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The kilogram has gained weight

Whoa. This is heavy.

I thought kilograms measured mass, rather than weight?

"The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

Gonz: I thought kilograms measured mass, rather than weight?

If one gains mass while the gravitational forces of Earth remain consistent, then one's weight (the measure of Earth's gravitational forces on said mass) will also increase.

Does not approve.

The international standard, a cylinder-shaped hunk of metal that defines the fundamental unit of mass, has gained tens of micrograms in weight from surface contamination, according to a new study.

If it's the international standard, then any increased or decreased mass becomes the new standard, by definition.  If we perceive the standard as being wrong and it needs to be cleaned so that it's reduced to our expected amount of mass, it sounds like our expectation is more the true standard than the cylinder.

Lumpmoose: The international standard, a cylinder-shaped hunk of metal that defines the fundamental unit of mass, has gained tens of micrograms in weight from surface contamination, according to a new study.

If it's the international standard, then any increased or decreased mass becomes the new standard, by definition.  If we perceive the standard as being wrong and it needs to be cleaned so that it's reduced to our expected amount of mass, it sounds like our expectation is more the true standard than the cylinder.

No. If it's the international standard, it should remain constant. Having contamination means that it needs to be cleaned so that it can get back to being what it's supposed to be. No different than a white shirt getting dirty. Have your wife clean that so that it's white again.

They should just throw that cylinder out and keep whatever they used to weigh it that showed them that it's too heavy.

Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

ronaprhys: Lumpmoose: The international standard, a cylinder-shaped hunk of metal that defines the fundamental unit of mass, has gained tens of micrograms in weight from surface contamination, according to a new study.

If it's the international standard, then any increased or decreased mass becomes the new standard, by definition.  If we perceive the standard as being wrong and it needs to be cleaned so that it's reduced to our expected amount of mass, it sounds like our expectation is more the true standard than the cylinder.

No. If it's the international standard, it should remain constant. Having contamination means that it needs to be cleaned so that it can get back to being what it's supposed to be. No different than a white shirt getting dirty. Have your wife clean that so that it's white again.

Then yo momma come bustin in tha door, talkin bout oh yeah!

I have way more surface area, so from now on I'm claiming any weight gain on environmental contamination due to age.

FoxNews. So I'm sure the science is sound.

Can't they keep it somewhere where it won't get surface contamination? Clean room or something?

does this mean I can get my sentence reduced?

I thought they changed the kilogram standard to the most perfect sphere created by man to date, made out of a perfect silicon crystal lattice? Was this never officially adopted? Wouldn't solve the problem of people leaving traces of their grubby mitts on it, just curious and too lazy to look it up...

This is why metric sucks.

It's all literal and sciencey and stuff.

Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

"I get some pledge"

I love how the kilogram pictured is framed by an inch-based ruler...

"Long-term, however, most scientists want to get away from defining the kilogram based on a hunk of metal."

It appears this artcile was written with the assumption that a kilo is an arbitrary measure. But isn't a kilogram determined by the weight of a liter of water?

What are they weighing it with? If it's measured by another cylinder, wouldn't that one have gained weight as well? Which would leave the experiment impossible to resolve...

pkellmey: I have way more surface area, so from now on I'm claiming any weight gain on environmental contamination due to age.

Ring Dings don't count as "environmental contamination".

There is also a Dinosaur Comic for every occasion.

JustMatt: I thought they changed the kilogram standard to the most perfect sphere created by man to date, made out of a perfect silicon crystal lattice? Was this never officially adopted? Wouldn't solve the problem of people leaving traces of their grubby mitts on it, just curious and too lazy to look it up...

Have you seen how quickly lattice wilts?

JustMatt: I thought they changed the kilogram standard to the most perfect sphere created by man to date, made out of a perfect silicon crystal lattice? Was this never officially adopted? Wouldn't solve the problem of people leaving traces of their grubby mitts on it, just curious and too lazy to look it up...

It's called the Avogadro project. It's under consideration, but hasn't been taken to committee since they haven't determined if it will be more stable in the long term than the current standard. There are other proposals as well to try and move away from a physical artifact as the standard. The generally favored ones are to define the kilogram in terms of the Planck constant, but that's on hold until 2014, according to wikipedia.

TofuTheAlmighty: While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

The issue I take is that, in translating the weight of a kilogram to pounds, she also felt the need to translate it back to metric in parenthesis. Take out the pounds part and, oh, a kilogram is the equivalent of a kilogram? Really.

By this standard, I bet the article only goes out of the house on mornings when she doesn't take a shower, because she gets stuck in there for hours when she reads "Lather, rinse, repeat."

This is what happens when you adopt the Arabic's metric system. Like everything else they, it's inherently flawed.

/gets forty rods to the hogshead in my Prius.

Is this really a bad attempt by Fox News to try and discredit the metric system?

Pfighting Polish: TofuTheAlmighty: By this standard, I bet the article only goes out of the house on mornings when she doesn't take a shower, because she gets stuck in there for hours when she reads "Lather, rinse, repeat."

Edit: "writer of the article"

/Minored in Comm myself
//Majored in Computer Science

You Must Construct Additional Pylons.: This is why metric sucks.

It's all literal and sciencey and stuff.

I don't think the lead singer is literally breathing under water. It's a metaphor; and scientifically impossible.

/get this song out of my head!

TofuTheAlmighty: Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

Perhaps he was referring to the line after 2.2 pounds: "(1 kilogram) is the definition of the kilogram."

Does this kilogram make my ass look fat?

Faux News is so fake, that its cue-card holders are cardboard cut-outs.

Handsome B. Wonderful: Is this really a bad attempt by Fox News to try and discredit the metric system?

No, it's an attempt by LiveScience to discredit the metric system.

palan: JustMatt: I thought they changed the kilogram standard to the most perfect sphere created by man to date, made out of a perfect silicon crystal lattice? Was this never officially adopted? Wouldn't solve the problem of people leaving traces of their grubby mitts on it, just curious and too lazy to look it up...

It's called the Avogadro project. It's under consideration, but hasn't been taken to committee since they haven't determined if it will be more stable in the long term than the current standard. There are other proposals as well to try and move away from a physical artifact as the standard. The generally favored ones are to define the kilogram in terms of the Planck constant, but that's on hold until 2014, according to wikipedia.

That's what I was thinking of. Thanks for the additional info!

JohnCarter: "I get some pledge"

[25.media.tumblr.com image 200x281]

I got something she can wax.

/I wish

Zoidfarb: [www.qwantz.com image 735x500]
There is also a Dinosaur Comic for every occasion.

I hope they are funnier than that one. I want those 5 minutes back.

Pfighting Polish: Pfighting Polish: TofuTheAlmighty: By this standard, I bet the article only goes out of the house on mornings when she doesn't take a shower, because she gets stuck in there for hours when she reads "Lather, rinse, repeat."

Edit: "writer of the article"

/Minored in Comm myself
//Majored in Computer Science

In the past, it might have been called movable type.

Atomgirl: "Long-term, however, most scientists want to get away from defining the kilogram based on a hunk of metal."

It appears this artcile was written with the assumption that a kilo is an arbitrary measure. But isn't a kilogram determined by the weight of a liter of water?

The gram (not kilogram) was determined by a cube of water in the 1800's. it changed because the weight can vary by temperature, pressure and composition. Since the weight is determined by the isotopes composing the water was deemed problematic and tried to find a stable artifact to base the mass on, leading to the weight they used.

To clean them, a skilled technician will rub the cylinders with chamois dipped in alcohol.

abhorrent1: Can't they keep it somewhere where it won't get surface contamination? Clean room or something?

Came here to ask the same. I was thinking vacuum container inside a sealed red-light clean room, weighed and observed via the console in an adjacent clean room, with the whole thing inside an underground vault.

Unless the whole concept of a platinum-iridium reference weight just isn't that important, in which case keeping it in a glass jar is fine. Industrial scale manufacturers probably have a pretty good idea of how to make their own accurate kilogram. 1000ml of 4°C distilled water at sea level... or something.

Atomgirl: "Long-term, however, most scientists want to get away from defining the kilogram based on a hunk of metal."

It appears this artcile was written with the assumption that a kilo is an arbitrary measure. But isn't a kilogram determined by the weight of a liter of water?

That's what I thought.

1kg = the mass of 1L of water
1L = 0.001 cubic meters
1m = so many wavelengths of light from a decaying element, or the distance light travels in a vacuum over a given time

Sim Tree: TofuTheAlmighty: Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

Perhaps he was referring to the line after 2.2 pounds: "(1 kilogram) is the definition of the kilogram."

It's just poorly written in general. I'm sure the editor added the (1 kilogram) because that's what their editorial standard demands, not because it makes any sense or is necessary in any way. I'm half surprised they didn't say (2.2 pounds) after every mention of the word kilogram throughout the article.

The IPKs are stored in filtered laboratory air at constant temperature and pressure, but there's no way to completely isolate them from air pollution and contamination, Cumpson told LiveScience.

Couldn't you cut down on the air pollution by sucking all the air out of their storage environment? After all, how often can these things get used?

last i heard it was losing weight by abrasion of gloved hands

To clean them, a skilled technician will rub the cylinders with chamois leather dipped in alcohol.

If the piece of leather used to 'clean' the metal is old, perhaps it is the cause of the mercury contamination? Mercury was once used to process leather.

Also, i'm pretty sure leather has carbon atoms in it.

Maybe they shouldn't have wiped their expensive chunk of metal with alcohol soaked tanned skin?

There's a tanning mom joke in here somewhere, but yo mamma's so fat she's blocked out the sun and I can't see it.

Karac: The IPKs are stored in filtered laboratory air at constant temperature and pressure, but there's no way to completely isolate them from air pollution and contamination, Cumpson told LiveScience.

Couldn't you cut down on the air pollution by sucking all the air out of their storage environment? After all, how often can these things get used?

Vacuums cause outgassing of materials they come in contact with (think of how water boils easier at lower pressures). This vapor could then settle on the object. So you'd have to really clean the storage container, which is harder than cleaning the object itself and filtering the air.

CandidCallie: If the piece of leather used to 'clean' the metal is old, perhaps it is the cause of the mercury contamination? Mercury was once used to process leather.

Also, i'm pretty sure leather has carbon atoms in it.

Maybe they shouldn't have wiped their expensive chunk of metal with alcohol soaked tanned skin?

There's a tanning mom joke in here somewhere, but yo mamma's so fat she's blocked out the sun and I can't see it.

You may be right, and why they need a new touchless version of cleaning.

Don't forget that heat makes metal expand, so at some level you must blame global warming.

So... In Rod we Trust?

WorkingInParadise: Don't forget that heat makes metal expand, so at some level you must blame global warming.

Nice try but the issue is the mass of the cylinder. It doesn't matter if it expands or contracts.

They should replace the standard weights with \$1 trillion coins.

WorkingInParadise: Don't forget that heat makes metal expand, so at some level you must blame global warming.

That's not going to change its mass though.

Acharne: WorkingInParadise: Don't forget that heat makes metal expand, so at some level you must blame global warming.

That's not going to change its mass though.

Oh you!
Global warming is magic and can do anything.

meter = distance covered by light in 1/299792458 second
kilogram = that thing
second = 9192631770 hyperfine transitions of cesium 133
ampere = current needed to pull two thin wires 1 meter apart 2x10-7 newton/meter
kelvin = 273.16K is the triple point of water about 32f
mole = how many atoms of carbon 12 are in .012 kilograms, some day we might know exactly how many atoms this is but not yet
candela = 1/683 watt per steradian at 540x10^12 hertz

The problem with units is defining a kilogram in something that you can do in a lab. So for instance it would be easy to just say a kilogram is "so and so" many atoms, but we have no way to counting atoms in the lab. We can measure light and current derived from physical constants.

i do think the way to go is definite like how we defined the amp, from other physical constants, and once you have a newton you can derive the kilogram from that.

exick: Gonz: I thought kilograms measured mass, rather than weight?

If one gains mass while the gravitational forces of Earth remain consistent, then one's weight (the measure of Earth's gravitational forces on said mass) will also increase.

That assumes that the gravitational forces of Earth remain consistent, which is a pretty big assumption.

bonerici: once you have a newton you can derive the kilogram from that.

How? Earth's gravity fluctuates from point to point and time to time. I guess it depends on how accurate you want to be.

This article expands my confusion on measurement almost as much as last weeks article about measurements below absolute zero.

Lumpmoose: The international standard, a cylinder-shaped hunk of metal that defines the fundamental unit of mass, has gained tens of micrograms in weight from surface contamination, according to a new study.

If it's the international standard, then any increased or decreased mass becomes the new standard, by definition.  If we perceive the standard as being wrong and it needs to be cleaned so that it's reduced to our expected amount of mass, it sounds like our expectation is more the true standard than the cylinder.

I'd figure the standard is what it was when it was put into the case and defined as such. Hell, it's not like they take the thing out on a regular basis to use with a set of balance scales.

The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram.

No, it isn't. It's a standard for a kilogram, which is an entirely different thing.

A definition of a kilogram would be something like "a mass equivalent to 1/12 kMol of Carbon-12".

jigger: bonerici: once you have a newton you can derive the kilogram from that.

How? Earth's gravity fluctuates from point to point and time to time. I guess it depends on how accurate you want to be.

You could go up into free-fall and take an inertial measurement. Expensive, but not actually technically difficult to do. We like to use standards instead because they're both easy and cheap, but obviously that's vulnerable to the standard being contaminated or damaged (or, in the case of TFA, just getting a bit dirty, which is a bit hard to deal with since most methods of cleaning will also remove some surface material).

jigger: bonerici: once you have a newton you can derive the kilogram from that.

How? Earth's gravity fluctuates from point to point and time to time. I guess it depends on how accurate you want to be.

that's not a newton 1 newton is approximately the force of gravity on a mass of 100 grams. But to be more exact it is the force requires to accelerate a mass of one kilogram at a rate of 1 m/s^2

the earth's gravity varies according to where you are on the planet but the newton is derived from the kilogram and from time.

Alternatively if you are able to define the newton in terms of the other physical constants you can derive the value of a kilogram from it.

TofuTheAlmighty: While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

Pounds are both a unit of force and a unit of mass. It should not surprise you that an object with 1 lbm weighs 1 lbf on earth's surface. 1 lbf = 32.2*lbm*ft/s^2, approx.

So saying that a kg is equivalent to 2.2 lb is, in fact, entirely correct, if somewhat nonspecific. 2.2 lbm of material will always have the same weight as 1 kg of material as well as the same mass, so long as you're weighing them in roughly the same place.

Smoky Dragon Dish: To clean them, a skilled technician will rub the cylinders with chamois leather dipped in alcohol.

You're gonna love my nuts

Gonz: I thought kilograms measured mass, rather than weight?

Well, technically it is a measure of the potential energy stored by the quarks in their stable, bound configuration with a smidgen of lepton resistance to movement through a nonzero Higgs field. But for everyday conversation in a roughly constant gravitational potential, you can say weight.

bonerici: meter = distance covered by light in 1/299792458 second
kilogram = that thing
second = 9192631770 hyperfine transitions of cesium 133
ampere = current needed to pull two thin wires 1 meter apart 2x10-7 newton/meter
kelvin = 273.16K is the triple point of water about 32f
mole = how many atoms of carbon 12 are in .012 kilograms, some day we might know exactly how many atoms this is but not yet
candela = 1/683 watt per steradian at 540x10^12 hertz

The problem with units is defining a kilogram in something that you can do in a lab. So for instance it would be easy to just say a kilogram is "so and so" many atoms, but we have no way to counting atoms in the lab. We can measure light and current derived from physical constants.

i do think the way to go is definite like how we defined the amp, from other physical constants, and once you have a newton you can derive the kilogram from that.

Newton = fruit and cake.

TofuTheAlmighty: Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

Uh, and where does the approximation come in? A standard is a defined value, not a best estimate.
Approximately 2.2 pounds isn't the same as 2.2 pounds. Either the kilogram is an actual hunk of metal and weighs 2.2 pounds thus matching the standard, or it isn't. I can't just grab a 2 pound weight and say it's approximately a kilo and call it good as it doesn't match the set standard. Thus the definition of a kilo is 2.2 pounds or it isn't.

Either way it's shiat "journalism." Either break it down into its exact weight or leave out the approximately crap. After all, we are dealing with a world standard and not the corner farmer's market with the various non-conforming weights and measures which may be an ounce or more off.

Jim_Callahan: The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram.

No, it isn't. It's a standard for a kilogram, which is an entirely different thing.

A definition of a kilogram would be something like "a mass equivalent to 1/12 kMol of Carbon-12".

jigger: bonerici: once you have a newton you can derive the kilogram from that.

How? Earth's gravity fluctuates from point to point and time to time. I guess it depends on how accurate you want to be.

You could go up into free-fall and take an inertial measurement. Expensive, but not actually technically difficult to do. We like to use standards instead because they're both easy and cheap, but obviously that's vulnerable to the standard being contaminated or damaged (or, in the case of TFA, just getting a bit dirty, which is a bit hard to deal with since most methods of cleaning will also remove some surface material).

I do believe they took into consideration the loss of material which is why they use objects with a lower hardness and solvents that won't harm the base metal to remove the other bits they don't want there. King of like you can use various abrasives that are of a lower hardness to clean granite etc. without harming the rock.

They did after all go with platinum and palladium and not talc for a reason.

ReverendJynxed: TofuTheAlmighty: Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

While journalists are typically not the most scientifically literate, the sentence is not incorrect. She didn't write that a kilogram is defined as 2.2 lbs., she noted that a kilogram weighs 2.2. lbs. Though to be most rigorous, she could've written that it weighs 2.2 lbs on Earth.

Uh, and where does the approximation come in? A standard is a defined value, not a best estimate.
Approximately 2.2 pounds isn't the same as 2.2 pounds. Either the kilogram is an actual hunk of metal and weighs 2.2 pounds thus matching the standard, or it isn't. I can't just grab a 2 pound weight and say it's approximately a kilo and call it good as it doesn't match the set standard. Thus the definition of a kilo is 2.2 pounds or it isn't.

Either way it's shiat "journalism." Either break it down into its exact weight or leave out the approximately crap. After all, we are dealing with a world standard and not the corner farmer's market with the various non-conforming weights and measures which may be an ounce or more off.

Journalism in this instance isn't the same as writing for a Scientific Journal. They want the writing to be relatable for the public. Approximating to a commonly used measurement for the audience makes a lot of sense. They obviously fumbled a bit writing this, but making it relatable is essential and not one of their mistakes.

Why are things so heavy in the future? Is there a problem with the Earth's gravitational pull?

Gwyrddu: Why are things so heavy in the future? Is there a problem with the Earth's gravitational pull?

Yeah, the older it gets, the more the earth just sucks.

Jim_Callahan: Pounds are both a unit of force and a unit of mass.

A pound is force. A slug is mass. A pound-mass is a mass which is simply a constant multiple of a slug. A one slug mass in a one g field produces a one pound force. This whole "let's make up the name pound-mass for people too stupid to understand the difference despite having a perfectly serviceable mass unit" is nonsense.

Definitions of measurements are seldom if ever defined by artifact, but procedurally. A kg is not defined as 2.2 lbs nor the reverse (although the pound-mass is defined as an exact number of kg). And the lump of metal is not a definition of the kg, just a standard. The definition is procedural and the lump of metal was a convenient surrogate for the actual definition.

Without knowing the alloy ratio I can't figure it for sure, but 2.2 lbs. of platinum comes to almost \$55k.

Saying 2.2 lbs. kind of makes the argument for metric. To calculate the value I multiplied the closing cost of an ounce of platinum by 32, to get 2 lbs., then by 1.1 to get to 2.2 lbs. I don't mind systems that don't use base 10, (I'd actually prefer we genetically engineer people to have an extra finger on each hand, base 12 is much cooler) but this article converted base 16 into base 10. There isn't a standard measure '.1' pound.

ReverendJynxed: TofuTheAlmighty: Pfighting Polish: Yes please: "

Uh, and where does the approximation come in? A standard is a defined value, not a best estimate.
Approximately 2.2 pounds isn't the same as 2.2 pounds. Either the kilogram is an actual hunk of metal and weighs 2.2 pounds thus matching the standard, or it isn't. I can't just grab a 2 pound weight and say it's approximately a kilo and call it good as it doesn't match the set standard. Thus the definition of a kilo is 2.2 pounds or it isn't.

It isn't. It's an actual hunk of metal that weighs approximately 2.2 pounds. That right there is good jounalism. One kilo weighs exactly 2.20462 pounds. This doesn't make sense though as you need to represent the fraction of a pound in ounces not as a decimal. It's not an exact number though so it's much better to say 'approximately 2.2 pounds'.

Arrrrrgh so much fail/misunderstanding in this thread. And half of it is nitpicking the wrong nits.

Frederf: Definitions of measurements are seldom if ever defined by artifact, but procedurally.

Man, I wish this were true, but it isn't. Let me quote the CIPM (International Committee on Weights and Measures):

"The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram."

You can make the argument that this sentence is the definition, but that's picking such fine nits with the English language that your average grammar nazi will turn up his/her nose.

Pfighting Polish: Yes please: "The cylinder, which weighs approximately 2.2 pounds (1 kilogram), is the definition of the kilogram."

I saw this myself. Ever notice that, in college, the journalism/comm school tends to have the least intelligent people?

Amusingly, this sentence actually has no problems. Remove the parenthetical phrase (which is not the part of the sentence between the parentheses, it's the part between the commas, so maybe we should be simply annoyed at the English language) and you get: "The cylinder is the definition of the kilogram." The parenthetical phrase helps the non-metric (i.e., American) audience understand what a kilogram is, i.e. about 2.2 pounds. Did "(1 kilogram)" need to be in there? Probably not, but I can imagine some people might believe that our definition of the kilogram doesn't use a one kilogram object.

Atomgirl: It appears this artcile was written with the assumption that a kilo is an arbitrary measure. But isn't a kilogram determined by the weight of a liter of water?

Like that.

abhorrent1: Can't they keep it somewhere where it won't get surface contamination? Clean room or something?

Hey, I bet these people, who work for a living at keeping track of weights and measures, might have thought of that! This thing sits under a glass bell jar, which sits under a glass bell jar, which sits under a third evacuated bell jar. That, along with six other theoretically equal cylinders, sit inside a vault in a basement in a Paris suburb. The vault requires three keys held by three separate people. And the whole thing is monitored for constant temperature, pressure, and humidity. Look, clean rooms are not magic; for a computer hardware environment, or NASA, a few billion random atoms of carbon floating around aren't a big deal, as long as they're not clumped together as dust particles. But for the kilogram, a few million atoms here, another few million there, start to add up over time.

And it has to be taken out of its housing every so often, to calibrate its sisters, which are the ones that fly around the world to calibrate other countries' kilogram prototypes.

----

Now, the headline (TFA's, the Fark headline was amusing) is wrong... sort of. The International Prototype Kilogram has been shown to have picked up tiny amounts of other substances, which means it must have gained a small amount of mass. But the kilogram, by definition, is equal to the mass of that cylinder. In reality, all of the various prototype kilograms around the world have deviated from one another, and given that the IPK has picked up extra stuff, chances are that every one of the other standards has picked up mass as well, just in different amounts.

----

Personally, I think the CIPM's proposal of using the Planck constant to define mass, and the Boltzmann constant to define temperature, makes a hell of a lot more sense than continuing to use these little museum pieces and the difficult-to-measure triple point of water. But then again, none of this matters for anyone who needs less than 6 significant digits, which isn't a ton of people.

waffle299: Gonz: I thought kilograms measured mass, rather than weight?

Well, technically it is a measure of the potential energy stored by the quarks in their stable, bound configuration with a smidgen of lepton resistance to movement through a nonzero Higgs field. But for everyday conversation in a roughly constant gravitational potential, you can say weight.

And here's a really good reason to use the Planck constant.

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