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Standard Kilogram Gains Weight

Soulskill posted about a year and a half ago | from the too-many-gram-crackers dept.

Science 177

mrbluze writes "The standard kilogram weights used by countries around the world for calibration have variably increased in mass by tens of micrograms. This poses a threat to the precision and comparability of measurements in science, engineering and trade. The problem is due to surface contamination, but a safe method of cleaning the weights has only recently been devised by the use of ozone and ultraviolet light (abstract). 'The ultraviolet light-ozone treatment removes hydrocarbon contamination that has built up on the metal surface, gunk that comes from the emissions of an industrial society. Cumpson suspects that because the kilos living in national labs have been retrieved and handled more frequently than the international kilo, more carbon-containing contaminants have built up on them over time. Incubating the kilograms with a set amount of ozone and ultraviolet light "gently breaks up the carbonaceous contamination at the surface."'"

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Excellent (5, Funny)

mister2au (1707664) | about a year and a half ago | (#42528745)

I think the kilogram should be adjusted upwards every holiday season ...

Nothing like a bit of seasonal normalisation on the scales to justify festive binges.

Re:Excellent (5, Funny)

Acapulco (1289274) | about a year and a half ago | (#42528825)

I came here to ask precisely this.
So I've actually lost weight? Woohoo! go science!

Mititant metric user (1)

mjwx (966435) | about a year and a half ago | (#42528769)

Has anyone measured the standard ounce or hogs head lately?

BTW: we've spoken with the frenchies, they'll stop feeding the standard KG more than one bacon and cheese croissant per day.

Re:Mititant metric user (5, Informative)

godrik (1287354) | about a year and a half ago | (#42528787)

French do not eat bacon and cheese croissant...

Re:Mititant metric user (1)

SuperAlgae (953330) | about a year and a half ago | (#42529027)

Maybe not, but their standard weights do. Darn things just can't get enough bacon and cheese.

Re:Mititant metric user (4, Funny)

jrumney (197329) | about a year and a half ago | (#42529345)

Lard et fromage then, you informative pedant.

Re:Mititant metric user (2)

damaki (997243) | about a year and a half ago | (#42529931)

I am French and, well, we should. This sounds amazing and definitely mouth-watering.
And BTW, ham, cheese and "bechamel" croissant is really tasty [ceinfo.fr] . One could easily replace the ham with crispy bacon.

Re:Mititant metric user (0)

Anonymous Coward | about a year and a half ago | (#42529677)

Has anyone measured the standard ounce or hogs head lately?

Sorry, there's no such thing as a "standard ounce". The leagacy units are defined terms of SI units.

begs the question... (2)

johnsnails (1715452) | about a year and a half ago | (#42528777)

how do they know this reliably?

Use the method they used to determine this to define 1KG

Re:begs the question... (2)

Joce640k (829181) | about a year and a half ago | (#42528949)

how do they know this reliably?

Use the method they used to determine this to define 1KG

Yep.

The summary itself says "...the kilos living in national labs have been retrieved and handled more frequently than the international kilo".

ie. Some of them are stored more carefully than others and aren't gaining as fast.

Re:begs the question... (2)

brelovich (746983) | about a year and a half ago | (#42528971)

The only way to know is to compare the reference weights. The definition of 1kg is that it is the mass of the international 1kg prototype, stored in Paris. It's quite a big problem that it, and the national references, seem to be gaining.

Re:begs the question... (1)

unixisc (2429386) | about a year and a half ago | (#42529987)

Why not simply define 1 gram as the mass of an Avogadro number of Hydrogen atoms? Solves the issue!

Re:begs the question... (2)

Kell Bengal (711123) | about a year and a half ago | (#42530149)

Excellent idea. Exactly what is the value of Avogadro's number, again? Unfortunately, it's not quite so simple [wikipedia.org] .

Re:begs the question... (1)

unixisc (2429386) | about a year and a half ago | (#42530545)

Okay, 2^79 will be 604,462,909,807,314,587,353,088, which is the nearest exponent of 2 to Avogadro's number. Take this number, divide it by 16 (again, I'm dealing only in powers of 2 here for computational efficiency), and that gives us 37,778,931,862,957,161,709,568. Take that many atoms of C-12, and re-define the kilogram as being the mass of all that. You have a number higher than Avogadros, a total mass less than the weight of C-12 (since I divided by 16), and define that absolute number to be the mass equivalent to 1 kg. That would change the current mass of a kilogram, but give it a strict definition for good.

Ha! (5, Funny)

phantomfive (622387) | about a year and a half ago | (#42528779)

If you'd all use imperial, this wouldn't happen. Just need to know how long that guy's foot is.

Re:Ha! (1)

hydrofix (1253498) | about a year and a half ago | (#42529811)

I like how that plays with your sig.

Definition (0)

Anonymous Coward | about a year and a half ago | (#42528801)

IIRC, it's defined as "the mass of so-and-somany atoms", so that wouldn't matter.

Re:Definition (2)

Dahamma (304068) | about a year and a half ago | (#42529067)

As long as you can exactly count all of the atoms in a weight. Otherwise it's more useless for comparative measurement than a king's foot.

Re:Definition (1)

edibobb (113989) | about a year and a half ago | (#42529091)

Use a perfect crystal (or almost perfect), measure it's size, and multiply to get the atom count. It's a little more complex than this, but it works.

Re:Definition (1)

Dahamma (304068) | about a year and a half ago | (#42529223)

Now you're just trading for an inaccuracy of linear measure. With a KG weight it's impossible (under any current technology) to create a perfectly geometric crystal. And with the scale needed to guarantee it's a perfectly geometric crystal it's impossible to accurately sum enough of them to make exactly a KG.

Re:Definition (1)

sFurbo (1361249) | about a year and a half ago | (#42529667)

From wikipedia [wikipedia.org] :

Most silicon monocrystals are grown by the Czochralski process, in the shape of cylinders up to 2 m long and 30 cm in diameter (figure on the right)

The size of the monocrystal is not the problem.

From http://www.acpo.csiro.au/avogadro.htm [csiro.au]

The limiting factors currently are:

The variability from sample to sample of the isotopic abundances M(Si)
The content of impurities and vacancies (n)
Realisation of accurate density standards (m,V)

Re:Definition (5, Informative)

Sique (173459) | about a year and a half ago | (#42529269)

No, it's defined as "the mass of the international kilogram prototype". There are alternative proposals (the Avogadro Project, counting the Silicon-28-atoms in a defined sphere of Silicon-28 and the Watt balance [wikipedia.org] ), but none of them is ready yet to replace the Kilogram prototype.

mo3 do3n (-1)

Anonymous Coward | about a year and a half ago | (#42528805)

Re:mo3 do3n (-1)

Anonymous Coward | about a year and a half ago | (#42528891)

What's your point?

How does a geek lose weight? (4, Funny)

deek (22697) | about a year and a half ago | (#42528809)

He (or she) redefines the standard.

Now all we need are electronic scales that can receive updated firmware via the internet.

whats the problem (1)

Osgeld (1900440) | about a year and a half ago | (#42528813)

seal it in something already, its not a desk toy. There would be no gunk if it was not exposed to it

Re:whats the problem (5, Insightful)

BradleyUffner (103496) | about a year and a half ago | (#42528833)

seal it in something already, its not a desk toy. There would be no gunk if it was not exposed to it

It's kind of useless as a reference if no one can actually refer to it.

Re:whats the problem (-1, Redundant)

Osgeld (1900440) | about a year and a half ago | (#42528975)

its a matter of record keeping

if you know it weighed X in 2000, and it weighs Y in 2013 whats the problem, it grew shit or dorito boy finger fucked it 30 feet away from the ocean

the whole idea seems backwards, there are changes we can not control, but instead we change the thing we actually can?

Re:whats the problem (1)

donaggie03 (769758) | about a year and a half ago | (#42529969)

So how do you determine if something weights Y in 2013? You put it on a scale right? And how do you know that scale is accurate? You put the reference material on the scale and make sure it reads Y. This is called calibration, and you can't do it accurately without actually handling the reference material.

Re:whats the problem (0)

Anonymous Coward | about a year and a half ago | (#42528871)

The problem is that it is a reference object, and you regularly need to get it out to compare all your more commonly used reference kilos against it. Sealing it only makes the comparison more complicated, as the gunk will be on the wrapper and you got to account for the wrapper when comparing. Until we can disconnect the SI kilogramm from a specific physical reference object this problem will stay

Re:whats the problem (3, Informative)

sFurbo (1361249) | about a year and a half ago | (#42529733)

The kilogram is sealed and only taken out every approximately every 50 years or so to compare to the secondary standards (and being cleaned, I think). It has apparantly lost weight relative to the secondary standards.

Re:whats the problem (1)

bickerdyke (670000) | about a year and a half ago | (#42529845)

AFAIK, the reference kilo is already stored in a safe in a protective, inert gas atmosphere.

Glad to be an American. (5, Funny)

zippo01 (688802) | about a year and a half ago | (#42528815)

That why I'm glad to live in America, where we still use the good old pound. Now all I have to do it sit back and watch your metric world unravel.

Re:Glad to be an American. (5, Funny)

boundary (1226600) | about a year and a half ago | (#42528873)

I'm glad you're there too.

vive les USA :P (1)

Anonymous Coward | about a year and a half ago | (#42528925)

This is the same problem for any mesure system (including Imperial system).
The only chance is that USA is the only developped country that still use it as a reference. So there is little issue for the world if a pound reference change thru time or space.

Re:vive les USA :P (1, Funny)

Joce640k (829181) | about a year and a half ago | (#42528951)

Nope. Feet are continually being renewed as part of a natural process and hundreds of new measuring cups are made every day, they don't have time to accumulate any gunk.

Re:vive les USA :P (0)

Anonymous Coward | about a year and a half ago | (#42529297)

Wrong! French fail!

Vives (plural) les États-Unis (United States).

HTH,
HAND

Re:vive les USA :P (1)

Anonymous Coward | about a year and a half ago | (#42529611)

I hope 'vives' was a joke. Vive is correct and if you really want to use a deprecated plural you could use vivent [etudes-litteraires.com] .

Re:Glad to be an American. (3, Funny)

sidevans (66118) | about a year and a half ago | (#42528927)

The "Pound" is used to weight American Beef, the "Kilogram" is used to measure things like Uranium. Surely you can join the dots from there...

Re:Glad to be an American. (0)

Anonymous Coward | about a year and a half ago | (#42529015)

...as opposed to the already-broken backwards-designed logic-voided imperial system and it's pound, known to be ignorant about basic physics and it's laws?
Wouldn't the US pound need to be normalized every 1,6 years by taking in account the average weight of a McCrap's QuarterPounder?

two things... (5, Informative)

slew (2918) | about a year and a half ago | (#42529039)

Although I'm sure you're kidding, it's probably worth bringing up the following 2 bits of trivia

1. Sadly, the American "pound-weight" has mostly been defined in terms of the kilogram and has its most recent official relationship updated in 1959 (now exactly 0.45359237 kg, down from 0.4535924277 kg back 1901).

2. The kg artifact itself is soon to be rendered obsolete. In 2014, the kg is likely to be redefined in terms of the planck constant (well technically, planck constant will be fixed to a specific number and since it has the units kg*m^2/s, and the second and meter are defined in terms of oscilations of a Ce133 atom and the speed of light, these will now determine the kilogram).

That is until we discover a grand unifying theory where the Planck constant is not actually a constant. Then you can really see the world unravel...

Re:two things... (0)

Anonymous Coward | about a year and a half ago | (#42529205)

That is until we discover a grand unifying theory where the Planck constant is not actually a constant. Then you can really see the world unravel...

Nah, they will just define the kilogram in terms of the Planck constant at STP...

Re:two things... (2, Informative)

Rockoon (1252108) | about a year and a half ago | (#42529273)

2. The kg artifact itself is soon to be rendered obsolete. In 2014, the kg is likely to be redefined in terms of the planck constant (well technically, planck constant will be fixed to a specific number and since it has the units kg*m^2/s, and the second and meter are defined in terms of oscilations of a Ce133 atom and the speed of light, these will now determine the kilogram).

I suspect that you are a little bit confused. "Planck constant" has no real meaning without agreeing on some units beforehand, and "some specific number" certainly doesnt convey the likely choice.

The Planck Units [wikipedia.org] are based off the 5 known fundamental physical constants of the universe, where each constant is given the non-arbitrary value of exactly 1.0.

you can read all about then new kg (2)

slew (2918) | about a year and a half ago | (#42529797)

You can read all about the new kg here [bipm.org] ...

Re:two things... (1)

Anonymous Coward | about a year and a half ago | (#42530301)

I suspect that you are a little bit confused. "Planck constant" has no real meaning without agreeing on some units beforehand, and "some specific number" certainly doesnt convey the likely choice.

The GP is correct, I think.

Let me start with a simpler example. The second is defined as being exactly 9,192,631,770 periods of the radiation emitted from a certain energy transition of a Ce-133 atom. The speed of light is defined to be exactly 299,792,458 metres per second. From these, we find the definition of the metre: it's the distance that light travels in 9,192,631,770 / 299,792,458 periods of the radiation from a Ce-133 atom.

The planned definition of the kilogram is similar. The second and the metre are defined as above. If we then define the Planck constant (in units of kg*m^2/s) to have some precise value, then the definition of the kilogram follows from that.

You are worng (-1, Redundant)

Anonymous Coward | about a year and a half ago | (#42529715)

Your error: " the American "pound-weight" has mostly been defined in terms of the kilogram"

Sorry, you fail. The US Govt maintains a standard "pound", a standard "foot", etc. These units are precisely defined mathematically and also there are standard objects in their facilities that match the definitions and (for units of mass) are made of a metal that is not decaying (sorry, I don't recall what metal they used but you can probably google it). Any US measuring device that is sold as a "calibrated instrument" has documentation showing its "traceability" back to those standards. The "closer" an instrument is to the NIST standard (in other words: somebody calibrated something to the actual "standard" at NIST, and then used THAT to calibrate other things, which were then used to calibrate other things etc), the more accurate it is presumed to be.

Your error is that you apparently misunderstood that the US Govt has defined a set of standard conversions which are acceptable to use to mathematically convert from things like meters to feet, or kilograms to pounds where such conversions are more practical and where the user understands what he is doing

Re:You are worng -- no ! (1)

jcdr (178250) | about a year and a half ago | (#42529905)

It seem that the legal definition of pound is bound to the kilogram: http://en.wikipedia.org/wiki/Pound_(mass) [wikipedia.org]

"The pound or pound-mass (abbreviations: lb, lbm, lbm, [1]) is a unit of mass used in the imperial, United States customary and other systems of measurement. A number of different definitions have been used, the most common today being the international avoirdupois pound which is legally defined as exactly 0.45359237 kilograms."

This is not a surprise as the USA have, from the international point of view, endorsed the SI units since a half century.

Re:You are wrong (4, Informative)

slew (2918) | about a year and a half ago | (#42530009)

Perhaps you should read this document [nist.gov] from NIST about the history of weights and measures in the US.

According to this document...
1827 a troy pound was obtained from London.
1828 a brass artifact (which was compared to this troy pound) declared standard for the US mint, not the avoirdupois pound
1866 the metric system was made lawful for commerce in the US. Legally defines avoirdupois pound as (1/2.2046) kg
1875 17 governments (incl the US) established the international bureau of weights and measures
1890 The US receives standard kilogram artifacts #4 and #20 for use as the national prototype
1894 The US tweaks the definition of the pound relative to this kilogram artifact to make it closer to the UK pound

The US makes various other tweaks over the years in the pound's definition relative to the standard kilogram artifact that the US government maintains.

The "troy" pound artifact is only used for Mint operation in the US and is not related to the avoirdupois pound used in commerce.

Also all NIST calibrations are done in metric units (as of 1959).

Re: You are worng [sic] (1)

wesley96 (934306) | about a year and a half ago | (#42530057)

Actually, the US government has defined the imperial units as a converted value of metric units ever since the Mendenhall Order back in 1893.

In other words, the imperial values are pegged to the metric definition. The conversion values are not for "acceptable use" - they are the very definition.

NIST is where one of the copies of the standard kilogram is kept. NIST prefers SI standards.

http://www.nist.gov/pml/wmd/metric/metric-program.cfm [nist.gov]

Office of Weights and Measures "ensures traceability of state weights and measures standards to the SI", so while there may be "standard pound" of sorts, it's measured back to SI standard (kg) to keep them in check.

http://www.nist.gov/pml/wmd/ [nist.gov]

Re:Glad to be an American. (0)

Anonymous Coward | about a year and a half ago | (#42530137)

That why I'm glad to live in America, where we still use the good old pound. Now all I have to do it sit back and watch your metric world unravel.

Are you aware that a pound is defined as 0.453 592 37 kg exactly?

It's happening *everywhere* (4, Funny)

mark-t (151149) | about a year and a half ago | (#42528823)

I guess obesity really *IS* an epidemic problem.

Hey.... somebody had to say it.

Re:It's happening *everywhere* (1)

Grayhand (2610049) | about a year and a half ago | (#42529187)

I guess obesity really *IS* an epidemic problem.

Hey.... somebody had to say it.

The point is the weigh gain isn't just an American problem

Re:It's happening *everywhere* (0)

Anonymous Coward | about a year and a half ago | (#42529985)

The standard Paris Kilo was also on a diet 30 years ago. I don't remomber the method they used, but it was chemical.

The meter is based on the speed of light (0)

Anonymous Coward | about a year and a half ago | (#42528865)

The meter is based on the speed of light. Its length can be determined with extremely high precision. With this very high precision you can make a cubic container 1/10 of a meter cubed. First weigh with all the accuracy you can, the weight of the container. Then zero the scale with that weight, and fill the container with absolutely pure water. The weight of that water is exactly 1 kg. No special reference needed (although you can make a reference from this). Oh, and while we are at it, we will make a temperature scale. Where that water freezes, we will label zero, and where it boils we will label 100. So 100 steps between freezing and boiling (not 180), and we won't have a 32 degree offset either (so freezing won't be 0+32, and boiling won't be 180+32). What was the 32 for again? Where brine freezes?

Re:The meter is based on the speed of light (1, Informative)

bickerdyke (670000) | about a year and a half ago | (#42529909)

The meter is based on the speed of light.

You can't define a distance based on speed.

You need a well defined speed AND TIME unit.

It doesn't get any better from there...

Then zero the scale with that weight, and fill the container with absolutely pure water. The weight of that water is exactly 1 kg. No special reference needed (although you can make a reference from this).

When do you consider it "full"? Water has the nasty habit to form a spherical surface due to surface tension. Do you consider it full when the middle or the border is aligned with the "full" mark on your comtainer? And good luck getting any "absolutely pure" water that does not fall apart into ions and reforms all the time... look up the definition of ph-value. millions of hydrogen ions are making water not acidic.

Re:The meter is based on the speed of light (0)

Anonymous Coward | about a year and a half ago | (#42530535)

>>The meter is based on the speed of light.
> You can't define a distance based on speed.

You do understand that there is a difference between "based on" and "defined by"?

A cake is based on flour, but this does not make flour the sole ingredient.

This affects all measurement units (3, Informative)

lingon (559576) | about a year and a half ago | (#42528875)

Just to preempt all comments about imperial or home-grown measurement systems: All measurement systems in the world are defined from the metric base units, which are in turn defined from a few physical constants and this kilogram prototype. When the kilogram prototype gains mass, this affects the kilogram, pound, liter and fluid ounce equally.

Re:This affects all measurement units (2)

hawguy (1600213) | about a year and a half ago | (#42529031)

Just to preempt all comments about imperial or home-grown measurement systems: All measurement systems in the world are defined from the metric base units, which are in turn defined from a few physical constants and this kilogram prototype. When the kilogram prototype gains mass, this affects the kilogram, pound, liter and fluid ounce equally.

Not for me, I still define the pound as 7000 grains of barley. Must more stable than some unreliable reference standard that let's a little hydrocarbon tarnish screw it up

Re:This affects all measurement units (1)

homsar (2461440) | about a year and a half ago | (#42529957)

When the kilogram prototype gains mass, this affects the kilogram, pound, liter and fluid ounce equally.

The litre is just another word for cubic decimetre; since the metre is defined in terms of the speed of light and the second (which in turn is defined by atomic properties), and not in terms of the kilogram, the litre will not change volume. Similarly the fluid ounce is defined as a fraction of a gallon; the gallon is defined in terms of cubic inches; the inch is now defined as 25.4mm: again the metre is the only dependence. So again, even though fluid ounce sounds like it should depend on mass, in fact it is a unit of volume and so behaves like one.

Why isn't there a precise atomic standard? (2, Insightful)

Joshua Fan (1733100) | about a year and a half ago | (#42528917)

The mass of X number of molecules of element Y = 1 gram.

Like there is for the second [wikipedia.org] :

"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Re:Why isn't there a precise atomic standard? (2)

Areyoukiddingme (1289470) | about a year and a half ago | (#42528937)

There's supposed to be a redefined kilogram based on the Planck Constant, but that hasn't happened yet. Not until 2014 will they talk about it again. Then maybe they can solve that problem.

Re:Why isn't there a precise atomic standard? (5, Informative)

denelson83 (841254) | about a year and a half ago | (#42528945)

The mass of X number of molecules of element Y = 1 gram.

Like there is for the second [wikipedia.org] :

"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Because we don't yet have an accurate-enough measure of the Avogadro or Planck constants.

Re:Why isn't there a precise atomic standard? (1)

hyperfine transition (869239) | about a year and a half ago | (#42529863)

It doesn't work that way.
In the case of the Avogadro sphere, for example, you count the number of atoms of Si 28 and then choose a certain number to be equal to 1 kg, this number being chosen to give agreement with the prototype kg held by the BIPM in Paris. This in effect defines the Avogadro constant.

Re:Why isn't there a precise atomic standard? (0)

Anonymous Coward | about a year and a half ago | (#42530049)

What about now with the Higgs Boson? Can't we use this to define mass extremely precisely?

Re:Why isn't there a precise atomic standard? (0)

Anonymous Coward | about a year and a half ago | (#42529037)

So you propose that we pick some radioactive substance to define 1 kg. That's an excellent idea indeed. We'll no longer have this problem of "kilos being frequently retrieved and handled". Surface contamination problem is solved!

Re:Why isn't there a precise atomic standard? (1)

fufufang (2603203) | about a year and a half ago | (#42529087)

The mass of X number of molecules of element Y = 1 gram.

Like there is for the second [wikipedia.org] :

"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Because it is hard to make a standard like that. Counting individual atoms on such a large scale is very complicated.

Re:Why isn't there a precise atomic standard? (0)

Anonymous Coward | about a year and a half ago | (#42529229)

No, but you can calculate the mass and base weights off of that.

Re:Why isn't there a precise atomic standard? (1)

VortexCortex (1117377) | about a year and a half ago | (#42529151)

The mass of X number of molecules of element Y = 1 gram.

First off, it should be atoms not molecules... Secondly, the atomic masses aren't actually constant between atoms. Primarily due to isotopes, but additionally due to electrons (though very minimal they too have mass), so you should also state the charge at least. Ah, but now we know of sub-atomic particles, and may even have discovered and measured the field / particle responsible for mass itself, so we should instead describe mass in terms of interaction with the Higgs Field...

Ah, but all the quantum fields and particles are really just forms that energy can take, so we should instead define mass in terms of energy in a closed system...

Considering we still haven't gotten scientists to agree on how to define units of atomic mass (currently 1u (unified atomic mass unit) = One Dalton = one twelfth a neutral (no charge) unbound carbon-12 atom, but in 2012 it was proposed the dalton be redefined as being 0.001/NA kg, thus diverging from AMU), I suspect the heat death of this universe to occur long before a correct standard mass is adopted...

Re:Why isn't there a precise atomic standard? (2)

hyperfine transition (869239) | about a year and a half ago | (#42529695)

Well,there is one proposed.
This is the Avogadro Project, one of two candidates for a redefinition of the kg, the other
being the Watt balance.
You take a lump of isotopically pure crystalline Si (Si 28) and optically polish it to a 'perfect' sphere.
You then use very accurate laser interferometry to measure the volume of the sphere (and with a suitable set
of measurements and model you can correct for any residual non-sphericity)
You use X-ray diffraction to measure the lattice spacing. You can now calculate the number of atoms
in the sphere. There are also corrections for the oxide layer at the surface,residual impurities etc.
The nice thing, apart from the kg being defined by dimensional measurements (which are then traceable to the SI second) , is that if you chip your kg standard, you just repolish it and remeasure it.
You then define what one kg is by saying a certain number of Si 28 atoms is equal to 1 kg. This number would be chosen to agree as closely as possible with the current definition of the kg. This process is similar to the way the second was redefined, from an astronomically defined value to a value defined by a microwave transition in the caesium atom.

Re:Why isn't there a precise atomic standard? (1)

mister2au (1707664) | about a year and a half ago | (#42530435)

Every SI measure will cascade down the 'second' definition:
- second define meter
- second & meter define kilogram
- second, meter & kilogram define Kelvin
- etc etc

So we are seriously screwed if we ever decide time is not constant (at least with reference to caesium-133 at rest and 0 K)

Someone finally said it (1)

proca (2678743) | about a year and a half ago | (#42528999)

Everyone had been thinking it, but when international standards had to be changed to accommodate the weight gain, Kilo decided to cut out the daily Big Gulps

Revised Standard (5, Informative)

Thorfinn.au (1140205) | about a year and a half ago | (#42529003)

It is being worked upon, to make the kilogram a sphere of a specified diameter of a pure element. The element chosen is silicon and as a mm is defined very well this will avoid all these problems as a new standard can be made and measured repeatably in every country. Did work in this field some years ago with contact with the people involved.

Re:Revised Standard (1)

fufufang (2603203) | about a year and a half ago | (#42529077)

It is being worked upon, to make the kilogram a sphere of a specified diameter of a pure element. The element chosen is silicon and as a mm is defined very well this will avoid all these problems as a new standard can be made and measured repeatably in every country. Did work in this field some years ago with contact with the people involved.

Why didn't they stick with the good old 1 dm^3 of water?

Re:Revised Standard (0)

Anonymous Coward | about a year and a half ago | (#42529153)

Storage? Liquid easier to 'contaminate' than a solid?

Re:Revised Standard (1)

Thorfinn.au (1140205) | about a year and a half ago | (#42529189)

water is not an element and a liquid with a high vapour pressure => rapid evaporation

Re:Revised Standard (2)

Neil Boekend (1854906) | about a year and a half ago | (#42529237)

What is water? Pure H2O is a myth. You always have H3O+ and OH- in there. Unless they have exactly the same density as H2O then you'll have a slightly varying fault there.
By the way: water is a universal dissolver. It dissolves literally everything (albeit slowly). So what are you going to make the container out of? As soon as you put the water in there it'll start contaminating the water. Now your dm3 of water is a bit more dense.
1 dm3 of water is good enough for 99.99% of all cases (guess), but not for some sciences.

Re:Revised Standard (1)

bickerdyke (670000) | about a year and a half ago | (#42529923)

line the container with a protective sheet of plastic....

Re:Revised Standard (1)

ra25093 (2811813) | about a year and a half ago | (#42530173)

Last I knew which was a couple years ago they were already machining a pair of spheres, and were going to make the standard based on the number of atoms in said spheres.

Re:Revised Standard (0)

Anonymous Coward | about a year and a half ago | (#42530381)

Have they finished counting them, yet?

It used to be losing mass (1)

hawguy (1600213) | about a year and a half ago | (#42529009)

A few years ago, the kilogram reference standard was losing mass -- coincidentally, they said it had lost 50 g, the amount of mass it's now said to have gained. So it should be just right by now.

http://www.sciencedaily.com/releases/2007/09/070921110735.htm [sciencedaily.com]

Re:It used to be losing mass (0)

Anonymous Coward | about a year and a half ago | (#42529057)

50g! Forget Avogadro's constant and spheres of silicon, I could do better than that with a brick and a shoebox.

Re:It used to be losing mass (3, Informative)

hawguy (1600213) | about a year and a half ago | (#42529117)

50g! Forget Avogadro's constant and spheres of silicon, I could do better than that with a brick and a shoebox.

Oh sorry, I typed "50 ug", but I used an ASCII "mu" but it seems to have been eaten by Slashdot and I didn't notice it in the preview. For the record, Slashdot doesn't accept the µ HTML entity either)

Re:It used to be losing mass (4, Informative)

Xtifr (1323) | about a year and a half ago | (#42529485)

There is no ASCII mu. ASCII is a seven-bit encoding which only covers unadorned latin alphabetic characters, arabic digits, and some random punctuation. Even latin1 (aka ISO8859-1) lacks a mu character. I'm not sure what you think you typed, but it definitely wasn't ASCII.

There's also the problem of potential confusion between U+00B5 MICRO SIGN and U+03BC GREEK SMALL LETTER MU (among others), but neither of those is remotely ASCII.

Anyway, yeah, slashdot sucks when it comes to international character support.

Re:It used to be losing mass (0)

Anonymous Coward | about a year and a half ago | (#42530391)

Pedantry gets modded to '5'? This must be /.

quick! (1)

Anonymous Coward | about a year and a half ago | (#42529051)

We need a weapon of mass destruction!

Make up your mind (1)

TheBeardIsRed (695409) | about a year and a half ago | (#42529063)

In the title it's "Standard Kilogram Gains Weight", in the description you say "variably increased in mass". There _is_ a difference between weight and mass. I understand that the minutiae of this may be lost on you since you're sourcing articles from pop news sites. Care to update one of those to reflect on this? Is this due to the acceleration of the Earth (weight is a function of mass and acceleration)?

Re:Make up your mind (1)

edibobb (113989) | about a year and a half ago | (#42529105)

It's because all the helium is flying away from the earth, raising the average density of the earth more than enough to make up for the loss in the helium's mass, thereby increasing the weight of a mess of masses.

Re:Make up your mind (1)

fatphil (181876) | about a year and a half ago | (#42530249)

In commercial and everyday use, and especially in common parlance, weight is usually used as a synonym for mass.
-- NIST

Really? (0)

Anonymous Coward | about a year and a half ago | (#42529085)

Would someone please tell me why they made the "standard" out of a metal that reacts with the environment and kept it in physical contact with said environment, instead of making it out of a chemically inert substance that is also very stable in terms of nuclear decay?!?

Are these people fucking retarded? Instead of pulling the standard out, why don't they house the standard and NEVER remove it, then use a strain gauge (like the one in the experiment that "weighed" the Earth, to do the comparison by using an object of known mass and a torsion system to measure force against known resistance?

Or maybe it's time for a new unit of mass, like a mole of carbon 12. Of course, I wouldn't want to be the one to count that out, as I know it would take a while.

Re:Really? (1)

Anonymous Coward | about a year and a half ago | (#42529149)

It was made in the 1800s. Why they haven't made a new one is anyone's guess.

Re:Really? (1)

bickerdyke (670000) | about a year and a half ago | (#42529939)

The've choosen platinum as it is already the most inert material they could find. And even if they might be less reactive, inert gases are completly out due to handling issues.

The truth is (2)

Grayhand (2610049) | about a year and a half ago | (#42529215)

It's an archaic system that needs revising. Cleaning something and not expecting it to not change is a little like the heisenberg uncertainty principle. How can you clean something through physical contact and not expect a change?

Re:The truth is (2)

serviscope_minor (664417) | about a year and a half ago | (#42529631)

It's an archaic system that needs revising.

You don't think they don't know this already?

Of course they know it. It's just very very very hard to come up with a system that can be made independently to represent 1kG with almost no error.

1kg is 1 kg (2)

dave69 (2786111) | about a year and a half ago | (#42529643)

Since it is the standard, surely its the world that needs to bend a little (space-time wise) to fit in with the new standard? surely the standard (master) kilo still weighs exactly 1 kg by definition?

Well, Good Golly, Miss Molly! (-1)

Anonymous Coward | about a year and a half ago | (#42529737)

Them thar stoopid hick 'mericans are such idiots..... They need to go Metric NOW! They just keep refusing to see how obviously sooperior the metric units trooly are!

Oh wait, the kilogram's not reliable? Well see here now.... if those dumb yankees had moved to the metric system, meybe nobody woulda noticed! Yeah, that's the ticket! It's a frame-o-reference thang! The kilogram's FINE and the pound is what's been changing!

Water? (1)

gmuslera (3436) | about a year and a half ago | (#42529813)

Maybe the meter is somewhat arbitrary, but in particular weight can be measured against i.e. 1 liter of pure water?

New definition proposal (1)

jcdr (178250) | about a year and a half ago | (#42529855)

http://en.wikipedia.org/wiki/New_SI_definitions [wikipedia.org]

"The definition of the kilogram is undergoing a fundamental change - the current definition defines the kilogram as being the mass of the international prototype kilogram, the new definition relates it to the equivalent energy of a photon via Planck's constant.

Current definition: The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.

Proposed definition: The kilogram, kg, is the unit of mass; its magnitude is set by fixing the numerical value of the Planck constant to be equal to exactly 6.62606X×1034 when it is expressed in the unit s1m2kg, which is equal to Js.

One consequence of this change is that the new definition makes the definition of the kilogram dependent on the definitions of the second and the metre."

Higgs Boson? (0)

MadCow-ard (330423) | about a year and a half ago | (#42530055)

What about using the newly discovered Higgs Boson? Couldn't that be used to more precisely define 1Kg mass?
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