Talk:Metre/Archive 3

Confusion
I'm a bit confused by this claim:

In 1668 Wilkins proposed using Christopher Wren's suggestion of a pendulum with a half-period of one second to measure a standard length that Christiaan Huygens had observed to be 38 Rhineland or 39¼ English inches (997 mm) in length.[2][3]

How is it possible that 38 Rheinland inches equals 39.25 English inches and that equals 997 mm in 1668 using using an inch millimetre conversion of 25.4 mm per inch that didn't come into existence until 1960?

From this webpage: http://home.fonline.de/fo0126/geschichte/groessen/mas7.htm

1 rhein. Fuß = 1,07536 bayer. Fuß = 0,31385 Meter [0,31374 m (seit 1816)]

This would mean that in the early 1800s, the Rheinland fuss would be equal to 26.154 mm. Thus 38 Rheinland zoll (inches) would be almost 994 mm and not 997 mm.

Dividing 994 mm by 39.25 inches gives an English inch to millimetre conversion of 25.32 mm/inch. Because pre-metric units kept changing over time and a precise conversion into millimetres may never be known especially for the values in 1668, wouldn't it be better to convert to a range of possible values, such as 994 mm +/- 2 mm in order to give a more accurate relation?

--72.196.146.78 (talk) 12:12, 22 August 2010 (UTC)


 * This confusion is due to both the Dutch and the Germans having a Rhineland. The Dutch Rhineland foot was 1.033 English feet (and was in use as a legal unit of measure for land transactions in South Africa until the early 1970's.  I certainly had that conversion figure drummed into me at school.  Multiplying 38 by 1.033 gives 39.254 (ie 0.004 of an inch (0.1 mm) discrepancy between the two. Martinvl (talk) 15:48, 22 August 2010 (UTC)

Choice of alloy
It would be interesting to mention why the standard in use in France was composed of platinum/iridium alloy. Does anyone know the reason for this?Jimjamjak (talk) 10:52, 17 April 2009 (UTC)Encyclopædia Britannica.

According to Encyclopædia Britannica, the bar was 90% platinum and 10% iridium because this alloy is much harder, stiffer, and more resistant to chemicals than pure platinum, but is still easily worked.  D b f i r s   19:19, 19 April 2009 (UTC)
 * Very late response: According to the Ken Alder book "Measure of all things", it was becuase the first bar was made from the purest platinum they could make at the time, which turned out to have about 10% iridium left in it. Later bars were made of the same alloy for consistency. --Wtshymanski (talk) 16:59, 11 May 2010 (UTC)

Pace

 * KISS (keep it simple)
 * The meter is the standard double step of the French Infantry. It was used to standardise and analyze the movement of troops.  It reflects the general belief that most battles can be won through mathematical analysis.  The double step was used to compensate for the difference in the left and right steps.  The double step measurement has been adopted by many Infantries around the world.  It originates thousand of years before the French introduction.  The Infantry was the predecessor of public education.  I do not want to interfere with the precision offered by angular time/distance measurements offered by "the well intentioned" scientists nor with other definitions.  In general military can not have copyrights or patents.  — Preceding unsigned comment added by 99.145.163.89 (talk) 16:41, 29 July 2011 (UTC)
 * Unless the infantrymen in question are very tiny or are tip-toeing across the battlefield, that's not even remotely accurate. The meter is a decent measurement of how far an infantryman can walk in one second, though. The rest of the above is, of course, complete nonsense. - Alltat (talk) 10:07, 22 November 2011 (UTC)
 * Probably 99.145.163.89 was confusing the French metre with the Roman mile which was indeed a thousand double paces, but was significantly longer than a kilometre.   D b f i r s   21:59, 22 November 2011 (UTC)

Awful introduction
The introduction is so tacky. There are too many symbols and just too much bs. Who needs a pronunciation guide to pronounce such a simple word, seriously? A link to light? A link to second? If you don't know about these things, why exactly are you reading about measurements of distance? The article also isn't clear enough in pointing out that 'meter' is a customised (American) spelling of the word; the way it's introduced makes it seem as though people just can't decide how to spell it sometimes. It should just say (US: meter), then have one of those superscript links to the spelling section. I'd fix these things up myself, but last time I improved this article, I got a whole lot of stubborn control-freaks trying to hijack the article in an attempt to shove their customised version of English onto the rest of the English-speaking world.Owen214 (talk) 13:43, 21 May 2010 (UTC)


 * I have overhauled the introduction. I trust that it is to people's liking.  Make I make the point that no material has been removed - everything that I junked is repeated elsewhere in the article. Martinvl (talk) 15:10, 21 May 2010 (UTC)


 * I like your rewrite, Martinvl. Good job. I've also rearranged the infoboxes at the top of this talk page to give more prominence to the ones that address the spelling issue. It won't solve the bickering, but it may help a bit. -- BPMullins | Talk 15:56, 21 May 2010 (UTC)


 * In the box that used to say that Wikipedia uses "metre", I have changed it to say that this article uses "metre", because articles that use American spelling generally use the "meter" spelling. Jc3s5h (talk) 17:14, 21 May 2010 (UTC)


 * What the metre IS needs to be in the lede - and is certainly more important than what is was intended to be 2 centuries ago. I have restored the def & reduced the wikilinks - though kept the link to second because the defs are so intertwined. --JimWae (talk) 19:43, 21 May 2010 (UTC)
 * I've reverted the removal of the pronunciation guide since it is common on many articles and useful for non-english native speakers. It also doesn't take up much space. Otherise people might think is is pronounced like "metro" or "metal" . -SimonLyall (talk)

Spelling
If we can ignore nationalistic issues and pride for a moment. I did a quick corpus analysis and found that the 'USA' spelling of metre/meter is used more commonly in most English speaking countries, outside of the USA/UK. So the line "Metre is used as the spelling of the metric unit for length in all English speaking nations except the USA.[16]" should really be deleted or amended. Many people want certain spellings to be used; it does not mean that they should be used or are used. However this article might use the 'metre' as it is the original. (User: anonymous newbie) This edit (placed at the top of this preexisting section) was by 210.0.205.213 on 08:29, 15 November 2010. -- 110.49.234.141 (talk) 21:52, 15 April 2011 (UTC)
 * I don't know how you did your analysis, but I would suggest that your conclusion is in error. Is your research as fake as your signature?  To most speakers of English outside the USA, a meter is a measuring device.  I agree that the statement might be slightly too strong.  Do Canadians also use "meter" sometimes?    D b f i r s   10:31, 15 November 2010 (UTC).
 * Canadians, to my knowledge, frequently use "meter" for the unit of length; as far as I can tell, not one child has been rendered homeless as a result of this. But let's keep the US English/ Indian English spelling wars alive - there's no issue more cosmically important on the Wikipedia. I suggest we add "trial by combat" to the list of Wikipedia dispute settlement mechanisms. --Wtshymanski (talk) 14:50, 15 November 2010 (UTC)
 * I suspected that this might well be the case, even though the "official" Canadian spelling matches the International spelling. No need for "trial by combat", but we all wish to keep statements in Wikipedia articles as accurate as possible.  I'll edit the sentence that offended our anonymous friend with the fake signature above.  (This sub-section should appear at the end of this section.)    D b f i r s   22:20, 15 November 2010 (UTC)
 * I actually never knew Americans spelt metre wrong until I checked this page. If I hadn't checked and someone told me I wouldn't have believed them. America is Retarded. 210.11.147.157 (talk) 12:36, 9 June 2011 (UTC)

The page should be at "Meter" instead of "Metre", since Meter is the correct spelling.


 * Only in your country. Where I live, meter is incorrect.  Most Wikipedia editors understand regional differences in spelling.    D b f i r s   18:53, 19 April 2009 (UTC)
 * More Wikipedians are American than British, so the American spelling should be used.


 * Your claim is probably true, but there are more speakers of English outside the USA than within. American spelling is used in very many Wikipedia articles, and this is accepted by most British editors.  Wikipedia does have a policy on spelling, and I think it has been followed in this article, and it is accepted by most American editors.  Best wishes from across the pond.    D b f i r s   07:27, 27 April 2009 (UTC)

As well as this, it should be noted that the UN, ISO and other supranational world organisations recognise metre (and British English - Oxford variant) as the legitimate form of spelling. There are also possibly more native British/Commonwealth English speakers in the world due to India (150 million speakers?), Australia and New Zealand. Canada has distinct spelling though, I'll agree.


 * There are more speakers of American English as a primary language in the U.S. than there are such for British (or any other variant) English in the world. The "rest of world" arguement doesn't hold much water and is fairly arbitrary anyway.  Also, ISO and the UN have no authority to dictate to the common dictionary how something is spelt.   They can only state their own preferences.  Their preferences have bearing here, but are not the final word on the matter.  The reason why metre is preferred by them is that it closer in appearance to the french word for the same.  The problem with the metre spelling is that it looks like it should be pronounced as "me-tree", not "me-ter". 64.174.75.3 (talk) 15:29, 10 June 2009 (UTC)


 * ...and how do you pronounce "table"?

This is fun! Fight, fight, fight! Oi Yanks, don't let the English pretend they invented the English language (the corresponding names are coincidental, of course - it was invented in NEW England) or that the French (who spell it 'metre', by the way) invented the met?r?! And Limeys, don't let the Yankee upstarts pretend they started Wikipedia! Ignore the facts! Fight fight fight! I'm South African, and so I prefer 'metre', myself, since it does remove ambiguity when talking about e.g. 'parking meters', where the word comes more directly from the Greek. Less ambiguity is a good thing, though it can make people trying to learn the language suffer. But to say either is 'wrong' is idiotic, and whoever says that should go back to year one/first grade NOW. The wording of the founding document of the United States (plus Noah Webster's almost popular schemes soon afterwards) imply that the Americans have given up all rights to dictate terms to the English heritage (including the language) the US seceded from. There are more American first language English speakers on the one hand, but then probably less text read per capita in the US. And I had no idea Americans could get so heated about the idea of the English language being treated as, well, an English language. Nor that the English could get so heated about what IS ultimately an American site (this one) using their own, equally valid spelling conventions. The article opens up with both spellings anyway - and it's the difference between 're' and 'er'. Finally, how can the English or Americans get so pent up and nationalistic about a tiny spelling difference of a French invention anyway? They seem to hate the French enough for both countries to regard the marvellous invention of the metric system as deeply unpatriotic in itself anyway! America hasn't adopted it at all really, and there are still `This England' articles on crusades to sabotage metric signposts! It's quite sad, really. So neither of you has any right to complain. Please grow up. (anon editor 41.145.114.80 at 11:48, 21 June 2009)


 * There have been suggestions that the current wikipedia should be renamed am.wikipedia.org or us.wikipedia.org, and have only US spelling, then we could copy most of it and translate it into real English for the rest of the English-speaking world. Don't take this too seriously, though!  :-P    D b f i r s   12:06, 21 June 2009 (UTC)

Good point. That may clinch the British argument - but perhaps a bit more linguistic unity is what we need instead. What about enuk/enus, and maybe a few others (enca, enau, ennz, enie, ensa, enjm, enin, entt, enzm, etc...) - not that I'm taking you too seriously. That might confuse matters sufficiently! The thing no-one likes to admit of course is that by normal standards standard British, American, Canadian, Australian, New Zealander, Irish, Australian, etc., English are all the same dialect - just different variants within one - let alone the same language. If anyone (though perhaps not many linguists) can consider Cantonese and Mandarin 'dialects' of the same language, or for that matter Venetian and Sicilian - or Swabian and Saxon - that sets the bar for 'dialects' pretty high. The fact that it is possible to read a book for 20 pages in English and not know where it comes from makes it pretty clear we're fussing a bit too much. Given the size of the English language, it's amazing how homogenous it is. Most English speakers are barely aware when a spelling they use is 'American' or 'British' anyway!

Yankees you don't even use metres, so don't tell us how to spell it! Time to get into the 21st century guys. 121.217.29.88 (talk) 01:34, 20 October 2009 (UTC)


 * The spelling of metre isn't British or American, it is defined by the International System of Units as metre and its symbol is m. That's just the way it is.  Like Pascal is spelt Pascal and its symbol is Pa, there are no creative options here.  The whole of the above on usage is interesting but kind of irrelevant.  It's spelling has been defined, let's just get on with it.  If SI redefines it as meter then we go with that one, they haven't.  The optional meter in the intro is misleading people, maybe we need to be a bit more precise about this in an encylopedia E x nihil  (talk) 02:37, 8 December 2011 (UTC)

Circumference of the Earth 'off'
Given the knobbliness of the earth etc., surely an arbitrary redefinition of the average height of the earth (depending on whether you're looking at sea level, etc.) would make 0.2mm negligible? How was it really defined in the 18th century, strictly? Sea level? I'm not sure the article makes that clear.

Newton
I think a reference to Newton would show another a big advantage of the metric system, besides the fact, that a meter is properly separated in a decimal way, unlike foot and inch.

1 newton = 1 kg * 1 meter / sec ^ 2

(a newton is the power needed to accelerate decelerate one kilogramm in 1 sec at 1 m / sec) —Preceding unsigned comment added by 84.142.223.164 (talk) 22:00, 19 May 2009 (UTC)


 * Perhaps you've never heard of the dyne or the poundal? (btw you meant force not power)    D b f i r s   23:54, 10 June 2009 (UTC)

The symbol for second is s, not sec. —Preceding unsigned comment added by 157.130.108.226 (talk • contribs) 16:51, 23 September 2009 UT

Table
I think the table "Orders of magnitude (length) in E notation" does not serve any useful purpose. In addition, the first entry "0 m" does not belong to the table as this does not show any order of magnitude relation". This set of standard SI prefixes can go elsewhere. Ck.mitra (talk) 15:19, 25 July 2009 (UTC)


 * Agree that the table is ugly and unsightly in context, but provides useful navigation links to distance associations. A wide table exists in WP, so I replaced the vertical table with a horizontal table in the 'See also' section. Kbrose (talk) 15:32, 25 July 2009 (UTC)

Help edit reference
I can't find the template to add a book reference. Wiki doesn't make it easy for new folks to contribute. I searched for how to add a book and couldn't find it so if someone wants to fix my Adler addition please do so. --76.31.242.174 (talk) 23:56, 17 July 2009 (UTC)


 * Some people like citation templates, such as Citation or Cite book. Some don't. The compromise that has been reached at WP:Citing sources is that articles that consistently use templates will continue to use them, and articles that just have the citation typed by the editor will continue to do that.


 * This article does not use citation templates, so your citation is fine just as it is. However, since it was not used to write the article, I have moved it from the References section to a new Further reading section. --Jc3s5h (talk) 00:33, 18 July 2009 (UTC)

Sweet. thanks --76.31.242.174 (talk) 00:56, 18 July 2009 (UTC)

Ugly text
If we were looking to nominate for the ugliest text on Wikipedia, I'd nominate the current opening paragraph. You've got your superscript references. You've got perfectly ordinary dictionary words with links. You've got two fractions, acronyms, and a very dull and clutterly looking "infobox" that gives redundant information. This text has gone right past "bad article"(BA) status and could be nominated for "Misfeatured Article", exemplifying some of Wikipedia's worst work. --Wtshymanski (talk) 13:56, 7 August 2009 (UTC)
 * In the spirit of you found it, you fix it, here's what I think the opening paragraph should look like. --Wtshymanski (talk) 14:10, 7 August 2009 (UTC)

Circular reference
The first citation in this article (Metre) refers in disaccordance with CIRCULAR to a section of another Wikipedia article, American_and_British_English_spelling_differences. As such, I have replaced it with Template:Citation_needed. Perhaps one of the citations used in American_and_British_English_spelling_differences would be more appropriate. 99.90.200.121 (talk) 06:07, 6 December 2009 (UTC)
 * I don't see why it's even needed. It's a pretty common word. ←Baseball Bugs What's up, Doc? carrots→ 06:20, 6 December 2009 (UTC)


 * I'll go along with Baseball Bugs view that the footnote isn't needed. But for future reference, not every footnote is a citation, and thus not all footnotes need to refer to a reliable source. Furthermore, it suffices to provide one reliable source for a claim in an article. If the claim is mentioned more than once, the citation need not be repeated every time. The article already contains a citation to a reliable source for the "meter" spelling. --Jc3s5h (talk) 15:55, 6 December 2009 (UTC)
 * Generally speaking, the first paragraph should summarize the article, and does not use footnotes and references, because those should all be contained within the body of the article already. ←Baseball Bugs What's up, Doc? carrots→ 16:36, 6 December 2009 (UTC)

Proper length
The meter is now defined to be a unit of proper length. Should we state that here and should we give more detail. Martin Hogbin (talk) 10:49, 22 March 2010 (UTC)
 * No. Although I have no references and so will be shouted down by cries of and, I strongly suspect that virtually all our readers are not relativistic physicists and so don't need a rather opaque and rarified definition of "proper length".  If you *must* include this in the article, in the name of the Mercy of Jimbo, don't put it in the opening paragraph! It's really got nothing to do with a bread-and-butter unit of measurement and is more a concept from physics. --Wtshymanski (talk) 13:11, 22 March 2010 (UTC)
 * Qualified yes - There is certainly a place in the article for such a discussion - probably ahead of the heading Timeline. This would enable those who do not understand the concept to skip over it. I would also suggest that a discussion on the concept of a quantum vacuum as both on that actual realisation of the metre be discussed at that point. The header could read Quantum and relativistic considerations and all discussion of that nature be confined to that section. Martinvl (talk) 13:38, 22 March 2010 (UTC)
 * I think anything about quantum vacuum should be removed from the article. As far as I know, this concept plays no part in the definition of the metre. Martin Hogbin (talk)

Wtshymanski, I know where you are coming from, I do not want to re-create the chaos we had at the Speed of light article a while ago. On the other hand I do not think we should try to dumb down the subject. As measurements of distance and times become ever more precise, more and more details start to matter, for example gravitation has started to become important in the definition and measurement of time. I am not sure if it has any practical effect on distance measurement yet, but it probably will do one day. Organisations like the BIPM like to keep ahead of the game and have have now defined the meter as a unit of proper length. Martin Hogbin (talk) 18:52, 22 March 2010 (UTC)
 * I am more than happy to see mention of quantum vacuum being removed from this article. The article quantum vacuum failed to tell me whether or not such a vacuum had actually been created or whether it is still a theoretical concept.  If it has not been created, then any mise et practique for measuring the distance travelled by light in a specified time cannot take it into account. Furthermore, if refractive index and pressure have a linear relationship (I am not sure about this), then making measurements at 10-5 atmospheres instead of a pure vacuum will result in an error of less than 1 part in 10-8.  I don't know if a short discussion about this would be appropriate? Martinvl (talk) 20:37, 22 March 2010 (UTC)
 * I am sure you are correct but we should only show calculations of such things from suitable sources. Martin Hogbin (talk) 20:55, 22 March 2010 (UTC)

Metre/meter
Martin, I improved the wording of the spelling section and the opening paragraph to this article, it is annoying for someone to undo my useful work and cite some sort of consensus. I didn't remove any information and I made the article clearer, so I can't think of any consensus that would have been broken. Instead of hacking away at other people's contributions, it might be useful to make some improvements of your own to that poorly-written article. Owen214 (talk) 01:58, 7 April 2010 (UTC) [Comment copied from my talk page] Martin Hogbin (talk) 08:31, 7 April 2010 (UTC)
 * American_and_British_English_spelling_differences are a common source of contention in WP. In this article there is a consensus to show the normal US spelling in brackets after the usual UK spelling.  If you want to discuss the subject further then please do so here before making any further changes to the article. Martin Hogbin (talk) 08:38, 7 April 2010 (UTC)

This edit seems to have no apparent relation to the edit summary: Spelling: removed disagreement between source and this article Therefore I have reverted the edit. Jc3s5h (talk) 23:56, 25 April 2010 (UTC)

Non-contiguous dates in the lead.
JimWae corrected the dates in my change to the lead. This leaves the lead reading, 'The metre (or meter) is the basic unit of length in the International System of Units (SI). Since 1983, it has been defined as the distance travelled by light in free space in 1⁄299,792,458 of a second.[1] From 1889 until 1960,[2]  the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium  bar, which was designed to represent one ten-millionth of the distance from the Equator to the North Pole along the Paris Meridian'. This leaves the reader wondering what happened from 1960 to 1983. Should we add a sentence on this? Martin Hogbin (talk) 09:02, 10 April 2010 (UTC)
 * Yes, it does leave an obvious gap. I am undecided whether it is better to add a brief mention of the standard definition which I learnt at school, or whether it is better to remove the From 1889 until 1960 ... sentence from the lead on the grounds that it is repeated below.  What does anyone else think?    D b f i r s   12:33, 10 April 2010 (UTC)
 * I'd prefer to remove the historical info from the lead. As User:Dbfirs points out, that's covered below. BPMullins | Talk 15:50, 10 April 2010 (UTC)
 * I am inclined to agree, except that it leaves the lead rather thin. Martin Hogbin (talk) 17:00, 10 April 2010 (UTC)
 * It would be a little more honest to state what the definition was between 1960 and 1983! Wasn't this the era of the defintion being stated in terms of so many wavelengths of light from a particular spectral line of a specified krypton lamp? The definitions are steadily becoming more abstract...from the length of the King's nose to a couple of scratches on a bar to the outcome of a physics exeriment. We no longer research the speed of light, we refine the definition of a second. --Wtshymanski (talk) 13:12, 12 April 2010 (UTC)
 * Yes, I'm closely attached to this definition because I learnt it by heart in the early 1960s, so I consider it essential to the article. The question is just where we put it.  Is there space in the lead to explain it fully, or should we just have a brief mention in the lead, then a full explanation lower down.    D b f i r s   13:26, 12 April 2010 (UTC)
 * The krypton lamp discussion is there, deep in the article. I suppose we can't bog down the lead with the whole history - every time a new crop of grad students comes along, a new definiton of the metre is made - so I've proposed some wording now which I hope alerts the reader to the changing definitions. As usual with Wikipedia articles, we're heavy on "what" happened but with very little discussion of *why* it was thought desirable to switch from an intuitively obvious distance between two scratches to a rather complex and circular-seeming definition in terms of the speed of light and the second.  We should also let the reader know about continuity of the definitions - the changes don't show up on a tape measure or, I suspect, on a machine shop working standard level. --Wtshymanski (talk) 13:47, 12 April 2010 (UTC)
 * I have no real objection to adding a brief description of the history of the metre to the lead but I think we should start with the current definition of the metre, in other words we first say what it is rather than what it is no longer. This approach is, I think, generally recommended in WP. Martin Hogbin (talk) 15:36, 12 April 2010 (UTC)
 * The metre is still the 1889 bar (in a sense). We just have a more accurate way to measure it.  I've re-hashed the lead to include an outline history (there were bars before the 1889 one).  Please comment and improve.    D b f i r s   16:51, 12 April 2010 (UTC)
 * Thanks for improving. I'd forgotten to put the current definition first.    D b f i r s   19:07, 13 April 2010 (UTC)

Table needed
It would be very interesting to have a table showing the differing definitions of the metre and how much they vary from the current definition, and the uncertainty of each definition. We should compare the uncertainties with those allowed in practical matters such as land surveying or precision machine tool manufacture. --Wtshymanski (talk) 14:03, 12 April 2010 (UTC)
 * Good idea. Should this follow the detailed historical account?    D b f i r s   16:05, 12 April 2010 (UTC)
 * Found a reference. We now define the metre a million times more precisely than in 1795. Even a 1795 metre has reasonable precision for many activities. I'm just reading the Alder book now and am impressed at the precision of the original measurement during the turbulent French Revoloution. --Wtshymanski (talk) 18:07, 21 April 2010 (UTC)
 * Thanks for the excellent table. Just a minor quibble (and I'm not an expert on this, so I might be wrong): the last entry is really the current practical realisation of the metre (claimed as of 2.5×10−11 for the iodine-stabilised helium-neon laser).  In theory, up to Heisenberg uncertainties, the lastest definition should have even greater possible accuracy shouldn't it?    D b f i r s   09:42, 22 April 2010 (UTC)
 * If you can source it, please change the table accordingly. The reference is from a 2003 book quoting a 1995 source and so is 15 years behind the leading edge of metrology. I'm just finishing the Alder book adn I was amazed to read that there were no statistical techniques or other analyses of error done in the 18th century; in fact, analyzing geodetic results such as those of the Paris meridian measurement was a motivating factor in developing the least squares method and generally in distinguishing between accuracy and precision. I can highly recommend the book. --Wtshymanski (talk) 13:26, 22 April 2010 (UTC)
 * I haven't found an on-line source yet, but the best accuracy I have found so far is the calcium realisation:
 * ''MEP 2005  CALCIUM (λ ≈ 657 nm)  Absorbing atom 40Ca, 1S0 – 3P1; ΔmJ = 0 transition
 * ''1. CIPM recommended values
 * ''The values f = 455 986 240 494 140 Hz   λ = 657 459 439.291 683 fm  with a relative standard uncertainty of 1.8 × 10−14 apply to the radiation of a laser stabilized to Ca atoms. The values correspond to the mean frequency of the two recoil-split components for atoms which are effectively stationary, i.e. the values are corrected for the second-order Doppler shift.
 * ''2. Source data
 * ''Adopted value : f = 455 986 240 494 140 (8) Hz uc/y = 1.8 × 10−14 for which: λ = 657 459 439.291 683 (12) fm uc/y = 1.8 × 10−14 calculated from f / Hz uc/y source data 455 986 240 494 144 1.2 × 10−14 [1] 455 986 240 494 135.8 7.5 × 10−15 [2, 3] Unweighted mean: f = 455 986 240 494 140 Hz
 * ''The CCL decided to adopt the unweighted mean of the two values, with an uncertainty of 8 Hz, equal to the difference between the values.
 * ''3. References
 * ''[1] Degenhardt C., Stoehr H., Lisdat Ch., Wilpers G., Schnatz H., Lipphardt B., Nazarova T., Pottie P.-E., Sterr U., Helmcke J., Riehle F., Calcium Optical Frequency Standard with Ultracold Atoms: Approaching 10-15 Relative Uncertainty, Phys. Rev. A, 72, 062111/1-17, 2005.
 * ''[2] Wilpers G., Oates C. W., Hollberg L., Improved Uncertainty Budget for Optical Frequency Measurements with Microkelvin Neutral Atoms: Results for a High-Stability 40Ca Optical Frequency Standard, Appl. Phys. B 85, pp. 31-44, 2006.
 * ''[3] Wilpers G., Oates C. W., Diddams S. A., Bartels A., Fortier T M., Oskay W. H., Bergquist J. C., Jefferts S. R., Heavner T. P., Parker T. E., Hollberg L., Absolute Frequency Measurement of the Neutral 40Ca Optical Frequency Standard at 657 nm based on Microkelvin Atoms, Metrologia, 44, pp. 146-151, 2007.1. CIPM recommended values The values f = 455 986 240 494 140 Hz λ = 657 459 439.291 683 fm with a relative standard uncertainty of 1.8 × 10−14 apply to the radiation of a laser stabilized to Ca atoms. The values correspond to the mean frequency of the two recoil-split components for atoms which are effectively stationary, i.e. the values are corrected for the second-order Doppler shift.
 * You will probably understand this better than I.   D b f i r s   14:01, 22 April 2010 (UTC)
 * You presume too much. I'm not a physicist, I make my living sitting in meetings and intialling drawings. Is this the current CGPM recommended way of defining a metre? The table value is probably not too misleading since that was the uncertainty realizable at the time of the proclamation. I suppose we could add a last row to the table saying "Currently realizable uncertainty" with a date that could be updated each time someone publishes a new experiment. I need a "metrology for dummies" book. --Wtshymanski (talk) 14:35, 22 April 2010 (UTC)
 * Sorry, my reply wasn't very helpful. I meant to add that this is just one of twelve recommended ways of measuring an exact metre.  I think this is the most accurate of the 12, but I need to investigate further.  Meanwhile, I think your table your table should stand as written.    D b f i r s   16:31, 22 April 2010 (UTC)
 * Meanwhile, should the table use 'μm' instead of 'um'? BPMullins | Talk 17:28, 22 April 2010 (UTC)
 * Oh, yes, I missed spotting that. I've made the correction.    D b f i r s   23:22, 22 April 2010 (UTC)

Date format
This 2003-APR-08 edit appears to be the first to use a date format. It used MDY. As such, absent any explicit consensus to change, that should be the presumed format of this article. Spelling-var has nothing to do with date-var. --JimWae (talk) 22:23, 11 May 2010 (UTC)


 * The article contains the invisible template use dmy dates. You should find when this was added and what the justification was. Jc3s5h (talk) 22:46, 11 May 2010 (UTC)

use dmy dates was added with this 2010-FEB-26 edit. There was no discussion - nor did the edit summary  actually state what was being done. ENGVAR is not "DATEVAR" and metre/meter is an SI (System International) unit - with no strong national ties to any country --JimWae (talk) 23:03, 11 May 2010 (UTC)
 * Given the origins of the metre, dates should be given in the proper format.    --wtshymanski (talk) 0:18:07 23 Floréal CXVIII

Simple mnemonic for unit conversion.
I just came up with this and couldn't locate any matches on Google. So I referenced myself.

A simple mnemonic aid exists to assist with conversion;
 * 1 meter is equivalent to 3 feet, 3 and 3/8 inches.

This is accurate to 0.5 thousandths of an inch (less than a human hair). ~ Agvulpine (talk) 09:02, 19 May 2010 (UTC)
 * Better just to remember that 1 inch is exactly 25.4 mm. Martin Hogbin (talk) 09:06, 19 May 2010 (UTC)


 * I agree with Martin Hogbin. Ever tried entering 3 feet, 33/8 inches on a calculator, or do you prefer doing your computations by hand?  Martinvl (talk) 10:49, 19 May 2010 (UTC)
 * 39.375 inches is easily enterable on a calculator. As is feet / .3048 = meters, roughly. :) ←Baseball Bugs What's up, Doc? carrots→ 11:03, 19 May 2010 (UTC)


 * Possible yes - but at the cost mentally converting feet and inches to inches, mentally converting a vulgar fraction to a decimal fraction and then inserting five rather than four digits in the conversion constant- all so that you can get an approximate rather than an exact answer. In my book, not a bargain. Martinvl (talk) 12:22, 19 May 2010 (UTC)
 * .3048 is close enough, and it's not hard to remember. ←Baseball Bugs What's up, Doc? carrots→ 16:15, 19 May 2010 (UTC)
 * For "close enough", read "exact". David Biddulph (talk) 09:22, 12 July 2010 (UTC)
 * The approximation was very useful at the time of metrication because many British people worked in feet, inches and eighths of an inch. It was a well-known conversion at that time, but has probably been largely forgotten now that eighths of an inch are rarely used.    D b f i r s   17:16, 19 May 2010 (UTC)
 * I guess none of you owns a 'standard' tape measure, have ever tried cutting a meter length of wood, or otherwise live in America. :) In the USA, the physical world works in vulgar fractions, and converting from decimal to fraction is impossible for most people. If the conversion is needed in a calculator, one simply punches "3[/]8 [+] 36 [+] 3" into a cheap calculator. The reason I came up with this mnemonic was when I was tasked to mark off a 10 meter distance and was given a 100 foot tape measure. (They suggested 10 yards would be accurate for a race.) ~ Agvulpine (talk) 19:43, 19 May 2010 (UTC)
 * Agvulpine, please do not add your own clever ideas to Wikipedia, see WP:No original research. Another editor claims this mnemonic is well-known. I would like to see a source for that, because I don't ever recall hearing of it.


 * It's true that not too many Americans have to measure in metric units, but the ones who do so very often will buy metric measuring tools. Although they are a little hard to find at the hardware store, they are easy to obtain on the web. Jc3s5h (talk) 20:03, 19 May 2010 (UTC)


 * Whilst I agree that original research should not be added to Wikipedia, I (the other editor) do not consider this conversion to fall into that category (though I don't doubt that Agvulpine discovered it independently). There are several websites that mention this approximation (and are not copies of Wikipedia).  The earliest published usage I can find is from 1906 in the "Proceedings of the International Railway Congress" (Volume 1 page 398) also in Volume 7 of 1908 .  Another citation from 1922 is a conference publication (Brussels, P. Wessenbruch), page 39, again related to railways, but that is not the context in which I met the approximation at the time of metrication in the UK.    D b f i r s   10:17, 25 May 2010 (UTC)


 * If you used proper measurements instead of comparing everything to your body parts and your farm, you wouldn't need to worry about conversion of units anyway. Nevertheless, well done on your hillbilly trick.(Huey45 (talk) 08:22, 12 July 2010 (UTC))


 * I regularly use both metres and inches. I don't see why a measurement based on an inaccurate estimate of a semi-meridian is inherently "better" than one based on units I carry round with me!  What has my (non-existent) farm got to do with the matter? Hu?  Ey?    D b f i r s   19:05, 12 July 2010 (UTC)
 * Ohh! Fight! Fight!  There can be only one TRUTH!  Go get 'em. --Wtshymanski (talk) 19:22, 12 July 2010 (UTC)
 * On a more serious note, I have not kept British government leaflets issued at the time of metrication, and I cannot find them on-line (there is no reason why anyone should put them there). Is there a remote chance that anyone has kept the one that mentioned three feet three and three eighths inches?  An editor has (justifiably) requested a reference for this in the article.    D b f i r s   09:53, 17 December 2010 (UTC)
 * The only recent reference I can find is | this and it is not based on the metrication leaflet.   D b f i r s   12:50, 16 January 2011 (UTC)
 * ... (after checking) ... Sorry, that link is now dead. It did say  "39 3/8 inches" on page 14 last time I checked.    D b f i r s   12:56, 16 January 2011 (UTC)

Sources of spelling
The spelling section mentions that the N.I.S.T. chose the alternate spelling of 'meter' because the US government style manual had it that way - isn't it more logical then to discuss why the US government style manual had the alternate spelling? It doesn't seem especially relevant to mention what the N.I.S.T. does if they didn't actually think of the change themselves. Owen214 (talk) 14:55, 26 May 2010 (UTC)


 * The publication in which the comment occurs, NIST Special Publication 330, has been recognized by the US Secretary of Commerce as the lawful interpretation of SI in the United States. Therefore, the lawful spelling is "meter". Although the interpretation does not provide any enforcement mechanism, I would think that if any local, state, or government agency within the US accused an entity of making an error by using the spelling "meter", the Special Publication 330 would serve as an ironclad defense.


 * It would be interesting to figure out why the Government Printing Manual chose the spelling "meter". Jc3s5h (talk) 15:24, 26 May 2010 (UTC)
 * Because American English doesn't use "-re" spellings? Think about "centre/center", "theatre/theater", etc. --Khajidha (talk) 19:05, 21 October 2010 (UTC)

Based on speed of light...
Since they're defining the metre by the speed of light, wouldn't it have made more sense to shorten it a little and make it the distance it travels in 1⁄300,000,000 of a second instead? 64.30.122.19 (talk) 19:18, 30 May 2010 (UTC)


 * Yes if they were defining a new unit, but the length of the metre has remained constant (within the limits of experimental accuracy) since it was first defined. Imagine the chaos that would result from confusion between old metres and new metres!    D b f i r s   19:01, 12 July 2010 (UTC)

spelled vs spelt
BE spellings are far more globally widespread and used than AE. However that is not  the point. An excellent solution  to  the use of one or the other is established in  the MOS. However, Due to an incorrect edit summary, I  may  have inadvertantly  reverted an edit.
 * According to  Webster's:
 * Main Entry: 2spelt
 * Pronunciation: \ˈspelt\
 * chiefly British past and past participle of spell''

However, the original creator began with spelled, therefore, consistency (MOS) is the rule,  so  I've reverted my  revert.--Kudpung (talk) 07:17, 18 June 2010 (UTC)

Merge from Redefinition of the metre in 1983
To move the process along I've changed that article to a redirect. Hopefully a bot will take care of the template at the top of this page. I had a look at what should be brought across but It was not clear to me what should be - this article already covers both the pre and post 1983 definitions, the latter in some detail. It's not clear it needs further expansion, especially as more information can be found at speed of light, linked a the start of the definition. But perhaps someone more familiar with the content of Redefinition of the metre in 1983 will have a better idea what could be used.-- JohnBlackburne wordsdeeds 02:47, 10 August 2010 (UTC)
 * It seems the AfD result has been reviewed and changed from merge to no consensus, so I've removed the merge tag at the top of the page; Phantomsteve has taken care of the other article. The deletion review is here if anyone else wants to look at it.-- JohnBlackburne wordsdeeds 11:49, 10 August 2010 (UTC)

Meridional definition
There seems to be some confusion about which meridian was measured: it was the meridian running through the Paris Observatory (which, as Dan Brown fans will know, also runs through the Église Saint-Sulpice). The measurements were made from Dunkerque to Barcelona, but neither of these towns lies exactly on the meridian. Physchim62 (talk) 09:39, 22 October 2010 (UTC)
 * So presumably they measured the distance from Dunkerque to Barcelona then corrected to sea level, then corrected for the fact that the line was not quite north-south. It shouldn't make any difference that this was not quite the correct meridian because if the earth has rotational symmetry (idealised), then all meridians measure the same.  Were they aware of minor irregularities in rotational symmetry (other than height) at that time?  I've made another alteration to the text that I hope reflects what the survey did.  More detail might be available in Ken Alder's book but the link provided has a missing digit transposed digits in its ISBN.  Wtshymanski has just read it - perhaps he can help us here.    D b f i r s   10:16, 22 October 2010 (UTC)
 * No missing digits but two were transposed, now fixed. It won't let me read the book from where I am so I can't help with the content query.-- JohnBlackburne wordsdeeds 11:39, 22 October 2010 (UTC)
 * Thanks for correcting the link. I don't have access to it either, but reviews suggest that the mathematics of the survey are not given in detail.    D b f i r s   12:08, 22 October 2010 (UTC)
 * The line from Dunkerque to Barcelona is not a meridian: Dunkerque is to the east of the Paris meridian while Barcelona is to the west. But as long as they had one reference point to the meridian (not even necessarily on it, simply a known distance away from it), the correction is simple spherical geometry. I've read some 19th century descriptions of the process, and I've never seen any indication that they took into account the minor irregularities in rotational symmetry (apart from height above sea level, obviously). I would imagine that they were insignificant compared to the measurement uncertainties in the surveying (which, all the same, was remarkably accurate). Every description I've come across says that they were aiming to determine the flattening factor, and this is the scientific justification for choosing the Paris meridian (long accessible segment spanning 45°N). Méchain and Delambre's result was actually incorrect because of a calculational error, which was quickly discovered, but it remained the de facto metre until 1960, regardless of better measurements (see History of the metre). Physchim62 (talk) 14:24, 22 October 2010 (UTC)
 * ... and their determination still remains the "de facto" metre because each subsequent "re-definition" was simply a more accurate way to realise the same length.   D b f i r s   00:16, 23 October 2010 (UTC)

Metro cattolico
"Metro cattolico" should be "catholic metre", not "metre catholic" - or is "metre catholic" conventional? --Wikiain (talk) 01:18, 28 January 2011 (UTC)
 * No objections, so I've changed it. This and the ref to it in the Burattini article now read the same. --Wikiain (talk) 00:23, 31 January 2011 (UTC)

Equivalents in other units
I appreciate that a lot of effort was put into the section "Equivalents in other units", but unfortunately much of that effort was ill-directed as the editor got confused between survey feet and international feet - the main reference that was used was dated 1959 and the change came into effect in 1960. In the scheme of things, the survey foot is now a unit of measure that is used for one purpose only and in one country only, so it is a "minor unit of measure" that does not warrant the attention given it in this article - that information belongs in the article survey foot. Martinvl (talk) 15:18, 30 May 2011 (UTC)