From Wikipedia, the free encyclopedia
Jump to: navigation, search
Good article Kilogram has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it.
Article milestones
Date Process Result
October 2, 2008 Good article nominee Listed
December 20, 2008 Featured article candidate Not promoted
Current status: Good article
          This article is of interest to the following WikiProjects:
WikiProject Measurement (Rated GA-class, Top-importance)
WikiProject icon This article is within the scope of WikiProject Measurement, a collaborative effort to improve the coverage of Measurement on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
 GA  This article has been rated as GA-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.
Note icon
This article has been listed as a good article under the good article criteria.

This article has comments here.

WikiProject Physics (Rated GA-class, Top-importance)
WikiProject icon This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
 GA  This article has been rated as GA-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.

This article has comments here.

Wikipedia Version 1.0 Editorial Team / Vital
WikiProject icon This article has been reviewed by the Version 1.0 Editorial Team.
 GA  This article has been rated as GA-Class on the quality scale.
Taskforce icon
This article is a vital article.
This article has an assessment summary page.

Measurement incorrect[edit]

Kilogram is 10cm^3 and not 1cm^3 — Preceding unsigned comment added by (talk) 13:23, 21 June 2014 (UTC)

This is nonsense. Do not put this nonsense into the article or you will be blocked. Jc3s5h (talk) 19:50, 21 June 2014 (UTC)

Errr... Jc3s5h, i think the ip editor is correct. A kilogram is approximately the weight of one litre of water, which is 10x10x10cm or 10cm^3. Also, using bold font and threatening off the bat with blocking a user is not a very polite way to engage in a conversation and may be the reason why so far no one clarified this in the lead. PizzaMan (♨♨) 12:26, 15 March 2015 (UTC)

The convention of writing measurements is that an exponent only applies to the unit, not the number. I will also use the available Wikipedia editing markup to write the exponent correctly. I will also insert a nonbreaking space to separate the number from the unit, as is conventional. So the markup becomes 10&nbsp;cm<sup>3</sup>. It is rendered as 10 cm3. It means 10 (cm3). To express a cube 10 cm on a side, you would write (10 cm)3. Jc3s5h (talk) 12:37, 15 March 2015 (UTC)
Actually i think the ip editor was possibly just confused because in the lead of this article about the kilogram, it says "the gram is defined as...". That, in turn, lead me to misread it. I added a "1/1000th of a kilogram" to avoid that. PS Note that the very first sentences of a WP article often contain stuff that no one really cares about as the result some tedious discussion about definitions or other details. So i caught myself skipping to the second paragraph to start reading and i expect i'm not the only one. So at that point especially, it's confusing to talk about grams in stead of kilograms. PizzaMan (♨♨) 12:44, 15 March 2015 (UTC)
The pattern I've noticed, which I can't explain, is that after any kind of contentious series of edits (such as the edit warring in June 2014 where another editor using several IP addresses decided to cruise in and change to British spelling) other IP editors decide to pile on and commit various kinds of vandalism. So I have less tolerance for goofy edits right after an edit war than at other times. Jc3s5h (talk) 13:12, 15 March 2015 (UTC)
Didn't know this was following an edit war. In such a case indeed it's questionable whether you still have to assume good faith. PizzaMan (♨♨) 18:52, 15 March 2015 (UTC)

Doesn't the watt balance still use an artifact?[edit]

The goal is redefine the kilogram without using any artifacts like that mass under the bell jars. However, the watt balance doesn't eliminate this! It measures the force of gravity of an object as a specific point within earth's gravitational field. In essence, the entire earth itself is the artifact and you have to return to the exact same location everytime if you want to accurately measure the kilogram. (because the earth's gravitational field varies over the surface of the earth. — Preceding unsigned comment added by (talk) 18:17, 29 April 2015 (UTC)

When using the Watt balance, the Kilogram is defined with respect to the local gravitational field, but the local gravitational field is in turn measured using a gravitometer that does not depend on the mass of the kilogram. Thus, the definition can be generalized to any accelerated frame of reference, not just a particular point near the Earth's surface. Therefore, no artifact is used as part of the definition. As a practical matter, we use a large mass (e.g. the Earth) as part of the practical implementation of the definition, because a location within the gravity field of a large mass is the most stable accelerated frame of reference we currently have access to. -Arch dude (talk) 04:18, 19 July 2015 (UTC)


It seems strange and out of place that this article is supposedly written in American English. Considering that the subject matter is more applicable in British English contexts (US is the primary geographic where the kilogram is not an everyday unit of measure), I propose to switch this article to British English, just as is already the case with most other articles relating to SI. —Quondum 04:43, 8 July 2015 (UTC)

Yes this article has deviated from the other SI unit articles for too long. An early major contributor wanted it that way. LeadSongDog come howl! 05:00, 8 July 2015 (UTC)
I've removed the edit note claiming American English as being without basis in MOS:TIES, and I feel that in this case WP:RETAIN is not sufficient to motivate retention of the claimed variant. In particular, the articles relating to SI act as a set and consistency across these articles is IMO appropriate. While there are not strong national ties to British English, there are strong usage ties, which seems to me to be the way that MOS:TIES should have been worded in the first place. I will allow some time for comment before implementing this proposal. —Quondum 13:37, 10 July 2015 (UTC)

This article has no British ties either, so I disagree that the English variant should be British, and disagree with the premature change. The article has always had US English spellings, so it should be changed back. Irn Bimba (talk) 21:16, 18 July 2015 (UTC)

• User:Bimba is precisely correct. WP:RETAIN and the related rules under WP:ENGVAR are perfectly clear. There is zero consensus here to do as you unilaterally took upon yourself to do (change the style of English) with this edit, Quondum. The only strong national tie the SI system has is to French; that issue is clearly moot here on en.Wikipedia. Please take the time to read and understand Wikipedia’s manual of style and engage others on the talk pages there to understand what the rules are and why they exist. To flout the bedrock rule of WP:ENGVAR requires, per WP:CONLIMITED, an overwhelming and wide consensus, which does not exist here—not by any stretch. WP:RETAIN is a bedrock principle intended to avoid untold wikidrama and flamewars that occurred all over en.Wikipedia for a number of years. Greg L (talk) 04:22, 19 July 2015 (UTC)

I missed the demurring comment when I made the change; had I realized that there was dissent I would not have made the change. It is certainly not my intent to act in a controvertial fashion. —Quondum 05:02, 19 July 2015 (UTC)
Thank you, Quondum. Best wishes and happy editing. Greg L (talk) 05:10, 19 July 2015 (UTC)

Mass of the IPK cannot change[edit]

The article currently says "After the International Prototype Kilogram had been found to vary in mass over time,...". But that's clearly incorrect. The mass of the IPK is always exactly 1kg, by definition, and so it cannot vary, even if the IPK changes its physical composition in such a way that the kilogram is no longer the same as it was in the past. We need a better way to phrase this. What is really happening is that the IPK is changing its physical composition and therefore the mass of everything else in the universe, as measured in kilograms, is varying. Mikeplokta (talk) 06:47, 19 July 2015 (UTC)

The way you are phrasing this, you are confusing a change of mass with the change of the measurement of mass in terms of a unit. Even if the effect was more pronounced (say 10% per annum), we would refer to it as the IPK's mass changing. One could refer to the measurement of mass in kilograms of everything else changing, while at the same time saying that the mass of stable objects (such as an object consisting of a defined number of atoms of a specific element) remaining constant. One would say that the unit of measurement varies with time, not the mass of the object measured in terms of it. —Quondum 13:31, 19 July 2015 (UTC)
No, I could chop 10% off the IPK, and its mass still wouldn't change. It would be exactly 1kg (at least until such a time as my assault was noticed, and the definition of the kilogram was changed). If you think that removing a piece from the IPK would change its mass (as measured in kilograms), please answer the following two questions: What was its mass before a piece was removed, and what was its mass after a piece was removed. I know it's counter-intuitive, and that's why they propose to improve the definition of the kilogram so that it's not dependent on a physical reference sample. Mikeplokta (talk) 14:53, 19 July 2015 (UTC)
Quondum is correct. The mass of the IPK certainly can change; and it undoubtedly has—and is, Mikeplokta. Read the citations to Metrologia , where many scientists responsible for maintaining the IPK write about their concern over its clear lack of mass stability. This article's terminology is consistent with the citations; that's all that Wikipedia requires of its wikipedians. If you read the citations and still think you have keen insight beyond that of the scientists, you should take it up with them. Please tell them of the title you chose for this discussion thread (“Mass of the IPK cannot change”); if you can convince them of that, they will be greatly relieved.
By your reasoning, if the mass of the IPK changes, the magnitude of the kilogram changes (which is true), and therefore, the IPK's mass doesn’t change (false) because the IPK is still one kilogram by definition (true). But scientists know that the mass of the proton, for instance, has not changed in the last 100 years even though the unit of measure for expressing the proton's mass (the gram and kilogram) has clearly drifted by an unknown amount. This is why the scientists are endeavoring to define the unit measure of mass in terms of an invariant property of nature rather than a hunk of platinum/iridium that may well be absorbing atmospheric mercury or, possibly, hydrogen ions from unfortunately chosen hydrocarbon solvents (platinum is a catalyst that can atomize, ionize, and absorb ions into its structure).
You concluded your paragraph with a correct sentence, Mikeplokta: …therefore the mass of everything else in the universe, as measured in kilograms, is varying. If the article makes that statement with that particular clause (“in terms of kilograms”), then you would be right to correct the error. But the article does not; it refers to the instability in the IPK’s “mass”, not how the number of “kilograms” comprising the IPK is changing (it’s always precisely one kilogram by definition).
You seem to be getting rather hung up with circuitous logical fallacy, that “kilogram” means “mass.” Alas, it does not. The kilogram is but a unit of measure, or an equivalency. One could theoretically characterize the mass of the IPK in proton equivalents, which is a perfectly stable quantity and equally stable unit of measure for quantifying mass. As the mass of the IPK has drifted, it will be precisely one kilogram until the definition of the kilogram is formally redefined. However, the IPK’s unstable mass, as expressed in terms of the number of proton-equivalents, would change; the IPK currently has a mass of about 5.978638×1026 protons. Quantifying mass in terms of atom counting is the objective of the Avogadro Project. In fact, surprising results from the Avogadro Project resulted in a mild shakeup in how research on the watt balance was done. How do I know this? Because I exchanged scores of emails with a key researcher at the NIST while working on this article.
(BTW, in addition to proton-equivalents, I was going to also mention Planck masses—the fundamental natural unit of measure for mass—but I anticipated that would drag in a discussion about how, as the magnitude of the IPK changes, and the magnitude of the kilogram, many of the Planck unit's equivalent units of measure like Atomic mass unit and Electronvolt would also change. *Sigh*). Greg L (talk) 17:07, 19 July 2015 (UTC)
In fact, while it wouldn't be a particular good standard, they could have defined the kilogram to be the mass of some duck somewhere in Sèvres France and the IPK to be that very duck. As that duck eats or poops, it's still defined to weigh exactly one kilogram. So, relative to that IPK, I suppose that you could say that everything else in the Universe is changing, but I think the rest of the Universe would say it's the duck that's changing. (talk) 04:34, 20 July 2015 (UTC)
Pretty much. That’s the gist of the issue with the stability of an artifact that underpins much of the SI system of measurement. They thought that protecting it under three nested bell jars at atmospheric pressure would be sufficient to isolate it from mass-changing influences, but they were wrong. Something is making nearly all the copies increase in mass relative to the IPK. Given that the IPK is the best protected of the mass artifacts, it is likely that it too is increasing in mass; just not as much as most of its copies. Greg L (talk) 05:20, 20 July 2015 (UTC)

External links modified[edit]

Hello fellow Wikipedians,

I have just added archive links to one external link on Kilogram. Please take a moment to review my edit. If necessary, add {{cbignore}} after the link to keep me from modifying it. Alternatively, you can add {{nobots|deny=InternetArchiveBot}} to keep me off the page altogether. I made the following changes:

When you have finished reviewing my changes, please set the checked parameter below to true to let others know.

N Archived sources still need to be checked

Cheers. —cyberbot IITalk to my owner:Online 12:32, 26 August 2015 (UTC)