Talk:Metre/Archive 4

Ooops!
Looking back at the sources, I think I'm wrong in my assertion that Méchain and Delambre formally measured the Paris meridian! This plate from the official report of the survey (written by Delambre, Méchain having died "in service", and published in 1806) indicates that the calculations were made for the Dunkerque meridian. In particular, the meridian is shown going east of the Panthéon, which itself is to the east of the Paris Observatory. I've only flicked through the earlier sections, but Delambre does complain that many of the landmarks he would have liked to have used as reference points in the Paris area had been destroyed during the Revolution, so maybe that is one explanation for the difference. Of course, it is also mathematically simpler to choose one of the end points as the fixed point of the "verified meridian". Physchim62 (talk) 15:22, 22 October 2010 (UTC)
 * I picked up a copy of Alder's book today. I don't think there's any doubt that the intent was to measure the Paris meridian. There had been other measurements of that meridian before. According to Alder, Delambre set out to find the points from which Cesar Cassini had made his measurements 50 years earlier. He discovered that some of the towers Cassini had used had been demolished, some were unsafe to climb, and some were no longer useful because the trees had grown in and obscured the horizon. Thus his complaint. More later after I've had a chance to read the book. -- BPMullins | Talk 03:44, 23 October 2010 (UTC)
 * ... so did they just multiply by the cosine of the angle to true north for each section? Technically, this would give a very slight over-estimation because of the oblateness of the earth, but the difference would be much smaller than the measurement errors.    D b f i r s   07:05, 23 October 2010 (UTC)
 * The oblateness was exactly what they were trying to measure, so no, the difference wasn't smaller than the measurement errors! It's not quite as simple as multiplying by the cosine, because you're dealing with spheroidal geometry, but the principle is the same: a triangle with all three angles and one of its sides known, calculating the length of another of the sides. Physchim62 (talk) 11:32, 23 October 2010 (UTC)
 * I thought it was just the length of the meridian that was being measured. For the short lengths of line-of-sight, spheroidal trigonometry coincides with Euclidean trigonometry to a better accuracy than their measurements.  Was the length of the equator already known?    D b f i r s   12:47, 23 October 2010 (UTC)
 * ... (later) Ah, I see that Pierre Louis Maupertuis had already established the oblateness by measuring a degree along a meridian in Lapland in 1736.    D b f i r s   13:05, 23 October 2010 (UTC)
 * Yes, the oblateness of the Earth was well known and accepted by the time of Méchain and Delambre; their expedition was to find a more precise value for the flattening (oblateness). Once they had a value for the flattening, the calculation of the length of the meridian was trivial. Imagine it this way: You have a huge triangle from Dunkerque (D) to Barcelona (B) to some point in the Mediterranean (M) at the latitude of Barcelona and the longitude of Dunkerque. The angle at M is obviously 90°. The length of the side DB and the angles at D and B are what were found in the survey (according to the diagrams, at least). That large triangle cannot fit on the surface of a sphere – the angles are wrong. So you need to find the oblate spheroid which will accomodate the triangle DBM. Once you've done that, it is 'simple' spheroidal geometry to find the length DM, which is the meridian arc. Because you know the latitudes of Dunkerque and Barcelona (trivial compared to the other measurements), you know the length of the whole meridian.
 * To answer a related point above, I've had a closer look at the original report, and Delambre was aware that the Earth might not be perfectly spheroidal, that is that, maybe, not all meridians were the same length. He bases this on several previous surveys, particularly the survey of the Mason–Dixon line which, being east–west would show any effect the greatest. He concluded in the report (but without formal proof) that any east–west variation in their survey would be negligible. Physchim62 (talk) 18:02, 23 October 2010 (UTC)
 * Yes, I see. This methodology should have given a more accurate result for the total meridian.  Was the error in the fitting of the spheroid, or in the calculation of the distance?  I haven't checked this mathematically, but, intuitively, I think there are many possible spheroids (but only one ellipsoid) that satisfy your triangle.  Did they choose a spheroid that was not sufficiently oblate at the poles?    D b f i r s   01:00, 24 October 2010 (UTC)

I just noticed something that seems totally wrong: The meter/metre is nowhere near 1 ten-millionth, but 1 ten-thousandth of the distance polar-equator! That's what I learned in school, that's what you can find in other Wikipedia articles - e.g. the one giving the dimensions of Earth. In fact equivalently 40 mio. m (the supposed circumsphere of earth according to this article) is in fact almost one third of the earth-sun distance!!! I don't want to make a correction, since I have no idea if in the 18th century they actually intended to use the 1 ten-thousandth as the metre, or if they had originally meant to use the 1 ten-millionth, but came up with something as small as the mm and decided to use the 1 ten-thousandth instead. IAM 00:14, 1 January 2012 (UTC) — Preceding unsigned comment added by 69.58.115.9 (talk)
 * I think you are confusing metres and kilometres. 10,000 metres for equator to poll would mean you could walk the distance in a couple of hours. - SimonLyall (talk) 00:51, 1 January 2012 (UTC)


 * You seem to be confusing the meter with the kilometer (km). 10,000 m is just 10 kilometers, less than the length of Manhattan. --Macrakis (talk) 00:49, 1 January 2012 (UTC)
 * Ooops!!! Yes, you're definitely right. I was thinking in terms of km instead of m. IAM 02:55, 2 January 2012 (UTC) — Preceding unsigned comment added by 69.58.115.9 (talk)

Comma after speed-of-light formula
The Speed of light section has this formula

I think that it is c/nf followed by a comma for grammatical reasons, because the text after it refers to f not f-prime. However the way it current displays, a reader might easily read the formula as f-prime.

I suggest that if it is a comma, it be removed. In this instance any advantage in having a correctly punctuation sentence (which starts before, includes, and ends after the formula) is outweighed by the ambiguity of the comma/prime symbol. Of course if it really is f-prime, then the text after the formula probably needs to be changed. Mitch Ames (talk) 06:06, 30 July 2011 (UTC)


 * Good point. I've removed the comma -- it's not necessary to the sentence because the new line serves as a pause, and it's not f-prime.    D b f i r s   21:50, 22 November 2011 (UTC)

Relation of metre to frequency
The article presently contains the statement: "In this way the length is related to one of the most accurate measurements available: frequency." Now it is undeniable that measurement of frequency is accurate, and also that the relation:
 * $$ \lambda = \frac{c}{n f} \ $$

relates wavelength to frequency.

It also is undeniable that a length known to be &nu; wavelengths &lambda; with an accuracy of ±&Delta;&nu; wavelengths has the accuracy actually decreased by the conversion of &lambda; to metres, the decrease being the added error introduced by the uncertainty in measurement of frequency.

Contrariwise, as I read the statement in the article, it seems to suggest that by relating a length to "one of the most accurate measurements available" that somehow this shift has increased the accuracy of the length determination. That would be a misconception easily arrived upon with the present wording.

So how can the accuracy of frequency measurement be entered into the discussion more carefully? Here is a (possibly unnecessary) exposition of what has to go into this discussion.

First, one may note that the accuracy of frequency determination is not fundamental to the new length definition. The switch to the time-of-transit definition made &lambda; irrelevant because the speed of light is not dependent upon wavelength in classical vacuum. Length is related to &Delta;t/c0, which requires no measurement of &lambda; at all, and which makes all colors of light equally useful. This may be clear to all assembled here, but it is not so clear in the article.

I'd guess we'd all agree that frequency enters the discussion of length when one has to use the above &lambda;-f equation. The recourse to frequency using the above &lambda;-f equation is necessitated because the length has been measured as some number of &lambda;'s instead of using time-of-transit, thereby requiring the conversion of &lambda; to metres using this equation.

But, even if one is going to do things this way, and use wavelengths instead of &Delta;t, there is an advantage to the defined-speed-of-light definition nonetheless. The advantage is that one can interrelate different sources by comparing their frequencies rather than their wavelengths, and that is more accurate. That is the role for the accuracy of frequency measurements: it facilitates the choice of sources.

If one wished to digress, one could also point out that comparisons of wavelengths also has improved, compared to the days before 1983, but not to the point that one wishes to go back to wavelength comparisons of sources in place of frequency comparisons.

I hope these ideas can be formulated to make a clearer presentation of the role of frequency in the article. Brews ohare (talk) 17:42, 30 November 2011 (UTC)


 * I have made changes in this direction. Brews ohare (talk) 19:20, 1 December 2011 (UTC)

There seems to be some confusion in the way this section currently reads between the way the metre is currently realised in its most precise realisations and general measurement in metres. Martin Hogbin (talk) 11:57, 3 December 2011 (UTC)

I have reverted the addition of classical vacuum becuse the sources do not use this term, they simply say vacuum. It is not open to us to speculate on what they might have meant. Martin Hogbin (talk) 11:59, 3 December 2011 (UTC)
 * Hi Martin: There really is no doubt whatsoever that what BIPM, NIST and the General Conference on Weights and Measures mean by vacuum. The various electromagnetic properties of vacuum are found on the NIST website, which is linked by BIPM and provides the CODATA results. They are c, c0, ε0, μ0. Of course, you are free to believe that classical vacuum, although it has exactly these electromagnetic properties is only one of a set containing many media, all sharing these identical, defined (not measured) electromagnetic properties. However, I doubt you will find any source that supports the view that there is any distinguishable difference between these ideal media, either experimentally or in principle. The problem in distinguishing between them is that the parameters c, c0, ε0, μ0 completely determine the electromagnetic behavior. Brews ohare (talk) 14:06, 3 December 2011 (UTC)
 * By the way, as pointed out at classical vacuum, the adjective "classical" is added only to clearly distinguish between this reference medium of the SI units with properties c, c0, ε0, μ0 and field-theoretic vacuums such as QCD vacuum. Brews ohare (talk) 14:32, 3 December 2011 (UTC)
 * I think we must assume that if the bodies you mention felt in necessary to distinguish between different kinds of vacuum they would use the appropriate wording in their definitions. Martin Hogbin (talk) 14:37, 3 December 2011 (UTC)
 * Hey, Martin, do you also assume they meant c, c0, ε0, μ0 to apply to their vacuum? If you do, then their vacuum has the same properties as classical vacuum. If you do not assume they meant their vacuum to refer to classical vacuum, then what are they doing linking c, c0, ε0, μ0  to their vacuum on their web sites? Brews ohare (talk) 14:44, 3 December 2011 (UTC)
 * To elaborate, here is a quote: "&epsilon;0= 1/µ0c2 is the electric constant (permitivity of vacuum) and µ0 is the magnetic constant (permeability of vacuum)." Brews ohare (talk) 14:53, 3 December 2011 (UTC)
 * I provided a link to "vacuum" that doesn't use the adjective "classical". It seems to me that this link is useful in directing the reader to the other electromagnetic properties of "vacuum". I hope that constitutes sensible compromise. Brews ohare (talk) 15:21, 3 December 2011 (UTC)
 * That is fine with me. Bear in mind that µ0 etc are just constants that appear in EM equations in certain systems of units. Whether you think of them as 'properties of a vacuum' or not is up to you.  Martin Hogbin (talk) 18:29, 3 December 2011 (UTC)

Nonfunctional NIST links
It appears that NIST has reorganized its web site, and links to NIST in this article are now nonfunctional. Brews ohare (talk) 15:40, 10 December 2011 (UTC)

Link to vacuum
This recent change introduces an inaccuracy into the article by linking "vacuum" to the general topic of vacuum rather than to the specific, technical meaning of "vacuum" appropriate to the article, namely the vacuum of electromagnetism. The metre is defined in terms of the speed of light in the vacuum of electromagnetism, which is a very specific electromagnetic medium with electromagnetic properties defined by NIST and the BIPM as c, c0, μ0 and the subsidiary derived properties with the exact values ε0 and Z0.

In contrast, vacuum as used in ordinary English has a rather more vague meaning, possibly referring to a partial vacuum with imprecise electromagnetic properties that have to be measured. Moreover, "vacuum" as used in scientific circles also is ambiguous, and may very well refer to field-theoretic vacuum, or specifically to QCD vacuum, which vacuums also have electromagnetic properties different (at least in theory) from c, c0 and μ0 due to virtual particles and vacuum fluctuations.

This topic has been discussed at great length with Martin Hogbin on his Talk page here, but he seemingly does not wish to accept that the word "vacuum" as used by standards organizations naturally is in agreement with the properties of this vacuum that they specify on their web sites. The link should be returned to refer to vacuum of electromagnetism. Brews ohare (talk) 17:02, 10 December 2011 (UTC)
 * I disagree. BIPM and NIST just use the term 'vacuum' in relation to the definition of the metre. You may think you know exactly what they mean but that is your OR.  If the standards bodies wanted to specify a type of vacuum they would do so. Martin Hogbin (talk) 12:18, 11 December 2011 (UTC)
 * Martin, you are not paying attention to these links: c, c0, μ0 and the subsidiary derived properties with the exact values ε0 and Z0. They specify the electromagnetic properties of 'vacuum' as employed by BIPM and NIST. If they meant some other 'vacuum', for example partial vacuum or field-theoretical vacuum, I feel confident that you would agree that in such vacuums these electromagnetic properties do not apply. Brews ohare (talk) 13:27, 11 December 2011 (UTC)


 * If more is needed, you can find a discussion of the properties of field-theoretical vacuum and its electromagnetic properties in and more recently in  and also . Of course, partial vacuum such as air has its measured electromagnetic properties as well, expressed in SI units relative to the reference of 'vacuum' with properties c, c0,  μ0 and the subsidiary derived properties with the exact values ε0 and Z0. Brews ohare (talk) 14:32, 11 December 2011 (UTC)
 * I've just restored this, again, for the above reasons and based on the principle of least surprise. If the link is to 'vacuum' and there's an article 'vacuum' that's not a disambiguation page or redirect then just link to vacuum. It's what the user will expect, not to be redirected to some midpoint of the article which already assumes they know the definition and will simply confuse readers. Such piped links make sense if the article does not exist, but there's an appropriate section of an article. But vacuum does exist and it's what users will be expecting when they click on that link.-- JohnBlackburne wordsdeeds 14:43, 11 December 2011 (UTC)
 * John: I am not sure that the "principle of least surprise" is properly applied here. The link vacuum directs the reader to an article primarily concerned with partial vacuum, which is an inaccurate reference. The reader must then be savvy enough to scan the ToC to find vacuum, which I'd suspect will happen only in a minor subset of cases. A different application of "the principle of least surprise" would be to break out the section Vacuum as a separate article, say Vacuum (electromagnetism) and link to that article. That approach might be valuable anyway, as it would separate this very technical use of 'vacuum' from the much broader meaning of partial vacuum that is the main thrust of the article vacuum.
 * John, you have not addressed Martin's unfortunate contention that 'vacuum' as used by the BIPM and NIST is a vague term that may not refer to Vacuum with its specific electromagnetic properties as provided on their websites. If there are many readers inclined in that direction, the link to Vacuum will be of no assistance in focusing them upon the correct interpretation.
 * Are you in favor of letting this matter stand? Brews ohare (talk) 15:39, 11 December 2011 (UTC)
 * Creating a separate article would be going against the recent consensus for a merge. And again, when readers see the word 'vacuum' linked they should be taken to the article that explains the word. Anything else is surprising and confusing. Whether the article at vacuum is the right one is another question which should be raised as a move discussion.-- JohnBlackburne wordsdeeds 15:54, 11 December 2011 (UTC)
 * John, perhaps you could suggest how a "move discussion" might proceed, especially as you have expressed disfavor over creating a separate article for the technical usage of 'vacuum in electromagnetism'.
 * Can you also explain further how the precept applies that: "when readers see the word 'vacuum' linked they should be taken to the article that explains the word". As it is now, when readers click on the link vacuum they are not at all taken to the meaning of the word in the present context of the definition of the metre, but to the irrelevant distraction of partial vacuum.
 * Perhaps you could engage a bit more in this situation, rather than aiming to Cut the Gordian Knot? Brews ohare (talk) 16:05, 11 December 2011 (UTC)
 * I think I have exaggerated somewhat, as the link vacuum also mentions the perfect vacuum as an unobtainable state with zero particles. That still is less satisfactory than a link to the very specific Vacuum that is a very precisely defined reference state with very specific electromagnetic properties used as a baseline. Brews ohare (talk) 16:30, 11 December 2011 (UTC)
 * Brews, I am not contending "that 'vacuum' as used by the BIPM and NIST is a vague term..." I am pointing out that in their definition of the metre they use the unqualified term 'vacuum' so that is what we must do here. If BIPM thought it important to qualify the term 'vacuum' in the standard for the metre then they would do so in the standard.  Martin Hogbin (talk) 16:48, 11 December 2011 (UTC)

←outdent I have resolved this matter by separating the "everyday" meanings of 'vacuum' from the physicists' meanings in two independent paragraphs in the introduction to Vacuum. With the two clearly separated, I believe a link simply to Vacuum is OK.

To Martin: I agree that BIPM and NIST have deliberately not "qualified" their use of the term 'vacuum', I suspect because the historical usage of 'vacuum' in the context of SI units will define it by implication. One might, however, inquire whether a general reader of WP will understand that very specific context without a little guidance. Although it is possibly uncharitable of myself, I do subscribe to the (possibly erroneous) idea that you are resisting changes here less because of the espoused reasons than because you fundamentally wish to avoid any indication that vacuum in the context of SI units refers to Vacuum. If I am mistaken about this, please tell me so. Brews ohare (talk) 17:00, 11 December 2011 (UTC)

If there were any ambiguity in NIST's and BIPM's use of the unqualified term 'vacuum', their use of the term is made crystal clear with their web-site postings of c, c0, μ0 and the subsidiary derived properties with the exact values ε0 and Z0. Do you agree? Brews ohare (talk) 17:12, 11 December 2011 (UTC)
 * However clear you may think it is that BIPM meant something different from that which they wrote I think we must use the actual words they used in the standard.


 * My reasons for this are not so much that I actually disagree with you but that I think you are jumping to conclusions. I am happy to discuss this on my talk page. Martin Hogbin (talk) 21:18, 11 December 2011 (UTC)


 * Apparently our discussion on your Talk page has not proved fruitful. Although I am in accord with using the term 'vacuum' in quoting BIPM definition of the metre, I feel that this term is used by them in a narrow context where they are confident the history of the metre makes their meaning clear. That meaning is less clear to a general reader of WP, which should lead to some elaboration. That elaboration is now presented in the article vacuum instead, so I am satisfied a reader can figure things out. Brews ohare (talk) 16:06, 14 December 2011 (UTC)

Brews latest additions and changes
I am not going to get involved in an edit war but it looks to me as thought Brews is adding his own personal thoughts and opinions to this article (despite the citations). After a long discussion with him I still have no idea what he is getting at but the material added to this article seems to me to serve no encyclopedic purpose. I will leave it to others to argue the point. Martin Hogbin (talk) 10:05, 17 December 2011 (UTC)
 * Just noticed your comment after going through and fixing misplaced Americanisms, a second vacuum link with pointless piping and an inline EL to a badly formatted page of maths and sentences that seemed to be about it (the sentences implied the page was a web calculator but it looked more like a lecture handout to me). The rest of it I was not so sure about: it looks like undue focussing on the details of measurement, on which there already was far more information than most readers need, but I'm not especially familiar with it so did not want to touch it.-- JohnBlackburne wordsdeeds 10:27, 17 December 2011 (UTC)


 * John, your changes to British spellings are OK, I guess: I don't know what they should be. The reference to the NIST calculator as a "lecture handout" is due to a too cursory look at the matter. This link provides the explanation and documentation for the calculator and had you looked at the index on this page, you would have found this link and this link to the calculator, based on either of two nearly identical formulations. This calculator is set up by NIST (whom I hope you won't feel is a flaky organization) to calculate a wavelength in air given the wavelength in vacuum c0/&lambda;. It has value in this article in several ways.
 * First, measurement in air is the most common venue for length measurements in practice, and this calculator is therefore useful to know about.
 * Second, the formulas used in the calculator are referred to an excellent list of sources where the documentation behind the corrections can be found.
 * Third, this is a complete example of how the standard metre can be set up, showing all the steps if one wishes to see them by looking at the NIST calculator.
 * You may have noticed in the original text (see the last paragraph in this section), which is not of my construction, that the standard metre is realized as 1,579,800.298728(39) wavelengths of helium-neon laser light in vacuum. The NIST calculator applies this definition to a realization in air. As noted in a subsequent sentence, also deleted by you, this same procedure can be used in any partial vacuum. It also could be done in argon, for example, but then one has to come up with one's own formulas.
 * I find the deletion of this material to reduce the usefulness and the clarity of the article. Perhaps you would rethink this matter? Brews ohare (talk) 15:57, 17 December 2011 (UTC)


 * I have reordered the paragraphs in this section to place the definition in vacuum first, and then used this with the NIST calculator to relate the result to a metre in air. I've added several references and made the description of the NIST calculator more extensive so a reader can find both the calculator and the documentation and the discussion on the NIST web page easily. Brews ohare (talk) 19:22, 17 December 2011 (UTC)

I have made some fairly minor and, hopefully non-contentious, changes to the 'Speed of light' section but I feel it still contains unnecessary duplication which I would like to remove. Martin Hogbin (talk) 11:41, 23 December 2011 (UTC)

Archived talk page
See the archives to read all about "re" vs. "er" and other topics. --Wtshymanski (talk) 17:38, 31 January 2012 (UTC)

A move of this article to Metro has been proposed
I, Agustín Cordes, propose a move of this article to Metro.


 * 'Metro'? That's not even English. As for the spelling 'meter' see the note at the top of the page.-- JohnBlackburne wordsdeeds 01:44, 26 October 2012 (UTC)


 * The proposal was made by user:2013 asylum from senscape. I wonder if Agustín Cordes wanted a translation into his own language, perhaps Spanish?    D b f i r s   07:02, 26 October 2012 (UTC)

The section "name"
If you want to add material about the concept of a universal measure, that is fine, but it should not be in the section about the name "meter". No connection between Wilkins' book and the name "meter" is given by any source, so it is a clear case of original research to include him. Burattini belongs there because he used the word metro (essentially "meter"), not because he called it cattolico. The word "meter" alone does not imply universality or require it. Alternatively, rename the section somehow. Zerotalk 00:50, 10 January 2013 (UTC)


 * Yes, you are correct that neither Wilkins nor Burattini invented the name, so I've removed the misleading heading and corrected the translation of Burattini's Italian. "Metro" meant "measure", of course, not "metre", at that time.  It's possible that they both wrote in the same language, using Latin "metrum", "measure".  Can we find the original documents?    D b f i r s   08:16, 10 January 2013 (UTC)


 * Thanks for agreeing with me, but I don't agree with you ;). It doesn't change things if "metro" means "measure", since so does "meter". Anyway, Burattini wrote in Italian and there seems no doubt that he was writing a proposed name for a unit of length, not just referring to a measure in some generic sense.  Look how he uses capitals for "Metro Cattolico", a name he says he derives from Greek, compared to lower case for the Italian expression "misura universale":
 * "Dunque li Pendoli saranno la base dell’opera mia, e da quelli cavarò prima il mio Metro Cattolico, cioè misura universale, che così mi pare di nominarla in lingua Greca, e poi da questa cavarò un Peso Cattolico.” (So, Pendula will be the basis of my work, and from them I shall first originate my Catholic Meter, that is the universal measure, as I think I have to name it in Greek, and then I shall originate a Catholic Weight from it.)
 * I took the Italian and English from page 26 of this lovely paper. Zerotalk 14:19, 10 January 2013 (UTC)
 * On the other hand, Wilkins uses the phrase "universal measure" as a concept but does not propose it as the name of his unit of length. He is very clear on that:
 * "Let this Length therefore be called the Standard; let one Tenth of it be called a Foot; one Tenth of a Foot an Inch; one Tenth of an Inch a Line. And so upward, Ten Standards should be a Pearch; Ten Pearches, a Furlong; Ten Furlongs, a Mile; Ten Miles, a League, &c." (Wilkins, p192, italics in the original). So if Wilkins is to appear in the "name" section it should state correctly that he called his unit a "standard". Zerotalk 14:46, 10 January 2013 (UTC)
 * I've added Agnoli and D'Agostini's paper. A small point. Their paper dates Jean Picard's proposal for a universal foot (pied universel), equal to 1/3 of the length of the seconds pendulum, to 1668, which would make his explicit ref to a universal measure contemporaneous with Wilkins's 'standard'.(p.8). Robert Tavernor, Ear: The Measure of Humanity,'' Yale University Press 2007 pp.48-51, puts Picard's 'universal foot' two or three years later. Nishidani (talk) 15:30, 10 January 2013 (UTC)
 * Thanks for the useful cites. There were evidently several proposals for a standard unit of length around that time.  Clearly neither Picard nor Wilkins invented the word "metre".  I think Italian had two different words for measure at that time, "metro" from the Greek and "misura" from the Latin (mēnsūra), and "metro" was subsequently used as the Italian word for the French unit, so Burattini could be considered as the "inventor" of the Italian word now used for the unit (though "metro" meaning measure had been used in Italian from the fourteenth century, just as "metre" had been used in English since Chaucer and earlier for the measure of poetry), but not as the originator of the word "metre" (or "meter") which is from French (who got it from Greek, who got it from an ancient Indo-European word partially preserved in Sanscrit "mā").  I suggest that the full account of the history is appropriate for the article, leaving the etymology for Wiktionary.  Interestingly, but irrelevantly, in 1790, T Jefferson proposed a base-ten system of capacity with a “metre” equal to a thousandth of a bushel.  His proposal wasn’t adopted.    D b f i r s   19:16, 10 January 2013 (UTC)

About that Metre
I think we have another problem with the metre. The December_10 article says France adopted the metre as its standard unit of length in 1799. THIS say it was in 1793. Can someone clarify this, please? Thanks … ! Cuddy2977 (talk) 16:12, 2 December 2014 (UTC)


 * This article is technically correct: the metric system was adopted by the Republican government in 1793 and a provisional metre established. In 1799 a definitive metre was constructed which was to have been constructed from the measurements of Delambre and Mechain. In fact the old data was used! All this is discussed in great detail in the excellent book by Alder (in Further Reading): he gives references to the primary sources and I would accept his account as fairly authoritative. There are several ways in which the 'Meridional' section could be improved and the December_10 page also needs further qualifications. (Apologies for the minor rewording of the previous comment.)  Peter Mercator (talk) 22:10, 2 December 2014 (UTC)

Lead minutiae
I'm loathe to open a talk section about the lead - tinkering with the lead is notoriously attractive but subject to the law of diminishing returns. But we should also avoid corresponding only in edit comments, so I'll address a couple of quick points here.
 * If we're to describe the distance as being measured at sea level, we should attach the descriptive phrase to "distance", much in the same way that we talk about sea-level pressures and the like. We are not talking about "the North Pole at sea level" and if we phrase it that way then the poor reader suffers a jarring moment before they understand what's being described.
 * We should not describe the reasons for the redefinitions as simply "greater precision". There is much more to them and to the development of SI and of metrology in general, such as repeatability, the inter-relationship of SI units and of ISQ quanitities, and philosophical or even cosmological questions. That's why I used the phrase "as metrology has developed".
 * Similiarly, the editorial gloss "something very difficult to measure" sits badly (the correct punctuation, btw, would be a comma). It implies that redefinition was driven by convenience, an implication that should be clearly addressed and sourced in the body of the article before placing it in the lead.

I'll adjust the lead accordingly. NebY (talk) 17:30, 2 May 2015 (UTC)


 * We've been tinkering with the lead again, but I agree about diminishing returns. Perhaps we should discuss changes here first, especially when we are deleting the additions of others?    D b f i r s   11:30, 14 June 2015 (UTC)

Quarter or half meridian?
As the word quarter meridian is sometimes called half meridian, it might be useful to explicitly mention in the article the confusing difference that Meridian (astronomy) is a great circle, whereas Meridian (geography) is a half of that. The article used 'quarter meridian' three times, against 'half meridian' one time, so for consistency I changed that half in quarter. The article is still inconsistent because its wiki link refers to Meridian (geography). There is something else that confuses me. Why did the 18th century scientists define the meter as one ten millionth of a quarter meridian, instead of one hundred millionth of a full meridian? I guess they were aware that the latter is more decimal, and closer to the traditional standard unit, the foot. Ceinturion (talk) 13:05, 10 January 2015 (UTC)
 * Hi, I stumble upon this remark only after correcting the three occurances of meridian in the other direction...
 * My reasoning to use the geographical definition of a meridian was that this is what I found to be used in other articles about the meter (f.e. History of the metre) and also in the other articles on meridians we link to. Further, our linking to Meridian (geography) seems to have caused another editor to incorrectly change the definition of a geographical meridian to the astronomical definition in that article already...
 * Anyway, I fully agree with you that consistency is very important. Therefore, I'm open to the definition being flipped to the astronomical meridian, if a) this is supported by the historical sources, b) we change it in all articles discussing the meridional definition ‎of the meter, and c) we explicitly explain the definition we're using and the fact that different definitions exist in order to avoid any future confusion.
 * --Matthiaspaul (talk) 21:08, 13 October 2015 (UTC)

Picture
Although the image of the two shiny metre bars lying on a red background is pretty, it's a computer-generated image masquerading as a photograph. It's always bothered me because I can't imagine that metre standards were ever tossed around in the careless fashion shown in the image. I see we have a much less pretty photo of (part of) a real metre bar, that also shows the cross-section (perhaps not as well as the pretty fake image). Should we not put the real photo in the top of the article and remove or de-emphasisze the one depicting a metrology disaster? --Wtshymanski (talk) 19:59, 13 August 2014 (UTC)
 * Agreed. --Macrakis (talk) 20:40, 13 August 2014 (UTC)
 * Yes - it's bothered me before but I've never stopped to analyse why. Nicely done. Let's remove the fake completely and use the real one instead, but on this occasion keep the real one in its existing position too, as the caption's informative. Later someone might find a good picture showing the length of a metre that would suit the infobox. NebY (talk) 13:37, 15 August 2014 (UTC)
 * The discussion above suggests that the image was removed, but since it is still in the article, I have removed it now (again?). I agree that a computer-generated image of what is described as historical prime meter is highly misleading. --Matthiaspaul (talk) 21:22, 13 October 2015 (UTC)

Exact location of Méchain's meridional measurement on Montjuïc hill?
See Talk:History of the metre
 * --Matthiaspaul (talk) 01:22, 21 October 2015 (UTC)

Timeline values
I'd like to note that the timeline doesn't have actual values in it, but those might be fairly useful. This might be because those values aren't easily found for all, but for any that can be found, I think they ought to be put in. The first one can be calculated, at least, and would be about 0.993961 modern metres, using the small angle pendulum equation.

192.249.47.163 (talk) 14:32, 1 September 2016 (UTC)Elmshire

Specious and non-NPOV arguments for misspelling the title of this article
It's not established at all that "almost all English speaking countries" spell meter the way this article does. You haven't cited all the proof you would need to establish that, and you can't, because it's not true! Why are we letting a minority impose their regional spellings on en.wiki? Also, when you say "almost all except the United States," you're admitting that you are trying to sustain a usage in decline. The spelling fighters who are constantly trying to impose UK spellings onto this site are only making it look unprofessional, and give the distinct appearance that the editing staff are extremely biased and happy to impose their personal preferences on what is otherwise a neutral encyclopedia. This article, like several others on this site, is embarrassing to en.wiki, and should be changed. Cecoppola (talk) 20:35, 9 March 2017 (UTC)
 * Please actually read WP:NPOV It's about addressing views in content. --Neil N  talk to me 00:18, 10 March 2017 (UTC)


 * Thanks for the suggestion. This article, like others on en.wiki, tries desperately to defend minority spellings, with claims that have no proof. (As I mentioned above). It is not hard to see this violates the idea of finding a neutral entry. Cecoppola (talk) 00:36, 10 March 2017 (UTC)
 * Please educate yourself and read Metre Convention. --Neil N  talk to me 00:44, 10 March 2017 (UTC)


 * Actually...you should educate yourself. Referencing documents signed in 1875 is not relevant to how words are actually spelled in 2016. Your bias is starting to show. https://trends.google.com/trends/explore?date=all&q=meter,metre Cecoppola (talk) 00:51, 10 March 2017 (UTC)
 * You realize that google link means nothing, right? Hint: look at the "Related queries". --Neil N  talk to me 00:56, 10 March 2017 (UTC)


 * No, you're wrong. I'm sure the people who will review this article will find it very relevant to the topic at hand. Much more useful to the discussion than anything that happened in the 19th century, for sure! :) Cecoppola (talk) 00:58, 10 March 2017 (UTC)


 * This is a WP:WASTEOFTIME. Unfortunately, the way this is going, only an editing restriction may end this disruption. Dr.   K.  01:13, 10 March 2017 (UTC)
 * Looking at these answers, I honestly still can't tell if we're being trolled or not. But congrats, your misuse of the NPOV tag has stuck around for a little while at least. --<b style="color:navy">Neil N </b> <i style="color:blue">talk to me</i> 01:16, 10 March 2017 (UTC)


 * Accusing those with whom you can't disagree intelligently of trolling is a tired and pathetic excuse. Anyone trying to silence disagreement should certainly be restricted from propagating their minority views on en.wiki. NPOV is being used here correctly, and revealing this gang activity is making that very apparent. There are significant objections to this article that should be reviewed by some DIFFERENT editors! :) Cecoppola (talk) 01:19, 10 March 2017 (UTC)
 * You can argue all you want on the talk page about the spelling the article uses. Some of what you say might be useful (though not so far). But I start to take an interest when you misuse article tags. --<b style="color:navy">Neil N </b> <i style="color:blue">talk to me</i> 01:25, 10 March 2017 (UTC)


 * I'm defending my post. Who knows what overzealous or irrational user is going to come here and delete my comments because they have no good reason for their point of view. I am happy to remind anyone that NPOV clearly applies here since the article title is misspelled, and there are unverified claims used in the article to support that minority point of view. If you think the 85% dominance of the correct spelling on the English internet is not a major problem for this article, then you are a part of the NPOV problem. Cecoppola (talk) 01:29, 10 March 2017 (UTC)


 * As far as I know, the official spelling was considered to be 'metre' from the conception of the metre as an SI unit onwards. The spelling 'meter' is only mainly used in the US and they still largely use imperial units, so shouldn't this imply that 'metre' is the correct spelling in UK English? (which is the language most of Wikipedia is in) I personally think that the official spelling for both languages should be 'meter' to avoid confusion (and it makes it a nicer word overall), but sadly it is not thus, and while it isn't, this article needs to reflect that. I vote to remove the NPOV tag. Caelus5 (talk) 05:07, 10 March 2017 (UTC)


 * You're already starting from an invalid place if you think there is such a thing as "official" spellings. Dictionaries use common usage, and in this case, there is no question of what that is. The lack of neutrality comes from the obvious fabrications in the article attempting to deceive readers into thinking their regional spelling is common, which it obviously isn't. Inspecting literature and the internet will quickly cure anyone of that notion. And although it's not the reason for edits, "most" of English wikipedia is not in UK English (another good example of this gang problem). So the article, as well as the these types of rumors make the non-NPOV clear. Cecoppola (talk) 05:36, 10 March 2017 (UTC)

Here's a nice reference that says the US is the odd-man-out: http://www.metricationmatters.com/docs/Spelling_metre_or_meter.pdf The author, Pat Naughtin, works extensively in the metrication field in multiple countries (including the US) and has done a lot of research on the history, spelling and usage of the metric system.  Stepho  talk 22:24, 10 March 2017 (UTC)

And here's another reference: http://grammarist.com/spelling/meter-metre/ As a general rule, grammarians tend to be a very picky group of people that really like to get it right.  Stepho  talk 22:34, 10 March 2017 (UTC)

Can someone (else) please remove the NPOV tag? It's not really appropriate for WP:ENGVAR disputes. --<b style="color:navy">Neil N </b> <i style="color:blue">talk to me</i> 22:27, 10 March 2017 (UTC)
 * I agree. This is an ENGVAR dispute, disguised as an NPOV issue. Not only that, but this is basically a page-move request disguised as an  NPOV dispute. If this were a proper move request, I suspect it would result in a SNOW close.  Dr.   K.  22:48, 10 March 2017 (UTC)


 * I'd leave it in for the time being. Technically he was supposed to put a tag on the phrase 'nearly all' instead of an NPOV tag on the article but it does the job of pointing out that something needs to be addressed. I'd rather discuss the issue than waste time about which tag is right.  Stepho  talk  23:00, 10 March 2017 (UTC)


 * I didn't see your comment before I removed the NPOV tag, but this is clearly not an NPOV dispute, so the NPOV tag removal was appropriate. If you would like to add a "cn" tag, please be my guest. Dr.   K.  23:08, 10 March 2017 (UTC)
 * How are we defining "English-speaking nations"? That doesn't really make much sense because English is the the global lingua franca. --<b style="color:navy">Neil N </b> <i style="color:blue">talk to me</i> 00:54, 11 March 2017 (UTC)
 * If we go by this redirect, it may mean territories using English as an official language. Dr.   K.  02:12, 11 March 2017 (UTC)
 * Just FYI, Cecoppola. Look at your search comparison again. Now look at what regions "meter" is popular in. You'll note that the Netherlands is second there, which makes sense because we use "meter" too. And yet we're not English-speaking. How did you plan on accounting for foreign-language searches? Bataaf van Oranje (Prinsgezinde) (talk) 10:35, 28 May 2017 (UTC)

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Sorry to be pedantic
The article now says:

"30 March 1791 – The French National Assembly accepts the proposal by the French Academy of Sciences that the new definition for the metre be equal to one ten-millionth of the length of a quadrant along the Earth's meridian through Paris, that is the distance from the equator to the north pole."

Shouldn't that italicized fragment be "the distance from the equator to the north pole along that quadrant "? Added text underlined. Thanks, SchreiberBike &#124; ⌨   00:05, 31 October 2017 (UTC)


 * ... or "along the surface of the Earth"? (for anyone who doesn't know that meridians are drawn that way)   D b f i r s   08:33, 31 October 2017 (UTC)


 * To clarify the terminology, a Meridian (geography) is a half circle that goes from the North Pole to the South Pole. And a quadrant is 90° of that same circle (a quarter of 360°), or half of a meridian. A quadrant is typically taken as the line going from the North Pole to the equator (or the southern equivalent for those of us down under). Which makes the original sentence correct but perhaps it could be worded clearer.  Stepho  talk 13:08, 31 October 2017 (UTC)


 * Yes, the question was whether the original might be misinterpreted as the straight-line distance by someone not familiar with spherical geometry.   D b f i r s   19:05, 31 October 2017 (UTC)


 * Ah yes, now I understand. Yes, I fully support adding that sentence fragment to clarify if it was a 3D point-to-point measurement or a 2D measurement along a (smoothed) 3D surface.  Stepho  talk 22:27, 31 October 2017 (UTC)
 * Was the measure specified to be through Paris? The quadrant was a theoretical distance on a idealized sphere at sea level, so it wouldn't have mattered . The actual triangulation survey that was used was only about one ninth of the actual distance, didn't go through Paris, and didn't even run north-south. Meters (talk) 00:46, 1 November 2017 (UTC)
 * Sorry, don't know what I was thinking. This triangulation survey determined an arc that was indeed north south and passed very close to the Paris Meridian. Meters (talk) 08:12, 1 November 2017 (UTC)
 * Thank you for the feedback. I made the change SchreiberBike &#124; ⌨   18:44, 4 November 2017 (UTC)

Original research in the "History of definition" section
I'm concerned about the validity of the first paragraph in the introduction to the Metre section in the article. No secondary source is provided to enable verification of the implication that Wilkins's essay played any part in the definition of the metre, and indeed the final sentence states "No official action was taken regarding this suggestion."

For this reason I believe it should be removed as contravening WP:NOR. To that end I removed it, but was reverted by. The only source provided is Wilkins's essay - but that obviously doesn't (indeed cannot as it was written more than a century before the metre was defined) claim that his work played any part in the definition of the metre, so for me, the synthesis that it did, without any supporting secondary source cited, clearly goes against WP:PSTS. Any thoughts anyone? Is there a valid reason to keep that paragraph here? -- DeFacto (talk). 19:42, 4 December 2017 (UTC)


 * I would recommend that this, and the other pendulum definitions, be retained in the general history section because they were considered (but rejected) by the French Academy of Sciences in 1791. Wilkins' was the first such proposal I could find a reference for, but it's possible there were earlier suggestions.  I agree that the pendulum definitions were not part of the definition of the modern metre, but the modern definition seems to have been chosen to be close to the length of the seconds pendulum, so those suggestions played a part in the choice of the length of the modern metre.   I see that you have been systematically removing mentions of Wilkins from other articles.  I agree that he was not involved in the eventual development of the metric system, but he did suggest it long before the French Academy, and I find it difficult to believe that they were not aware of the Royal Society when they chose the meridional metre.  D b f i r s   22:30, 4 December 2017 (UTC)
 * What Dbfirs said basically. This belongs in the article and is not WP:OR. Headbomb {t · c · p · b} 22:39, 4 December 2017 (UTC)
 * you don't address the missing secondary sources though. Without those we have Wikipedia editors synthesising from Wilkins's essay that his thoughts have enough weight to be included. That contravenes both WP:PSTS (e.g. "Do not analyze, evaluate, interpret, or synthesize material found in a primary source yourself; instead, refer to reliable secondary sources that do so.") and WP:WEIGHT in that we cannot say it deserves a mention without support from secondary sources that mention it in this context. If we can find secondary sources to support the assertions though, we should be okay with keeping it in. -- DeFacto (talk). 22:54, 4 December 2017 (UTC)
 * Wilkins is likely not the first (and the article doesn't say he was), that was likely Mersenne who did something like this in 1644. See seconds pendulum, which gives a better history of this (or /). Headbomb {t · c · p · b} 23:01, 4 December 2017 (UTC)
 * ... but Wilkins proposed a base ten system using the length of the seconds pendulum.   D b f i r s   23:11, 4 December 2017 (UTC)
 * The problem isn't whether Wilkins was first, or about what his specific proposal was. The problem here is that we need reliable secondary sources that make the association between Wilkins and the definition of the metre, because currently we do not have that - we currently only have our WP editor original synthesis based on one primary source. We need to make these claims adequately verifiable, and that means citing them to reliable secondary sources, if we are to keep them. -- DeFacto (talk). 12:46, 5 December 2017 (UTC)
 * I take your point that a secondary source is better than a primary source. We do have Anne Rooney, of course (I've added her as a secondary source).  I didn't read the claim as being that Wilkins was directly involved in the meridian definition of the metre. Clearly he wasn't, but he did propose a similar system based on the seconds pendulum.  Other precursors could also be mentioned.    D b f i r s   14:17, 5 December 2017 (UTC)
 * Yes, I too think that if we are to keep this info we need more context around it. At least we have a secondary source now, although it is one which was deemed inadequate as a "pop work" when it was used for a similar purpose here. I wonder if, the editor there, would be interested in this discussion. In the meantime, there is another, and possibly more acceptable source that we can use for context and positioning on this: From artefacts to atoms by Terry Quinn, as used in International System of Units. -- DeFacto (talk). 20:21, 5 December 2017 (UTC)
 * Thank you for that more reliable source. I've added it to this article.   D b f i r s   21:10, 5 December 2017 (UTC)


 * Thanks for the ping. I think Wilkins is the most interesting person you never learned about in school, and I spent two summers studying his Real Character/Philosophical Language, but his measurement proposal was outside the topic I was pursuing so I didn't spend too much time pondering it. Wilkins was extremely creative and inventive but his best ideas came from borrowing the best from others and synthesizing them in some extraordinary way. Hooke was working intensively on clocks and watches and I'd be astounded if, were the truth known, the whole measurement proposal wasn't built on ideas from Hooke and others. With respect to the edit linked above, any source that says Wilkins' work "lay undiscovered until 2007" (or whatever) is trash, and can't be trusted, period. <b style="color: red;">E</b><b style="color: blue;">Eng</b> 22:57, 5 December 2017 (UTC)


 * Yes, lots of people studied the seconds pendulum, and Wilkins probably just extended the suggestion of Christopher Wren to the Royal Society a few years earlier. I agree that Anne Rooney's book cannot be regarded as serious research (she probably meant rediscovered in 2007).  Fortunately, DeFacto has found a more reliable source.    D b f i r s   23:39, 5 December 2017 (UTC)


 * Personal note: If you have access, I heartily recommend this discussion of Wilkins' Real Character. It's wonderfully written (though with a few inaccuracies). If you don't have access, send me an email and I'll mail it back. <b style="color: red;">E</b><b style="color: blue;">Eng</b> 23:45, 5 December 2017 (UTC)

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How to avoid the ambiguity of "quadrant"?
This article in three places uses the word quadrant. According to Webster's Dictionary, this term can be used to refer to:
 * an arc of 90 degrees that is one quarter of a circle

or
 * the area bounded by such an arc and two radii.

In the article we mean the first of these meanings, but the two wiki-links take us to circular sector, which describes only the second meaning. So someone not familiar with the term will be trying to work out what is meant by the length of an area, and certainly won't be able to work out whether it was the arc or chord length that was the intended meaning. I can't find a Wikipedia article that we could link to that explains the intended first meaning. Maybe something could be inserted into the Arc (geometry) article. The alternative would be to avoid the use of quadrant in this (metre) article. But I am a little reluctant to make that change in case the wording is deliberately mirroring the language used in the historical documents. Thoughts please. Jmchutchinson (talk) 12:55, 23 October 2019 (UTC)


 * Quadrant (circle) (aka circular sectordoes talk about the definition that we want. The article can be a bit clearer by saying the quadrant arc length or similar.  Stepho  talk 22:20, 23 October 2019 (UTC)


 * I've clarified by saying "great circle quadrant". This is explained earlier in the article.   <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  10:34, 24 October 2019 (UTC)
 * And I've now added to the wikilinked definition of quadrant in circular sector to explain that it can refer to just the arc. Jmchutchinson (talk) 14:33, 24 October 2019 (UTC)

mistaken unit
The article mentions an astronomical measurement of "9 1/2 inches" - this probably should have been  "9 1/2  arc seconds" which is the parallax of the sun. — Preceding unsigned comment added by 100.15.118.7 (talk) 18:41, 1 December 2019 (UTC)