Talk:Metre/Archive 6

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International prototype metre bar

Our section on the international prototype metre bar is instead a detailed account of developments in geodesy. It included a digression on the nature of error which I removed, only to see it reinserted further up. One of its images dominates the whole article, possibly shown at great size to accommodate what may be Wikipedia's longest caption. Much is irrelevant to the metre or provided in far too much detail; one example somewhat at random, is the formation of the International Latitude Service, complete with its head office's location, which came six years after the creation of the prototype bar and had no effect upon it.

Some of this material may also be found in History of the metre and Carlos Ibáñez e Ibáñez de Ibero, and possibly elsewhere, but duplicate or not, it's excessive here. I believe some serious copy-editing and trimming is required, but that will be difficult if any deletions are simply reinstated in different paragraphs. NebY (talk) 17:51, 27 August 2023 (UTC)

The gigantic image and gigantic description is frankly an embarrassment. It looks ridiculous, and the excessive details belong either in the article or elsewhere. Concur with user NebY. cheers. anastrophe, an editor he is. 20:16, 27 August 2023 (UTC)

Thank you for sharing your opinions. The material in the article has been substantially reduced. Charles Inigo (talk) 06:44, 28 August 2023 (UTC)

I think the digression on the nature of error was important there for the same reason why I mentionned polar motion, because even if polar motion had not been exensively studied when the length of the metre was determined this was a source of error, as was vertical deflection which had not been defined as such at that time. Charles Inigo (talk) 13:33, 28 August 2023 (UTC)

I have a remark about the text you reverted :

"In the second half of the 19th century, the creation of the Geodetic Association marked the adoption of new scientific methods. The association proposed the application in the field of geodetic observations of the method of least squares, discovered simultaneously by Legendre and Gauss, then developed by the latter. At that time, statisticians knew that scientific observations are marred by two distinct types of errors, systematic errors on the one hand, and random errors, on the other hand. The effects of the latter can be mitigated by the least-squares method. Systematic errors on the contrary must be carefully avoided, because they arise from one or more causes that constantly act in the same way and have the effect of always altering the result of the experiment in the same direction. They therefore deprive of any value the observations that they impinge. As science progresses, the causes of errors are sought out, studied, their laws discovered. These errors pass from the class of random errors into that of systematic errors. The ability of the observer consists in discovering the greatest possible number of systematic errors in order to be able, once he has become acquainted with their laws, to free his results from them using a method or appropriate corrections. The progress of metrology combined with those of gravimetry through improvement of Kater's pendulum led to a new era of geodesy. If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs and all determinations of the force of gravity by the mean of pendulum".

This is not just a digression on the nature of errors. It explains why the BIPM was founded. The scientific reason of BIPM foundation was the efforts to take in account temperature errors which could not simply be corrected by the least squares. It means that European scientists knew that the metre was to short, but that as statisticians they knew that they needed a decimal unit and an institution where standards used in the field could be compared at controlled temperatures. Charles Inigo (talk) 16:06, 28 August 2023 (UTC)

There are several issues with that passage. It hardly needs saying, in this day and age, that scientists wish to avoid error; there is no need for a prolix lecture on it. It is marked by dramatic phrasing and rhetorical flourishes that wander into unsourced exaggeration and are not in good English either (outstandingly, "They therefore deprive of any value the observations that they impinge", but in many ways that is characteristic of the whole passage). It remains focused on geodesy rather than geodesy's contribution to the metre. Your one-sentence summary "European scientists knew that the metre was to short, but that as statisticians they knew that they needed a decimal unit and an institution where standards used in the field could be compared at controlled temperatures" is closer to what we need; not yet appropriate, but closer.

There are similar and other problems with the whole section. You don't have to fix them yourself; other editors may respond to the tag I've restored, and I'll tackle it when I can dedicate the time to it, in a couple of days or so. NebY (talk) 17:25, 28 August 2023 (UTC)

Thank you for your help. As you probably gessed English is not my native language. I hope you will find a way to rephrase my ideas. I think the creation of the BIPM and the international prototypes were focused on geodesy's need rather than contribution of geodesy to the metre which was the project of the French Academy of Science in the end of 18th century. In the second half of the 19th century the idea was to find ways to discover the greatest possible source of systematic errors and free the results of the observations from them using a method or appropriate correction (for instance compare at controlled temperatures the standards in order to define their coefficient of expansion, determine the personal equation of the astronomers or to measure the longitude of the extremity of arcs of parallel thanks to the invention of telegraphy). That's the reason why I inserted both the images of a geodetic standard and of a gravimeter with informations on the methods used to correct systematic errors of these measuring instruments. Charles Inigo (talk) 18:56, 28 August 2023 (UTC)

Hello, I just wanted to add to this discussion that I inverted some paragraphs of the section Meridional definition with some paragraphs of the section International prototype metre bar of the article Metre in order to restaure chronologic order and to keep all the discussion on the creation of the first scientific associations in the section International prototype metre. I suppressed a citation by Cajori and replaced it by another on Hassler apparatus and restored a paragraph on the Ibáñez apparatus as was suggested by Anastrophe. Charles Inigo (talk) 13:27, 1 September 2023 (UTC)

Moving details around doesn't deal with the essential problem of too much detail expressed in somewhat impenetrable prose. I'll restore the tage so that other editors may assist; please don't remove it again. NebY (talk) 17:56, 2 September 2023 (UTC)

Ok. I whish you the best. Charles Inigo (talk) 21:22, 2 September 2023 (UTC)

Mnemonic ("three threes")

I removed the mnemonic ("1 metre is nearly equivalent to 3 feet 3+3⁄8 inches."), and @Jmchutchinson: put it back. Nothing to make a big fuss about, but fwiw, here is why I removed it:

• It is not encyclopedic information, rather it is a "how-to" hint for learners. It is possible that in fact this is/was a widely taught guideline in some circumstances, in which case there should be a cited reference to this as a social phenomenon.
• It is not very good: actually you have to remember not just "three 3s", but "3 3 3 8", otherwise you might misremember it as 3' 3 3/4" or 3' 3 3/16".
• It is not actually much use: back-of-the-envelope calculations these days are done with calculators, but you would need a calculator supporting mixed-base arithmetic and binary fractions (as in the problems I did at primary school: divide 3' 3 3/4" by 7).
• You only need to remember "one inch = 2.54 cm" (three digits, again), and you can calculate anything precisely correctly using a normal calculator.

Imaginatorium (talk) 14:05, 4 September 2023 (UTC)

The points Imaginatorium makes about calculators being ubiquitous are valid. But if someone in the US (and perhaps the Canadian building trades?) were faced with measuring out a length stated as a whole number of meters and only had a customary tape measure, the mnemonic would be useful. I'm not sure if that's common enough to be worth mentioning. Jc3s5h (talk) 14:12, 4 September 2023 (UTC)

They also need to still have good mental arithmetic (despite calculators) to convert 3 or 4 metres to feet and inches with this mnemonic, and we already have a narrow audience anyway (US building trade, tape in customary units only being used to measure a round number of metres). NebY (talk) 15:33, 4 September 2023 (UTC)

In addition to Imaginatorium's points, that mnemonic was added in 2010 with the edit summary "created a simple mnemonic; 1 meter is 3 feet, 3 and 3/8 inches" and as a reference <ref>Original work; no known references ~ ~~~~.</ref>.[1] That was changed to <ref>Well-known conversion, publicised at time of metrication.</ref> with the edit summary "well-known",[2] presumably referring to Metrication in the United Kingdom in the 1970s (going by the editor's userpage, anyway). That ref was tagged {{where}} later in 2010 and removed in 2019.[3] In short, the statement has never had a source for the mnemonic's existence, let alone the statements that it's simple and assists; all we have is an editor's claim that it was publicised about fifty years ago and is, or was, well-known somewhere. NebY (talk) 16:05, 4 September 2023 (UTC)

I restored the paragraph because I think approximations are in principle knowledge worth including in an encyclopedia. The classic example is the various approximations of pi (22/7 etc.), which have considerable historical as well as practical significance. Generally I am also sympathetic to including useful well-known mnemonics in an article. Yes they are "how to", but they are also useful to readers, and often even a bit fun! But I agree now that the case for inclusion of this particular mnemonic is questionable. We don't need a reference to support its truth ("sky is blue"), but it would indeed be desirable to be able to show that it is or was in use rather than made up afresh by an editor. On the question of whether this mnemonic is useful, yes I think it is even in these days of mobile phones. We all know that a metre is a bit more than a yard, but this does indicate how much more in a handy, memorable way; it's really not as convenient to have to multiply 2.54 by 36 to work that out even if a mobile phone is within reach. So, if someone can find a reference to its use (which I couldn't), I would vote to keep it. JMCHutchinson (talk) 17:15, 4 September 2023 (UTC)

Much as pi's historic and easily remembered approximation 22/7, plus calculators, left little demand for mnemonics for pi, I suspect that the approximation 3' 3", the precise 25.4 and tape measures in feet and metres left little room for this mnemonic. Many are created, few catch on. NebY (talk) 10:26, 5 September 2023 (UTC)