Talk:Metric system/Archive 4

Article needs formal statement of purview
It would hugely benefit this article to have a formal statement of purview in the lead or shortly thereafter.

There's not a single thing in this article about conventions of metric notation in formal writing. It's seems to me reading this that the purview of metric is to provide a comprehensive set of ranged units for physical measurement and a standardized notation for expressing these ranged units, but it doesn't seem to have much to say about whether one correctly writes "2L jug" or "2 L jug" or "2-L jug" or "2 litre jug" or "2-litre jug".

Is this formally outside the bailiwick of the metric system? There is a section covering this in the SI article. Is it SI itself that extends the metric system with these niceties?

Surely someone eminent must have once sat down and said "this is our scope". What was stipulated?

Do countries legally adopt metric or do they legally adopt SI, or do they implicitly adopt metric via SI, or do they formally adopt both as separate entities? How does that work?

Do scientific journals say "we expect you to use metric" or do they say "we expect you to use metric measurements written in notation as codified by SI" or do they say "we expect you to conform to the national standard, which is presently Metric/SI"? Why does that make me think of GNU/Linux? &mdash; MaxEnt 03:03, 1 August 2014 (UTC)

The USA adopted the metric system in 1866
> The metric system has been officially sanctioned for use in the United States > since 1866, but it remains the only industrialised country that has not > adopted the metric system as its official system of measurement.

This is false. The USA adopted the metric system in 1866 and it has the same official legal status as the US Customary system (in fact, the customary system is defined in terms of SI). What you really mean to say is that the USA has not banned the US Customary system. — Preceding unsigned comment added by 174.125.234.34 (talk) 17:43, 27 November 2014 (UTC)


 * No the metric system does not have the same official legal system as the US customary units. The US has thousands of government regulators at the federal, state, and local level. Many, probably most, of these government units issue regulations stated only in customary units, require people to file information stated in customary units, or both. Jc3s5h (talk) 17:56, 27 November 2014 (UTC)

Proposed Oregon State Senate Bill 166 - Proposes to switch Oregon's system of measurements to the International System of Units
Hi, I have been following the movement towards Metrication in the United States, and I have read some recent news. There is a proposed bill in Oregon to require State agencies to use the International System of Units by January 1, 2018, if the bill passes. I strongly suggest that this bill and movement in Oregon is mentioned somewhere in the article, because if this bill passed, it would really mix things up about Metrication in the United States. Here is more information about the proposed bill in Oregon. Also (AzaToth), I suggest the map of the U.S. (image below), be split into 50 states, with Oregon highlighted as Yellow (instead of grey), meaning a proposed bill could switch the system of measurements to the International System of Units. Here is another link to the Oregon International System of Units bill. Thanks!  CookieMonster755  (talk)   23:11, 1 March 2015 (UTC)


 * I don't see any need for a change to the article yet. State legislators are constantly introducing ill-considered bills which the rest of the legislators just ignore. Let's just wait to see if it passes. Jc3s5h (talk) 23:35, 1 March 2015 (UTC)
 * Okay, thank you Jc3s5h — for your reply, I totally understand what you mean, and I really appropriate your time to reply on the subject.  CookieMonster755  (talk)   23:50, 1 March 2015 (UTC)
 * Have to agree with Jc per WP:CRYSTALBALL. However, we might hear a lot more about it in the near future. Bataaf van Oranje (talk) 14:55, 21 June 2015 (UTC)

External links modified
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Remove inappropriate citation
Jc3s5h, in your edit comment you asked for an explanation of the deletion of a citation. My reply is that it is an inappropriate citation in the paragraph "original metric system" because it doesn't support the statement at all. So it is better to cleanup. Ceinturion (talk) 13:02, 3 June 2016 (UTC)

"Burma" or "Myanmar"
On New Year's Day "Burma" was changed to "Myanmar" in the article. I'm not sure this is valid. Both names are commonly used in English. Jimp 04:25, 14 October 2016 (UTC)


 * History of the name change (and the onging dispute over its usage) can be found in the article for Myanmar. Mediatech492 (talk) 16:58, 15 October 2016 (UTC)

Map of countries using the metric system
On that map up top, how come Antarctica is shown? It isn't a country to adopt or not adopt the metric system. — Preceding unsigned comment added by 198.203.84.2 (talk) 14:26, 7 December 2016 (UTC)


 * I’ve changed that. The new map doesn’t include Antarctica. --Œ̷͠²ð·¨´´̢́̕͘³͏¯̞̗ (talk) 10:59, 25 April 2017 (UTC)

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Metric? system
why don't use Scientific Units, SU, instead. is there any other "scientific" units? [I don't mean SU v.1.0 ( ͨ m, gr, "h) ]. Tabascofernandez (talk) 01:08, 15 July 2017 (UTC)

Primary topic
In the edit summary of this edit asserts that Metric system is the primary topic for Metric. But if that were true: Also, where is the discussion where it was agreed that this is the primary topic? --  Dr Greg   talk  21:43, 26 October 2017 (UTC)
 * Metric would redirect to Metric system
 * the disambiguation page would be Metric (disambiguation)
 * "Primary topic" in the MOS:DABORDER #1 sense, not the MOS:DABPRIMARY sense (I've started a discusion about that ambiguity here). The point is, there has never been a need for a dab page to end in (disambiguation) for it to have prime targets at the top; if that were the case, thousands of dabs would need to be "corrected". It's overwhelmingly clear that metric system is the leading topic, by far, for the dab page metric. — swpb T go beyond 12:54, 27 October 2017 (UTC)

What is the symbol for are
Here we have the symbol for the are as "are" - it was just restored to that after being changed to "a". While in the Hectare article it is stated to be "a" (in the caption to a diagram and in the tables). Neither this article or that one has an RS to support it though. So which is correct? -- DeFacto (talk). 15:51, 10 December 2017 (UTC)

Lead
The metrics system is fundamentally a system of unit measures for everyday use. The MOST significant thing is what are those units? We have at least the obvious ones: length, weight, time and an electrical unit, and a few miscellaneous ones. The niceties of how they related to each other are next, but secondary to most peoples' direct experience of it. Yet, no mention of the fundamental units is in the lead. Sbalfour (talk) 05:08, 16 January 2018 (UTC)

Fixed, by adding a first paragraph of description. Now what we have though is a paragraph of description followed by four paragraphs of mostly history. This is an article about science, not history. The rest of the lead can be scratched, or integrated into the history section if it makes sense. The metric system has a set of very recognizable properties. Where are they? Most people have never heard of CGPM - it doesn't belong in the lead. They wouldn't recognize the metre des archives if it fell in their soup - no need to mention it in the article at all. Most people probably wouldn't know that speed and acceleration for example aren't actually part of the system - how do they fit in? Sbalfour (talk) 05:49, 16 January 2018 (UTC)

OK, now the lead has a science-like description of the metric system in the initial paragraphs, but it is untenable long, at least twice as long as a suitable lead needs to be. I think the best fix is to just move all the old paragraphs into the History section, and pull up any details relevant to the system as it exists today, as if the system had just popped into existence yesterday. There is a whole article devoted to history, History of the metric system, and arguably, ALL history from this article should be moved there. Since that article exists and is long and good, what column space we have here should be devoted to the science. Sbalfour (talk) 16:34, 16 January 2018 (UTC)

Done - essentially the lead has been rewritten to reflect the science rather than the history, and history from the lead moved to the history section. The lead is 7 paragraphs, and that is unconventionally long. However, it is 23 lines of about 20 words, about average as leads go. If form is valued over function, the paragraphs can be split and merged to obtain 4 paragraphs of 5.5 lines each, quite normative for the encyclopedia. But compositionally, that'd be a disaster.

If some of the "summarized" content doesn't actually exist in the article, then the article itself needs better coverage, because the essentials of the metric system as a science are stated in the lead. Sbalfour (talk) 17:49, 16 January 2018 (UTC)

History
I can't see what useful purpose having a history section here can serve. That history is in three parts, which are the primary content of three other articles: Original metric system  (History of the metric system), International adoption (Metrication) and International standards (International system of units). What can we usefully say here that isn't even more useful in those articles? Writing scholarly text is hard work; isn't that hard work better spent elsewhere? The encyclopedia's cluster-like structure of articles around a topic means each article needs to set and maintain a tight focus. It's a question of where the information is MOST expected to be found, and that's where we should put it. That keeps duplication of effort and column space to a minimum. I think the most logical action is to strike the history from the article; the other articles are large and detailed, and there isn't anything here that can be meaningfully merged there.

Future developments is also a history section of sorts, and covered both in International system of units and History of the metric system articles, as well as Proposed redefinition of SI base units. So now we have 4 copies of that piece.

What might be usefully said in a history here, from the top? Not another narrative (we already have 2, because there's also one in International system of units History section). Maybe some kind of structural history, rather than a narrative one, which aids in understanding the scope of the metric system as a science, and as a human endeavor. It should say something not said as such elsewhere, and be strictly limited in length - 3-5 paragraphs are more than enough. This article not about history. Sbalfour (talk) 18:16, 16 January 2018 (UTC)

I would write something like this here: The history of the metric system is a bit more than 200 years. It spans four eras: the latter part of the Age of Enlightenment, the Age of Science, the Industrial era, and the modern age. It begins in 1792, with an experiment in measurement, a survey of earth's meridian in order to use a fractional part of it as a unit of length. It extends through at least 1960, with the introduction of the modern metric system.

The first metric system in Revolutionary France was two-dimensional; it defined units of length and mass. A third dimension, that of time, was recognized early in the 19th century. Together they constituted a system of mechanical units that were the basis of several metric systems over the next 70 years, including most the variants we know today. But the systems were fragmented because they were missing a more subtle unit, an electrical one, identified just after the turn of the 20th century. These units formed an integral and substantially complete system.Two auxilliary units were added in mid-century, along with a number of derived units, and it became the modern metric system. It emphasizes units over properties of the system, so needs revising. But it's an informative overview, one not available elsewhere. Sbalfour (talk) 00:46, 17 January 2018 (UTC)

Variants
No mention of the EMU, ESU, Gaussian, International system, or Heaviside-Lorentz systems of electrical or electrical+mechanical units. We still use some of these today in special fields. The first complete three-dimensional system of mechanical units did not have a name, and was that of Gauss around 1832, and its units were gram, millimeter, and second. It existed until around 1873, with the definition of the CGS system by the British Association for Advancement of Science. Sbalfour (talk) 18:36, 16 January 2018 (UTC)

Under this section, we have a subsection International system of units. The International system of units is not a variant of the metric system - it is the metric system, the only one that can be meaningfully called that for ordinary purposes. It should have its own level 2 section. Variants are essentially part of history - there are no variants today, with piddling exceptions. The Variants section can probably be subordinated to the History section (if one remains in the article), or if not, subordinate to the (raised) International system of units section, since they are essentially precursor variants of it. We don't want to draw attention to these, they're a distraction from the science and should not remain as a level 2 structuring section - they're not a structuring part of the metric system. Sbalfour (talk) 22:24, 16 January 2018 (UTC)

Realisability
I'm not sure I can divine from the whole section that the kilogram standard is still a man-made artefect. It's the largest impediment to advancement of the metric system, and should be stated in the first or second sentence.

The length of the meter is now defined in terms of the speed of light, and "can be reproduced by any suitably equipped laboratory." This is an article about everyday science for the man-in-the-street. The metre or metre-stick is the most recognizable object on all of earth. I'm in a laboratory with a flashlight, mirrors, a stop watch and measuring tape (possibly in feet and inches) and I need to make a metre. Now what? To the average person, it doesn't make sense to define any length in terms of the speed of light, because we can't "see" it move. Even a college-level physics laboratory won't be equipped to measure the speed of light well enough to make a reasonable metre. The reader walks away from the article with the vague feeling he should know something he wasn't told. These things are so familiar yet so far way. An article like this should make science accessible. It could be explained, in just a few sentences, how the technology is used. No, it won't enable someone to go down in their basement and make a meter, but it would make it believeable that a competent physicist with precision equipment could do it. The encyclopedia isn't a "how-to" manual, as the purists would object. But sometimes, a little of the how-to is necessary to convey understanding. In this case, it is understanding that it is both possible and useful to define a meter as some fraction of the disance light travels in some unit of time.

Realisability is a subsection under features, parallel to things like coherence. It's not actually a "feature" of the metric system. It's the flip side of the whole science, the experimental side. No, they're not independent - it's not very useful to define something if we can't make one, nor is it useful to make something because it's easy and use that as a definition, because such a definition may not be useful. Making a ball of mud is very easy, but defining a kilogram as such a thing is not very good. The section needs its own structuring level 2 section. Things like base/derived units, coherence, rationalization, decimalization, etc are the properties of the system.

Sbalfour (talk) 19:24, 16 January 2018 (UTC)

Features
The subsection Universality is mislabeled - it's about history, not science. I'm not sure what it should be called, but it belongs in the history section. I've already noted above that the subsection Realisability needs it's own level 2 section, and doesn't belong here.

The design properties of the metric system are enumerated in a paragraph of the redrafted lead. There are about 6:
 * a base unit/derived unit structure
 * units taken from natural phenomena
 * prefixes for multiples and fractions
 * decimal ratios
 * coherence
 * rationalization

There are a few more auxiliary properties not so much a part of the design as the applicability: as stated, universality; rationally related units; and extensibility. Rationally related units is not so obvious: in the 19th century International system of units, the unit of length was 107 meters, and the unit of mass 10-11 grams. These are not rationally related, so the system wasn't very practical for anything but its electrical units. Universality is more about making concessions to existing systems of measure by allowing units of those systems alongside the metric system or giving them definitions in terms of the metric base units so that the metric system is usable by all. Extensibility in practice means that it's easy to add new base and derived units to the system as has been done.

There's also an implicit completeness axiom that defines the system: the 4 electromechanical base units together can measure any known quantity. In the 19th century, it was believed that only three were required, and the system fell into chaos. We have three other base units which are defined today, but are not independent. Some explanation for why these exist and make sense is part of the science. Each of the 6 primary properties needs it's own subsection here. An additional subsection could cover the applicability aspects. An insider who knows the science can write the last subsection, possibly an interpretive one, on the character of the non-orthogonal base units.

Sbalfour (talk) 20:33, 16 January 2018 (UTC)

Usage around the world
The first and largest (unamed) section under this heading isn't about the science, but about adoption or metrication. There's even a hatnote telling us that. It belongs under History, in the subsection International adoption which it's directly a part of.

This whole article is terribly muddled about what's pure science, what's applied science (metrication), and what's history. If I threw out everything that's not science, I think the article would shrink by 2/3 or even 3/4. I have to say, given the structure of the encyclopedia now, that metrication is not a proper aspect of this article. There are at least 10-12 articles about metrication, and more appear regularly. Surely one or more of those is where that information is expected to be found. What usefully can we say about metrication or adoption here? Maybe it's worth a bare few paragraphs but not more. The fragmentation of the encyclopedia is daunting,but that's what we have to work with.

Sbalfour (talk) 21:10, 16 January 2018 (UTC)

What are the units??
This is an article about the metric system, I'd say the lead one, or the one at the top of the pyramid, the one with the broadest scope and most content. The one likely to attract the most eyeballs, where most people will come for their information. So I come here to get answered a simple question: what are the units? How about litre, foot and pound? Maybe not? Well, then what are they? All of them, because there's only a few, so I hear. A list, or a sentence giving their names and possibly their dimensions. I suppose each of their names is mentioned somewhere at least once, but even if I find some of them, how do I know I got them all? And well, there's a rather longer list of derived ones, so maybe a bullet list, or a modest table. It's sadly disturbing that neither can be found here. That info is found somewhere else, and how will the reader know where that is? And even if it is, the reader is here, and this is where he should be. This is the main article for the metric system. Laser beam to the brain. What's the content? Sbalfour (talk) 22:05, 16 January 2018 (UTC)
 * Damn good question. As far as I can tell there is no article on WP describing metric units in the general sense, including non-SI units such as the dioptre or the litre. For what it's worth I tried to make such an article but it was deleted. (See remark at the bottom of this page) Dondervogel 2 (talk) 20:24, 13 February 2020 (UTC)

What's a kilogram?
A man buys a sack of flour, and it's labeled "one kilogram". He weighs it, and the scale says "2.2 pounds". But someone told him that a kilogram is a unit of mass, not weight. Should a kilogram weigh 2.2 pounds? So he figures maybe the difference is something like that between dry and wet ounces. The merchant might've labeled the bag that way in order to cheat him, figuring he won't know the difference anyway. He doesn't know if he's being cheated, but he's dubious. Can this article resolve the problem? That's surely science. A kilogram is not a unit of weight, though it will surely weigh a kilogram (2.2 lbs in this case).

Will it ever matter for practical purposes? An analogous case is that of a pendulum clock whose pendulum is about .994 meter. If you take that clock to the equator (or the north pole) or just about anywhere, it will no longer keep accurate time, and it will be noticeable after a few days. For the same reason, taking a kilogram of flour to the north pole will result in it no longer weighting 2.2 lbs. But a kilogram of flour, properly measured anywhere on earth, will be the same amount of flour as a kilogram of flour at the north pole. Does that matter? A scientist will not take 2.2 lbs of any substance to the north pole. He will take a kilogram.

Somewhere in the article, this bit of science should be done, because all of our customary systems of weights and measures include a unit of weight (or several) and man-in-the-street, even one in a metric world, may not have a good notion of what the metric unit of mass really means.

Sbalfour (talk) 22:58, 16 January 2018 (UTC)

Structure of the article
Now it has become clear from my remarks, what the structure of the article should be. The topic of the article is one about science, so information on metrication and history should be dispatched to articles on those topics. The level 2 structuring sections are as follows:

1. units
 * base units
 * derived units
 * auxilliary and accessory units

2. Realization of units
 * as natural measures
 * as man-made artefacts
 * as synthetic phenomena
 * as constants of physics

3. properties as a system
 * taken from nature
 * decimal ratios
 * prefixes for multiples and fractions
 * base/derived unit structure
 * coherence
 * rationalization
 * properties of applicability: universality, extensibility, rationally related units
 * 'completeness' of electromechanical units

4. International system of units
 * Historical variants

5. metric system in the real world (glitches and gotcha's)
 * weight and mass
 * liter and cubic decimeter
 * human factor in units (sievert and candela)

6. conversion table

That's about the right number of level 2 structuring sections. In my experience, it should be 5-8, no more. Before writing, or reorganizing, it helps to lay it out, so subtopics become apparent.

Sbalfour (talk) 23:30, 16 January 2018 (UTC)
 * Ok. most of the level 2 restructuring has been done. Several level 3 sections are missing; a few others need to be moved or removed.  The text under International system of units is oral flatulence, another piece of history that's not part of the science of this article. Most of the cruft has been collected into the History section which has been moved to the end of the article. There's no sense spending any effort to reorganize this section, it's dead-ended: it will be merged into other articles, removed or split into some kind of separate article.

Sbalfour (talk) 04:50, 17 January 2018 (UTC)

weight and mass
All customary systems of weights and measures since the days of Charlemagne and as far back as the classical civilizations of Greece and Rome, included a measure of weight, often several. As we now know, the weight of an object is the force of earth's gravity on it. Gravity was unknown until Newton's Principia in 1687, so the weight of an object was regarded as a fundamental property, and was the same everywhere. Newton told us that the earth does not have uniform shape, and that as a consequence, the force of gravity varies by latitude and altitude. The metric system does not have a unit of weight, but one of mass.

An object in outer space loses its weight, but not its mass. If a weightless rock is thrown in outer space and strikes an object, it will strike with force. The object has a property which does not depend on earth's gravitation. That property is mass. Mass is an intrinsic dimension of matter. An object's mass is proportional to the amount of matter in it. That amount can be determined very precisely by the amount of force over time required to accelerate the object to a specified velocity. Its mass is therefore referred to as its inertial mass, when the context leaves room for ambiguity. An object's inertial mass is the same everywhere on earth, and anywhere in the universe as far as we know. An object's mass can be weighed, but that weight represents the local force of earth's gravity upon it, not its mass. Earth's gravity varies by only a few parts in 1000 over the surface of the earth (from pole to equator), and a scale capable of measuring that would typically be found only in a scientific laboratory.

Names
Like so many of these related articles, this one includes an assortment of organization and political/administrative body names. Here's a partial list (I probably missed a few):


 * CIPM
 * BIPM
 * CGPM
 * BAAS
 * CIE
 * IAU
 * Assemblee
 * IUPAP
 * IEC
 * ISO
 * ISR
 * NIST
 * CCU

This article on science can be written in a way that is fully accessible and richly detailed without any of those names. I have written the lead; it covers most things of importance in a topical way, and does not mention any of them. A couple of those names appear ten times or more in the article. Only one of those names, CGPM is worth a mention in the article, and that sentence should be to carefully define its mission with respect to the science. It could be in a sidebox rather than embedded in the article. Organizations don't do science; men do. And there are not so many men mentioned in the article. Saying those names are vital to the science is equivalent to saying if the organization changes name or ceases to exist, some part of the science becomes invalid.

The article can also be written without mentioning the names of any of the historical men of science - their place is in the companion article on history. I do think it would focus editors on writing about science rather than organizations, people, proposals, administration and other things. There's also a bad habit of popping in names we know nothing about, forcing the reader to jump to another article (if it's wikilinked, and it may not be), back and forth for each name. A sentence like "Kelvin proposed in 1848..." where it's the first mention of the name. Instead, "19th century English scientist William Thompson (Lord Kelvin, for whom the SI unit Kelvin is named) proposed ..." The date of the proposal might be important, but likely not. We can also say, more meaningfully, "In the middle of the 19th century, the bottom of the Kelvin scale was established at -2730C, very close to its known value today." We don't need to know the name, or it could be put in a footnote, so we focus on the science rather than the person.

I know why editors write these kind of things: it's much easier to write a factoid: "The CIPM proposed ..." than to write about science. To write about science, one has to think. To write a factoid with a name, one only has to copy. It's scarier still to think the editors don't actually know the science, they only know what they copy.

I'm going to rephrase the article to get rid all the organization names, and move most of the person names if they are meaningful, into footnotes, else into the article on history Sbalfour (talk) 18:16, 17 January 2018 (UTC)

International system of units#Historical variants
I enlarged the section considerably, now I think I regret it. I added a section on MKS, for example, which is WAYYYYY more important then Gravitational systems. Still, the longest running and only standards-based metric system while it existed, is not listed. Right: the French system of 1799 which lasted at least through the 1873 definition of the CGS system by the BAAS. New standards weren't fashioned until 1889, so figuratively, it lasted 90 years. The French system doesn't exist anymore, but the Gaussian (EMU + ESU) system is still in active use in theoretical physics. However, the whole level 2 section is now a chunk of history. Given the anemic level of science in the article generally, should we be taking a sharp left turn into history here? There's already a whole article on the International system of units, which has been proposed to be merged here, so we of necessity need to be summary in this section. What exactly should be the content until that merge is completed? Anything written will become a future burden to merge.

Sbalfour (talk) 19:56, 17 January 2018 (UTC)

Other base units
Too many names, too much history, too much wind. Funny how those go together. Oh, in case I forgot, not very much science. How, exactly do you count a second in vibrations of the cesium atom? How does one 'catch' light and break it into meters? We go into our basement laboratory, and conduct a scientific experiment. What do we have there, and what do we do with it? That's science. High schoolers learning science come here. They don't know how it can be meaningful to define a meter in terms of something intangible like light. We can give them that understanding. And no, they won't be able to conduct a useful experiment to make their own meter, but they might be able to conduct some other experiments related to other base units.

Some raw facts are pertinent to this section. But most pertinent is an understandable explanation of wny units are realized the way they are, and some physics as to how they do that. Sbalfour (talk) 21:36, 17 January 2018 (UTC)

It says: None of the other base units rely on a prototype – all are based on phenomena that are directly observable... That's wind. What would be a prototype of an ampere? A lightning bolt in a jar? Is an ampere directly observable? It's precisely because the dimensional manifestation of electromagnetism is not directly observable that it took about a century for an electrical unit to be recognized as the fourth essential component of an electromechanical system of units. The ampere is NOT realized the way it was in 1881, which is the impression gotten from the text. What should actually be said here? One unit, Kelvin, isn't mentioned at all (a temperature scale which is not part of the SI is mentioned instead). mole and candela are mentioned by name, but no description of how they are realized is given. I'm in a laboratory, and need to measure one of these things. What do I do? Only the second has a satisfactory description of its realization, and it's buried in a heap of history. That sentence gets to stay; the rest of the subsection is superfluous.

This section (and the one for metre and kilogram, which should probably be merged into this one), ostensibly should consist of two things: a statement of how the unit is defined, which is a realizable relationship, and a statement of how to get from that relationship to an SI unit usable where it is needed, i.e. a laboratory procedure. The definitions may appear elsewhere, like in the Units section (which previously did not exist), in which case only the statements about laboratory realization need appear here, and which currently none do. How do you get from vibrations of a cesium atom to a clock that ticks in seconds? It matters practically as well as theoretically: we had to change the definition of candela because it was in practice not very reliably replicable. So now it is not very meaningful, but can be very accurately measured. The definitions tend to converge to realizable representations, but the definitions themselves are NOT the realizations. So this entire section is essentially vacant of appropriate content.

Sbalfour (talk) 18:49, 18 January 2018 (UTC)


 * I've removed the "completeness" section completely. It had no sources, so its thesis was seemingly based on some random editor's opinion; it incorrectly referred to "electromagnetism" as a dimension, which it isn't; and, ironically, it was incomplete as it didn't discuss luminous intensity, temperature, or amount of substance. Hairy Dude (talk) 13:17, 1 June 2018 (UTC)


 * That section did have the feeling of being inadequately sourced, even though the underlying thesis should not be regarded as unfounded. I'm intrigued by your counterpoint "ironically, it was incomplete as it didn't discuss luminous intensity, temperature, or amount of substance".  SI defining the corresponding units as base units does not dictate to physics: they are not physically independent quantities (their inclusion in SI as independent quantities reflects human issues and convenience, not physics; this is sourcable, e.g. the Chyla reference).  —Quondum 15:25, 1 June 2018 (UTC)

Realisation of units

 * I've dumped this whole section (2 subsections) into history, which is what it is/was. The section now gets a new on-point start.  A significant factor, not previously mentioned, is how precise are the realizations?  The whole point of the science here is how good we can make them.  There's no doubt at all that we can make them - anyone can machine a kilogram.  The goodness would usually be expressed as on order of  10-x parts.

Here's the basic thesis: realization of units of measurement proceeded through 4 stages of refinement.

The first was observable phenomena of nature. The most convenient and omnipresent object in nature was a human being. Hence we got foot, span, cubit, toise, etc. Weights were usually defined in terms of volume of some substance, especially volumes of a monetary substance like silver. Realization of a unit was the unit: a span is a hand, etc. Long distances were defined in terms of the Roman stride or double-step. A thousand Roman strides was (and is) a mille = 1000 strides, or mile. Roman soldiers didn't carry toise-long iron bars around to measure miles. But measures based on nature aren't very reproducible because nature isn't actually all that constant as we learned with pendulums in the 16th century.

So standards used in trade tended to be artefacts that replicated familiar quantities from nature. Man-made artefacts represented the second stage of refinement of measures. But the problem remained. When an artefact deteriorated or was lost, a new standard had to be made, one taken from original circumstances in nature. Or someone somewhere else, who didn't have access to the standard, made one of their own using knowledge of how the standard was derived. Everyone has a foot, but not everyone's foot is the same.

Starting in the middle of the 20th century, we had scientific laboratories that could very accurately measure things using synthetic quantities like wavelength of characteristic spectral lines of some substance. This isn't exactly a phenomenon of nature. There's nothing natural at all about krypton-86; we have to make and purify it in a laboratory. But the excitation wavelength is very precise; that from all krypton-86 atoms will be exactly the same. So synthetic phenomena represent the third stage of refinement of measures. But even synthetic phenomena can vary somewhat. The excitation energy of krypton-86 can affect the wavelength of the spectral line. So an implicit part of the definition is that excitation energy.

But there are some things that are truly invariant in the physical world, though they may be measurable only in a laboratory. They lie at the core of existance. They are relations between matter, energy and the quantum properties of space. Things like the speed of light and Boltzman's constant. They can be very precisely known, because directly or indirectly they define the results of all scientific experimentation. There are only a very small number of such truly invariant things. But in terms of them, everything else that does vary can be defined. That is the fourth stage in refinement of measures, and we are very close to that today.

Sbalfour (talk) 23:02, 17 January 2018 (UTC)

History section retired
History is another article. The history here was a mishmash of history of the science, history of adoption, and history of administration by the CGPM and subsidiary organizations. Editors who sincerely wish to work on that can help us out in the history articles. Editors who work here, can now focus on the science. Sbalfour (talk) 20:43, 18 January 2018 (UTC)
 * I don't understand why the history section was retired. Most subjects have a small "history" section, with a link to the detailed article. It should be the same here, it's interesting and it relates to the subject. Kokonino (talk) 11:15, 16 November 2018 (UTC)
 * PS: I don't intend to edit or do anything on this article, I'm just surprised.

POV pushing?
, there are at least five problems with this addition of yours - in no particular order: I propose reverting this addition. -- DeFacto (talk). 16:14, 3 January 2019 (UTC)
 * 1) You present a subjective opinion as fact (that the metric system has benefits), this violates policy WP:WIKIVOICE (I already raised this problem with you on your talkpage)
 * 2) You conclude that the metric system must have benefits because 190+ countries use metric as the predominant system of units, 3 do not - yet the cited source does not say that - that violates policy WP:SYNTH
 * 3) You cite a non-reliable source (the biased opinion from a self-published website of UKMA, a single-issue metrication pressure group from the UK) in support of your synthesis. This violates policy WP:SELFPUBLISH
 * 4) You editorialise the statement by the use of the word "despite" which contraves guideline WP:EDITORIAL
 * 5) You are restoring your edit without consensus which violates policy WP:CONSENSUS
 * I have removed the reference that can be regarded as POV and will not add it again.
 * It's puzzling that 192 countries say yes to Metric and 3 refuse to do so. I wonder why... B. Fairbairn (talk) 12:14, 4 January 2019 (UTC)

roentgen
The units of R are NOT m²/s² but 0,000258 C/kg Roentgen_(unit). It is just silly to put it in one box with rad and gray! Ra-raisch (talk) 11:55, 2 February 2019 (UTC)

Why is the base unit for mass the kilogram?
My understanding of the Metric System is that the gram, not the kilogram, is the base unit of 'Mass' measurement. — Preceding unsigned comment added by Drlambert100 (talk • contribs) 19:38, 12 February 2019 (UTC)


 * OK. I did a little investigating and this is what I found. The name "kilogram": a historical quirk Drlambert100 (talk) 19:55, 12 February 2019 (UTC)


 * The explanation on the web page that you linked to is misleading. It implicitly suggests the base unit of all metric systems (original, CGS, and SI) is necessarily the kilogram because of a situation in the 1790s. That suggestion is false, because the CGS system, which was the main metric system for decades, and which still is in use in some areas, has a different base unit: the gram.


 * Although that web page says it wants to answer the question why kilogram is the name of the base unit of mass, it actually answers another question: why the kilogram became the primary standard, or artefact, in the 1790s. It remained the primary standard in CGS and SI. However, the base unit is an entirely different beast. The original metric system had no base units. Base units were introduced later, when electromagnetic units were embedded into the metric system, officially when the CGS system was internationally adopted (1875). The scientists who designed the CGS system, Maxwell and his standards commission, chose 1 gram as the base unit of mass, because they wanted the density of water to be 1, when expressed in base units (g/cm3, in CGS). Unfortunately, the coherent electrical units of CGS (abvolt, abampere, etc., using their names from 1903) were different from the "practical" electrical units that electrical engineers, who were working on telegraphy and submarine cables, preferred in practice (volt, ampere, etc., using their names from 1881). The practical units were not coherent with CGS, they were merely decimal compatible. This also applied to the units watt and joule, that had been derived from the practical units in 1893 (watt = volt-ampere, and joule = volt-ampere-second, originally). To harmonize the metric system with the practical electrical units Giorgi proposed a different set of base units, MKS(A), in which the practical electrical units are coherent, and in which the density of water did not need to be 1. His proposal led to the adoption of SI in 1960 (and earlier, to the adoption of MKSA in 1948). It is easy to show that kilogram is the necessary base unit for coherence with the practical electrical units volt and ampere. The unit of electrical energy (volt-ampere-second = V A s = joule) should be equal to the unit of mechanical energy. So $$[E_{el}] = [F\cdot L] = [(M\ L\ t^{-2})\ L] = [M]\ [L]^{2}\ [t]^{-2} \rightarrow [M] =  [E_{el}]\ [t]^2\ [L]^{-2}$$. Hence in SI, $$[M] = 1\ J s^{2} m^{-2}  = 1\ kilogram \,$$.


 * In summary, the kilogram became the base unit in the 20th century, when the CGS system was replaced by SI (and earlier MKSA). If the 19th century electrical engineers had chosen other values for their practical electrical units, resulting in another value for the joule, the kilogram would not have been the base unit today. Ceinturion (talk) 20:54, 10 June 2019 (UTC)

Metric system = SI?
"It is now known as the International System of Units (SI)."

Really? My understanding has always been that the litre, tonne, hectare and bar are part of the metric system, though not part of SI. Furthermore, here in the UK, probably elsewhere as well, a lot of consumable products would be in breach of regulations if the litre weren't a metric unit.

Furthermore, if they were synonyms, why would there be a separate International System of Units article? — Smjg (talk) 15:38, 10 August 2019 (UTC)
 * I agree that could be better phrased. The metric system has evolved since its inception in 18th century France, through various forms, and its current internationally agreed incarnation is the SI. The litre, tonne, hectare and bar are metric units but not SI units, and the SI committee has accepted that they can be used alongside SI units, and has given the first three symbols, though not the bar - so its full name has to be used as its "symbol". -- DeFacto (talk). 17:37, 10 August 2019 (UTC)
 * Hmm. Are there SI units that aren't metric units?  The metre and kilogram are undisputedly metric units, but what about the second, ampere, mole, kelvin and candela?  I realise the bar depends on the second, and moreover Metric time talks about decimal powers of 10 being used with the second, but I'm not sure that we can draw any conclusions from this.  And furthermore, significant portions of this article amount to confusion between the two terms and duplicate information on International System of Units.
 * Furthermore, 'mb' gets used as a symbol for 'millibar', so surely 'b' is valid as a symbol for 'bar'? Or is the point that these symbols weren't invented by the SI committee? — Smjg (talk) 17:32, 28 December 2019 (UTC)
 * There are many units that are metric, but entirely different from the SI unit that measures the same quantity. A good example is the metric-but-not-SI unit millimeters of mercury to measure pressure, versus the SI equivalent, the pascal.
 * SI is intended to use the same symbol in all languages, so symbols based on a particular language are not part of SI. For example, cc as a symbol for cubic centimeter is not SI because "cubic" is an English word. The SI symbol for the same unit is cm3.


 * In addition, having a variety of names or symbols to measure the same quantity is a disadvantage because it's harder to learn them all. So one good reason to exclude the bar from SI is because the pascal is already available to measure pressure. Jc3s5h (talk) 00:14, 29 December 2019 (UTC)

Objection
Wikipedia has multiple redundant articles on metric systems. Articles it does not need. But it has none on metric units as a concept (describing all metric units, regardless of system). Then when I create one you delete it. Why? Dondervogel 2 (talk) 20:12, 13 February 2020 (UTC)
 * You asked me to discuss here so I did. Getting no response to my objection (to your revert), I see no reason not to revert that revert. Before doing so I will wait 24 hours for an explanation (from you or any other editor) for where to find an article describing metric units. This one (as implied by its name) describes an (evolving) metric system - it makes no attempt to define all metric units. Dondervogel 2 (talk) 13:51, 15 February 2020 (UTC)
 * I uploaded the article Metric units. The scope covers all metric units, including logarithmic units following a decimal scales, and is therefore broader than any one metric system. Perhaps the logarithmic units deserves an article of their own? Suggestions for improvement are both solicited and welcome. Dondervogel 2 (talk) 14:56, 16 February 2020 (UTC)
 * I have tried to follow the various discussions that have already taken place, and agree with the broad problem that having this article claiming to be solely about SI units, a separate International system of units article, and nothing comprehensive about "the metric system of units" makes no sense. I may have missed some discussions, but it seems that the critical one is at Wikipedia_talk:WikiProject_Physics.  This was making good progress, but did seem to peter out somewhat.  However, I don't see any consensus for creating Metric units as a new article in addition to this one.  There did seem to be support for heavily rewriting this article, with a view to perhaps renaming it in the future.  If you want to produce that edit from scratch, it would seem that draft or sandbox would be the place to do it.  We don't need to make things worse with further duplication.  Metric units is linked from a number of Wikipedia pages and no doubt much more widely, and we shouldn't replacing with a redirect to a good article with a work-in-progress, especially when the good article still exists.  Lithopsian (talk) 17:36, 16 February 2020 (UTC)
 * A redirect to Metric system is not the solution because that does not address the scope of Metric units. Metric system is too narrow because it is limited to the (evolution of) the SI. My interest in this started at Litre, where it was suggested that litre was not a metric unit because it is not part of the SI. This is what led me to proposing the new article with a broader scope, but the discussion at Physics was leading nowhere. What do you suggest we do instead? Dondervogel 2 (talk) 17:48, 16 February 2020 (UTC)

Removal of SI?
Can anyone explain why SI "doesn't fit here"? (and yet cgs still does). I certainly can't, thus I've reverted it. Explanations and opinions invited. Andy Dingley (talk) 17:56, 17 February 2020 (UTC)
 * I think I might be in a good position to explain it, I'm not sure why I wasn't pinged on this. I think that this article is a disgrace to Wikipedia, and I was being bold and taking the bull by the horns. Perhaps you didn't notice that it was being systematically tidied up - top-down - and each step was being explained. Perhaps the explanations could have been more verbose, but to me it is pretty clear that the stuff on the SI belongs in the SI article, and not duplicated in this one too. "SI" is not synonymous with "Metric system", and this article should not be burdened with all that duplicated content. Sure a summary of the SI could be added, and would have been, but serious pruning is required first, to remove all the dead wood and get the structure and the framing in order. Or do you think that Wikipedia needs yet another entry in the ongoing competition to create the most bloated article about the SI possible? -- DeFacto (talk). 18:52, 17 February 2020 (UTC)
 * I agree there was way too much duplication with SI. In fact I think an article that purports to describe the Metric system should redirect to SI. If this article has a place at all it should describe either all Metric systems or all Metric units, and be renamed accordingly. Dondervogel 2 (talk) 19:21, 17 February 2020 (UTC)


 * Why is it "a disgrace" ? What's the problem?  Did this address it?
 * SI is essential to an article on metric. It's the current incarnation of the whole thing. I can see some room for debate as to whether SI should be in here or not, but how can we logically (not just pedagogically) keep cgs here and yet remove SI?
 * It's still a matter of surprise to some that inches are not merely equal to 25.4 mm but have long been defined as such. Yet that important role has gone too. Yes, it's not part of "How to measure in mm" but it's still essential within the scope of metric system (which is broader than that).
 * The concept of seven fundamental dimensions is another one which seems unimportant to those who are unaware of it, yet is fundamental to such key concepts in physics as dimensional analysis. Why did that have to be removed?
 * I can't see the "disgrace" here, I can't see the need to remove these sections and I certainly can't see that the stripped version has improved in any way or addressed such issues. Andy Dingley (talk) 03:17, 18 February 2020 (UTC)
 * I repeat what I have already stated: there is too much duplication. This article starts by saying the Metric system is the International System of Units. If that is an accurate description of its scope then it should be merged with International System of Units. Dondervogel 2 (talk) 09:03, 18 February 2020 (UTC)
 * Actually, what the article says is Metric system refers to the internationally recognised decimalised system of measurement known as the International System of Units (SI), or to one of its predecessors. I do think there's to much focus on the SI here, and that's unnecessary, as there is already an excellent article on the SI itself. The correct solution is to deemphasize the SI, and refocus this article on the metric system more generally. Tercer (talk) 09:32, 18 February 2020 (UTC)
 * I can live with that, but then I think it should be renamed Metric systems, and should focus on the multiple units systems themselves and (to avoid duplication of History of the metric system) not on their development. Dondervogel 2 (talk) 09:54, 18 February 2020 (UTC)
 * I think it is counter-productive to argue about the name of the article, this kind of discussion generates lots of heat but little light. The actual issue is the content. Tercer (talk) 10:00, 18 February 2020 (UTC)
 * The name is important because it implies a certain scope, and it is unhelpful to discuss content unless we first agree on scope. Therefore I think it makes sense to first agree on the scope, then on a (provisional) name that reflects that scope, and then move on to content before revisiting the name. Dondervogel 2 (talk) 12:49, 18 February 2020 (UTC)
 * I think the article let's the side down because...
 * The lead is being used, not as a summary of the main article, but to add material not found anywhere else in the article which: bigs-up the SI, promotes the urban myth about Liberia, Myanmar and the US and attempts to diminish respect for the US customary system and the British imperial system.
 * The article contains unjustified rehashing of content that can be found in abundence in the International System of Units article, and it's subsidiary articles such as SI base unit, SI derived unit, Metric prefix, History of the metric system, and in Coherence (units of measurement), and probably in many other articles too.
 * The article does not have a coherent or logical structure, reads poorly and is badly referenced, relying too much on primary sources and "personal opinions".
 * I hope that makes my case clearer for you. -- DeFacto (talk). 10:47, 18 February 2020 (UTC)

Restructure proposal
My objective was to structure the article with headings something like below, with simple summaries and reference to main articles where they already exist. A Metric system is any one of the systems of measurement that succeeded the decimalised metre-based system introduced into France in the 1790s. The most recent such system is the internationally recognised International System of Units (SI).

Background French revolution, etc...

Principles

Realisation (units based on the natural world) Base and derived unit structure

Decimal ratios

Prefixes for multiples and submultiples

Coherence

Rationalisation

Variants

Gaussian second and the first mechanical system of units

EMU, ESU and Gaussian systems of electrical units

Centimetre–gram–second systems

International system of electrical units

MKS and MKSA systems

Metre–tonne–second systems

Gravitational systems

International System of Units

See also

References

External links What do others think? -- DeFacto (talk). 11:42, 18 February 2020 (UTC)


 * It would definitely be an improvement on the current state. Make the edit and I'm sure it will attract more attention than abstract talk-page discussion.  I think we can claim consensus that something needs to be done.    Lithopsian (talk) 18:11, 20 February 2020 (UTC)
 * Okay, encouraged by the only response to my proposal being a positive one (thanks ), I have (my second attempt), in an attempt to start the process of constaining the content of this article to match its title, re-worked the article to the above scheme. -- DeFacto (talk). 20:02, 21 February 2020 (UTC)
 * You have my support as well to give this a go. I encourage a suck it and see approach. I'll try to chip in myself every now and then. Dondervogel 2 (talk) 21:30, 21 February 2020 (UTC)
 * Yipes – I've just stumbled across the Unified Code for Units of Measure. Does this qualify as a variant of the "metric system"?  I'm glad to see that it treats angle as a base quantity.   —Quondum 02:06, 15 March 2020 (UTC)
 * Interesting. My opinion on this depends on whether we are describing the metric system or multiple metric systems. We need consensus on that first. (I know you agree with me but we haven't yet heard from others) If the former then Yes, very much so; it is clearly a variant of the metric system. If the latter then No; it is not a metric system. As a temporary measure I have added UCUM to 'See also'. Dondervogel 2 (talk) 07:18, 15 March 2020 (UTC)

Questionable sentence about adoption of the SI system
The article contains the following sentence: "The International System of Units has been adopted as the official system of weights and measures by all nations in the world except for Myanmar, Liberia, and the United States, while the United States is the only industrialised country where the metric system is not the predominant system of units."

Given that:
 * 1) The SI is not the official system in the UK, where the imperial system is also an official measurement system.
 * 2) Metric measures became official in the US in 1866.
 * 3) The sentence was sourced to the CIA Factbook, which is clearly not a reliable source for measurement system related facts, as on the same page it also claims that "... the American adaptation of the British Imperial System known as the US Customary System", which is untrue too.
 * I chose to remove it as a dubious statement supported by an unreliable source. However, objected, and restored it.

I guess we need to either rework it into a factually accurate sentence, and provide reliable sourcing for it, or remove it from the article altogether. I propose removing it for now - rather than potentially misleading readers, pending a consensus over a new wording or removal. -- DeFacto (talk). 20:43, 22 February 2020 (UTC)


 * According to this CNN article "Only three nations do not use the metric system today: Myanmar, Liberia and the United States" and "America is the only industrialized nation in the world that does not conduct business in metric weights and measures". Dondervogel 2 (talk) 21:20, 22 February 2020 (UTC)
 * On the other hand according to a NIST source "It's a compelling story and often repeated, but you might be surprised to learn that it's simply untrue! While it's true that metric use is mandatory in some countries and voluntary in others, all countries have recognized and adopted the SI, including the United States." Dondervogel 2 (talk) 21:28, 22 February 2020 (UTC)
 * NIST also say of the CIA Factbook that it "is one of the often cited sources of the U.S./Liberia/Burma metric myth", and describe why they think the CIA say that and how it is "perpetuating the metric myth and elevating the map to a pop culture meme", on this webpage. -- DeFacto (talk). 22:01, 22 February 2020 (UTC)
 * And this short piece by a BBC journalist describes the turning point which resulted in the UK keeping the imperial system in official use for trading, and ensuring that it was not supplanted by the SI. And this one further describes the continued use of imperial in the UK. -- DeFacto (talk). 22:13, 22 February 2020 (UTC)
 * Perhaps you could take a look at Metrication and its references. The sentence is perfectly accurate, if lacking in detail. Metric is the official system in the UK, from European Union law, with imperial units being allowed in limited cases. Are you really disputing the fact that the United States doesn't use metric units? And that the U.S. units derive from the British ones? Or are you just arguing about some minor technicality? Tercer (talk) 22:35, 22 February 2020 (UTC)
 * Metric is only one of the official systems in use in the UK, imperial is the other - so it is incorrect to assert that SI is the (implying only) official system there. The EU conceded in 2007 that the UK could continue to use imperial (see the BBC refs I mention above), and there are applications where imperial is mandated and where metric is unlawful. And yes, I certainly am disputing, per the NIST articles linked above, that the US doesn't use metric units. How would you answer NIST's charge that the CIA factbook is helping to peddle those myths? And the US customary system is definitely not an adaption of the British imperial system, it is derived from the much earlier English (not British) units, as is the British imperial system. -- DeFacto (talk). 23:02, 22 February 2020 (UTC)
 * I see, so the US unit are derived from the British units, it's just that they were called English units at the time, and they are different from the current British units. That's just splitting hairs. The BBC references you link describe precisely what I said: metric is official in the UK due to EU law, and imperial units are allowed in limited cases. As for NIST's charge, that's pure wishful thinking. The US does not use metric. I find it bizarre that this point even needs to be argued. See Metrication in the United States for the long history about how the US failed to adopt the metric system. Tercer (talk) 00:04, 23 February 2020 (UTC)
 * no, you are conflating two different unit systems here. There are three systems in total involved (each with its own Wikipedia article), let's call them EU (English units), BI (British imperial) and USC (US Customary). Both BI and USC were derived independently from EU (after US independence), so did, in effect, diverge from each other. A source considered to be reliable for matters related to measurement systems would be expected to know the distinction between these three different systems, but what the CIA Factbook is effectively saying is that USC is an adaptation of BI, which is factually incorrect as USC is an adaption of EU, and not of BI. It is not just a question of semantics, or "splitting hairs", it is a basic misunderstanding/misrepresentation of the underlying facts. BI was conceived in the 1820s, more that 40 years after US independence, by which time USC was already being developed and based on EU, that the US inherited (long before the UK was even formed) when they went independent in 1776. -- DeFacto (talk). 10:55, 23 February 2020 (UTC)
 * I'm not conflating anything. EU (you're going to trigger some British editors with this choice, by the way) was the system of units used in the British Empire at the time. You're just objecting to the CIA calling it "British Imperial System", because it can be confused with its later evolution which you call BI. That's just splitting hairs. CIA is perfectly correct in saying that the US system is derived from the British system, their terminology is just a bit ambiguous. Not that this has anything to do with the matter at hand! You're just using this technicality to discredit the source about its about its statement of the obvious, that the US has not adopted the metric system. Tercer (talk) 12:08, 23 February 2020 (UTC)
 * Also, both the article about Liberia and Myanmar state that they don't use metric, even though both countries intend to adopt it. Tercer (talk) 22:39, 22 February 2020 (UTC)
 * it's the assertions about the US and the implications about the UK that I am disputing, I don't know anything about what happens in Liberia or Myanmar. -- DeFacto (talk). 23:05, 22 February 2020 (UTC)

Let's pause this, and the flood of sources below. We still need the article to reflect the fact that if this Australian goes to the UK I encounter a place with a bit of a mixture of units, but where everybody understands the metric system, and metric units are commonly available for almost everything. This is simply not the case in the US. When I visit America I have to dig out of my ageing brain all those pounds, yards and gallons that I haven't used for 45 years. Not a criticism of anyone, mind you. Just a reality to observe and describe. Let's not pretend the US and the UK are alike on this front. HiLo48 (talk) 01:59, 23 February 2020 (UTC)
 * you are missing the point here. I am not arguing that the UK and US are at the same place wrt metrication, I'm saying that the UK's position is being overstated and the US's position is being understated by saying the former has been metricated and the latter has not. The UK has two official unit systems, imperial and metric, with imperial being mandated for some applications and metric for many others. It could be that the UK is 75% there and the US 40%, for example, but it is not 100% and 0%. -- DeFacto (talk). 11:03, 23 February 2020 (UTC)
 * I think I could say that in common understanding, it's much closer to 100% and 0%. Maybe the latter should be above zero, but not 40%. Everyone in the UK understands metric units. How many Americans do you reckon understand them? During my visits to the US I unthinkingly use metric units to describe things at times. (45 years of brain training will do that.) I am inevitably confronted with blank stares from the vast majority of people. Sure, things were different when I visited NASA, and I'm certain other scientific institutions would be like that too, but not down the shops with the general public. HiLo48 (talk) 22:52, 23 February 2020 (UTC)
 * But we are talking about activities which officially use the metric system, not level of understanding of it amongst the general population. In the UK there are still many activities that officially use imperial and in the US there are activities that officially use metric. It isn't a black and white 100% for the one country, 0% for the other. -- DeFacto (talk). 07:10, 24 February 2020 (UTC)

asked "How would you answer NIST's charge that the CIA factbook is helping to peddle those myths?" Ever since the Metric Conversion Act of 1975 NIST has tried to pretend that the US was going metric, and that US government agencies were doing what they were supposed to do under that and subsequent acts. But NIST is living in a fantasy world and their claims about the extent to which the US in general, or federal government agencies in particular, have adopted SI are unreliable. Jc3s5h (talk) 02:37, 23 February 2020 (UTC)
 * it is clear that the US does use metric officially for some appliations, so I guess the true position is somewhere between what the CIA Factbook says and what NIST implies. -- DeFacto (talk). 11:10, 23 February 2020 (UTC)
 * If you read carefully the NIST article, you'll see that it is written by the coordinator of NIST's Metric Program. Because of my passion for all things metric..., which explains why it is advocating for this fantasy. Moreover, its argument that the US has adopted the metric system is simply that the US units are defined in terms of SI units. That's laughable. Tercer (talk) 12:12, 23 February 2020 (UTC)

Relevant sources

 * Chemistry LibreTexts "countries such as the United States, Liberia, and Berma have not officially adopted the International System of Units as their primary system of measurements"
 * CIA Factbook "At this time, only three countries - Burma, Liberia, and the US - have not adopted the International System of Units (SI, or metric system) as their official system of weights and measure"
 * Liberian Observer "The metric system is an international system of measurement adopted universally with the US, Liberia and Myanmar being the only exceptions"
 * NIST "While it’s true that SI use is mandatory in some countries and voluntary in others, all countries have recognized and adopted the SI, including the United States."
 * NIST (phys.org) "You've probably heard that the United States, Liberia and Burma (aka Myanmar) are the only countries that don't use the metric system (International System of Units or SI). You may have even seen a map that has been incriminatingly illustrated to show how they are out of step with the rest of the world. It's a compelling story and often repeated, but you might be surprised to learn that it's simply untrue!"
 * Physics for Geologists "There is some confusion in the USA because their industries, and even some of their scientific journals, continue to use units that are not consistent. Twenty five years ago, 136 countries were metric or changing to metric, and the only countries not going metric were Barbados, Jamaica, Liberia, Nauru, Sierra Leone, S. Yemen, Sultanate of Muscat & Oman, Tonga and the USA!"
 * Smithsonian Magazine "At press time, only three of the world's countries don't use the metric system: the United States, Myanmar and Liberia. But it didn't have to be this way."

The lead
After our promising "new start" with this article, has now chosen to revert the lead back to the earlier poor quality version that has been discredited. I reverted it back to the new starter version, explaining the purpose of the lead, but was quickly re-reverted back again.

In that last revert, Tercer asserted that this is how the lead was for years, when the article was WP:GOOD. Well if we look at the diff between the 'GA' version and the current Tercer version we see that actually, the lead in the then 'good' version's was very different from this. In the 'good' version we had "The metric system has been officially sanctioned for use in the United States since 1866" and "Although the United Kingdom uses the metric system for most official purposes, the use of the imperial system of measure, particularly in unregulated sectors such as journalism, is widespread", for example (which also echoes the views I added to what we've been discussing at Talk:Metric system). And the 'good' version lead had none of the irrelevant stuff about the British imperial system or the US customary system being defined using the metric system.

So perhaps we could revert back to the pre-Tercer lead again as a basis for serious improvement, and stop this unnecessary disruption. The lead should reflect the article, not contain stuff not mentioned in the article, and is ideally created after the article content has stabilised. -- DeFacto (talk). 22:30, 26 February 2020 (UTC)


 * You're removing information that is both true and relevant just because you find it offensive. This is borderline vandalism. Also, I don't see any justification for leaving the lead mostly blank until some unspecified time in the future when you decide to work on it. You're taking a WP:TNT approach to an article that definitely doesn't need it. Please remember that Wikipedia policy is WP:PRESERVE. Tercer (talk) 07:09, 27 February 2020 (UTC)
 * I vote we assume good faith all round and focus on finding a stable version of the lede that we agree not to touch while the Work in Progress banner is in place. My suggestion (for stable version of the lede) is the one that was in place on 1 Jan 2020. The reason for choosing that date was that there were no human edits (anywhere in the article) for a 4 week period around it (15 Dec to 10 Jan), indicating stability. Other suggestions welcome. Dondervogel 2 (talk) 08:54, 27 February 2020 (UTC)
 * I would be fine with that. Note though that my version of the lead was meant to be more agreeable to DeFacto than the stable one, it incorporates a couple of their edits, and I changed the phrasing a bit to make it less SI-centric. Tercer (talk) 10:18, 27 February 2020 (UTC)
 * I'd rather have an empty lead whilst we're working on the content, but, for the sake of cordial discussions, I'm happy to see that version you suggest - even though it embodies much of what I believe was wrong with the article. I applaud your invocation of the "assume good faith" mantra too, as we have to assume that the end goal of all participants is the best article possible. -- DeFacto (talk). 06:56, 28 February 2020 (UTC)
 * I have reinstated the lede of 1 Jan 2020 just because it was stable. No other reason. I feel comfortable with that because I think it's what an uninvolved editor would have done, had we called one in to arbitrate. We all agree the entire article was in dire need of improvement, and some of those flaws were no doubt reflected in the lede. Let's leave it alone for now, warts n all, and revisit once the article content has stabilized. Dondervogel 2 (talk) 08:16, 28 February 2020 (UTC)
 * The beginning of the article is too wordy. Surely the following edits would be acceptable to all:
 * with notable holdouts being > except for
 * In subsequent decades and centuries, > Since then,
 * There is no virtue in verbosity. Michael Glass (talk) 12:06, 14 March 2020 (UTC)
 * I agree that simpler is better and have no objection to the changes you propose. But I have reverted other changes to the lede for the same reason and thought it best to be consistent. What do others think? Dondervogel 2 (talk) 12:48, 14 March 2020 (UTC)
 * Perhaps the comment and nosection template parameters could be used to capture the consensus about the editing context? It could help reduce this kind of thing – I made an edit earlier without first reading the talk page.  OTOH, does anyone intend to work on it in a way that justifies use of the template?  —Quondum 15:53, 14 March 2020 (UTC)
 * There's no consensus for that. I agreed with Dondervogel 2's suggestion on the 27th of February in order to avoid an edit war. The problem is, nothing happened to the article since then. I don't find it acceptable to keep an article frozen and reject contributions because you want at some unspecified point in the future do something about it. Nobody WP:OWNs the article. This is specially bad with such a high visibility page, it had 46,785 views in the last 30 days. You know, draft space and sandboxes exist precisely for this reason. Tercer (talk) 16:51, 14 March 2020 (UTC)
 * Sure, no-one owns the page, but policy is clear that consensus is required to make changes, and if changes are made against consensus they are reverted. -- DeFacto (talk). 16:59, 14 March 2020 (UTC)
 * I've not been following the changes to the main content in any detail, but I just skimmed through it now. My impression is that it is good enough to warrant composing the lede around that content. Why don't we do that here, on the Talk page? We could either start from scratch (if someone is willing to compose a stub) or start from the existing lede and edit that. Thoughts? Dondervogel 2 (talk) 18:11, 14 March 2020 (UTC)
 * Here's a very modest proposal, that I hope will be acceptable to all. Revise the wording with only the following changes:
 * with notable holdouts being > except for
 * In subsequent decades and centuries, > Since then,
 * If those small changes are acceptable, that's great; if not, I'm not going to war over it. Michael Glass (talk) 20:35, 14 March 2020 (UTC)

I think we need to start from scratch and remember that the lead should summarise what is already there in the body, and not introduce material otherwise absent. Here's my humble offering to start the ball rolling:
 * The metric system is a system of measurement that has developed through various standardised forms since its inception as the decimalised metre-based system introduced into France in the 1790s. The most recent form is the internationally recognised International System of Units (SI).
 * The metric system has developed to comply with the following basic concepts. There should be a single base unit of measure for quantities of each of the fundamental dimensions of nature (e.g. the metre is the base unit for length). To measure quantities derived from the fundamental dimensions, units derived from the base units should be used (e.g. the square metre is the derived unit for area, a quantity derived from length). For the sake of universality, the base unit standards should be realisable anywhere from natural phenomena, rather than having to be copied from a single centralised standard physical artefact. A set of standard prefixes should be used to define units which are decimal multiples and sub-multiples of the base and derived units. No conversion factors should be required to convert between units, thus ensuring coherence.
 * The metric system has evolved since the 1790s as science and technology has evolved, to provide a single universal measuring system which can be used for all measurement applications.

-- DeFacto (talk). 20:45, 14 March 2020 (UTC)
 * While not wishing to disagree with either proposal (both are improvements on what we have) there's an important point of scope that needs settling. Is this article about the one and only metric system or about multiple metric systems, including the MTS and various CGS systems in its scope? I don't think it should be the former because we already have a fine article that performs that function. Therefore it should be about the latter. Dondervogel 2 (talk) 23:27, 14 March 2020 (UTC)
 * I agree with this point: there is no single metric system, and "metric system" is not a synonym for "SI" even though the SI is a metric system. WP does need an article about metric systems, and I see this article as being it.  As such, the SI is merely the currently dominant metric system, and should not be given too much weight in this article.  —Quondum 23:49, 14 March 2020 (UTC)
 * Incidentally, we also have a good article History of the metric system, which should also not be the topic here. I think the focus here should be on listing the metric system variants and their characteristics/differences, while staying light on historical detail.  —Quondum 00:01, 15 March 2020 (UTC)
 * In that case, should we move it to Metric systems? Dondervogel 2 (talk) 00:12, 15 March 2020 (UTC)
 * I would suggest holding off on that, and if desired, reconsider after the article is showing its final form. For a start, articles on a topic are not generally named in the plural, and are often named for a member of a class.  Another part of my reasoning is that the term "metric system" is a sort of collective umbrella term for the shared characteristics and history of metrication: the metric systems do not cleanly separate, and many people might think of it as a collective system.  For example, in an informal sense, there is no difference between the cm of CGS and the cm of SI.  —Quondum 00:44, 15 March 2020 (UTC)
 * Sure. Let's revisit this question once the lede has been reconstructed. Dondervogel 2 (talk) 07:10, 15 March 2020 (UTC)
 * yes, I think it should be about all metric systems, but the article name is still probably okay. Here's a slightly reworded version of my lead proposal to reflect that more accurately (per my proposed outline in the discussion above actually):
 * A metric system is any one of the systems of measurement that succeeded the decimalised metre-based system introduced into France in the 1790s. The most recent such system is the internationally recognised International System of Units (SI).
 * Metric systems have developed to comply with the following basic concepts. There should be a single base unit of measure for quantities of each of the fundamental dimensions of nature (e.g. the metre is the base unit for length). To measure quantities derived from the fundamental dimensions, units derived from the base units should be used (e.g. the square metre is the derived unit for area, a quantity derived from length). For the sake of universality, the base unit standards should be realisable anywhere from natural phenomena, rather than having to be copied from a single centralised standard physical artefact. A set of standard prefixes should be used to define units which are decimal multiples and sub-multiples of the base and derived units. No conversion factors should be required to convert between units, thus ensuring coherence.
 * [Here, perhaps, a list of short descriptions of each of the main metric systems]
 * Metric systems have evolved since the 1790s as science and technology has evolved, to provide a single universal measuring system which can be used for all measurement applications.
 * -- DeFacto (talk). 09:15, 15 March 2020 (UTC)
 * Went with that for now. -- DeFacto (talk). 15:38, 19 March 2020 (UTC)
 * Went with that for now. -- DeFacto (talk). 15:38, 19 March 2020 (UTC)

Base units
Two authors have now made the claim that there are more than seven SI base units - without any references. I will quote an edit summary: "it is widely known the SI includes multiple derived units (pascal, hertz, watt to name but a few)" I would suggest that both authors read SI base units and relevant citations in that article. The claim that the pascal, hertz, and watt are base units suggests a serious lack of WP:COMPETENCE in this subject - they are all described as derived units in the lead of their respective articles. The claim that "it is widely known ..." reveals a similar lack of understanding of Wikipedia policies. Suggesting that I tag the article is not a sufficient excuse for reinstating statements without references after they have been challenged. Should I tag it and then delete it because it lacks a reference? Seriously, get it together and demonstrate with reliable sources that I'm an idiot, or take a pause and think about what you're doing. Lithopsian (talk) 20:27, 9 March 2020 (UTC)
 * User:Lithopsian's latest edit contains "In the modern form of the International System of Units (SI), it consists of a set of seven base units...." That's ungrammatical. I suppose ", it" should be removed, depending on the meaning
 * The edit begins by saying the SI consists of the base units. At the end of the paragraph it says "These, together with their derived units, can measure any physical quantity." It is unclear if this means any old units that are derived from the base units, or if this sentence is walking back the claim that the SI consists of the base unit, and acknowledging that SI also contains guidance on how to derive units, and named derived units.
 * The real situation is that the derived units are just as much a part of SI, and are intended to improve communication between different user communities by discouraging different communities from adopting different derived units to measure the same quantities. Part of this guidance is establishing named derived units, which are preferred over other derived units when possible.
 * The portion of an edit summary criticized by Lithopsian, "it is widely known the SI includes multiple derived units (pascal, hertz, watt to name but a few)", plainly states that pascal, hertz, and watt are derived unit. Lithopsian's assertion that edit-summary fragment is saying these are base is just wrong. Jc3s5h (talk) 21:17, 9 March 2020 (UTC)


 * I think the problem here is the English language. For a start, this sentence is not good English - it is ungrammatical: "In the modern form of the International System of Units (SI), it consists of a set of seven base units:..." It should probably be: "The modern form of the International System of Units (SI) consists of a set of seven base units:..."
 * However, that implies that it is only made up of the seven base units, and nothing else. Hence the first edit summary: "SI consists of a lot more than the seven base units". That is saying there are other things as well as the seven base units, not that there are more than seven base units. Then, following the reverted revert, the second edit summary: "it is widely known the SI includes multiple derived units...", that is in addition to the seven base units.
 * So to clarify that, the sentence was changed to make it clear that the seven base units are not all that the SI is made of:
 * "The modern form of the International System of Units (SI) comprises has seven base units:..."
 * That is better because "has" doesn't exclude other stuff like "comprises" does.
 * Think of this - would you say "the human body is made up of ten fingers" or "the human body has ten fingers"? -- DeFacto (talk). 21:35, 9 March 2020 (UTC)
 * No one is claiming there are more than 7 base units, only that the SI consists of more than just base units. Dondervogel 2 (talk) 22:12, 9 March 2020 (UTC)


 * Just to clarify, the changes were not "my edits", they were simply reverts to the previous content. I was reverting edits which I felt gave the impression that there were more than seven base units.  Lithopsian (talk) 17:45, 10 March 2020 (UTC)


 * I have now made an actual edit of the offending paragraph. It is fairly bold, but is intended to address the whole point of the current restructuring which is to redefine the purpose of this article as covering any metric system of units and not solely the SI units.  It also has a reference, a first for this section ;)  The section is titled Background and could arguably be considered as a summary or introduction to later fully-referenced content, but it doesn't seem at all clear that that is actually the case.  If it is the case then I suggest merging it with the lead, which commonly lacks references and is widely understood (sic) to only summarise material discussed in the body of the article.  Lithopsian (talk) 17:45, 10 March 2020 (UTC)
 * The new version contains the phrase "lumen (W-1)," (coded as . This gives the impression that lumens are simply reciprocal watts. It just isn't that simple. Jc3s5h (talk) 18:34, 10 March 2020 (UTC)
 * Fixed. Then replaced with lux instead, since the expression of lumens in terms of the base unit candela is not entirely self-explanatory in a short parenthetical expression.  Lithopsian (talk) 21:11, 10 March 2020 (UTC)

Overidealization
The are more of a description of the culmination of the development of metric systems than of metric systems in general. The idea of having base units as central is not really a principle, but a convenient way of expressing that dimensions form a vector space with a basis, and choosing a basis for it. A statement such as "There should be a single base unit of measure for quantities of each of the fundamental dimensions of nature" is, well, like saying that there are fundamental x-, y-, and z-directions in nature. Let's not systematize the historical metric systems. That there were a limited number of independent dimensions was recognized in the development of the various metric systems, but all we can say is that the systems were built on the understanding that known dimensions could be expressed in terms of a limited number of independent dimensions. Even the number of independent dimensions considered was not uniform: CGS-Gaussian didn't have an independent dimension for electric and magnetic charge, just as we need not have an independent dimension for time (due to the very fundamental Poincaré symmetry of local spacetime. We need to be careful about inserting synthesized/editorial material.  —Quondum 16:54, 22 April 2020 (UTC)
 * I agree that we need to be careful, and that the phrasing was unfortunate. At the same time, one should realize that up until roughly the 1920s, lots of workers thought that there is something truly fundamental about both the number and the identity of the base dimensions—as R. C. Toleman put it in 1917, that the dimensions of a quantity are a shorthand restatement of its definition and hence [are] an expression of its essential physical nature. Bridgman discusses that here, starting with the second paragraph on p. 24 (There is therefore no meaning…; the quote from Toleman is on p. 26).


 * But even if we leave such borderline-mystical aspects aside, it is still true that, in the 19th century, I don't think anyone would doubt that the base dimensions of mechanics must definitely include at least length and time.

Note that Giorgi here actually runs afoul of Bridgman's principle of nearly absolute freedom to choose one's dimensions. Bridgman would not think there is anything particularly strange about electrical resistance having the dimensions of velocity (or its inverse), and would not think that anything other than sheer convenience recommends the systems where electrical quantities are represented by a fourth dimension over the older, purely mechanical three-dimensional systems.
 * Moreover, it was popular to think that the mechanical dimensions (and in particular [L], [M], and [T]) are somehow truly fundamental and truly underlie all the rest. Here is how Giorgi himself described, in 1934, how that opinion eventually changed (the last paragraph on the first page here): "In the meantime [i.e. roughly coinciding with Heaviside's development of Maxwell's electromagnetic theory], the theory of physical dimensions was beginning to be better understood, and the opinion was no longer held that everything in the physical world depended necessarily on three fundamental mechanical dimensions. Physicists recognised that entropy, temperature, loudness of a sound, light intensity, etc., brought into play some dimensions which were not dependent on [L], [M], [T]. Why ought not electric and magnetic magnitudes to be treated in the same way? The pretention of making them dependent on length, mass and time has led to such strange consequences of attributing to electrical resistance the dimensions of a velocity (in the electromagnetic system) or of the reciprocal of a velocity (in the electrostatic system). Accordingly, the principle of having a fourth fundamental dimension entering into the electric and magnetic magnitudes gradually became universally recognised. An independent dimension means also an independent and arbitrary unit; but this conclusion was not drawn at once."


 * Given that this Wikipedia article must of necessity be a bit historical in outlook, I think it is probably necessary to mention some of these considerations, maybe even in the lede. I am not at all sure what is the best way of doing that, however. --Reuqr (talk) 13:50, 28 April 2020 (UTC)


 * A lead, by necessity, usually omits subtle details such as this; it should mention at most that evolution of the underlying definition of quantities strongly influenced the definition of units in each system. Much of this detail would really belong in History of the metric system, without much duplication here, though having an outline of the prevailing concepts (which you highlight here) as context in each system is useful to have in this article (what are currently called "principles").  This article can then reference sections in that article.  I get the point about introducing the guiding prevailing concepts here for understanding of each system being necessary, though we should not put it in the voice of Wikipedia.
 * To précis my original point(s): the article should make it clear when it is presenting a perspective of the context rather than stating currently accepted fact, and it should discuss each of the metric systems on essentially equal footing. —Quondum 17:51, 28 April 2020 (UTC)
 * Agreed, at least for the most part. I just suspect that the overlap with History of the metric system will turn out to be larger than one might think. For example, the following is an obvious question to address even in this article: why the switch from the once well-established cgs system to the mks system (+ one extra purely electrical unit)? The answer has everything to do with the fact that the mks units of power and energy happen to be consistent with those of the International System of Electrical and Magnetic Units. And why were the latter the way they were? Because they were conveniently sized decimal multiples of the cgs-emu units. And why cgs-emu units? Because of work of a Committee set up by the British Association for the Advancement of Science. And the foundation of that work, in turn, was the work on 'absolute' measurements by Gauss, Weber, and Neumann. A lot of the obvious why's about the metric system(s) can only be answered historically, which is not that surprising considering how many arbitrary choices one needs to make when deciding on a system on units. --Reuqr (talk) 17:55, 28 April 2020 (UTC)
 * Yeah, don't take what I said about duplication too strongly. As long as you are aware of the existence of that article.  (I wish I could nudge some of the "why"/"what" in SI sometimes – we still have definitional issues from decisions very much like the Gaussian define-charge-in-terms-of-force oversimplification, with plenty of similar confusion resulting (angle, logarithms, information).  Weird even at the time: mass was not defined in terms of the Newtonian gravity force equation, but charge is defined in terms of the essentially identical Coulomb force equation.)  —Quondum 21:46, 28 April 2020 (UTC)
 * Just out of curiosity, what do you mean by oversimplification? --Reuqr (talk) 02:22, 29 April 2020 (UTC)
 * By that I mean any discarding of degrees of freedom in a definition in the interests of apparent simplification that obscures the symmetries of the model or that removes useful information (e.g. for disambiguation or dimensional analysis). Removing constants by formally equating them to 1 typically fits this criterion.  Another way of describing it is adding structure that is not implicit in the problem.  —Quondum 03:15, 29 April 2020 (UTC)

"A" versus "The" metric system
This article inconsistently uses a definite or an indefinite article - "the metric system" versus "a metric system". The rest of Wikipedia seems to use a definite article, e.g. Outline of the metric system. This article should either use a definite article consistently, like the rest of Wikipedia, or explain in the introduction what the difference is. Gaiacarra (talk) 12:34, 28 April 2021 (UTC)
 * There are multiple metric systems so the indefinite article is usually appropriate. If the definite article is used, it should refer to a specific (and specified) metric system. Dondervogel 2 (talk) 13:32, 28 April 2021 (UTC)
 * It varies. Alternatives such as "metric systems" or "a metric system" don't work in sentences such as "The metric system was designed to have properties...". One would give the impression they were independently designed, the other that only one was so designed. We'd need an awful amount of periphrasis to follow your rule in that and the many other sentences. Better to accept that sometimes we're talking about an evolving thing that's had many distinguishable forms, sometimes about a family of very similar systems and sometimes a specific formalised system. Fortunately English does work like that and we can trust our readers to keep up. NebY (talk) 13:58, 28 April 2021 (UTC)