simple consequence of the 1983 adoption of the metre as the "distance traveled by light in 1/299 792 458 s", which number, we may note, could have selected as any other fraction of a second whatsoever.

I am not who you seem to think I am. Brews ohare (talk) 18:58, 18 September 2009 (UTC)

Comments from David Tombe

The debate at speed of light has been characterized by an atmosphere of intimidation that has been created exclusively by one side, due to their attempts to get their opponents silenced. The evidence for this exists in the form of two AN/I threads for this purpose, as well as many isolated comments even at this arbitration hearing, particularly from editor Physchim62. Physchim62 has even proposed that two of the disputing parties be banned for the duration of the hearing. The unsubstantiated allegations of disruption, that are exclusively coming from one side, are in fact the only behaviour in the debate that actually constitutes disruptive behaviour. These ongoing allegations constitute sheer intimidation. The readiness of an administrator to instantly pander to one of these malicious allegations, without any apparent investigation, played a major role in this atmosphere of intimidation. David Tombe (talk) 18:22, 12 September 2009 (UTC)

Comments from Martin Hogbin

Problems with editor David Tombe

As shown by Tim Shuba's and Sbyrnes321's evidence, it is quite clear that David Tombe is attempting to promote what can only be described as crackpot physics on Wikipedia. Even terms like 'fringe' and 'alternative', which suggest some, albeit small, body of support, do not properly describe the science that he is trying to push. — Preceding unsigned comment added by Martin Hogbin (talk • contribs)

Response to Brews ohare - Problems with Editor Martin Hogbin

As you will see from the examples quoted by Brews I have not attacked him personally but I have attacked his scientific misunderstandings.

Regarding some of my deletions, they are all regarding subjects that had been previously discussed at length with Brews. — Preceding unsigned comment added by Martin Hogbin (talk • contribs)

Comments from Sbyrnes321

David Tombe is impossible to deal with in physics articles under normal wiki rules

There are plenty of fringe POV pushers on wikipedia, and it's not normally a problem. They are reverted and ignored, and eventually blocked. However, this is proven to not work for David. In article after article, editors initially try to revert/ignore him, but he nevertheless sucks them into substantive arguments that go on and on. How? For example, when someone shows him a source that contradicts what he says, he disputes the interpretation or validity of the source, rewords his claim, or finds different sources which he can claim (incorrectly) to be supporting his point of view. The only way to respond is to argue about the details of what the sources are saying, what the symbols and terminology means, etc.

Here is an example. Note how editors try many times to end the argument by invoking WP:OR and WP:RS, but that David deflects it every time and successfully keeps the argument going.

Moreover, David has the time and energy to outlast almost any editor in an argument, and is smart enough to not overtly break rules like 3RR or AGF. (At least, not too often.)

He is an unusual case where all the wikipedia rules and procedures fail. Even after a year and a half of editing, numerous administrator noticeboard incidents, and even a permanent ban that was successfully appealed, he's still here and he's still wasting people's time with his fringe opinions--in this case, that the definition of the "metre" adopted by BIPM in 1983 (and used for precision measurements every day) is in fact a vacuous and impossible definition.

I believe the only good solution is to ban David from editing any physics-related article on wikipedia. — Preceding unsigned comment added by Sbyrnes321 (talk • contribs)

Comments from LouScheffer

Brews Ohare is unwilling to follow normal scientific conventions

Of course, re-examining fundamentals is his right, but an encyclopedia article is not the right place to do this. For example, in physics, it is normal to say that "such-and-such happens in a vacuum". It is understood this this refers to a hypothetical perfect vacuum whose characteristics depend on the exact experiment to be performed, and that if something is measured in a physically real and hence imperfect vacuum, the results may need to be corrected. This is understood to the point where NIST, the champion of 16 digit measurements, does not even specify this: "The metre is the length of the path travelled by light in vacuum during a time interval of 1⁄299 792 458 of a second.". But see [8] for an example of Brews replacing the word vacuum in this simple and unambiguous definition by free space, where is not needed, technically incorrect (I believe NIST really means vacuum, as it physically exists - they are not prone to careless statements), less familiar to a casual reader, and a distraction to boot. It's even less needed, and more of a distraction, in the lead paragraph of the speed of light article to which it's only peripherally related - see the edit in the first section above. — Preceding unsigned comment added by LouScheffer (talk • contribs)

The use of a link to free space as in [[Free space|vacuum]] is, I think an extremely minor one, especially as free space is not a misdirection, but a link to the article that presents 'vacuum' in the sense of 'classical vacuum', which is the meaning demanded by electromagnetism. Brews ohare (talk) 04:52, 14 September 2009 (UTC)

It should be said that theres a lot of talk page discussion about this one: an RFC in February 2009 and more in July 2009 [9] [10]. It's true also that free space presents 'vacuum' in the sense of 'classical vacuum', but it's important to note that it doesn't present free space in that way (two refs removed for clarity):

Today, however, the classical concept of vacuum as a simple void is replaced by the quantum vacuum, separating "free space" still further from the real vacuum – quantum vacuum or the vacuum state is not empty.

No need to guess who added that sentence to free space: Brews ohare, of course, a major contributor there. One has to wonder why there is a (relatively) long section entitle "What is the vacuum?" in an article entitled "Free space": in fact, the section doesn't seem to come up with any conclusion to the question. It seems to imply that "free space" is different from "quantum vacuum", but admits that "the meaning of the quantum vacuum state is not settled."

I removed a couple of references from the quotation above because reference sections on talk pages are a bit unwieldy. The first was a footnote containing references to the classical meaning of "free space" (why is this discussion in a footnote?); the second is to a book devoted the quantum vacuum. While I realise that I'll be trying readers patience here, it is worthwhile quoting the first paragraph of that book (the link Brews gave in the reference is to page one, after all):

During the development of quantum field theory, it has become a popular point of view to consider the quantum vacuum as a medium. The manifold phenomena which arise from the presence (or the provoked absence) of virtual particles in the vacuum, such as the Lamb shift or the Casimir effect, tempt one to assign real properties to the vacuum. On the other hand, a physicist can hardly accept an establishment of this kind of "modern ether" without reservations; it is, at least, unsatisfactory to formulate a fundamental theory with the aid of some ingredients which elude direct measurement.

(italics as in the original) Physchim62 (talk) 10:38, 14 September 2009 (UTC)

Physchim62: This whole matter is discussed at length on the Talk page of this article. Your confusions about the various kinds of 'vacuum' are discussed thoroughly in the article free space, which would set you straight on various confusions you exhibit. Brews ohare (talk) 13:57, 14 September 2009 (UTC)

Physchim62, Regarding the quote immediately above, isn't that a terrible dilemma for the scientific establishment? Quantum mechanics wants to bring back something like the ether, but that can hardly be accepted. David Tombe (talk) 12:26, 14 September 2009 (UTC)

Brew's Ohare is unwilling to compromise

This is an on-going problem. The best example is his insistence on free space instead of vacuum. Of course, it's normal for each editor to have issues with the viewpoints of others, and every editor is not quite happy with the way concensus editing turns out. But eventually most editors realize that their voice is only one of many, and that compromise is required. Brews does not seem willing to accept a version that does not emphasize his particular concerns. Surely 'vacuum' is surely more familiar to the general reader than 'free space', and so better by Wikipedia policy. It's also technically acceptable to even the most fanatical accuracy buffs (and since the NIST definition uses the word vacuum, it's technically more accurate as well, certainly in the definition of the meter). As far as I can tell, all other editors seem to thinks it's OK as well. But it's not acceptable to Brews, so free space goes back into the lead paragraph of speed of light and metre. This lack of willingness to compromise makes achieving a concensus essentially impossible. — Preceding unsigned comment added by LouScheffer (talk • contribs)

This matter is blown out of all proportion. On the Talk page I have supported Abtract and Dicklyon in versions of the lead that seem to me to be less a violation of WP:Astonish, and these two editors have marshaled some support for their version. To my mind that is cooperation, even if Lou doesn't happen to share this enthusiasm for this form of the lead. It certainly is no basis for a hearing like that underway here. Brews ohare (talk) 04:56, 14 September 2009 (UTC)

That minor point of "cooperation" can hardly counter the kind of persistent behaviour that Lou is referring to; and frankly, I suspect the proposals we made would have had a better chance without your support, since most editors have come to regard anything you try to do as worth resisting. Dicklyon (talk) 06:12, 14 September 2009 (UTC)

Dicklyon: Lou has not provided any evidence for "persistent behavior", and this remark of yours is nothing more than slander & slur. Brews ohare (talk) 13:51, 14 September 2009 (UTC)

Proposal to bring this hearing to a swift conclusion

This arbitration hearing is being abused by editors who want to widen the scope beyond the agreed terms, and by editors who are only interested in personal revenge and making unsubstantiated allegations which are irrelevant, and which amount to nothing other than noise. I would like to focus the attention of the arbitrators on what the dispute at speed of light is actually about. I made this statement on the talk page at speed of light for the benefit of the arbitrators. I want all the arbitrators to read this statement carefully. It is important for the arbitrators to realize that no physics background is required in order to understand the essentials of this argument.

This prolonged dispute has come about because of attempts to deny an important point that has been raised by Brews ohare. The matter has now gone to arbitration and the arbitrators will now be watching this page carefully. I think that it's only fair to the arbitrators, most of whom are probably not physicists, to make an attempt to explain to them, and eveybody else here, exactly what the distinction is that Brews has brought to our attention.

Everybody, whether a physicist or not, is familiar with the concept of the speed of light. It is the speed that light travels at, and it is generally known to be extremely fast and unreachable by any existing technology. Now let's imagine that I went unto a stage to give a speech on the speed of light. Imagine that I went unto a stage in front of 10,000 people and said that I am going to tell you all what the speed of light is. And then imagine that I stated "The speed of light is the speed of light". And with the speech ending at that, a loud clapping and stamping of feet erupts and lasts for the next twenty minutes. That sounds like a pretty ridiculous scenario. But in fact it is no more ridiculous than if I went unto the stage and stated the speed of light in modern SI units. If I were to go unto the stage and announce the speed of light in modern SI units, I would be stating "The speed of light is 299,792,458 times the distance that light travels in 1/299,792,458 seconds, every second". I could then expect the twenty minute clapping session to be no less sarcastic for me having just stated the obvious.

Brews has pointed out that it is not satisfactory to state the speed of light in modern SI units without some kind of extended elaboration, because the metre itself is defined in terms of the speed of light. Hence any statement of the speed of light in terms of that metre is merely a statement of the speed of light in terms of itself.

Now if we were to already accept the old classical concepts of length, I could go unto the stage and tell the crowd of 10,000 that I had performed an experiment to measure the speed of light using a Michelson interferometer on top of Mount Wilson, California. I could announce, that after performing some difficult calculations that I have found the speed of light to be in the order of 299,792,458 metres per second with an error bar of 0.04%. That would be news worth hearing. I would have given the audience a useful piece of information that had a physical meaning. It is this latter measurememnt that Brews and I have been referring to as the physical speed of light that can be measured. It is clearly a different concept from the defined speed of light that I described further up, and which tells us nothing that we don't know already, and which is beyond measurement.

This edit war came about because Martin Hogbin wanted to only include the new SI speed of light in the introduction. His argument was that since the SI system is the internationally established system of units, then it follows that we must exclusively use that system in the introduction. Martin has of course overlooked the fact that in the special case of the speed of light, where one of the staple SI units has itself been defined in terms of the speed of light, then it is not good enough to state the speed of light exclusively in SI units without any kind of elaboration.

Brews on the other hand wanted to make that elaboration for the benefit of the readers. Martin was determined to frustrate Brews in his efforts. A crowd then descended upon the article and tried to accuse Brews of being wrong, and of advocating fringe views and pseudoscience. These allegations against Brews, and also against myself, will simply not stand up even against the mildest standards of probity. David Tombe (talk) 14:01, 14 September 2009 (UTC)

David,

you could also tell this mythical audience of 10,000 that you had carefully measured the kilometre and arrived at the conclusion that it comes to exactly 1000 metres. Do you understand why this would be laughed out of court?

The speed of light is a measurable and defined quantity, just as the kilometre is. Everyone understands this, except David and Brews.

--Michael C. Price ^talk 15:17, 14 September 2009 (UTC)

A very pointed and useful comment designed to say nothing in an irritating manner. Brews ohare (talk) 19:24, 14 September 2009 (UTC)

True, but at least it was brief! Physchim62 (talk) 21:22, 14 September 2009 (UTC)

Actually it was designed to say a lot, but Brews and David are refusing to address the issue. The speed of light is just like the kilometre, in that it is both a defined and measurable quantity. Yet no one has a problem with the kilometre, why should we have a problem with the speed of light? --Michael C. Price ^talk 22:13, 14 September 2009 (UTC)

And it does say a lot. In fact, it says just about anything and everything that needs to be said about this whole situation. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 22:27, 14 September 2009 (UTC)

What it says is that Michael C. Price & Headbomb share these properties: they both treat this inquiry flippantly, and neither of them understand the speed of light issues. Brews ohare (talk) 23:25, 14 September 2009 (UTC)

Brews, Don't answer them back. The argument above is clear cut. Leave it to the arbitrators. David Tombe (talk) 06:53, 15 September 2009 (UTC)

That's very interesting. Both Brews and David refuse to address the core issue that a quantity can be both measurable and defined. A clearer demonstration of their inabiliity to engage in meaningful substantive dialogue I could not have expected.--Michael C. Price ^talk 07:12, 15 September 2009 (UTC)

I must confess to being confused ... are you saying that the speed of light is measurable in metres per second? and is that same 'metre' the one that is defined as exactly 1/299.. of the distance travelled by light in a second? Abtract (talk) 19:21, 18 September 2009 (UTC)

If I understand correctly, his point is that tying the speed of light and the metre to each other does not remove your ability to compare the speed of light to other speeds or the metre to other lengths in a meaningful way. --Christopher Thomas (talk) 19:56, 18 September 2009 (UTC)

I wonder if that is what they are saying? Abtract (talk) 08:21, 19 September 2009 (UTC)

That's a fairly weak version of what's being said, but it's certainly not incorrect. Purists would object that the metre is tied to the speed of light but the speed of light isn't tied to the metre, but that's a minor point for this discussion. I would add that its not just comparisons between the speed of light and other speeds that are possible, because the speed of light appears in dozens of physical relations: all of these can be compared, using a far wider range of principles than simply "speed equals distance per unit time".

To try to reply to Abtract's question, imagine the experiment that you would do. You want to measure the speed of light very accurately, so you take the best standard for the metre you've got. The "best standard" is a light source, but not all light sources are equally good (this was the problem with the 1960 definition, which tied the metre to a given wavelength of light). So you chose the best light source you have as your standard, and then you measure the speed of light from your second best source: you will have a measured speed of light, with a measurement uncertainty, in metres per second. This sort of experiment is fairly standard in metrology labs, but it's usually call "calibrating the equipment" rather than "determination of the speed of light": the principle is the same, though. Physchim62 (talk) 10:35, 19 September 2009 (UTC)

If I have understood correctly, you are saying that, although we might use light speed experiments, we would not be measuring the speed of light (because the answer has already been defined in SI units), but we would be measuring times and using them to calibrate the equipment. This seems to me to be close to what ohare is saying when he talks about a defined speed of light and a measured one ... but then I am only a humble student. Abtract (talk) 16:55, 19 September 2009 (UTC)

The point is that this doesn't change what can/cannot be measured. Using a yardstick as a distance reference, you'd be measuring the distance light travels in a second in terms of the yardstick's length. With the speed of light set by definition, you're measuring the yardstick's length in terms of the distance light travels in a second. In both cases, the items being compared are the same, and have the same relation to each other. So, several editors (including me) are arguing that this difference in measuring conventions isn't an earth-shattering change. --Christopher Thomas (talk) 19:54, 19 September 2009 (UTC)

It may not have changed what can be measured but you all (including ohare) seem to be saying that the speed of light can no longer be measured in SI metres per second since we already know the answer. This just leaves a difference of emphasis and wording ... surely that can be overcome without all this palaver? Abtract (talk) 20:29, 19 September 2009 (UTC)

On the contrary, metres per second is still the SI unit for velocity. The key concept is that any measurement of the speed of light, is by nature a comparison of the speed of light to something else. We've set the numeric value of the speed of light to an arbitrary exact value, so instead of trying to produce a revised number for it, we'd now explicitly state a ratio ("the distance light travels in one second is x times the length of this other yardstick I'm choosing to use"), whereas previously this comparison was implicit ("the distance light travels in one second is x times the length of this platinum-iridium bar"). In practice, that other yardstick will be the value of some other physical constant that's derived from the speed of light. Experimentally measuring the numeric value of, say, the permittivity of free space would allow more accurate measurement of the other parameters used (the permeability of free space, in this example), since the reference we're comparing distances to can be reproduced more precisely.

While I'm pretty sure most people here agree on these concepts (with the possible exception of Mr. Tombe), the disagreement on a) how important the change in measuring convention is, and b) how to best explain it in the article, seems to be sufficiently passionate as to have bogged down the talk pages of several articles and brought us all here to arbitration. People have been trying to resolve the debate by discussion for many months, and it doesn't seem to be working. The premise behind the ArbCom case and the AN/I threads, if I understand correctly, is that the reason discussion isn't working is that various editors (nobody agrees on who) are behaving in a disruptive or tendentious or otherwise-uncivil manner. After the ArbCom decides how each of the participants should change their behaviour, the discussion would hopefully resume in a more constructive direction. --Christopher Thomas (talk) 21:07, 19 September 2009 (UTC)

[outdent] I'd agree with pretty much everything Mr. Thomas says above. I'd add that I believe (maybe others don't) that you can still measure the speed of light in metres per second, so long as you take "metre" to mean "the best metre you've got available", something which is implied in any measurement. It would be a pretty pointless experiment, unless you're using it to teach people how to use the equipment or testing new equipment, but you could still do if you had a reason to do so. So no, I don't believe there's a difference between a "measured" speed of light and a "defined" speed of light, at least not in the case we're discussing. Physchim62 (talk) 21:31, 19 September 2009 (UTC)

But how can you measure the speed of light in SI m/s? Abtract (talk) 21:37, 19 September 2009 (UTC)

What do you mean by "measure the speed of light", if not comparing its speed, or the distance it travels in a given time, to some other value (or some other physical yardstick for distance)? If it exists in isolation, the choice of numeric value I give to it is pretty arbitrary. --Christopher Thomas (talk) 21:45, 19 September 2009 (UTC)

An example that may help: I'm attempting to determine the distance light travels in a second, in terms of the length of a particular metal rod I've stored in France. To perform this measurement, I'd set up a caesium-133 maser, and use interferometry to measure how many wavelengths (or fractions of wavelengths) long the bar is (call this x). I know that this source oscillates at exactly 9,192,631,770 cycles per second (it's used to define the second). This means that if the rod is x wavelengths long, it takes light exactly x/9,192,631,770 seconds to propagate down it. The number of rod-lengths light travels in one second is therefore the inverse of this: 9,192,631,770/x, where x is my measurement of how many wavelengths long the rod is.

By convention, we choose a "rod length" (the metre) defined as the distance light travels in exactly 1/299,792,458 of a second, or equivalently to be exactly 9,192,631,770/299,792,458 wavelengths of the microwaves emitted by the caesium maser we're using as a time reference. The choice of rod length is arbitrary, but we're still able to experimentally compare it to the distance light travels in one second. --Christopher Thomas (talk) 22:00, 19 September 2009 (UTC)

My experiment would be similar, but I would take a light source of very accurately known frequency (something like this; it might be a bit impractical to go quite so precise, but that doesn't alter the argument). I would then take a second light source, and measure it's wavelength in terms of the wavelength of the first light source (expressed in metres using the SI definition). Then I measure the frequency of the second light source against a caesium masar: c = fλ. So far, I don't think I've said anything controversial.

But am I measuring the speed of light in SI metres per second? I would say that I am. My first light source (the one with very accurately known frequency) is the best metre standard I have. It may well be equivalent to the best metre standards that anyone has. Insofar as I'm making measurements, it is the metre. Come to think of it, my caesium masar isn't at 0 K and the caesium atoms aren't at rest, so my time standard is only "as near as I can get" to the second, and there it really is as near as anyone can get).

In metrological terms, I'm talking about the difference between the definition of a unit and its realization. The definition is exact, well, by definition: the realization is the nearest we can get to the definition in practice, and so has a measurement uncertainty. That is true for all units of measurement, and always has been: there's nothing special about the metre or the speed of light or the change in definition in 1983. Physchim62 (talk) 22:29, 19 September 2009 (UTC)

Simplifying it, I think you are both saying that we use our best experiment to produce a measuring stick of length equal to the distance travelled by light in 1/299,792,458 of a second and we call that length 1 metre. Putting it another way, if we call the speed of light "c" m/s, then 1 m = (1 second's worth of c)/299,792,458. We then use our new (different) experiment to measure the speed of light in terms of that measuring stick and we get (say) 299,792,457 m/s (we might even go so far as to calculate an error factor of, say, +/- 10 m/s). My point is that, although our second experiment may be one that superficially measures the speed of light, what it is actually measuring is the distanced travelled by light in a period of time, say 1/299,792,458 second, and comparing this with the standard defined metre arrived at with our first more accurate experiment. Calculations then give either the inaccuracies built into the second experiment (1- 299,792,457/299,792,458) which would be a useful calibration number, or the speed of light 299,792,457 m/s which would add nothing to the sum total of human knowledge since we already know that the speed of light is actually 299,792,458 m/s ... after all, we defined the metre such that it is so!

Naturally "c" is measurable but it seems clear to me that it is not measurable in SI units because this sets up a circular arguement ... it should surprise no-one that, when experiments to measure the speed of light are carried out, the results are pretty close to 299,792,458 m/s. All we really prove when we use SI units to measure c is that 'some number very close to 299,792,458' ≈ 299,792,458 ... or 1=1. We could, of course, measure the speed of light using any units that do not set up this circular arguement. I believe this is at least part of the difficulty ohare has with some of the wording in the article; I know it has caused me difficulty on occasions. Abtract (talk) 00:01, 20 September 2009 (UTC)

Apparently I'm not phrasing my main point properly, as your response sidesteps it. Measurements are intrinsically relative - comparing one thing to another. Under the old system, we'd be improving our estimate of how many rod-lengths light travels in one second. Under the new system, we're improving our estimate of how many light-seconds long the rod is. In both cases, we learn something. All we're changing is which is the dependent variable and which is the independent variable. To put it another way, rather than measuring the speed of light using physical objects as yardsticks, we're now measuring the physical objects using light as the yardstick. The actual experiments being performed are the same, and the information they tell us is the same. It's purely a nomenclature difference. The "metre" is a specific division of a light-second used to make the numbers easier to work with. We could just as easily have used nano-light-seconds. Consider "metre" a funny prefix that's shorthand for "1/299792458", in this context. --Christopher Thomas (talk) 00:32, 20 September 2009 (UTC)

The speed of light when expressed in SI units is a fixed number. Hence the speed of light cannot be measured in SI units. The speed of light, when expressed in SI units is a tautology that tells us absolutely nothing about the actual physical speed of light. That is why it is unsatisfactory to introduce an article about the speed of light by stating the speed of light in SI units. If I stood up on a stage in front of a crowd of 10,000 people and then stated that light travels 299,792,458 times the distance that light travels in 1/299,792,458 seconds, every second, I would expect a short silence followed by a loud and prolonged sarcastic clapping, with whistles and stamping of feet, due to the fact that I had just stated the obvious.

This entire argument has arisen from the confusion that has been caused by attempting to describe a standard in terms of itself. The argument has never had anything to do with pushing fringe science or original research. And since it is a relatively new state of affairs dating back only to 1983, the full repercussions have probably not as yet been addressed in the scientific literature. Sources do however exist that have brought the matter to attention, and Brews has supplied some of those sources. Charvest produced another source a few days ago. David Tombe (talk) 09:29, 20 September 2009 (UTC)

I find it profoundly sad that, while myself and Christopher Thomas have tried to address the questions raised by Abtract, you choose to act as if the preceding kilobytes of text didn't exist and come in with a restatement of your views as expressed in almost exactly the same terms at the top of this section. You don't give any clues as to what this "actual physical speed of light" might be, except that it can't be the one used in the definition of the metre because you say they're different. Nor do you give us any idea what the "full repercussions" of the redefinition of the metre might be.

I'll point out, more for the benefit of other readers as you're already quite aware of the fact, that a conventional value for the speed of light was fixed in 1975, the same value that is used to define the metre since 1983. That's 34 years of having a fixed value (of one form or another) for the speed of light in SI units, and the sky has yet to fall on our heads… Physchim62 (talk) 10:36, 20 September 2009 (UTC)

Clarify this situation for me

I need a bit of clarification about the core dispute. I am familiar with electronics and their accompanying physics, and also possess a modest undergraduate level education in physics. I understand phenomena and mathematics as complex as electromagnetic wave propogation, counting for factors such as ambient noise, terrain, and so forth. Additionally, I also have a solid education in philosophy, including a comprehension of the philosophy of science.

I understand this dispute as centered on:

• The redefinition of the meter in terms of the speed of light.
• The practical impact of this redefinition.
• The philosophical impact of this redefinition.
• The degree to which these impacts are intertwined.
• The tone, presentation, and depth with which the above points should be covered in articles, especially "speed of light".

Is that a correct understanding of the main disagreement?

Secondary points of disagreement, in my grasp of the situation:

• How this change has affected the teaching and understanding of physics.
• How this change affects the nature of previous experiments and formulae.
• How the effect on the teaching and understanding of physics, especially in relation to previous experiments and resulted mathematical statements, should be presented (if at all) in articles, especially in "speed of light".

What I understand of the topic:

• The redefinition changed the principal quality of the speed of light from a measured quantity to a defined quantity notable as a conversation factor between measurements of time and space.
• The speed of light is universally regarded as a constant, outside of the far fringes.
• The unification of the measurements of time and space is considered one of the most notable and imporant factors of the change.

In one to two modest paragraphs, please tell me if my understanding of the main content dispute is correct and explain the following to me:

• What is the mainline opinion of the change and its importance in relevant literature?
• My first and second points under "What I understand of the topic" have been raised by both sides, and in my understanding both points are true and easily supported in reliable sources. My question here is what is the effect of the two combined?
  • How does being a constant affect it as a conversion factor?
  • Does being a conversion factor affect it as a constant?
• Am I missing an important point or overlooking anything?

Please avoid responding to each other at this juncture. I am looking for individual responses to my questions and general points. Please refrain from making comments about other editors. Off-topic, inflammatory, and overly long responses may be removed without prior warning. I am attempting to ensure that I understand what is under dispute and what people are saying about the matter. Vassyana (talk) 16:42, 16 September 2009 (UTC)

• Thank you to everyone for responding. I do agree with those that mention that behavioral issues are what needs to be addressed here, and indeed it is the fundamental focus of arbitration cases. It is helpful for me as an arb to understand the context in which the dispute is taking place. The responses helped me better understand the participants and the nuances of the disagreement. Thank you again. Vassyana (talk) 22:18, 19 September 2009 (UTC)

Comments by Christopher Thomas

This appears to accurately describe the core of the dispute at speed of light, from what I can tell as a WT:PHYS lurker. The main problem isn't that the dispute is occurring, but that the dispute is spectacularly disruptive to the normal editing of speed of light, and made WT:PHYS nigh-unusable when it spilled over there (hard to look for other changes when 95% of the edits are for these threads). Regarding specific points you raised, a couple of notes:

• The definition of the metre in terms of wavelengths of light, and of the second in terms of oscillations of light (equivalent to propagation time over a fixed number of wavelengths), is moot point if and only if the speed of light truly is constant. There's significant speculation that it may have changed in the early universe. This is considered an unorthodox proposal, but it does get press (someone claimed to have measured a change in the fine-structure constant, a derived unit, over long periods of time using astronomical data). If this occurred, then the definition only works for times near the present. In practice, this isn't a serious problem (if it's shown to vary over time, the change will be factored in as a parameter in equations when discussing distances in the early universe).
• Regarding scope of the dispute, at least one of the editors involved has caused a disruptive thread at WT:PHYS ([[11]]) on a related topic (the relationship between the speed of light, the magnetic permeability of free space, and the electric permittivity of free space). Problems may or may not have occurred at Talk:History_of_centrifugal_and_centripetal_forces as well (looked like a high-traffic thread with lots of arguing, but participants are the ones to ask about whether it was disruptive). If any of the editors involved in the speed of light case are found to be persistently disruptive, I'd suggest extending the scope of the case to deal with disruptive behavior elsewhere in addition to that involving speed of light alone.

I hope that these comments are useful to you. --Christopher Thomas (talk) 17:20, 16 September 2009 (UTC)

Comments by Physchim62

To address your first set of points:

• There is no dispute that the definition of the metre changed in 1983. I don't think there's much dispute that the change had little, if any, practical effect outside the world of metrology, that is the determination of "physical constants" to the highest precision possible.
• For me, the dispute is (almost) entirely philosophical. The speed of light seems to have a grip on peoples' hearts in a way that something like, say, the vacuum permeability doesn't. The vacuum permeability has been fixed in exactly the same way as the speed of light, but since the early 20th century. It caused so little disruption that I can't find a consistent date for the decision to fix the damn thing! (1901 or 1905 are the two that come out tops so far)
• Because there is a philosophical difference as to the nature of the change, there is a huge disagreement as to how it should be presented: views among parties to this dispute seem to vary between the "not important in the slightest" to the "fundamental to all of physics" (both of those are probably slight exaggerations, but not by much). Paraphrasing once again, editors can argue from the "it could be any value, so what if they've just chosen that one" to the "how can we have an article about a physical constant without quoting its value?" Physchim62 (talk) 18:24, 16 September 2009 (UTC)

To address your other points:

• As Count Iblis, quoting John Baez, mentions below there is a certain amount of philosophical discussion as to the "the true meaning of terms like 'fundamental constant', 'physical constant' and 'dimensions' […] " Without wanting to be too flippant, I would add that there has been centuries of philosophical discussion as to the true meaning of the term 'true meaning'!
• The International System of Units (SI) tries to get round this by defining itself as a "practical system of units of measurement" (International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), p. 108, ISBN 92-822-2213-6, archived (PDF) from the original on 2021-06-04, retrieved 2021-12-16, p 16 of the PDF file), with (IMHO) only limited "practical" success. To quote an official IUPAP publication: "The subject is a very pragmatic one: use is always made of the best measure available."
• Nevertheless, there is no mainstream dispute about whether or not we should define practical units of measurement in terms of the sort of physical constants that you get taught about in high school. There is even a queue of such units to be redefined, as this NIST press release indicates. Nothing will happen until 2011 at the earliest, and the kilogram will come first (refs on request, they seem to have disappeared from the corresponding articles), but, all the same, the remaining discussions are ones of details, not principle.
• There may be a discussion as to what constitutes a "fundamental physical constant", but the mainstream view is that they are more than mere conversion factors. For an example, see the diagrams on pages 67 & 68 (from the linked PDF file) of Template:CODATA2006 The diagrams show values of the fine structure constant and the Planck constant implied by different types of experiment, that is experiments relying on different physical relationships. If the assumptions are wrong (ie, the theory is wrong), the many different equations of physics will no longer add up; these diagrams are a graphical expression of how well our current physical theories (or, at least, the ones that have been used) tie in with experiment. The defined value of the speed of light enters into the relations for most (if not all, I haven't checked all of them) of the experiments referred to in those diagrams. Physchim62 (talk) 12:34, 17 September 2009 (UTC)

Comments by User:Count Iblis

I agree with Christopher Thomas and Physchim62 that these points are more or less the core of the dispute as it is debated in the speed of light talk page. Now, you mention "The philosophical impact of this redefinition", but I would say (in agreement with what Physchim62 writes) that while within the physics community there exists a philosphical debate about constants in general, there is no such debate specifically about the 1983 redefinition of the metre. Physicist and wiki contributor John Baez writes here that:

I think the true meaning of terms like "fundamental constant", "physical constant" and "dimensions" is a serious philosophical problem on which there's no consensus.

Then, I think, one has to step away from the 1983 redefinition of the metre and instead look at how the status of the speed of light is debated in the physics community. One can e.g. look at this article, or this article to see that there is indeed a debate going on in the physics community, reputable physicits have different opinions on this matter. It is possible i.m.o to reframe the debate on the speed of light talk page in terms of the analogous debate that does exist in the physics community (e.g. replace 1983 definition by putting c = 1) and then you can end up with some text that is acceptable for the article. Count Iblis (talk) 18:33, 16 September 2009 (UTC)

You had my hopes up: I thought maybe you had a "in the wild" example of this dispute. However, those sources are debating entirely unrelated points. They're debating how many fundamental units there are, and which should be considered fundamental. None of them are suggesting that the speed of light has been rendered unmeasurable in SI units. They're talking about considering c as a fundamental unit by which all velocity could be measured as a fraction of. Interestingly, a meter is a fraction of the speed of light. None of these people have any problem with expressing velocity in terms of c. None of them claim that such "tautologies" as c=1 are different from the "real, physical" speed of light. In fact, they say exactly the opposite. Cool Hand Luke 04:16, 20 September 2009 (UTC)

The question of whether to call the speed of light a fundamental physical constant, which has been a subject of some dispute in the article but not the main event, is a matter of differing definitions. As explained in Physical constant#Dimensionful and dimensionless physical constants, some physicists use fundamental physical constant to refer only to dimensionless physical constants; the speed of light does not satisfy this definition because it can only be stated using dimensional units of measurement: the number length units per (i.e., divided by) a time unit. However, according to another common definition of fundamental physical constant, dimensionful constants like the speed of light and the gravitational constant are fundamental physical constants. Finell (Talk) 05:39, 20 September 2009 (UTC)

Comments by Dicklyon

"Am I missing an important point or overlooking anything?" Yes; I think you're looking at this problem as a content issue, rather than as a behavior issue. I think the only content disputes are:

• how much prominence to give to the hot buttons of certain editors in the lead, and especially in the lead sentence
• whether to state that there are two distinct concepts known as "the speed of light".

There's a pretty good consensus to not do the latter (unless a source that explicitly supports it can be found), and a pretty good consensus to not belabor the philosophical implications of the 1983 redefinition in the lead, and not to add a section on the philosophy of units and constants in general (which keeps getting added, supported by sources that don't really connect the discussion to the topic "speed of light"). But the real problem is the editing style that makes it so difficult to collaborate and approach a consensus, or to respect the consensus that exists. The behavior is a problem in many articles, not just speed of light; we should not address it as just a speed of light issue, as that won't solve it. Dicklyon (talk) 18:41, 16 September 2009 (UTC)

Comments by Steve

My take on content, in three paragraphs:

The meter (since 1983) has been defined as the distance light travels in exactly 1/299792458 seconds. (The second is defined independently, by atomic clocks.) As a consequence, the speed of light in meters per second is exactly 299792458 m/s.

One aspect of these disputes is the general feeling among most editors (including me) that this is a pretty straightforward concept. For example, I believe I gave a complete explanation above, in just two-and-a-half sentences. Brews has the feeling that this is a rather deep, profound, inscrutable concept, needing a lot of explanation and discussion (much more than two-and-a-half sentences). I think much of the conflict has come ultimately from this.

Another aspect: Let's say (for the sake of argument) that the speed of light is half as fast on Saturdays as the rest of the week. Then the meter would be half as long on Saturdays as the rest of the week, because of the definition. Of course it would always be true that the speed of light is exactly 299792458 m/s. Brews takes that idea to say that there are "two speeds of light", one being the physical speed of light (which is different on Saturdays), the other being the number 299792458 m/s (which is the same every day of the week). The second thing isn't really a "speed" in the usual sense of the word, so people like me feel that his attempts to "explain" this point are actually counterproductive and confusing (not to mention unnecessary). Even though he's trying to say something that's true (and obvious), what he actually says comes across as something that's false. So a lot of recent conflict has come from this too. :-) --Steve (talk) 20:05, 16 September 2009 (UTC)

Comments by Brews_ohare

Vassyana: I agree with Dicklyon that the content issue is secondary. However, regarding your questions about the technical issues: Yes, you have a correct understanding of the center of the dispute, the main disagreement, all of which pivots about the SI Units. The secondary points are worth considering, but haven't got much attention. Your understanding of the topic: Point 1 is not correct: Yes, the speed went from measured to defined. The defined value does not connect measured values of time to measured values of space: what it does is institute time-of-transit measurements as a replacement for length measurements. Point 2 is correct, but I do not think it is an issue, despite strange claims by some that I disagree with this point. (I am not in the "far fringe", and I don't know anyone who is.) Point 3 is not correct: the space-time aspects, although they are of interest in themselves, are divorced from the SI Units discussion.

Behavior problems

The problem is behavior. That problem is not restricted to Speed of light. It is due to escalating polarization due to a variety of bad behavior that is easily identified, independent of technical content. That problem, although revealed though the actions of individuals, is fundamentally a problem of keeping the lid on this behavior before it gets out of hand, maybe controllable by administrative action exerted across the board on all participants.

I think the behavior problem is widespread: many editors do not observe four rules: (i) be civil and avoid put-downs, cracks, and derisive asides (ii) be specific, to the point, and helpful in criticism of text, not smart-ass, (iii) don't lecture like an omniscient show-off, and (iv) don't express your personal uncertainties about the text as if they were WP requirements, or vice versa. As to this last, confusion and heat results when a Talk page discussion is called WP:OR or WP:POV, when what is meant is "I don't agree with your explanation." or "I don't think your view agrees with my own." Waving guidelines about is a cowardly method to seemingly invoke higher authority to support your opinion, where instead dialog should be invited.

And then, there are editors that are never wrong. That impedes resolution of problems, because these editors are unmoved by argument or sources, and will resist until death any modification that (in their minds) mortifies them. Any correct description must be sufficiently convoluted to avoid clear distinction from their earlier wrong conception. I hope that strict confinement of comments from such editors to specific statements about specific text and a requirement to deal directly with sources might force these editors to retreat sufficiently to allow some sense to prevail. They must be prevented from launching into distortions, vague generalizations and incivilities.

Technical issue

The technical issue debated on the Talk page is a distinction between two things: the logical status of the number 299 792 458 m/s in the pre- and in the post-1983 definitions of the metre. I am focusing on this number, not the term "speed of light", which is too full of connotations.

The pre-1983 role of this number is the usual everyday idea that it is the approximate value of the speed of light as measured in everybody's notion of that term, just as when you refer to the speed of a car. The pre-1983 metre is a specific length, and light travels at a measured 299 792 458±1.2 m/s (well documented).

The post-1983 meaning of 299 792 458 m/s is different. Post-1983 all distances are defined in terms of times-of-transit (well documented). As an example of a time-of-transit length, if you say your office is ten minutes away, you mean it takes you 10 minutes to walk there. If you say the Sun is 8.3 minutes away, you mean it takes 8.3 minutes for light from the Sun to reach Earth. If you say a metre is exactly 1/500 000 000 s long, you mean it takes light 1/500 000 000 s to travel a metre. If we say a metre is exactly 1/300 000 000 s long, then it takes light 1/300 000 000 s. What we did say is a metre is exactly 1/299 792 458 s. In fact, we can make a metre any number of seconds we like (well documented) - it's only a unit, it isn't nature. But continuity suggests the time-of-transit metre should be close to the original one (well documented).

Of course, if a metre is the distance traveled by light in exactly 1/299 792 458 s, the "speed of light" is exactly 299 792 458 m/s. An exact value is made possible by the change to time-of-transit lengths, but the "exact value" cannot be interpreted as a measurement: it's an arbitrary number set by the BIPM & NIST. Calling this use of 299 792 458 m/s the "speed of light" is tantamount to an additional technical meaning to what is meant by the "speed of light": this new meaning does not refer to the "speed of light" as previously used, as in special relativity say, which is a property of the universe, not a purview of committee.

So, putting the two parts together, here is the difference between the pre- and post-1983 uses of the number 299 792 458: In one, it's an approximate measurement; in the other, it's a committee decision. If Speed of light were calm, there would be no difficulty dealing with this simple well-documented difference. However, at the moment any mention of the topic causes a Pavlovian response. Brews ohare (talk) 21:09, 16 September 2009 (UTC)

Brews, your "Putting the two parts together" is often inappropriate per WP:SYNTH. I don't think anyone has trouble understanding that in 1983 the speed of light expressed in metres per second went from an approximate measurement to a defined value. The claim of this being tantamount to an additional technical meaning to what is meant by the "speed of light" is what would need a WP:RS to be allowed in the article. The lead already says "In 1983, the metre was redefined in the International System of Units (SI) as the distance travelled by light in vacuum in 1⁄299,792,458 of a second. As a result, c is fixed at exactly 299,792,458 metres per second" (maybe this is more detail than we need in the the lead, but it's in there for now at least). And there's a history subsection speed of light#Meter defined in terms of the speed of light. How are these not enough? If there's support in sources for something not said already, let's point it out and put it in; but stop with the idiosyncratic POV of there being two speeds of light. Dicklyon (talk) 17:57, 18 September 2009 (UTC)

Response to Dicklyon: There are two issues here: what you think, and what you think should go into the article. It is difficult for me to understand how you could disagree with the obvious remarks that 299,792,458±1.2 m/s is a measured value, using the pre-1983 units and that 299,792,458 m/s in the post 1983 units is a defined value that could be any arbitrary number, were it not for a consistency requirement (a practical, not a logical matter). I count two (2) meanings. I see no need for additional sources to support that there are these two meanings. I don't see any way that this can be construed as my "idiosyncratic" POV or as WP:SYNTH (two is two). I find my explanation above of what I mean to be crystal clear and understandable by anybody that actually reads it.

I have not requested at any time that this information go into the lead. I have requested that the lead avoid the appearance of the wording: 299,792,458 m/s exactly, in a way that might be misinterpreted. I want to enforce WP:Astonish. If "exactly" is omitted, the issue can be delayed to the later section where detail can be provided. I have no objection to the present version of the lead. I do object to the sub-header Meter defined in terms of the speed of light, which I find puts the cart before the horse. Brews ohare (talk) 19:58, 18 September 2009 (UTC)

Please note: my objection is to the header of the sub-subsection Meter defined in terms of the speed of light, not to the sub-section itself, which I wrote myself. Brews ohare (talk) 01:00, 19 September 2009 (UTC)

Comments by David Tombe

Vassyana, I think that your grasp of the situation is pretty accurate. As regards your questions, I don't know the answer to your first question regarding mainstream opinions about the significance of the change, because I only became aware of the issue in August of this year. The first thing that flashed through my mind when I finally grasped the point that Brews was making, was that this will have a knock-on effect on the measured value of electric permittivity, and so I began to make some investigations. I discovered that the experiment to measure electric permittivity as was described in the 1979 Nelkon & Parker "Advanced Level Physics" texbook that I used as a teacher was absent in pretty well all of the modern physics textbooks in the university science library. On your final question, I would hold the opinion that the physical constant that is associated with special relativity is a separate issue from the constancy that goes with the new defined speed of light, and that the new definition has no bearing one way or another on the issue of the physical constancy of the speed of light that forms a postulate of special relativity.

As regards behavioural issues, the only thing that alarmed me was the total intolerance which I encountered when I raised these issues. David Tombe (talk) 01:12, 17 September 2009 (UTC)

Comments by A. di M.

Just a small point: the view of c as a "conversion factor between measurements of time and space" has been around in theoretical physics long before it was used to define the metre in 1983. Time and space are dimensions of the same spacetime, and, from a theoretical point of view, using the metre to measure lengths and the second to measure distances is no more (and no less) useful than using the nautical mile to measure horizontal distances and the foot to measure heights; and saying that one second equals about 300 million metres makes no less sense than saying that one nautical mile equals about 6076 feet. Also, the fact that it is exact by definition is a separated issue than whether it's a conversion factor: the number of metres in an astronomical unit, or that of atomic mass units in a kilogram, are obviously and unquestionably conversion factors, but they're not exact by definition. According to a particular point of view (with which I happen to agree, although I acknowledge it is not the only legitimate one), the same applied to the number of metres in a second before 1983.

Apart from that, your (Vassyana's) description sounds substantially correct to me. --___A. di M. 12:20, 19 September 2009 (UTC)

Response to A. di M.: It is true that c often is referred to as a "conversion factor" as in the metric of spacetime where distance is dx²−c²dt² so c "converts" time to space. However, that usage of conversion factor is not exactly what is involved in the SI Units definition, where the underlying issue is the replacement of comparisons of measured lengths (for example, interference fringe counts) with comparisons of times-of-transit in seconds. That change is a metrology and units issue, not a basic space-time relationship issue. The change was made because times-of-transit can be measured more accurately than fringes can be counted, so length comparisons are more accurate if they are based upon times-of-transit.

The switch to times-of-transit necessarily involves something that transits, and light seemed to be an obvious choice. The speed of what transits can be selected arbitrarily, as that choice simply determines the unit of length, which is arbitrary, and can be chosen by a committee that weighs the pros and cons of any choice (for example, the cost of conversion to the new units and the ramifications of the switch for other units involving length). Brews ohare (talk) 14:51, 19 September 2009 (UTC)

No, it's not arbitrary; for example, you couldn't choose the time-of-transit of wind, as the wind doesn't always blow at the same speed, so the length of the metre would vary depending on the weather. You need something which always travels at the same speed, such as light. (Any other massless thing would do — and have the same speed, but any massive thing would have a speed which depends on its energy, and it would even depend on the frame of reference one chooses. The only absolute speed is that of massless things, which is the constant c in dx²−c²dt². --___A. di M. 09:41, 20 September 2009 (UTC)

BTW, Vassyana, for some reason I hadn't finished reading your post, including "How does being a constant affect it as a conversion factor? Does being a conversion factor affect it as a constant?" The answer is that light and the structure of spacetime don't give a damn about what we call a metre; but you wouldn't want to use something which can change as a conversion factor. (For example, it appears that the International Prototype Kilogram is becoming heavier, thereby changing the conversion factor between the kilogram and, say, the atomic mass unit; as soon as this was discovered, several alternate definitions for the kilogram in terms of quantities which—we believe—cannot change were proposed, and it seems likely that in 2011 it will be redefined in terms of one of those.

Comments by Headbomb

Measurements are always done by comparing something to another thing. That's the most basic definition of something. For example, a atomic mass unit (u) is defined as 1/12 of the mass of a carbon-12 atom. If you want to know how much an atom of Iron-23 weights, you compare yourself to a carbon-12 atom, and you end up with something close to 23 u. Now what happens if you were to express the mass of an atom of carbon-12 in atomic mass units? Well the atomic mass unit is defined as being exactly 1/12 of the mass of a carbon-12 atom. Therefore, carbon-12 weighs 12 u, by definition. Is this a tautology? Yes! Is this a problem? No! It's simply the definition of your unit system.

For the speed of light, it is the exact same thing. The core of this issue is that the "units of speed" are usually presented as "distance/time", because that's how are human brains are wired. But how we like to present things is not important here, the only thing that is important is that there are three quantities, linked by definition of what they are. Speed = distance / time. The choice of the speed of light is particularly well-suited for this because it is constant in all inertial referential, meaning you can go to point A and to point B, and you don't have to worry that something changed from going from A to B. Since you know c doesn't change, it's the perfect standard. Whatever you do must give a value of 299,... to c. If you don't get c, then you calibrate your instruments so it gives c. If you build an experiment, say you place a detector at 20 meters (measured with a measuring tape) away from your light source, and you measure the time it takes for a light pulse to go from the source to your detector, and you take the ratio of 20 by the time it took, and you do not get exactly 299... as an answer, it means that the meters of your tape are somewhat off, or that the seconds of your timer are somewhat off. So no, you cannot ever measure the speed of light in SI units. But you do not need to, just like you cannot ever measure the mass of "The Kilogram" in SI units. It's not a problem for the kilogram, and it's not anymore a problem for the speed of light.

Now concerning the whole "time of transit" thing. Suppose I have a stick and I want to know how long that stick is. What I do is take a pulse of light, let it go for one second, and see where it's at. If the pulse of light is halfway through my stick, then I know my stick is twice as long as 299... meters. It needs to be clear that here I was not' comparing transit times, I was comparing distances. However, knowing that c is both fixed by royal decree and does not physically change depending on where you are, you can compare transit times if you want, and it will be mathematically equivalent to comparing distances, but it is not the same act.

Concerning the "conversion factor"/"fundamental constant". It is true that c is a conversation factor (it relates length and time), much like all the other fundamental constants such as the Planck constant (which relates energy and frequency), the Boltzmann constant (which relates energy and temperature), Gravitational constant (relates force, mass, and distance) and so on, are conversion factors. If it relates two different concepts, it's a dimensional fundamental constant. If it's a pure number (like the fine-structure constant, or the Fermi constant), then it's a dimensionless fundamental constant. Usage is very loose when it comes to the term "fundamental", some people say that the dimensionless constants are the only fundamental constants because they focus on the numerical value, others say the dimensional ones are fundamental as well because they focus on the link they make. The article follows the second use of "fundamental" (aka fundamental because it links two concepts, space and time). This distinguishes them from the other physical constants which no one would call fundamental, such as the index of refraction of glass being ~1.54, or the ionization energy of hydrogen being 13.6 electronvolts.

I hope this answers questions. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 07:34, 20 September 2009 (UTC)

Well, actually the NIST does refer to the "Rydberg constant times hc in eV" as a fundamental constant, as well as even weirder ones such as the lattice parameter of silicon or the unified atomic mass unit (whatever they mean by "fundamental"). --___A. di M. 10:17, 20 September 2009 (UTC)

Luke's notes for later use

• Wikipedia is not a debate clinic.[12]
• Edit count statistics can be misleading. Prefer counts of reverts or comments, but would be harder to make...
• Aug vote.[13]
• Motivated by fringe?[14][15] No direct advocacy of fringe views though.
• Cool Hand Luke 03:58, 20 September 2009 (UTC)