Talk:International System of Units/Archives/12/2008

Countries using SI
How about a list countries that have adapted SI as their official standard of measurement?
 * No. Too long, and the idea is covered by the statement that it has been adopted by every country except the US, Liberia, and Myanmar. It's unneccesary, it would clog the article, and make the article too long. There is no good reason to do it. -- R'son-W (speak to me/breathe) 22:24, 25 August 2006 (UTC)

Does Libya use SI? As far as I know, Libya abolished use of metric system in 1974, but I don't remember any reference.

a list might be too long, but a map might be suitable! 85.149.120.16 (talk) 14:58, 7 April 2008 (UTC)

Gentlemen, the status of the metric system in the US is rather misunderstood. It was formally adopted in 1866 as an acceptable system of measurement, and therefore official. However, its use was never mandated, and given how the (common) Law is structured in the US, it is questionable whether mandating the use of one system of measurement or another would be a constitutional act. The government could mandate the use of the metric system in contracts, however, which would be a strong influence in the wider adoption of this system. So, though the map's caption is technically correct, it is rather misleading. The English/Imperial System, in the US, actually (perhaps surprisingly) has NO legal status at all. It has never been adopted in any way, for any purpose. It is quite telling that the National Bureau of Standards (now the NIST) calls this the "US Customary System", i.e., the use of this system is merely customary, not mandated. Bejmark (talk) 16:23, 22 August 2008 (UTC) See http://www.unc.edu/~rowlett/units/usmetric.html for a nice discussion of this topic. 76.98.119.56 (talk) 01:20, 23 August 2008 (UTC)

Overlap with Metric system

 * 1. SI
 * 2. SI and
 * 3. SI

are all applicable to the metric system whilst


 * 4. Metric system

is best suited to SI. I suggest that 1, 2 & 3 be moved to Metric system and 4 be moved to SI. Jimp 28Sep05

I've started addressing this. See Talk:Metric system. Jimp 30Sep05

Bloated
Speaking of the Metric system article Christoph Päper wrote the following. "The sections 'The metre', 'The kilogram' and 'The litre' should be removed, because the information therein is already present in the respective articles where it belongs. This pretty much applies to 'Metric prefixes' ... as well."

Does this not equally apply here? The stuff I subsequently cut from that article is much the same as what can be found in the History section here. Jimp 30Sep05

After a week nobody has commented either way on this thus I've gone ahead and removed the text in question. Here it is. Jimp 7Oct05

Length
The most important unit is that of length: one metre was originally defined to be equal to 1/10 000 000th of the distance from the pole to the equator along the meridian through Paris. (Prior discussions had often suggested the length of a seconds pendulum in some standard gravity, which would have been only slightly shorter, and perhaps easier to determine.) This is approximately 10% longer than one yard. Later on, a platinum rod with a rigid, X-shaped cross section was produced to serve as the easy-to-check standard for one metre's length. Due to the difficulty of actually measuring the length of a meridian quadrant in the 18th century, the first platinum prototype was short by 0.2 millimetres. More recently, the metre was redefined as a certain multiple of a specific radiation wavelength, and currently it is defined as the distance travelled by light in a vacuum in a specific period of time. Attempts to relate an integer multiple of the metre to any meridian have been abandoned.

Mass
The original base unit of mass in the metric system was the gram, chosen to match the mass of one cubic centimetre of water. For practical reasons, the reference standard that was deposited at the Archives de la république on June 22, 1799 was a kilogram (a cylinder of platinum). One kilogram is about 2.2 pounds. In 1889, the first General Conference on Weights and Measures (CGPM) sanctioned a replacement prototype, a cylinder of a 90% platinum, 10% iridium alloy; this has served as the standard ever since, and is stored in a Paris vault. The kilogram became the base unit in 1901.

Also in 1901, a kilogram of distilled pure water at its densest (+3.98 degrees Celsius) under a standard atmosphere of pressure was used to define the litre, a more convenient unit than the very large cubic metre. Because this litre turned out to be different from the cubic decimetre by about 28 millionths, this definition was abandoned in 1964 in favour of the cubic decimetre.

The kilogram is the only base unit not to have been redefined in terms of an unchanging natural phenomenon. Such a definition, said to be in terms of an artefact (the cylinder in Paris), is particularly inconvenient, because, in principle, it can be used only by travelling to Paris and, with permission, comparing one's own candidate standard to the reference one. For this reason, as well as the effort required to protect the standard from absorption or dispersion of gases and vapours, at a meeting of the Royal Society in London on 15 February, 2005, scientists called for the mass of the standard kilogramme in Paris to be replaced by a standard based on "an invariable property of nature"; but no decision on redefinition can be taken before 2007.

Some talk also exists of setting the kilogram to a fixed number of silicon atoms.

Temperature
The unit of temperature became the centigrade or inverted Celsius grade, which means the mercury scale is divided into 100 equal-length parts between the water-ice mixture at 0 °C and the boiling point of pure, distilled water at 100 °C (under a standard atmosphere). This is the metric unit of temperature in everyday use. A hundred years later, the discovery of absolute zero prompted the establishment of a new temperature scale, the Kelvin Scale which relocates the zero point at absolute zero, with the difference between freezing and boiling water close to 100 K.

Time
The metric unit of time became the second, originally defined as 1/86 400th of a mean solar day. The formal definition of the second has been changed several times as more accurate definitions became possible, based first on astronomic observations, then the tuning fork clock, quartz clock, and today the caesium atomic clock.

Moved & Removed
I found the following paragraph in SI.

"Those countries that still give recognition to non-SI units (e.g. the US and UK) have defined many of the modern units in terms of SI units; for example, the common yard is defined to be exactly 0.9144 metres. In the US, survey distances are also defined in terms of metric units, but differently: 1 survey yard = 3600/3937 m. They have, however, not been redefined due to the accumulation of error it would entail and the survey foot and survey mile remain as separate units. (This was not a problem for the United Kingdom, as the Ordnance Survey has been metric since before World War II.) (See History of measurement for a history of the development of units of measurement.)"

What had it been doing there having nothing to do with writing style? Also I've removed the text in italics above. This has nothing to do with SI and is covered well elsewhere: U.S. customary units & English unit. Jimp 5Oct05

Merge to respective unit articles
I'm in favour of merging the SI prefixes section into the SI prefixes article. I don't think we should stop there. I also suggest moving the Base units section into the SI base units article and suggest moving the Derived units section into the SI derived units article. This would make the article much easier to navigate and to digest. Jimp 13Oct05

I've duplicated the info from here in these various unit articles (the little which wasn't already there). The next step will be to leave a summary & links here.

It's done. Jimp 14Oct05


 * Jimp, one drawback to this approach (of moving the basic tables out of this article) is that a person can now no longer learn how to use SI by looking at this article. He or she has to jump around between several articles. It would be nice to have the basic information on how to use SI all in one place -- and I think that place should be here (where else?) Hierarchy and organization are all very well, but I suspect most people are going to come to this article for a quick blast of essentials, and not find it. I suggest copying the table SI prefixes back in to this article, but leaving its associated chit-chat on the SI prefixes page. It could go right after the short paragraph on prefixes that follows the SI base units table in the present SI article. No additional writing is necessary: the existing short paragraph on prefixes looks sufficient to me. -- Honaroog 1 Dec 05

Merge with Metric system article?
Seems to me there's too much overlap and not really enough reason to separate Metric system from SI. I think we should probably merge the two articles. What do others think? ProhibitOnions 18:50, 30 March 2006 (UTC)
 * Yeah ... and further obscure the distinction between them. There's all the reason in the World to separate Metric system from SI.  The question is whether to merge SI into Metric system as SI is a subset of the metric system.  Now, there are articles on other subsets of the metric system too; we'd have to merge them all.  The result would be a very cumbersome Metric system article which would be difficult to navigate and to edit. No, bad idea. Jimp 09:42, 11 April 2006 (UTC)

Incorrect Base Unit
I didn't want to just edit this article without out first confirming my beliefs with others. I was under the impression that Current and its unit Amperes is not a base unit. Current is the flow of charge per second, eg Coulombs/Sec. Am I mistaken? I believe that the base unit should be Charge, with the unit of Coulomb (C). Check my spelling on Coulomb.

-Grimey


 * It would indeed make more sense if Coulomb rather than Ampere was a base unit, but SI is defined such that Ampere is base and Coulomb is derived. --Itinerant1 01:29, 30 October 2005 (UTC)


 * You have undue expectations of a "base unit", a term used with a specific meaning in metrology jargon. The choice of base units, and even the number of them, is quite arbitrary.
 * Your spelling of coulomb is only wrong because of the improper capitalization. Before you edit anything, some other rules include the proper symbol for seconds is "s" not "Sec", and don't mix spelled out names and symbols in one unit. But please don't claim in this article or any other article that the "ampere" (also lowercase) is not a base unit in SI. Gene Nygaard 01:56, 30 October 2005 (UTC)


 * Gene's right. From one perspective, it may seem that the base unit should be the coulomb ... after all, charge is the more fundamental physical quantity.  However, the choice of base units need not be determined by this way of thinking.  This choice has more to do with practicality than ontology.  Jimp 2Nov05


 * The Coulomb is a base unit. I just asked my physics teacher and he says it is. Also the ampere is a derived unit, being 1 Coulomb/1 sec. This guy has been teaching for many years...he should know.  Someone should change this in this article as well as the others.


 * Sorry but if you think a schoolteacher is an authority on anything you must be extremely young and nieve. The offical BIPM site is absoloutely clear ampere is base colomb is derived. Plugwash 20:00, 6 March 2006 (UTC)


 * Hmm, you're right, I'll have to show it to him and see what he says. This should be interesting.


 * Equally well you could say the coulomb is derived as 1 coulomb is an ampere-second. Or even that a second is derived because it equals one coulomb per ampere. The choice of base units is arbitrary, we need seven (or however many) basic units from which all others can be formed, the choice is arbitrary, as long as they are independent.Jameskeates 08:20, 23 August 2006 (UTC)

The base units are not even close to arbitrary. a coulomb is 1 mole of electrons per second -- that's a dependant relationship. The reason this is important is that while some are trying to make the unit of mass a solid sphere of atoms, there are many correction factors involved (space filling fraction, defects, impurities) but all you really need is the mole and second (and hence the amp) and a you can generate a force between two wires with this and then -- you have a new defintion of force that doesn't rely on all sorts of correction factors or a decaying cylinder in France. Also, temeprature, volume, and time can be used to develop a concept of force. Pdbailey 01:02, 26 September 2006 (UTC)


 * Actuallly, a coulomb is the amount of charge per second which passes a given point in a circuit when the current in the circuit is 1 ampere. Since the charge on an electron is about &minus;1.6 &#149; 10&minus;19 coulomb, that means that about 6.3 &#149; 1018 electrons have moved past the given point in the opposite direction of the electric current. A mole, on the other hand, consists of about 6 &#149; 1023 elementary entities. --Gerry Ashton 02:52, 26 September 2006 (UTC)


 * Thanks for pointing that out. The primary point remains regardless of a non-unity constant being used in the translation though. Alternately, there is no reason a faraday could not be the SI base unit. Pdbailey 13:15, 26 September 2006 (UTC)

Symbol for coulomb
I see C, q, and Q on various pages. If "q" it would be another exception to capitalizing symbols derived from person's names --JimWae 05:00, 6 March 2006 (UTC)

The coulomb's symbol is "q." C is used for capacitance (though not the unit symbol, which is why it's confusing), and Q is used when describing an electric field within a capacitor. --Eridani 00:10, 6 March 2006 (Eastern)

Then Coulomb seems to need editing too - and likely Ampere. It looks to me now that it would not be an capitalization exception - because the SYMBOL is not derived from the name --JimWae 05:19, 6 March 2006 (UTC)

Actaully, when talking about coulombs as an amount ,i.e. magnitude, the symbol is "C." When using it in a formula and drawing diagrams, it's a q. --Eridani 00:30, 6 March 2006 (Eastern)

The coulomb article repeatedly has the symbol as C --JimWae 06:04, 6 March 2006 (UTC)

It is q (italic), not q, that is used for electric charge, a quantity that can be measured in coulombs, whose symbol is an upright (not italic) C. This q could also be measured in obsolute units such as faradays or abcoulombs or statcoulombs.

It is C (italic), not C, that is used to represent the quantity capacitance, a quantity that can be measured in farads (not faradays). A farad is one coulomb per volt. Gene Nygaard 07:47, 6 March 2006 (UTC)


 * Gene's right: don't confuse physical properties with units of measure. Hardly anybody confuses them when dealing with statics and dynamics, but for some reason they are often confused in electrical.  Length (l) can be measured in metres (m): l = x m.  Momentum (p) can be measured in kilogram metres per second (kg·m/s): p = x  kg·m/s. Current (I) can be measured in amperes (A): I = x A. Charge (q) can be measured in coulombs (C): q = x C.  Indefatigable 22:30, 6 March 2006 (UTC)

Rename to "International System of Units"
I noticed the lack of descriptiveness in the current headline "SI" as I was looking at the External link to "SI" in metre, where a person looking at the name would not necessarily know what the article is about, whereas "International System of Units" has some meaning in its constituent words. A general encyclopedia must be accessible to a person who does not immediately know an obscure two-letter abbreviation, so most articles that are so accessible must refer to the System as "International System of Units". Being an abbreviation "SI", though it is more commonly used than other abbreviations, is likely inappropriate for an article title. What do you think? - Centrx 02:18, 7 April 2006 (UTC)


 * Agreed, but a merge with Metric system would be better.  Pr oh ib it O ni o n s   (T) 15:34, 18 May 2006 (UTC)
 * Done. (moved) - Centrx 01:26, 25 May 2006 (UTC)


 * I hate to be picky, tho I don't think I'm being picky- the proper name is Systeme Internationale, which is why they're called SI units. "International System Of Units" is a translation and colloquial. It may seem more descriptive to an english-speaker, but that's not the point. Systeme Internationale is a proper noun, which is why it's capitalised- just as one might write an article on "Cafe de Paris", but one wouldn't call it "The Cafe Of Paris". I appreciate that this may seem like nitpicking to people still stuck in the Dark Ages with feet, pounds and furlongs, but really the page should be called "Systeme Internationale".82.71.30.178 00:31, 17 January 2007 (UTC)


 * Notice that Système International d'Unités, Système International, and Systeme International already redirect to the International System of Units article. --Gerry Ashton 00:47, 17 January 2007 (UTC)

Consistency in redirects
I don't know where else to raise this, so I raise it here. micrometre redirects to SI prefix or something similar, while milligram redirects to kilogram. Neither approach is particularly helpful, last especially not, but what approach should we be taking here? Skittle 14:53, 18 May 2006 (UTC)


 * Here's where you can find the discussion on this topic. Jimp 06:31, 12 June 2006 (UTC)

Cultural Issues
I don't see the point of this section. It's hard for me to follow, seems to be original research and appears to be written to refute a point of view ("some SI units are cultural, therefore the system isn't scientific") that isn't very credible. I'd like to read comments from others, especially from those who disagree with me and think this section serves a purpose. Inter lingua talk email 02:08, 5 July 2006 (UTC)


 * I think the point is to explain why non-SI units (e.g. gram) are still used. But I agree it is poorly written and appears to be a long personal answer to a question that hasn't been put. I'm not sure who has a problem with gram. "Millikilogram" is clearly wrong. Celsius would seem more of an issue. --agr 10:37, 5 July 2006 (UTC)


 * Agreed. It is quite poorly written. IMHO, it's really the second and fourth paragraphs that are the most problematic. Perhaps they could do with being removed, or at least severely rewritten. --Morlark 23:06, 14 August 2006 (UTC)


 * The passage about grams seems confused. The only sense in which the gram has been depreciated in SI compared to earlier varieties of the metric system is that compound units involving mass are based on the kilogram rather than gram. For example, in SI, force is measured in kg•m/s², not g•m/s² as was popular in the early 20th century. --Gerry Ashton 23:34, 14 August 2006 (UTC)


 * I rewrote most of the section. I didn't change the heading because i couldn't come up with a better one, though i don't much care for it. Suggestions and edits welcome, of course. --agr 11:37, 15 August 2006 (UTC)

A change was just made in the example about electricity being sold in kilowatt hours rather than megajoules. Megajoules were changed to joules. Since kilowatt hours are a convienient unit for residential electricity consumption, it stands to reason that megajoules would also be convenient, since 1 kilowatt hour = 3.6 megajoules. Does anyone know what unit is used for power billing in various countries other than the USA? --Gerry Ashton 23:46, 16 August 2006 (UTC)


 * France, at least, apparently uses kWh. Here is a site explaining their rate system: http://particuliers.edf.fr/rubrique112.html --agr 13:55, 23 August 2006 (UTC)

Table problem
I don't know how to fix this, or I would, but on my browser the table referred to from SI and possibly other places, called non-SI units accepted for use with SI has above it the line:

Non-SI units not formally adopted by the CGPM Non-SI units with values obtained only by experiment Non-SI units whose use is not encouraged

It is shown all as one line, but clearly it is supposed to divide the table into three sections, one for not-formally-adopted units, one for experimental values, and one for deprecated units. In fact, looking at how the table is coded, that's exactly what the author tried to accomplish, since that language is embedded at three different points in the table. But it is rendered as a single line, above the table.

I don't know enough about how to code a table properly (apparently I'm not alone in that) but if someone could see about this, that would be a Good Thing. --Jeepien 07:24, 19 July 2006 (UTC)


 * It turns out the article incorporates template: SI acceptable units and I fixed it by breaking one table into four. I never used Wiki table markup before, but I've been editing table markup since about 1982 or so (using a predecesor of HTML). It seems that when you've seen one table markup language, you've seen them all. Gerry Ashton 00:12, 27 July 2006 (UTC)

MKS or mks
M=mega, K=kelvin, S=Siemens; it's a bit odd to use capitals. Stephen B Streater 09:15, 6 August 2006 (UTC)


 * David Halliday and Robert Resnick's book Fundamentals of Physics (Revised printing) published in 1974 by Wiley uses the lowercase mks on page 68. I think Mr. Streater would be justified in changing the abbreviation in the article. --Gerry Ashton 16:17, 6 August 2006 (UTC)


 * I'll change it for now then. Stephen B Streater 17:23, 6 August 2006 (UTC)


 * It doesn't sound odd to me at all. The reasoning against capitalization seems to presuppose that "MKS" are meant to be the symbols for the unit. That doesn't seem likely to me. A more likely explanation is that the name MKS is formed according to the usual practice (of using capital letters for acronyms and initialisms) from the names of the base units. Since the name is not itself an SI unit, there is no sense in trying to interpret it according to the rules for interpreting SI units. The abbreviation SI does not stand for Siemens anything either, for that matter. --71.123.61.112 14:20, 24 September 2006 (UTC)

Money
I notice that there is no SI unit for money, and that this is dimensionally independent and useful eg £/kg. I presume the European directive banning non-SI units on packaging doesn't apply to the €. Stephen B Streater 06:54, 20 August 2006 (UTC)
 * Okay… -- R'son-W (speak to me/breathe) 22:30, 25 August 2006 (UTC)

"SI" redirects here...
SI does not redirect to this page. It brings you to a disambiguation page, so remove that. --Scotteh 14:34, 2 September 2006 (UTC)


 * The disambiguation page is Si, not SI which is kept because many pages still link to it. Femto 17:54, 2 September 2006 (UTC)

SI units in everyday life
I would like to have also a section on the informal definitions of the SI-units, since they

1. motivate the modern, scientific definitions

2. come extremly handy when doing back-of-an-envelope calculations

Examples of informal definitions of SI-units.


 * 1 meter is choosen such that the equator has a length of 40.000 km
 * 1 liter is a cubic decimeter
 * 1 kilogramm is the mass of 1 liter of water (at 0 Degree Celsius)
 * 1 Newton is the gravitation force acting on 100 gram
 * 1 Watt second is the energy needed to lift 1 kilogram up 1 meter, it's also the energy generated by an electric current of 1 ampere over a potential difference of 1 Volt lasting for 1 second

Note: these definitions are correct with a precision of less than 1%, which is usually sufficient in every-day life.

To illustrate my point 2, i like the following example:

A pump with 1 horse power can lift 1 cubic feet of water 1 yard within 1 second. What is it's efficiency?

A 1 kilo-Watt pump can lift one liter of water 1 meter within 1 second. The efficiency is of course 1 percent.


 * If we want informal definitions that actually motivated the formal definitions, rather than just being useful approximations, I would eliminate "1 newton is the gravitational force acting on 100 gram" because the real motivation behind this unit, as well as being the formal definition, is a force, when applied to a mass of 1 kg, that causes an accelleration of 1 m·s&minus;2.


 * Also, 1 watt second is not the energy needed to lift 1 kilogram up 1 meter, it's the energy required to move an object a distance of 1 meter while applying a net force on the object of 1 newton.


 * By the way, the names of units are not capitalized when spelled out, except degree Celsius. However, when reduced to a symbol, the symbol is capitalized if the unit is named after a person. --Gerry Ashton 19:26, 10 October 2006 (UTC)


 * Yes, that proposed watt second "definition" is simply wrong. In the first place, the equivalent SI unit is the joule (J).  It is the watt which is defined as one joule per second.  A kilogram weighs about 9.81 newtons at sea level, so raising it 1 meter would require 9.81 J of work, not just one.


 * The definition of a liter as 1 cubic decimeter is not an informal definition at all; it is the current formal definition of the liter.


 * Also, the meter was not chosen so that the equator would be 40 000 km. It was chosen so that the distance from the equator to the north pole (along the Paris meridian, of course) would be 10 000 km.  That has a closer agreement to the current "photo-atomic" definition of the meter. =Jeepien 18:33, 11 March 2007 (UTC)

Usage on Wikipedia
Should Wikipedia always use SI?
 * Yes; SI with the other system in parenthesis. In the case of articles that are only related to countries that use other systems, it should be that system and the SI in parenthesis. Well, just my opinion. Please sign your comments with four tildes.--cloviz 12:43, 25 October 2006 (UTC)
 * Also note that the Manual of Style has this to say in the Scientific style section.
 * For units of measure, use SI units as the main units in science articles, unless there are compelling historical or pragmatic reasons not to do so (for example, Hubble's constant should be quoted in its most common unit of (km/s)/Mpc rather than its SI unit of s-1). For other articles, Imperial or American or metric units may be used as the main units of measurement.
 * --Gerry Ashton 18:41, 25 October 2006 (UTC)

SI OR IS
Does anybody know why it's called SI instead of IS? Im a little confused.

--169.139.56.79 18:12, 7 March 2007 (UTC)


 * Look at the picture of the official brochure at the top of the article. The name of the system in French is Le Système international d'unités and the abbreviation is based on the French word order. The abbreviation is SI in all languages. --Gerry Ashton 19:22, 7 March 2007 (UTC)

Squared and cubed metres?
How do we say m2? "Square metres" or "metres squared?" Likewise, is it "cubic metres" or "metres cubed?" —The preceding unsigned comment was added by Ronstew (talk • contribs) 14:30, 8 April 2007 (UTC).


 * As an example, I would say 3 square metres, meaning three squares, each of which is 1 metre on a side. If I were to say 3 metres squared, that might be interpreted as one square, 3 metres on a side, which would have an area of 9 square metres. --Gerry Ashton 14:38, 8 April 2007 (UTC)


 * Either way, but "square metres" or, when in denominator, "per square meter" is easier to understand and is understood by more people, because a square metre is a unit of area. "Apply manure at 5 kg/m2" is easier to grasp if you say "… kilograms per square metre". However, in some complicated expressions, there are no square metres (unit of area) involved, so it makes better sense to say "metres squared". I'll try to find an example.--MajorHazard 14:43, 8 April 2007 (UTC)


 * Example: http://en.wikipedia.org/wiki/Viscosity#Kinematic_viscosity:_.CE.BD Kinematic viscosity has units of m2s-1, which I would say "metres squared per second".--MajorHazard 14:47, 8 April 2007 (UTC)

Thank you, good people. While I agree with all your comments, I was worried that some bureaucrat had outlawed the term "square metre." I am just starting my career as a physics teacher, and want to make sure that I don't pass my bad habits on to the kids.Ronstew 16:06, 8 April 2007 (UTC)

SI is redundant in comparison to geometrized units
Here you have all needed conversion factors proofing redundance of the SI, that covers all the SI base units, and if not possible, their unique elements, because ampere is a dimensionless ratio of two lengths such as [C/s], and candela (1/683 [W/sr]) is a dimensionless ratio of two dimensionless ratios such as ratio of two volumes [kg*m^2/s^3]=[W] and ratio of two areas [m^2/m^2]=[sr], while mole is nothing else than dimensionless Avogadro number of any entities:

into m


 * G/c^2 [m/kg]
 * c [m/s]
 * ((G/(4*pi*(electric constant)))^0.5)/c^2 [m/C]
 * (G*k)/c^4 [m/K]

into kg


 * c^2/G [kg/m]
 * c^3/G [kg/s]
 * 1/(G*4*pi*(electric constant))^0.5 [kg/C]
 * k/c^2 [kg/K]

into s


 * 1/c [s/m]
 * G/c^3 [s/kg]
 * ((G/(4*pi*(electric constant)))^0.5)/c^3 [s/C]
 * (G*k)/c^5 [s/K]

into C


 * c^2/((G/(4*pi*(electric constant)))^0.5) [C/m]
 * (G*4*pi*(electric constant))^0.5 [C/kg]
 * c^3/((G/(4*pi*(electric constant)))^0.5) [C/s]
 * (k*(G*4*pi*(electric constant))^0.5)/c^2 [C/K]

into K
 * c^4/(G*k) [K/m]
 * c^2/k [K/kg]
 * c^5/(G*k) [K/s]
 * c^2/(k*(G*4*pi*(electric constant))^0.5) [K/C]

All these SI units represents nothing else than distance along dimension, that shows that SI is redundant in comparison to geometrized units, where to measuring all quantities one arbitrary unit is sufficient. You can try these factors in Google. 83.5.74.221 20:06, 17 April 2007 (UTC)

Proposed WikiProject
Right now the content related to the various articles relating to measurement seems to be rather indifferently handled. This is not good, because at least 45 or so are of a great deal of importance to Wikipedia, and are even regarded as Vital articles. On that basis, I am proposing a new project at WikiProject Council/Proposals to work with these articles, and the others that relate to the concepts of measurement. Any and all input in the proposed project, including indications of willingness to contribute to its work, would be greatly appreciated. Thank you for your attention. John Carter 20:40, 2 May 2007 (UTC)

year
The year is a common derived term and while not specifically mentioned, it's use is so common (it appears all over the place in law, life, scientific papers) that it bears inclusion in the non-SI section. Pdbailey 17:28, 17 May 2007 (UTC)

New named units
The article says there are many new named units. When was this text added, and why is there no list or link to them? --Belg4mit 19:51, 5 June 2007 (UTC)


 * Near the end of the history section, it says "In 1960, the 11th CGPM named the system the International System of Units, abbreviated SI from the French name: Le Système international d'unités." If I remember correctly, it was in 1960 that a number of new unit names were introduced, although a few have been adopted since then. --Gerry Ashton 20:21, 5 June 2007 (UTC)


 * Oh, okay. I sort of assumed a "recently" was in there somewhere, maybe from the new paragraph or something. --Belg4mit 02:36, 6 June 2007 (UTC)

UK using Imperial edit removed?
Earlier today, I added a sentence in Trade of this page, including a source, stating that the UK has been made exempt from converting to metric from imperial. It has been removed by Elektron, along with some vandalism (not by me). Was this deliberate, and if so why? Sonofdot 20:42, 11 September 2007 (UTC)
 * This type of detail belongs elsewhere, e.g. Metrication. We can't hope to cover everything in one article.  I don't know whether this was the reason it was removed but it's reason enough not to re-add it. Jɪmp 23:35, 11 September 2007 (UTC) ... On second thoughts, if we're already talking about the directive, noting the exception is only sensible.  Still, I'd argue that the entire Cultural issues could do with significant trimming ... even, perhaps to the point of moving the whole thing elsewhere. Jɪmp 23:46, 11 September 2007 (UTC)
 * I agree: really, this article is about SI units, rather than the metric vs. imperial argument. I only added it because I saw that the directive was mentioned. Sonofdot 05:53, 12 September 2007 (UTC)
 * Um, I removed the vandalism, but not anything in #Trade (I only moved the period) (diff). It is currently still in the article (diff). ⇌Elektron 14:34, 13 September 2007 (UTC)

Controversy
Someone should add a paragraph that says something to this effect:

Due to its inconvenience, many people, including the majority of the United States dislike the SI, instead supporting the much simpler standard system. —Preceding unsigned comment added by 75.15.160.108 (talk) 02:38, 22 February 2008 (UTC)
 * Which inconvenience would that be? --92.227.16.213 (talk) 21:31, 24 February 2008 (UTC)


 * Wow, a troll on Wikipedia. The SI IS the Standard System. Americans are the ones that use a stupid, backwards and archaic system that should be relegated to the middle-ages. Simpler? Don't make me laugh. --Dez26 15:48, 26 March 2008 (UTC) —Preceding unsigned comment added by Dez26 (talk • contribs)

Precisly. SI units are essentially the ONLY standard units of measure. The reason America uses a different system (That to my knowledge noone else uses) is because it has isolationist inclinations, the same reason why Webster wrote a dictionary that was a different as possible to Dr. Johnsons.(86.152.184.218 (talk) 23:43, 2 June 2008 (UTC))

Um, excuse me, gentlemen. Are all aware that the US implemented a decimal currency more than a century before the rest of the world went this way? A little less bigotry, please, especially when dealing with scientific matters! Regarding the inconvenience, that inconvenience is called money. How backward do you consider Canadians? Not very much so, I would suppose. Yet their railways are to this day based on miles, not kilometers. Speeds are regulated in miles per hour. Bridges, buildings, signals, and so forth are identified by milepost (to the tenth or hundredth place), not by kilometerpost (if such a term exists). Why?? How much money would you, dear reader, wish to donate to the railroads for the purpose of redrawing all blueprints, making new signs, etc.? And what would this truly accomplish? All for a "good boy" pat on the back? Bejmark (talk) 16:37, 22 August 2008 (UTC)

Survey: bit/s/Hz, (bit/s)/Hz or bit·s−1·Hz−1 as Spectral efficiency unit?
Please vote at Talk:Eb/N0 on which unit to be used at Wikipedia for measuring Spectral efficiency (bit rate divided by bandwidth). For a background to the controversy, see the discussion at Talk:Spectral_efficiency and at Talk:Eb/N0. Mange01 (talk) 19:22, 21 April 2008 (UTC)

Other alphabets
Are there e.g. cyrillic or greek symbols acceptable (or that have been acceptable in the past) for use in languages that use those alphabets - typewriters and some early computer character sets for them did not support the latin alphabet. --Random832 (contribs) 01:49, 10 July 2008 (UTC)

As a speaker of Ukrainian, I can vouch for the fact that Cyrillic letters were certainly commonly used for these quantities, at least on typewriters that did not have Latin letters included. I doubt this had any official standing, however. Bejmark (talk) 16:42, 22 August 2008 (UTC)

Found it - it's GOST 8.417:1981 and had official standing in the Soviet Union. --Random832 (contribs) 18:43, 22 August 2008 (UTC)
 * You can find the Cyrillic equivalents at ru:СИ, the Russian(-language) version of this article. The current standard appears to be GOST 8.417–2002, although my Russian isn't good enough to be sure about that. The Greek version of the article, el:Διεθνές σύστημα μονάδων, only uses the Latin symbols (except, of course, for µ). Same goes for jp:国際単位系] and [[:kr:SI 단위계: for Chinese, I would have to look into it further. Physchim62 (talk) 20:23, 1 October 2008 (UTC)

SI writing style
Currently the wording is "Any line break inside a number, inside a compound unit or between number and unit should be avoided, but if necessary the latter option should be used.", however, it is unclear which the "latter option" is. Ideally this could be spelt out in full for clarity. —Sladen (talk) 11:08, 13 July 2008 (UTC)


 * I think it means it is better to break between the number and the unit than to break within a number or break within a compound unit. Personally, I think this is good advise when using symbols but not when using spelled-out words. --Gerry Ashton (talk) 13:26, 13 July 2008 (UTC)

Good article nomination
This article is worth considering for good article nomination.pruthvi (talk) 09:05, 17 September 2008 (UTC)

WP:ENGVAR
In this edit, I converted several -ise spellings to -ize. The paragraph itself was not consistent, which is what caused me to choose between one or the other. There's not much to go on in the history, but this seems to be the first version to use a noun derived from an -i(s/z)e verb, and went with -ization. Feel free to comment if you think I've been too bold, but it seemed to me that consistency was more important then choice of spelling system! Physchim62 (talk) 00:27, 2 October 2008 (UTC)


 * Do you have a spelling checker that uses the Oxford spelling? It would be especially great if you had one that works with the aspell command used by the PC version of EMACS. --Gerry Ashton (talk) 03:34, 2 October 2008 (UTC)


 * I feel that the British English spellings should be used, i.e. -ise in favour of -ize. The Wikipedia guidelines say that British English spellings should be used in articles relating to or effecting English things, and that American English spellings should be used in articles relating to or effecting American things. Since the USA is not party to the SI system of units, and the UK is, it seems to relate to and effect the UK more than the USA. I propose a wholesale change. Any disagreements due to citable Wikipedia style guidelines? Δεκλαν Δαφισ   (talk)  18:13, 3 October 2008 (UTC)


 * See American and British English spelling differences. Some authoritative British sources prefer the -ize endings rather than the -ise endings. Also, the United States signed the Meter Convention in 1878 and its measurements have been based on metric standards since the Mendenhall Order issued in 1893, so you can hardly say "the USA is not a party to the SI system of units". --Gerry Ashton (talk) 19:04, 3 October 2008 (UTC)


 * As you say: some authoritative British sources prefer the -ize endings rather than the -ise endings. The British English standard is to use the -ise. When I say that the USA is not a party to the SI system of units this is because the article itself says "Three nations have not officially adopted the International System of Units as their primary or sole system of measurement: Liberia, Myanmar and the United States." A treaty or agreement is nothing more than a piece of paper until it has been ratified; the USA has never ratified the Meter Convention. On top of that, whenever I have visited the USA I've never been able to buy a litre of petrol, or a litre of milk. It's always been in pints and gallons. The link that you give is to a Wikipedia article. There is (although I must confess I can't find it) a Wikipedia guide which basically outlines the rule British English for mainly British things, and American English for mainly American things. Δεκλαν Δαφισ   (talk)  19:27, 3 October 2008 (UTC)


 * The US did ratify the Meter Convention, see http://www.state.gov/documents/organization/89668.pdf page 190. SI units are allowed for many purposes and mandatory for a few purposes in the US.


 * When you say "The British English standard is to use the -ise", how do you know? --Gerry Ashton (talk) 19:41, 3 October 2008 (UTC)


 * I was born, raised, and university educated in England. Besides being able to give a firsthand account, which historians seem to love, you might like to read the official website of the British monarchy. On this page you will find the text of The Queen's speech at the State Banquet in Turkey, 13 May 2008. The important sentence is: "For all these reasons, the United Kingdom attaches the highest importance to our relationship, recognised by the strategic partnership entered into by our two Prime Ministers last year." This was only the third page I checked on HRH's page. Maybe you'd like to check the webpages of parliament? Δεκλαν Δαφισ   (talk)  20:13, 3 October 2008 (UTC)

I've made the US to UK  edit as per WP:ENGVAR - Strong national ties. I hope that no-one objects. If there are any concerns then please raise them here before changing the article. It's my opinion that the article should have UK spellings, and I also feel that this fits with the WP guidelines. Of course WP is a democracy, so if there's anything anyone would like to add to this discussion topic then please let it be known. Δεκλαν Δαφισ  (talk)  12:58, 6 October 2008 (UTC)

My reasoning is this: The main English speaking countries are Australia, Canada, India, Ireland, the UK, and the US. Now the US doesn't use the SI system, so we are left with Australia (Australian English), Canada (Canadan English), India (India English), Ireland (Irish English), and the UK (British English) that do use the SI system. Out of these Australia, India, Ireland, South Africa, and the UK all use British English spellings. The Canadians use a mixture of British and American English. So the vote comes down to 4½ for British English against ½ for American English. Δεκλαν Δαφισ  (talk)  13:27, 6 October 2008 (UTC)
 * What you mean is that it's taken you eighteen edits to do that (plus one bot edit to restore the interwiki links that you happened to delete along the way). That is not anything to do with WP:ENGVAR, it's simple obsession, and I feel personally sorry for you. Physchim62 (talk) 13:35, 6 October 2008 (UTC)


 * I suggest that you read WP:CIVIL. I am not a very experienced editor and that is why it has taken me so long to get it right. I'm sure that many of those 18 edits were made when I was trying to correct some problems that I has accidentally caused to the article. Would you rather me have left the article broken? This is everything to do with WP:ENGVAR, as my posts quite clearly show. If you have something constructive to say then please say it, but don't resort to insults and name-calling. Δεκλαν Δαφισ   (talk)  13:42, 6 October 2008 (UTC)


 * After reading the article history I see that I had made 17 edits. Five of those were undos or attempted repairs. I prefere to edit section by section so I will have made four of five saves to get the whole article correct (that could actually have been done in one edit). Since I undid these I had to do them again, so that is why there are so many. There was actually only one or two edit sessions (original section-by-section changes, then reverts and re-edits) even though there were many individual saves. Δεκλαν Δαφισ   (talk)  13:49, 6 October 2008 (UTC)


 * The United States is on the metric system, see NIST's history of conversion . It merely has not prohibited the use of other systems of units within the private sector. "Federal agencies were required by this legislation, with certain exceptions, to use the metric system in their procurement, grants and other business-related activities by the end of 1992. While not mandating metric use in the private sector, the Federal Government has sought to serve as a catalyst in the metric conversion of the country's trade, industry, and commerce." JRSpriggs (talk) 14:37, 6 October 2008 (UTC)


 * But the article says that the US has "...not officially adopted the International System of Units as their primary or sole system of measurement." The UK, Australia, India, and Ireland all have. In fact, come 2009, all imports into the EU will have to by law be measured in SI units. Besides, even if the US had (which it hasn't), that would put the vote at 4½ for British English against 1½ for American English. Δεκλαν Δαφισ   (talk)  14:56, 6 October 2008 (UTC)
 * Then the article should be changed, because the information I gave you came from an official U.S. government source, the National Institute of Science and Technology. JRSpriggs (talk) 15:39, 6 October 2008 (UTC)
 * Possibly, although what legislation says and what people do on the high street are very different. The piece of legislation that you site only covers the US federal government and not supermarkets, petrol stations, school canteens, family kitchens, etc. The U.S. Metric Association exists "...to advocate U.S. conversion to the International System of Units" and so their use cannot be at all wide spread where as all packaging in Australia, Ireland, and the UK is by law in metric. I'm not sure about India. Δεκλαν Δαφισ   (talk)  15:57, 6 October 2008 (UTC)

There is no substantial issue with this article, because it used UK spelling all along. Declan Davis just prefers one variant of UK spelling over other variants. However, Declan's assertion that articles related to the International System of Units have strong national ties to every English-speaking country except the US is wrong. Although the sale of goods in shops is dominated by American customary units (even though it is mandatory to label most goods in SI too), American industry is dominated by SI units. I worked for more than 20 years for an electronics manufacturer, and the only thing we used American customary units for was ordering office supplies. SI was the only system used for manufacturing. Also, the only electrical units are SI, so the US uses SI for all electrial measurements.

If Declan comes across a metric-related artice that uses American spelling, he should be sure to leave it alone. --Gerry Ashton (talk) 21:23, 6 October 2008 (UTC)


 * Thanks for your input Gerry. Although we have already discussed your main point: the standard British English spelling (and thus Australian, Irish, Indian,...) is to use the "-ise" endings and not the American "-ize". I'm sure you'll agree that "standard" and "accepted" are quite different adjectives. For example 99% of a population may do something in one way, and that would be standard; 1% may do it another way, and that way has been accepted. As my earlier link to one of the British monarchy's website pages shows (please see The Queen's speech at the State Banquet in Turkey, 13 May 2008). The "-ise" ending is standard and widespread. The -ize is not standard UK (and thus Australian, Irish, Indian,...) spelling, although it is sometimes accepted (by the Oxford English dictionary and, no my knowledge, no other). I can understand that you may have personal feelings towards maintaining the US spellings, but that isn't enough to satisfy Wikipedia's guidelines. I know it's tempting to let personal preference overtake reason, but let's not.  Δεκλαν Δαφισ   (talk)  21:50, 6 October 2008 (UTC)


 * p.s. I have no problem, or objection, with the use of American English spellings. There is a time and a place for everything. I feel that, in the case of this article, using British English spellings fits with Wikipedia’s guidelines, common sense, and is better for the majority of people that may read this article (i.e. English speakers that use the SI system). In a world-wide neutral article then either spelling would be okay. I'll never understand Wikipedia: if I don't follow its guidelines I am told to do things differently by the admins, and if I do things by the book then editors get on my back.  Δεκλαν Δαφισ   (talk)  21:50, 6 October 2008 (UTC)

I apologise to Declan for the tone of the remarks above. I still think he was wrong to make the edits he made (according to WP policy), especially without discussing it here first, but I should have phrased it better. Physchim62 (talk) 21:57, 6 October 2008 (UTC)
 * user:Physchim62: I had already proposed the wholesale change (please read above). No-one objected on the grounds of WP policy; only on personal taste. I feel that I made the point using WP guidelines and common sense. That's why I changed it. If you still disagree then please drop me a line on my talk page I would appreciate your opinion. Δεκλαν Δαφισ   (talk)  22:29, 6 October 2008 (UTC)


 * Declan seems to have missed my point. I don't mind at all if he makes a spelling adjustment to this article that falls within the range of acceptable UK spelling. If he wants to change "-ize" to "-ise" in an article that uses UK spelling, that is fine. I would only have an issue if he found a different metric-related article that used US spelling (including "meter") and changed it to UK spelling. My reasoning is that SI is essential to the US. If the ability to measure in SI units disappeared tomorrow, the US would be back in the stone age within a month. So SI is no more connected to other English-speaking countries than it is to the US. As for use by average people, among the heaviest US users of Wikipedia are school children. Although they might not use SI when visiting the petrol station or supermarket with their parents, they make extensive use of it in their math and science classes, so I suspect a substantial amount of Wikipedia-reading by US school children involves SI units. --Gerry Ashton (talk) 22:13, 6 October 2008 (UTC)
 * Gerry: I'm sorry if I missed your point. I would never change an article that primarily effects the US and was written with US spellings. It's just that the SI units primarily effect the EU and the Commonwealth and as such are better left with British spellings. The official version of English in the EU is British, and the official language in the Commonwealth is British English. Δεκλαν Δαφισ   (talk)  22:29, 6 October 2008 (UTC)

I consider the statement "It's just that the SI units primarily effect the EU and the Commonwealth" to be incorrect, but so long as you do not act on this error, there will be no problem. --Gerry Ashton (talk) 22:34, 6 October 2008 (UTC)

Gerry, you are allowed to consider any comment you wish to be incorrect; wether it is correct or incorrect: that is the beauty of democracy. Here on Wikipedia, however, we require fact. Let me share with you some facts: The Commonwealth's official language is British English, and they have all (except the UK) been using the SI system as their primary system of weights and measures since around the 1970s. The Commonwealth has a population of around 1.9 billion (estimated in 2005). Let us now consider the EU. One of the official languages of the EU is British English (and thus the only accepted form of English in the EU); it’s population is about 500 million. The USA has population of 300 million (estimated in 2008). British English spellings should be used by the weight of numbers, by common sense, and by Wikipedia guidelines. If anyone has anything else to say then please let it be constructive fact, and not opinion. Δεκλαν Δαφισ  (talk)  23:30, 6 October 2008 (UTC)


 * Even in supermarkets you can find some items in metric units. I buy Coca-Cola in two liter bottles for example (in Montgomery County, Maryland USA). JRSpriggs (talk) 17:31, 7 October 2008 (UTC)