Talk:Kilogram/Archive 1

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Definition of Kilogram

All terms of science, including units of measure, use operational definitions, that is, definitions based on actually performable experiments and observable results. The kilogram is intended to represent the mass of one litre of water (where litre is defined in terms of metre, and metre is defined in terms of the measurable speed of light), but that's a theoretical thing --it's not possible with today's technology (nor was it in the past) to conduct any specific experiment with water to produce this value. The kilogram has always been officially defined in terms of the artifact in Paris (the metre once was as well, but now we have new experiments). There is a movement among some scientists now to redefine it in terms of a new experiment in which measurable electrical potentials move a specific mass, but this is still in the works. --LDC

The kilogram as = 1 L of water was true between 1901 and 1964 (definition of the Litre; see CGPM).

Urhixidur 20:29, 2004 Nov 23 (UTC)

I was under the impression that the kilogram had recently been redefined in relation to x moles of a certain isotope, rather than the kilogram at Sèvres. Is that not true? - montréalais

There are a number of competing plans to redefine the kilogram in terms of something repeatable. No plan has yet been decided on. -- The Anome 22:10 22 Jun 2003 (UTC)

According to the Bureau International des Poids et Mesures, the kilogram is still defined by the international prototype in Paris. Do you think it's fair use to put a picture of it from the BIPM site in the article? Basil Fawlty 15:12 22 Jun 2003 (UTC)

Seems like it would be fair if the source and a disclaimer tag were included. As the fair use page states, "Unique historical images which we cannot reproduce by other means" can be classified as fair use. The big pic is nice. -- Mjwilco 19:12, 11 Sep 2004 (UTC)

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What does this mean: "grain in now obsolete Portuguese spelling"? Is that supposed to imply that the word "gram" comes from obsolete Portuguese? Webster's 1913 says: "F. gramme, from Gr. ? that which is written, a letter, a small weight, fr. ? to write.". Or is it some weird reference to the imperial unit grain, meaning 1/7000 of a pound? -- ESP 05:37 20 Jul 2003 (UTC)

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Am I right in assuming that, by E=mc^2, if you heat an object, you will (ever-so-slightly) increase its mass, by adding thermal energy? (according to [[1]] to heat 1 gram of water by 1 degree C, requires ~0.465 femtograms of energy. Therefore any atom-based definition of the kilogram will require a temperature reference. CS Miller 11:39, Nov 23, 2004 (UTC)

You are quite right. In Einsteinian terms, we would refer to the zero K mass as the object's rest mass. Note that the SI definition of the second also takes care to specify that the ground state hyperfine transition used occurs at zero K.

Urhixidur 20:29, 2004 Nov 23 (UTC)

Kilogram as Base unit?

Has the kilogram always been considered a base unit? If so, why does it have a prefix? Why doesn't the metric system use a basic word for that unit, and instead call the gram milli-whatever? If it wasn't considered a base unit initially, when did it come to be considered the base unit? It has always seemed strange to me that a so-called "base" unit has a prefix Nik42 09:00, 26 Jan 2005 (UTC)

It really is quite stupid, but its too late to change that now :P. My theory is that the gram initially was the base unit, but people realised that it was smarter to use kg (less room for error when copying the base-sphere, and also derived definitions like the newton make more sense. That and it would be strange to measure the human body in grams "I weigh 75345 g, what do you wheigh?) So they just changed the base and kept the name to avoid confusion. This is my theory anyway Gkhan 04:33, Feb 27, 2005 (UTC)

Well, the weight thing's not really an issue. That's what prefixes are for anyways :-) I mean, no one would say that two cities were 52,000 meters apart, they'd say they were 52 kilometers apart. Still, kg definitely does make more sense as a basic unit for pretty much any purpose, which is why I find it odd that gram gets the basic name. - Nik42 07:50, 1 Mar 2005 (UTC)

Originally, the kilogram was supposed to be called the grave. The "new" system of units was commisioned by Louis XVI. A milligrave was to be 1/1000 of a grave, a kilograve 1000 graves. However, didn't come in effect until after the French Revolution. (Especially measuring the earth for defining the metre as one ten-millionth of the length of the earth's meridian along a quadrant, took a lot of time and was complicated by this Revolution) After the Revolution, the name "grave" was politically incorrect, because it is an alternative name for the title "count", and titles aren't compatible with the notion of égalité.

Also, scientists and industrialists feared that a grave would be too big or small for every-day use, so they choose gramme and tonne instead. But then that turned out to be to small or big, especially to make a defining prototype of, so they defined the original proposal (grave) under a different name (kilogram).

Or something like it.

See http://www.bipm.org/en/si/history-si/name_kg.html

All of that was already included in a summary of the above in the grave article, though.

–Adhemar

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AFAIK there is no atomic definition for kilogram. In 1967 the kilogram[2] was defined as the mass of 5.0188 X 10 (power 25) atoms of the carbon isotope of atomic mass number 12. The experimental uncertainty in the count was about 1 part in 20,000. -- Orionix 03:11, 4 Feb 2005 (UTC)

Clarify changes over the last 100 years

From the article: Although it is accurate to state that all other objects in the universe have gained 50 micrograms per kilogram, this perspective is counterintuitive and defeats the purpose of a standard unit of mass.

This makes no sense to me. If you counted the number of micrograms in a kilogram 100 years ago, you'd get a billion (if my metric conversions are correct). And the article is implying that if you count the number of micrograms in a kilogram today, you'd get 1,000,000,050? Wrong.

Maybe a more clear way to say it would be "It is accurate to state that any object in the universe (other than the reference metal in France) that had a mass of 1 kilogram 100 years ago, and has not changed since then, now is considered to have a mass which is 50 micrograms larger than a kilogram. This perspective is counterintuitive and defeats the purpose of a standard unit of mass, since the standard should not change arbitrarily over time."

--24.29.11.65 11:27, 27 Feb 2005 (UTC)

How is it known that the standard has lost weight? How can one compare a standard to itself over time? It seems like a paradox to me. Prometheus235 19:03, 16 Jun 2005 (UTC)

Presumably because you can compare the weight of other objects over time. If you consistently find that items measured 100 years ago appeared to possess slightly greater mass than they do today, the simplest explanation is not that all of those items gained mass, but that the standard lost mass. - Nik42 18:25, 17 Jun 2005 (UTC)

Also the standard has "official copies" that are stored and treated in the same manner as the standard itself. What's actually been found is that the standard is lighter in comparison to the average of these copies than it previously was. Pakaran 19:12, 17 Jun 2005 (UTC)

I think the whole paragraph save the first two sentences should be removed. I'm not going to edit it cause no-one else seems to have an issue but I mean, 1. the average person out there is (probably) going to be confused by it and 2. it's not really true; yes, in a way, everything has gained 50 micrograms relative to the SI mass, but our very awareness of this fact means that things haven't gained 50 micrograms from our perspective. It's a lot like saying "My bathroom scale is calibrated slightly high, therefore I have gained weight and need to diet", which is just silly. 202.37.62.123 04:11, 5 January 2007 (UTC)

I agree with you, actually. I'd integrate those first two sentences into the previous paragraph, and the result would be shorter and clearer. While the current version IS amusing and I love the word "paradoxical", I think we should be striving to be concise and understandable, not eccentric and amusing. In fact, I will (assuming we don't get a flood of comments here) integrate those first two sentences and delete the rest if you don't get to it in a few days. Enuja 05:18, 5 January 2007 (UTC)

Move the Article to "Kilogramme"

Wikipedia:Standardize Spellings specifies that articles may be written in either American or Commonwealth English depending on the subject matter. Seeing as how a kilogram is not a standard measure in America, it makes more sense in my opinion for this article to be moved to "kilogramme."

Where is the spelling "kilogramme" used? And it is used as a unit of mass in both North America and South America. 64.7.152.217 20:40, 13 September 2005 (UTC)

Well, it is used in scientific measurements, but not generally in commerce, in the US, where we tend to measure masses in terms of pounds. I am fairly certain than in all other parts of the Americas, the kilogram is the standard, including Canada, an English-speaking country. However, I would argue that it is not commonly spelled out. In fact, I would reccomend that the article be named kg (SI unit), and both spellings redirect to that, and all other SI units be named the same way. Unfortunately we have the majescule (capital) article title problem to deal with. --Mm35173 20:30, 28 September 2005 (UTC)

The United States was an original signer of the Meter Convention treaty of 1875; the U.K. didn't get on the bandwagon until decades later.

In case User: 64.7.152.217 is the "Commonwealth" version of Rip Van Winkle and hasn't noticed it yet, the kilogramme spelling has nearly completely disappeared from the rest of the English-speaking world as well. Gene Nygaard 15:46, 20 October 2005 (UTC)

You have you dates wrong I’m afraid, the US joined in 1878 and the UK in 1884 so that’s hardly decades is it? But yes you’re right, the US did sign first, however I’d argue since in real terms the US did not, and still does not really use the metric system whereas the rest of the English speaking world does, and bar perhaps Canada, spells it kilogramme then the article ought to be changed to reflect this. This would bring into line the English spelling with the original French spelling and the spelling of many other languages. Furthermore most of the other metric system measurements are listed in Commonwealth English so it is a bit of a mess to have most of the Metric system spelt in one convention but the remaining bit in another convention.

I wouldn't call the spelling "Kilogramme" a feature of Commonwealth spelling, I'd say it's an anomalous spelling only encountered in the UK. In Australia (which derives most spellings from Commonwealth English) the form "kilogram" is used exclusively. I'd be willing to bet it's the same in most Commonwealth countries. Leave the article where it is.--Scott Nash 05:23, 8 July 2006 (UTC)

The spelling kilogramme and gramme is pretty much restricted to the UK in the English speaking world. Even in the UK it's pretty rare nowadays. Therefore it certainly doesn't make sense to change an article from a majority spelling to a minority one. Leenewton 23:05, 8 February 2007 (UTC)

Removal of SI multiples section

User:Lee S. Svoboda recently deleted the SI multiples section, replacing it with a redirect to SI prefix.

That is unacceptable. What used to be separate articles at milligram and microgram and gigagram and the like now redirect here, to kilogram (megagram redirects to tonne, however). Part of the reason for including the prefixes here (and to similar unprefixed units for other quantities--the prefix is only included here because it is included in the SI base unit) was that people getting redirected here from a link to a prefixed unit were not finding anything about what the prefix means (and that's likely to be the main reason they click on a link to a prefixed unit). Part of the deal on eliminating the separate articles for the prefixed unit is that this information would be included in articles such as this one, not requiring people to chase all around the Wikipedia to find what they were looking for. Gene Nygaard 15:59, 20 October 2005 (UTC)

Approximate equivalent in pounds?

The absence of Imperial/US equivalents seems to be a major omission to me. Grant65 (Talk) 13:22, 13 November 2005 (UTC)

• The category link to "units of mass" is sufficient. Długosz

mcg for micrograms

Recently, an edit claiming that mcg is occasionally used for micrograms was reverted. The prefix mcg is used when the µ symbol isn't available, particularly in the medical field. Andros 1337 00:36, 23 November 2005 (UTC)

ug for migrograms

I see there is a citation request for the use of u for micro. In http://www.cofc.edu/~frysingj/lowtech.htm, the author cites the following reference:

American National Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units, ANSI/IEEE Std 260.1-1993 (Institute of Electrical and Electronics Engineers, New York, NY, 1994) section 6.1

I don't have access to that publication, but maybe someone who does can check it out? --Slashme 07:19, 21 July 2006 (UTC)

According to that link, u is the accepted workaround for use where one cannot use the greek letter mu (μ). The section on mu is:

For the lower case Greek letter mu, used to symbolize the prefix 'micro', use the lower case letter "u".
example:
    "The hair diameter is 68 µm."
    "The hair diameter is 68 um."
    (or "The hair diameter is sixty-eight micrometers.")
(note:  In typewritten texts, a "tail" should be added to the "u" by hand.) 

what coefficient?

I don't understand what is meant by: "The coefficient is close to the reciprocal of Avogadro's number: 1 unified atomic mass unit = 1.660 54 yg". What coefficient is being refered to here? The number in the sentence is exactly Avogadro's number. —Długosz

difrents

a kilogram is heveyer than a acsholy is little litter than a gram

you are a nonsense!

Cultural imperialism

Those 300 million of us who do not use the metric system should be informed how many pounds are equivalent to a kilogram. Lord knows the "pound" article is clogged up with kilogram crap. The article is hopelessly metric-centric, and refuses to acknowledge the existence of other units and measurements which are used by other cultures.

Go ahead, be bold, and add in the information you think is missing. Indefatigable 22:04, 19 January 2006 (UTC)

Okay, cool. I'll change it here - I would have done it earlier, but I felt like registering a complaint to draw attention to the wider unit biases on wikipedia. For instance, the total area of the U.S. state of Wyoming is given in square kilometers, with no square-mile figures provided - this for a state in a nation where the metric system is not widely used or understood. I'm unclear as to whether this bias is official policy or just a lack of information - it's so universal that it often seems to be the former. I'm trying to address the problem in general, and I might as well start here.

There is a bias because there should be. The vast majority of the world, uses metric predominantly. Even within the US, many especially scientists and engineers use professionally (and I would say prefer personally) metric. Also, while a fair number of people who use the pound and other non metric units find it necessary to have a good or excellent knowledge of conversions to metric units, many of those who use metric have only limited or no knowledge of conversions and have no real desire to know them. I'm not saying that we should ignore other unit systems or that there aren't improvements to be made but you appear to fail to appreciate how widespread metric usage is. Nil Einne 13:35, 21 June 2006 (UTC)

No doubt he has a chip on his shoulder about metric because it's French :o)

Problems of artifact definition

This article doesn't really elaborate on the problems of a physical artifact definition of the kilogram properly. It mentions the problem of a changing weight but other then that little else. However there are quite a number of problems. For starters, an artifactal definition could not be transmitted as information only. For example, we could easily send all other definitions out and in the unlikely event another intelligent race receives our signal and if they could work out our language etc they could easily understand our units and if they have a sufficient level of technology, they could therefore easily reproduce out units. However with the kilogram, all they would get/know would be that it's the same as some object stored in France which isn't particularly useful for them. This also applies for example if we were to all be wiped out or to regress to a low technological level area anyone who comes after us would have a similar problem. On a more basic level, with all other units, any scientist (or whatever) today with the required technology and understanding can indepedently measure/work out the unit. However with the kilogram, all they can do is visit their local agency and use that. Similarly although rather unlikely if some deranged person were able to get access, they could blow up or otherwise damage the kilogram and we would no longer have an official kilogram (we would have to take one of the replicas to be the new official kilogram). Or it could be lost (again very unlikely). And of course, if you want to get very sneaky, someone could replace the kilogram with an alternative thereby changing the definition of the kilogram (to some extent this is similar to the problem of a natural change to the kilogram) Nil Einne 13:56, 21 June 2006 (UTC)

In principle, aliens could work out the approximate mass by simply giving the density of certain objects. For example, 1 liter of water is very close to 1 kilogram. They wouldn't be able to derive an exact value from that, since there are variations in density based on pressure, temperature, etc., but it would be a very close approximation Nik42 02:31, 24 July 2006 (UTC)

It needs better examples in the Examples section. Check out the gram article to see what I mean.

Fundamental-constant approaches

i deleted incompletely defined "levitated superconductor approach". it does not say what physical constants are fixed to whatever value by the kg definition. it may be a perfectly good experiment to set up to define the kg, but it needs to say the definition: "the kilogram is such and such so that the physical constant so and so is set equal to some value." r b-j 21:55, 1 July 2006 (UTC)

It should be noticed that it is not possible to give an exact value to the von Klitzing constant. It equals half the speed of light times the magnetic permeability of free space divided by the fine structure constant. The speed of light and the permeability of free space are already defined as 299792458 m/s and 4π/10^7 N/A^2 respectively, so we'd need to know the exact value of the fine structure constant to do that. --Army1987 10:51, 1 August 2006 (UTC)

for some reason, when i was trying to clean up a similar sections of the definition of the Ampere, i ended up in a discussion/disagreement with User:Urhixidur at Talk:Ampere#erroneous_definition_for_Ampere. he said that:

1) CIPM, 1988, Recommendation 2 (PV, 56, 45 and Metrologia, 1989, 26, 70) recommends « that 25 812.807 W exactly be adopted as a conventional value, denoted by R_K-90, for the von Klitzing constant, R_K ».

and although i knew that it differered from CODATA and that the resulting alternative definition for the ampere (and Coulomb) could only happen as a consequence of a redefinition of the kg, i fixed it there and here in proposed redefinitions. i was trying to effect a compromise (since this was proposed definitions not the currently accepted definition) and still be accurate.

you might want to get User:Urhixidur's attention regarding this or, if you see something that is just wrong, fix it (and see if it survives). r b-j 14:58, 1 August 2006 (UTC)

i changed it. if User:Urhixidur objects, i think he has to persuasively answer User:Army1987 point (which appears perfectly valid to me). r b-j 20:32, 2 August 2006 (UTC)

multiples

Please don't remove multiples, for consistency they are in all seven base SI units.

Weight

I just added a link to the "weight" page in the "Link to Weight" section, because the section, while very explanatory, seemed over the head of a novice reader. Also, I couldn't find any other links to the weight page. If there is a better place to put the link, or if I simply missed a previous link, please change it. I know the word "weight" appears earlier in the article, but it is always a part of a title (weights and measures) or is a heading. Enuja 01:08, 5 January 2007 (UTC)

Repeatibility of Offical Standard

I combined the two paragraphs (in the history section) about the repeatibility of the standard, and took out the tangent about the change in mass of every single item, when measured in kilograms. An editor had recently suggested that the tangent was confusing (hidden up in the "clarify changes over the past 100 years" section), and another editor had changed the new mass of a hypothetical 1 Kg mass to 1 Kg - 50 micrograms instead of 1 Kg + 50 micrograms.

In the same paragraph, does anyone know why the official standard and it's copies are only of "roughy the same materials" when the previous paragraph describes them as all being "an alloy of platinum and iridium of 39 mm height and diameter"? In other words, what source did the content of the offical standard come from, so I can check to see that the standard and its copies are of the same alloy? Enuja 02:03, 9 January 2007 (UTC)

Kilogram in Popular Culture

While I doubt the kilogram makes many appearances in pop-references, it did just get mentioned in the latest Dinosaur comic:

http://www.qwantz.com/index.pl?comic=917 --MacAddct1984  03:33, 13 January 2007 (UTC)

The U.S. uses it as a primary measurement?

I want to know where this comes from. all I've been old they've ever used is the Imperial System, not this one. If I remember,they wanted this to be DIFFERENT... I'm likely wrong, though. So, to my understanding, this article seems to be focussing mainly on the U.S. with possible false information. Any Clarification would be good. --SBKT 16:31, 20 March 2007 (UTC)

The pound is defined in terms of the kilogram these days, so the pound's primary reference is the kilogram. I don't think anybody is arguing that the kilogram is in everyday usage (except in NASA).WolfKeeper 16:45, 20 March 2007 (UTC)

It's in common usage in the UK and Europe, and I'd imagine it's used in high-school level science and above in the US- constants like g and M_e use Kilograms as factors, and pV = nRT should use Pa as the unit for pressure right?81.77.175.47 14:53, 8 June 2007 (UTC)

Why is the US mentioned explicitly here? There is no need for it. It is phrased awkwardly, and adds no value.

I'm pretty sure Wolf was referring to everyday usage in the US. It's a well known fact that the kilogram has mostly been accepted for everyday usage in most of the rest of the world Nil Einne 12:26, 19 July 2007 (UTC)

the pound is metric

The current third paragraph is misleading. A pound is exactly 453.59237 grams. No appoximations needed. I will rewrite when I get around to it.CorvetteZ51 17:09, 14 April 2007 (UTC)

The current precision is a compromise, and I think, a good one. There is no need to for 8 significant digits in a lead section. Enuja 19:27, 14 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 Wikipedia:WikiProject Council/Proposals#Measurement 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 21:06, 2 May 2007 (UTC)

Redefining the kilogram

The latest on one of the attempts to redefine the kilogram [3] Nil Einne 07:14, 15 June 2007 (UTC)

http://www.reuters.com/article/scienceNews/idUSSYD9740620070615

Already added as a reference to the article.JimDunning 13:10, 16 June 2007 (UTC)

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