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Micron, micrometre

Conversation copied from WP:MoS, and closed there. It is sloppy for me to bring this over here without reading the archives, but I'm pressed for time. There's nothing on micron on MOSNUM, or (other than the following) in recent MoS discussions.

  • Temperatures doesn't explain why one uses °C and °F for Celsius and Fahrenheit, but just K (not °K) for Kelvin; it's because, unlike the other two, the Kelvin scale is absolute and thus not measured in degrees.
  • This section ought to include the rule that, to avoid ambiguity, millionths of a metre (μg) are known as microns, not as "micrometres" or, worse, "micrometers", because a micrometer is a measuring instrument.
  • Squared and cubic metric-symbols: what is the Wikipedia standard for the inverses of such units? For instance, in stationery shops I've seen good-quality paper as having a weight of "80g/m2" or of 80gm-2, both meaning "80 grams per square metre". Does Wikipedia have any preference for one or the other? —Preceding unsigned comment added by 217.171.129.75 (talk) 17:29, 9 April 2008 (UTC)
My comments:
  • Temperatures I've never seen an authoritative statement about why "degree" was dropped from Kelvin. The change was made by the General Conference on Weights and Measures. If you want to claim this is why, please supply an authoritative citation.

I'm going to take your word for that, Gerry, rather than pulling up a PDF with at least 155 pages, but this is a complete surprise to me. American Heritage does say "no longer in use". Micrometre and Merriam-Webster say that micron is fine. Scientists and engineers still use the word frequently. I'm fairly sure that a MoS rule that says to avoid micron will be widely and forcefully ignored by scientists and engineers, at least in 2008. I agree that micrometre/er is completely fine. - Dan Dank55 (talk) 20:36, 9 April 2008 (UTC)

This [i.e. WT:MoS] is the wrong venue for this discussion. The section in question is simply a summary of what is at Wikipedia:Manual of Style (dates and numbers), so any issues with its advice should be raised at WT:MOSNUM (other than MOS corrections to the accurate summarization of what is actually said at MOSNUM). — SMcCandlish [talk] [cont] ‹(-¿-)› 06:47, 10 April 2008 (UTC)

Actually, Dan's summary of the Micrometre article isn't quite accurate, it says "Some people (especially in astronomy and the semiconductor industry) use the old name micron and/or the solitary symbol µ (both of which were official[citation needed] between 1879 and 1967) to denote a micrometre." My electronics engineering experience was that μ in writing was common up to the early eighties, but after that μm was generally used. (The computers back then often didn't support Greek letters, and sometimes didn't even support lower-case, so "u" was often substituted for "μ".) The word micron was often spoken long after the written form had become "μm". --Gerry Ashton (talk) 16:49, 10 April 2008 (UTC)

I agree with Gerry Ashton. There is no need for the word "micron" to appear in any WP articles except those relevant to the history of the term. The modern term is micrometre (symbol μm). Thunderbird2 (talk) 17:02, 10 April 2008 (UTC)
Gerry, I was perhaps a bit sloppy, I didn't read any farther in the article than the second sentence, which is "It is also commonly known as a micron." Thunderbird2, I'm being a little hypocritical with regard to my usual "no original research" position, but my "original research" is that I read the word "micron" often, still, in 2008. I wouldn't object to prescriptive language; it's certainly true that "micron" has not been in SI for a while, although it continues to be used in other contexts. I'm just saying that I don't think we're going to get wide compliance. This isn't a killer, it's just something to think about. - Dan Dank55 (talk) 15:53, 12 April 2008 (UTC)

The primary source for SI units is the official SI website. Terms like 'micron', 'Centigrade', and 'degrees Kelvin' were once part of SI, but they are not anymore. The continued use of legacy terms is widespread in all sorts of domains and it should not surprise anyone that this happens in SI too.

This debate started because somebody wanted to know what the current SI units are. The answers are at the official SI website. Lightmouse (talk) 17:40, 10 April 2008 (UTC)

  • We don't need to cling to outdated terminology. A foot is a body part but if I mention a 100-foot tram, who's going to think it looks like a centipede?
  • Yes, that there's no need for degrees when it comes to kelvin is due to the scale's being absolute but there is still the degree Rankine. The MoS is no place for such details though.
  • I don't believe that any standard exists for inverting units. It seems that the slash is most common, I'd say just be consistant throughout an article.
JЇѦρ 18:13, 10 April 2008 (UTC)

Temperature: Gerry, re the dropping of degree with Kelvin, see this refLeadSongDog (talk) 21:41, 10 April 2008 (UTC)

Micron is used for dot pitch on LCD displays. DavidPaulHamilton (talk) 22:45, 10 April 2008 (UTC)

Perhaps, but very rarely anymore. Compare the hits for LCD "dot pitch" 2008 micron vs. LCD "dot pitch" 2008 mm vs LCD "dot pitch" 2008 and you'll see that less than one percent used micron, and in fact most of those were references to Micron (the company).LeadSongDog (talk) 00:04, 11 April 2008 (UTC)

The rules and conventions for writing inverted SI units is given at the official SI website 'Rules and style conventions for expressing values of quantities'. You may also find useful ISO and IEC standards and SI is generally compliant with those. The original query was about paper described as either "80 g/m2" or 80 gm-2. As far as I am aware, both forms are equally valid in official terms and are equally valid in Wikipedia terms. Toss a coin. Lightmouse (talk) 08:28, 11 April 2008 (UTC)

The relevant MOSNUM text reads:

  • When units are combined by division, use a slash to separate the symbols (e.g., for metre per second, use the symbol ‘m/s’, not ‘mps’) or use negative exponents (m·s−1). There should be no more than one slash per compound unit symbol, e.g. ‘kg/(m·s)’, not ‘kg/m/s’ or ‘kg/m·s’).

Therefore g/m2 and g·m−2 are both permitted, but g m−2 and gm−2 are not.Thunderbird2 (talk) 14:02, 11 April 2008 (UTC)

My two cents
Original poster says "the Kelvin scale is absolute and thus not measured in degrees." That is false on both counts:
  • It was "degrees Kelvin" and °K until 1967. It was also "degrees absolute" (°A) in some of the earlier texts.
  • The Rankine scale is an absolute scale, and its units remain degrees Rankine with the symbol °R.
Re the micron: The biggest remaining problem on Wikipedia isn't computer monitors, but rather those editors who insist on using it for wool, and who have even created a separate article at Micron (wool).
Thunderbird2 is mostly right, when he says: "Therefore g/m2 and g·m−2 are both permitted, but g m−2 and gm−2 are not." The latter negative exponent notation requires either a space (g m−2) or a centered dot (g·m−2),[BIPM SI brochure §5.1; NIST SP811 §6.1.5 (citing ISO 31) says centered dot recommended but space acceptable, and MOSNUM is silent on this point] not run-together as gm−2 (which may well be what the original poster has seen some manufacturers use; that doesn't mean it is acceptable here). The "gm" combination is especially objectionable because that was an acceptable symbol for grams, before the 1948 standardization of symbols by the CGPM—and it is still far too often used for grams; I've fixed it in many Wikipedia articles, yet there are likely still several using it here. The ² character can be used for the "g/m²" variant, but that doesn't work with the negative exponents in the other format.
However, even though the still-senseless MOSNUM rules call for non-breaking spaces in many situations where they are not needed, they still fail completely to address this one where if a space is used, it should be a nonbreaking space. It is a hell of a lot more important to keep the unit symbols from breaking up, than it is to keep from having a line break between the number and the symbol (the latter is something not in the rules of any measurement standards organization). Gene Nygaard (talk) 15:26, 12 April 2008 (UTC)

Thanks Gene, I enjoyed the micron (wool) article. I guess it's just a matter of time before we find micron (paper thickness), micron (wavelength) and micron (font size) ;-) Returning to your point about the space as a separator, MOSNUM is not completely silent:

  • When units are combined by multiplication, use a middle dot to separate the symbols (e.g., for newton metre, use ‘N·m’, not ‘N m’, ‘Nm’, ‘N-m’ or ‘N•m’).

I interpret that as ruling out g m−2. Do you read it differently? Thunderbird2 (talk) 15:43, 12 April 2008 (UTC)

Well, I probably overlooked it. However, the "combined by muliplication" part is a little confusion, when we are talking here should come under the "combined by division" rules which I looked at on the project page. Sure, it is multiplication by an inverse; that's basically what division is. But yes, I think it should be interpreted as applying, but it would be even stronger if you could show that that was an informed decision involved in the choice between a space and a middot. Gene Nygaard (talk) 14:16, 15 April 2008 (UTC)
My recollection is that it was a deliberate (and hopefully informed) decision to use a mid-dot rather than a space. I remember the discussion because my browser didn't display the mid-dot correctly. I will trawl through the archives to see what I can find ... Thunderbird2 (talk) 14:55, 15 April 2008 (UTC)
Regarding "trawl through the archives" ... keep on trawling, please, and see my suggestion on indexing all style guidelines talk archives at WT:MoS#Proposal to index. I would love it if someone else indexes the WT:MOSNUM archives, because there are so many words and I wasn't here for most of it. Regarding the &middot; ... the official SI link says to use them, and it would be great if the current bugzilla debate doesn't have to consider hard spaces between units because the "official" position is to use a mid-dot; that would help get us over the hump at bugzilla. There's also a relevant user-interface principle here, the Principle of least astonishment. In fact, that one belongs over at the bugzilla thread, where I'm headed now. On the other hand, typesetters' characters of all kinds become less common every year in persuasive online writing, since so many people are doing their own copyediting these days. (But on the other other hand, how could Wikipedia possibly do without multiplication dots in technical articles?) All things considered, I wouldn't mind a consensus to use the mid-dot, and if somehow we can do that quickly, it will help us make progress at bugzilla. - Dan (talk) 15:27, 15 April 2008 (UTC)
This (and subsequent related discussion) is what I was looking for. Thunderbird2 (talk) 15:54, 15 April 2008 (UTC)
Thanks kindly, I read the archived discussion. There are 12 million Google hits for "kWh"/"kwh", and almost all of the first 3 pages of hits are in this sense, so it would be very silly for WP:MOSNUM to say "You can't write 'kWh' ". Google hits or something like that would be the way to distinguish for me whether it's a good idea to string units together without a mid-dot. I'm hoping for a result from the bugzilla discussion that "uncommon" one- and two-letter words don't wind up at the beginning of a line, and this might mean that we don't have to worry about a no-break space in some cases. Obviously, this is an area that requires careful description before prescription. - Dan (talk) 16:11, 15 April 2008 (UTC)
It would not be at all silly for us to require kW·h. That is in use outside Wikipedia. But we, like anyone else, have a right to choose our own house style. It is part of the "look and feel" of Wikipedia. There is no reason whatsoever for us to be even tackling the elusive task of determining "most common used" because it isn't relevant. If we follow consistent, systematic rules, that is quite enough. Google results are often useless or deceptive in such cases anyway. Consider the fact that while a search for "kWh" gets 12,200,000 hits, a search for "kWh" but not "kW·h" gets only 610,000 hits. And, like you said, many of those hits on the simplest search are for "kwh" rather than "kWh"; you forgot to mention the "KWH" hits, and you didn't even try to search for "KWHR" which gets hundreds fo thousands of hits. Of course, searching for kW·h will also find people who write it kw/h even though this unit involves a multiplication, and not a division, but "kW·h" and not "kWh" gets 6,620,000 hits, more than 10 times as much as the other way around. Gene Nygaard (talk) 13:05, 16 April 2008 (UTC)
After I said that, I looked around at abbreviations, and saw that we have 3 different sets of guidelines on abbreviations, with little apparent hope of reaching consensus on many issues. I'm thinking that abbreviations is a subject I'm not ready to tackle. - Dan (talk) 13:17, 16 April 2008 (UTC)
That's part of the reason why consistent, systematic rules are especially important for a collaborative project such as Wikipedia. Don't be saying that people writing about rugby players can add an s to their ins and kgs and lbs, but nobody else can (we don't do so here—our rule applies across the board—but because of a couple of persistent editors, we certainly do need more help in cleaning them up—just Google lbs rugby site:en.wikipedia.org[1] to see how bad it is). Gene Nygaard (talk) 13:24, 16 April 2008 (UTC)

Circa and century

I noticed that the abbreviation for circa is given as "ca." or "c." The latter is wrong, as it is the standard abbreviation for century (e.g. "4th c.") If c is used to mean "circa" then it should not be followed by a dot (e.g. c10,000 men). This is confirmed by the supreme authority on the English language, the Oxford English Dictionary. It seems to me that, as a public work of reference, Wiki must follow standard abbreviations and not invent its own. EraNavigator (talk) 21:11, 16 April 2008 (UTC)

The 1911 Britannica apparently used c. as an abbreviation for circa, and still does. Oxford DNB seems to use it too. Maybe it's not entirely wrong. Gimmetrow 00:14, 17 April 2008 (UTC)
Can we agree that ca. is a better abbreviation for circa than c., on the grounds that it is less ambiguous? Thunderbird2 (talk) 05:59, 17 April 2008 (UTC)
It's not less ambiguous. Before a number "c." is either circa or chapter, which will always be determinable by context while after a number there are many things "c." could stand for such as cent, carat, cup, though it too is usually determinable by context. If we don't allow "c." for circa then it shouldn't be allowed for century either as "cent." is a standard ans far a less ambiguous abbreviation for century. Caerwine Caer’s whines 17:40, 17 April 2008 (UTC)
Regarding today's edit recommending "ca.", it's not clear what position it's taking on the phrase "around 2000". I would be very uncomfortable at WP:GAN changing "around 2000" to "ca. 2000" in most articles. I agree that "ca. 1802" is perfectly okay in any history article, and preferred in many of them. For some people who show up to have their articles reviewed, that's the first time they run into a long list of "you can't do this, you must do that, WP:MoS says so", and it's going to cause unhelpful friction to tell them they can't use the phrase "around 2000". - Dan (talk) 18:50, 17 April 2008 (UTC)
[2] I'm not so sure we should prefer "ca." to "c." when the Britannica and Oxford DNB links above do not even list ca. as an abbreviation! Gimmetrow 04:06, 18 April 2008 (UTC)
American Heritage says "c. or ca" (no period/full stop on the second). Random FAs and GAs from WP:HISTORY turned up one "c.", no "ca." - Dan Dank55 (talk) 04:56, 18 April 2008 (UTC)
It seems I was too hasty then, so I have reverted the change I made. I have seen both myself, but I still prefer ca. over c. On the other hand I agree with Dan that "around 2000" should also be acceptable. What about a preference for either ca. or about over (say) c. or approx.? Thunderbird2 (talk) 06:14, 18 April 2008 (UTC)
No thanks; see below. Septentrionalis PMAnderson 15:02, 18 April 2008 (UTC)
  • In my experience, the standard abbreviation for century is C. I would not recognize it lower case. Even if I am exceptional, this would not make c. for circa wrong; it would not even make it ambiguous unless it were so placed that it could mean either in context. There are only 26 letters; many abbreviations will have multiple senses. Septentrionalis PMAnderson 15:00, 18 April 2008 (UTC)

Queries

Hey folks: Greg L drew my attention to MOSNUM, a page I've been playing truant from for some time. I see that it has there have been a lot of changes this month, and I'm charged with producing a summary of substantive changes at the end of each month.

  1. Towards the end of April, it would be good to know whether the changes are stable in terms of the monthly summary.
  2. At what point does MOS need to be updated to relect these changes? At the moment, a good housecleaning is in order.
  3. I see that Crissov's edit on 6 April has made quite a major shift in terms of the default main units for non-country-related articles; specifically, that the metric system should generally be used (converted, of course, unless there's consensus not to in scientific articles). This is a change that I thoroughly agree with, and I hope that it will remain. TONY (talk) 09:07, 18 April 2008 (UTC)
    • I hope this reading was not Crissov's intent; it violates WP:ENGVAR: many articles in American English should not use metric unless about a scientific subject (where it would be idiomatic). For an obvious example, pound cake should use pound, not 450 grams. I trust an injunction not to violate idiom will be uncontroversial. Septentrionalis PMAnderson 15:05, 18 April 2008 (UTC)


My reading is that before the change:

  • US-related articles—main units US (converted to metrics)
  • UK-related articles—main units either system (converted)
  • Scientific topics—main units metric (unconverted if consensus)
  • All other articles—main units either system (converted)

Now, Anderson's recent modification is in italic below, and Crissov's change is bolded; both are fine by me.

  • US-related articles, and where idiom requires it—US units (converted to metrics)
  • UK-related articles: main units either system (converted)
  • Scientific topics—main units metric (unconverted if consensus)
  • All other articles—main units generally metric (converted)

TONY (talk) 15:53, 18 April 2008 (UTC)

  • If I were doing this from scratch, I would suggest whichever is natural on a given subject in a given national variety, and add examples. In American scientific articles (with field-dependent exceptions), this would be metric.
  • In numismatics, for example, precise values are important, and figures in the same field of study have been reported in grams (normally to one decimal point) and in grains. This may be a reason for inconsistency in detailed articles; but generally may cover this. Septentrionalis PMAnderson 17:01, 18 April 2008 (UTC)
I'm American, but I'm very comfortable with saying "prefer metric". Every country except the U.S. uses SI units for almost everything (with a few exceptions, as Sept points out), and there are lots of people in the U.S. who prefer metric to U.S. units, because there's so much movement across borders, and almost no one who's comfortable with both systems actually prefers the U.S. units. Also, SI is used consistently in science and tech and in many consumer products. I'm just guessing here, but I'd say somewhere between 100 million and 200M people in the U.S., a country of 300M, feel uncomfortable with metric units. That's in a world of 6.7 billion.
I think the important point here is that this is not a style issue; this is a "free flow of information" issue. The English Wikipedia has 2.3 million pages, but all of the Wikipedias have 10 million pages. Everyone knows that, if a conversion number is given in parentheses, you can't count on the accuracy of the second number as much as the accuracy of the first number; there will be a rounding error, at the least, and you won't be able to extract any fine-grained information from the number of significant digits used. So if the U.S. unit is given first, that makes it less likely that accurate information will travel between other Wikipedias and the English Wikipedia, or travel from or to anyone outside the U.S. - Dan Dank55 (talk) 17:07, 18 April 2008 (UTC)
One problem with prefer metric is that it can lead to our taking a source which uses customary units, doing our own conversion to metric, and then adding a conversion back to customary units. Septentrionalis PMAnderson 17:12, 18 April 2008 (UTC)
I agree, but the bigger problem with not saying "prefer metric" or "generally metric" (and being very specific about what the exceptions are) is that this conversion will happen in one direction or the other every time a new editor wanders in, which is so much worse. Better to give reasons that are easy to memorize and agree to about which is better in any given article, when possible. - Dan Dank55 (talk) 17:46, 18 April 2008 (UTC)
It would be simpler to say "when precision matters, use the units given by the source and add a conversion." (Precision doesn't always matter. If we convert "the fleet was about 400 miles west of Brest" [in 1794] into "The fleet was about 750 km west of Brest" we have not actually lost any precision; the guess wasn't that precise to begin with. Even there, leaving the original avoids the possibility of mistaken conversion; these are nautical miles.) Septentrionalis PMAnderson 18:12, 18 April 2008 (UTC)

I don't accept any connection between the variety of English used in an article, and the system of units listed first. Even though a particular variety of English is used in an article, the readership is worldwide, so the units should be metric unless the subject of the article is tied to the U.S. or U.K. If, for example, the subject of an article is beer, which has no ties to any particular country, and isn't necessarily a scientific article, the first unit of measure should be metric, no matter which variety of English it is written in. --Gerry Ashton (talk) 17:55, 18 April 2008 (UTC)

Btw Sept, I do support what you just said. We shouldn't start randomly trashing the accuracy or validity of the sources when U.S. units are used, that's a given. I could only support a "gradual push" towards metric for anything that isn't solidly tied to the U.S. - Dan Dank55 (talk) 22:17, 18 April 2008 (UTC)
  • So, what should the wording be? I am happy with the current Crissov version; "in general" and "where idiom prefers it" seem to neatly cover PMA's points about the use of such expressions as "the four-minute mile" and "poundcake", doesn't it? TONY (talk) 03:12, 19 April 2008 (UTC) BTW, I'm confused/ignorant about the difference between US and imperial units, and metric and SI. We do need to make these distinctions, do we? TONY (talk) 03:14, 19 April 2008 (UTC)
The difference between metric and SI is that anything related to the system started during the French Revolution is metric. However, in part due to relationships between different quantities that were not understood that far back, and the tendency of any trade or profession to create it's own units and take no interest in incompatible units for the same purpose created by other trades/professions, the metric system started to head in the same balkanized mess as earlier units. SI selected a set of coherent units from the various metric units, which are intended to be the one and only set of units to be used in every trade, every profession, every country, and every language. Everyone who uses non-SI metric units has a medieval guild habit of thought.
As for the difference between U.S. and U.K. customary units, I'm only familiar wiht the U.S. ones. If confronted with U.K. units, I'll look at the SI conversion; U.K. units are on the way out and are not worth learning. --Gerry Ashton (talk) 03:33, 19 April 2008 (UTC)
I think that Tony may have gotten the "before" part slightly wrong. The last bullet of his "before"—All other articles—main units either system (converted) was never in the guide. It has always been something like: For other country-related articles, the main units are metric; for example, 37 kilometres (23 mi) and when in doubt use metric first. We're already having metric units as the preferred/main unit on the majority of articles because of the way that we set up the MOSNUM. So there really isn't a need for a gradual push—we're already doing it.
Crissov's edit just changed the order of what was being stated. Except for taking out an "imperial/" and a heading, he didn't really change what was being stated. I would have reverted all of it if the content had changed without discussion, but the message stayed the same. Speaking of a lot of changes this month, which I believe was the reason for Tony's post, should we consider fully protecting the MOSNUM to force discussions before changes are made? Tony's right. Many changes are hard to keep track for some of us and this should be a slow-to-change document.
Lastly, Dank55, here's some food for thought that may break your theory above: I am an American scientist and I use both the metric system (at work) and the U.S. customary system (at work and real life). I am "comfortable" using the metric measurements but I "actually prefer" the customary system for work and play.—MJCdetroit (yak) 03:44, 19 April 2008 (UTC)
Thanks for the correction MJC. I'm always trying to use shorter sentences, but sometimes it doesn't get the idea across. There are plenty of Americans, including myself, who feel "more comfortable" with U.S. units. When I pull up the daily weather, I would rather see degrees Fahrenheit. What I meant is that people who have a long-standing attachment to both systems tend to choose metric, because it's in wider use and it's easier. - Dan Dank55 (talk) 17:33, 19 April 2008 (UTC)
    • Thanks to Gerry for his lucid explanation, and to PMA for directing me to those articles. The fact that UK units are "on the way out" suggests that we should not have bent to the screeching of British old-timers who insisted on the option for either (first it was more constrained for fuddy-duddy-speak, but I see that the circumstances in which it may be used have been broadened in the guideline, sadly). And thanks to MJCD for pointing out that there has been no radical change at all. Please bear in mind that I have to write a summary of changes that have occurred to MOSNUM over April, and I'm not looking forward to it. TONY (talk) 04:03, 19 April 2008 (UTC)
As to Tony’s question, I have to agree that there’s no real substantive change aside from the “all others” point, as noted by MJCdetroit. If I were writing it, though, I’d say that a better approach would be (my substantive changes italicized):
  • US-related articles—US units (converted to metric)
  • UK-related articles—main units either system (converted)
  • Scientific and technical topics—main units metric (unconverted if consensus) except where an original source or custom employs another (which should be converted to metric)
  • All other articles—main units generally metric (converted) except where idiom, custom or original source necessitates other usage (converted to metric).
This seems to me to fairly address the relevant issues. With regard to the “all others”, if we’re recommending “generally metric”, conversion would seem to be superfluous except where non-metric is employed. The added reference to “custom” in the area of scientific and technical topics captures an issue with which I have to cope regularly in the aerospace field in the U.S. In the past week alone I was asked to replace or provide conversions for kg and km to lb and ft or nm in a presentation I am drafting. Interestingly (and sadly IMHO), this request was made to satisfy young engineers as well as the graybeards – and that despite the considerable transition to metric that has been made in the field over the past couple of decades. In any case, requiring a universal change to metric in technical articles would require a massive amount of work on aircraft- and aerospace-related articles that would, ironically, result in the introduction of extensive “false-precision” in the main units of measure. (In working with numbers from Jane’s, which employs metrics preferentially and offers conversions to other systems, I am constantly amazed at the amount of seemingly precise metric values are nothing more than the illusory result of conversions of round numbers values from sources using non-metric systems. Askari Mark (Talk) 19:42, 19 April 2008 (UTC)
Seems good to me. TONY (talk) 08:49, 20 April 2008 (UTC)
We should normally convert to US conventional units (at least once even in the most technical of articles), for the sake of intelligibility; there is really is a large pool of readers whose eyes will glaze over at metric values, and another pool who will have to mentally convert.
I find Askari Mark's comments on Jane's to be depressing, but unsurprising; we should not follow suit. Illusions of precision are bad things. I would therefore add to his proposal, which seems quite sound otherwise:
  • If a quantity is exactly a round number of conventional units, express as such and include a conversion to metric. The wing is 100 ft (30.48 m) long.
Or possibly 30 meters; a design specification had better be correct to a centimeter, however. Septentrionalis PMAnderson 13:10, 21 April 2008 (UTC)
Sorry, but I don't agree with the technical part. If Jane's (or some other source) states that the wingspan of the MiG-27 is 13.8 metres, then reference that figure and use {{convert}} to convert it. {{convert|13.8|m|ftin|abbr=on}} --> 13.8 m (45 ft 3 in). Seems simple enough. However, if you can't trust your source perhaps you should look for a new source. Keep in mind that the guide does state that the "level of precision" of the converted value is dependant on the source value.—MJCdetroit (yak) 13:52, 21 April 2008 (UTC)
If the source says "30.48 m (100 ft)", it is perfectly trustworthy; merely unwise. The actual measurement they got was one hundred feet; we should treat it as we would any other sourced assertion of exactly 100 ft. Writing {{convert|30.48|m|ftin|abbr=on}} or 30.48 m (100 ft 0 in) is a misreading; we are not bots, we are editors, and we should not pretend to be as stupid as bots. Septentrionalis PMAnderson 15:17, 21 April 2008 (UTC)
MJCdetroit, Jane’s All the World’s Aircraft is considered the “bible” for information on civil and military aircraft; it’s as trusty a source as there is – of course, JAWA is certainly not “inerrant” in all respects. Its preferential use of metrics even when the original source did not, however, raises the problem of converting an already converted number. For instance, 45 ft 3 in converts to 13.8 m (rounded), which then converts back to 45 ft 3-5/16 in – over a quarter inch off. For that matter, it’s not always easy to tell when one is dealing with an already converted number in the first place. It turned out that three of the aircraft I had to provide conversions for in my presentation for work were non-UK European aircraft whose original source had been in English units of measure; I would have assumed otherwise. Accordingly, I agree with PMA that conversions of round numbers should be handled with care (although 30 m would seem a better significant-figure conversion of a round 100 ft), although I’m not sure his proposed bullet statement wouldn’t be better placed in the subsection on Conversions. Askari Mark (Talk) 04:01, 22 April 2008 (UTC)

Frequent changes to MOSNUM

Why is MOSNUM being changed so frequently? Lightmouse (talk) 17:54, 20 April 2008 (UTC)

Possible answers:
  • People are incorrectly applying WP:BRD rather than the rule at the top of every policy and guidelines page: "Before editing this page, please make sure that your revision reflects consensus."
  • There are a lot of people doing the right thing, namely, changing MOSNUM if they perceive that there's a strong consensus of "best" editors on WP doing something different (not gonna define "best" ... nuh uh ... but I'm talking about hundreds of editors, not a cabal).
  • There are a lot of people making changes for one of many wrong reasons; I really wouldn't know. One wrong reason that people don't always realize is a wrong reason is: changing MOSNUM because some new guideline (outside Wikipedia) came into being just this month. There's no rule that Wikipedia style rules have to constantly change; recent changes in usage outside Wikipedia could always change back, so it pays to be a little conservative rather than forcing article writers and reviewers to learn new rules every month.

- Dan Dank55 (talk)(mistakes) 18:19, 20 April 2008 (UTC)

Survey foot versus international foot

Should we include any guidance on the difference between these two? Granted, one needs to be doing conversions to 6 or more decimal places before encountering any noticeable differences in the metric conversions, but I can see the rare occasion where it would be significant. Caerwine Caer’s whines 19:26, 20 April 2008 (UTC)

Conversion of units defines 6 different varieties of foot. Is there a reason for singling out the survey foot? Thunderbird2 (talk) 19:43, 20 April 2008 (UTC)
I believe the U.S. survey foot is the only foot, beside the international foot, still in use. That said, I think foot means international foot unless stated otherwise, and no guidance is necessary. --Gerry Ashton (talk) 19:55, 20 April 2008 (UTC)
I see. Thanks for the explanation. Caerwine: is there a particular article you have in mind? Thunderbird2 (talk) 20:02, 20 April 2008 (UTC)
United States would be one such article as the square mile used for the area of the U.S. is the square survey mile. With 7 significant figures, that does make a difference in the last two digits. 3,794,066 square survey miles versus 3,794,081 square international miles. There are also a few other articles of large areas such as Asia, where the distinction matters, though in that article it looks like someone sloppily applied a Google conversion of the metric value to square international miles as I got the same value as that article now has, including an errant extra significant digit in the converted value. In survey square miles the value would be 16,915,293, not 16,915,360.3 Caerwine Caer’s whines 05:15, 21 April 2008 (UTC)
I'd agree that unless otherwise stated the foot can be assumed to be the international foot. Therefore if you see a conversion to miles, square miles, etc. you should expect that this will be the international version. Given that this is the case, why would we convert to US survey acres, square miles, etc.? It will be a concern where the original measurement was in survey miles/acres/etc.—care must be taken in converting to metric. However, in conversions from metric, I'd say we can safely ignore the fact that an alternative foot exists and convert to the international units—this will apply to (just about) every article on places outside the US (like Asia). JЇѦρ 06:43, 21 April 2008 (UTC)
While I agree an explicit conversion may be over the top, I think it's important to disambiguate in cases like this to the relevant definition (eg 3,794,081 sq mi), or similar. Thunderbird2 (talk) 07:20, 21 April 2008 (UTC)
That's probably a good idea; although I expect that the effect of mandating it would be that some good soul will "correct" to [[international mile|mi]] whichever unit has actually been used. A general caution about measurements with more than five significant figures would be helpful; liter has the same problem, since two different values can be found in the literature. Septentrionalis PMAnderson 13:18, 21 April 2008 (UTC)
I've just realised that specifying international mile doesn't help, because it just takes you to mile, so the reader is none the wiser. There needs to be something more than that. Thunderbird2 (talk) 16:47, 21 April 2008 (UTC)
I don't understand the problem with litre though. What's that about? Thunderbird2 (talk) 16:49, 21 April 2008 (UTC)
I'm assuming that PM was referring to the difference between the 1901–1964 definition of a litre as "the space occupied by 1 kg of pure water at the temperature of its maximum density under a pressure of 1 atm," which is approximately 0.001000028 m3, and the present (and pre-1901) definition of a litre as exactly 0.001 m3. Of course, if we use pre-1964 sources for extremely accurate measurements (I don't think we do this very often!), this might be an issue. -- Jao (talk) 18:03, 21 April 2008 (UTC)
Actually, not that uncommon; for one thing, our article oversimplifies: it took a decade or two for the ml and the cc to be accepted again as identical in principle. Septentrionalis PMAnderson 23:47, 21 April 2008 (UTC)

Returning to the international mile, I said before that a conversion is over the top, but I've changed my mind now. When such high precision is required, a conversion to an unambiguous unit (in this case the square kilometre) is the best solution. Thunderbird2 (talk) 20:06, 21 April 2008 (UTC)

If we have a statement in sq miles, we should quote it in square miles; doing otherwise may sweep other disagreements (what are the precise boundaries of Asia? does this include the surface of Lake Baikal?) under the rug. We should convert; and we should spedify whether we mean survey or int. miles if that is determinable. Septentrionalis PMAnderson 23:42, 21 April 2008 (UTC)

Capitalisation and pluralisation of the Erlang unit

I've just encountered the Erlang unit for the first time. The article talks of "1 Erlang" and "2 Erlangs", both of which look odd to me. (I would have intuitively written "1 erlang" and "2 erlang"). What do others think? Thunderbird2 (talk) 16:31, 20 April 2008 (UTC)

I found this definition at Rowlett's site:

  • erlang (E) a measure of telecommunications traffic density. The erlang is a dimensionless "unit" representing a traffic density of one call-second per second (or one call-hour per hour, etc.). The erlang is sometimes divided into 36 unit calls or 30 EBHC. Also called the traffic unit (TU), the erlang honors A. K. Erlang (1878-1929), a Danish mathematician who studied the mathematics of telephone networks.

That definition suggests that the unit is an erlang (1 E), with plural two erlangs (2 E). Comments? Thunderbird2 (talk) 16:36, 20 April 2008 (UTC)

SI units named after people are uncapitalised, this could explain your intuition. The unit in question, however, is not SI so whether it is to be capitalised is a matter seperate to the capitalisation of SI units. ... but now you mention Rowlett's site ... JЇѦρ 16:39, 20 April 2008 (UTC)
Those are rules of the English language, not rules of the International System of units; note that in the German language, for example, the SI units named after people are capitalized: Henry, Watt, whatever. So are the units not named after people, such as the Meter and Gram: all nouns are capitalized in German. They should be applied to all units named after people; it doesn't matter if they are SI units or not. It is also the quirkiness of the English rules in which a part of a unit which is an adjective derived from a personal name is capitalized, as in "degrees Celsius" and "degrees Rankine". Gene Nygaard (talk) 23:53, 24 April 2008 (UTC)
And note especially that, along with the change from an adjective to a noun, the old "degrees Kelvin" with an uppercase K became "kelvins" with a lowercase k. Gene Nygaard (talk) 23:57, 24 April 2008 (UTC)

Using a policy page as a scratchpad to develop a proposal

I have raised a MOS policy about policy changes question at the village pump. Feel free to read it and comment. Lightmouse (talk) 11:26, 23 April 2008 (UTC)

Thanks, I have responded there. On a completely different subject (probably not important enough for its own topic): does anyone object to having Miszabot do archives after 10 days after the last new comment in a section instead of 15? This talk page is running a little long. We've just dropped down to 10 days on WT:MoS. - Dan Dank55 (talk)(mistakes) 15:07, 23 April 2008 (UTC)
Quick update: I don't see any startling disagreement among Lightmouse, Kim Bruning and myself at WP:VPP. Kim believes that, contrary to what I said above, WP:BRD does apply, but on the other hand, "Before you hit submit on any edit (especially a BRD edit), you had better be sure of consensus. There's actually 4 questions you need to ask yourself before hitting submit. Here's a current discussion about that: Wikipedia_talk:Ignore_all_rules#Ignoring_the_rules_v._Ignoring_a_rule. More so than with other edits, it's important to have those 4 answers ready, because you're likely to have to answer those questions several times to several different people. :-)". Let's argue it in one place at a time, please, at the village pump. - Dan Dank55 (talk)(mistakes) 18:35, 23 April 2008 (UTC)
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