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US Objects To the Kilogram

Soulskill posted more than 3 years ago | from the weighty-subjects dept.

United States 538

Velcroman1 writes "For 130 years, the kilogram has weighed precisely one kilogram. Hasn't it? The US government isn't so sure. The precise weight of the kilogram is based on a platinum-iridium cylinder manufactured 130 years ago; it's kept in a vault in France at the International Bureau of Weights and Measures. Forty of the units were manufactured at the time, to standardize the measure of weight. But due to material degradation and the effects of quantum physics, the weight of those blocks has changed over time. That's right, the kilogram no longer weighs 1 kilogram, according to the National Institute of Standards and Technology. And it's time to move to a different standard anyway. A proposed revision would remove the final connection to that physical bit of matter, said Ambler Thompson, a NIST scientist involved in the international effort. 'We get rid of the last artifact.'"

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538 comments

Get rid of the artifact? (3, Interesting)

XanC (644172) | more than 3 years ago | (#34066696)

Last I heard, nobody had come up with a way to define mass without referring to an artifact. It seems easy but they all turn out to be circular.

Re:Get rid of the artifact? (4, Funny)

FooAtWFU (699187) | more than 3 years ago | (#34066760)

Well, you can try counting atoms. But apparently that turns out to be a royal pain.

Re:Get rid of the artifact? (0)

Anonymous Coward | more than 3 years ago | (#34066778)

You have to have *some* artifact, but it doesn't necessarily have to be a mass of something. You can use time to define everything if you like. Basically, find some artifact that won't change and define the others from it.

Re:Get rid of the artifact? (5, Interesting)

jdgeorge (18767) | more than 3 years ago | (#34066786)

Aren't they just proposing removing the dependence on the 1 kilogram cylinders?

From the article:

Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is. But all you need to know is, they're using it to determine the mass of one mole of silicon atoms.

From there on, they'll theoretically be able to deduce a perfect kilogram and it won't have anything to do with lumps of metal ever again. /quote

Re:Get rid of the artifact? (0, Redundant)

MartinSchou (1360093) | more than 3 years ago | (#34067062)

But all you need to know is, they're using it to determine the mass of one mole of silicon atoms.

From there on, they'll theoretically be able to deduce a perfect kilogram and it won't have anything to do with lumps of metal ever again.

Yes ... apart from the fact that silicon IS a metal, and that a large collection of atoms that closely together is rightfully called a "lump".

Essentially they're proposing replacing one lump of metal with another. It may not be a cylinder, but it's still a lump of metal.

Re:Get rid of the artifact? (1)

Guspaz (556486) | more than 3 years ago | (#34066800)

The gram was originally defined in relation to a cubic centimetre of water (the temperature originally being 0 degrees, later 4 degrees). Then the IPK was made based on this.

So, what's the problem here? Don't we have a fixed reference, the weight of a given volume of water at a given temperature? Why can't we re-calibrate from that?

Re:Get rid of the artifact? (1)

XanC (644172) | more than 3 years ago | (#34066858)

No, because the volume depends on pressure. Which has a mass component. Circular.

Re:Get rid of the artifact? (-1)

Anonymous Coward | more than 3 years ago | (#34066920)

No, because the volume depends on pressure. Which has a mass component. Circular.

liquid water is an incompressible fluid last time I checked...

Re:Get rid of the artifact? (1)

phyrexianshaw.ca (1265320) | more than 3 years ago | (#34067080)

that has nothing to do with the argument: all materials, water included, expand when heated, so the density of 1cm^3 of water is a product of the temperature.

the weight of 1cc of water depends on the temperature.

Re:Get rid of the artifact? (2, Insightful)

bdcrazy (817679) | more than 3 years ago | (#34067106)

I just love ideal physics land. Unfortunately the real world doesn't work that way.

Re:Get rid of the artifact? (0)

Anonymous Coward | more than 3 years ago | (#34066886)

Wouldn't the mass of the water change based on the mineral or contaminate content of the water? Would we have to specify steam distilled water?

Re:Get rid of the artifact? (1)

LWATCDR (28044) | more than 3 years ago | (#34067038)

Here I have the soluition. 1 gram = the mass of 6.02x10^12 carbon=12 atoms /12 not weight since that can very with location and atmospheric conditions.

Re:Get rid of the artifact? (5, Interesting)

Anonymous Coward | more than 3 years ago | (#34066808)

Nah, it's actually pretty easy. You say something like "one kilogram is the mass equivalent of the energy of 3.40812408 gazillion photons with a wavelength of 550.9466543 nanometers." The meter is already defined in terms of speed of light and the second, and the second is defined in terms of the natural frequency of the caesium-133 atom. So in the end, everything is defined in terms of the speed of light and the caesium atom, with no artifacts needed.

Re:Get rid of the artifact? (1)

phyrexianshaw.ca (1265320) | more than 3 years ago | (#34067112)

you want to patent a method to count exactly "3.40812408 gazillion photons" reliably and accurately?

if so, I'm sure the NIST may have an opening for you.

Re:Get rid of the artifact? (1)

Zerth (26112) | more than 3 years ago | (#34066826)

Um, the electron-volt(eV)?

I suppose you could use a reference electron, but any old electron will do.

Re:Get rid of the artifact? (1)

characterZer0 (138196) | more than 3 years ago | (#34066846)

Last I heard, nobody had come up with a way to define mass without referring to an artifact.

There are several ways to define a KG using constants or atomic weights. http://en.wikipedia.org/wiki/Kilogram#Proposed_future_definitions [wikipedia.org]

The trick is that you not only have to be able to define it, but measure it reliably and accurately.

Re:Get rid of the artifact? (1)

blair1q (305137) | more than 3 years ago | (#34067002)

The artifact system is not reliable and accurate, and certainly not easy to use. If you can't replicate the conditions of the definition in a remote lab, then the definition is bollocks. I mean, what if we lose these things?

The right way to do this is to reverse the definition of Avogadro's number. Instead of "Avogadro's number is the number of C-12 atoms in 12 grams of C-12," you say "Avogadro's number is exactly 6.022141500000000000000000x10^24 and that number of C-12 atoms is 12 grams."

Now anyone who can refine carbon and count its atoms can produce a 12-gram sample. Case closed.

Re:Get rid of the artifact? (1)

Sir_Sri (199544) | more than 3 years ago | (#34066896)

You could use an integer number of some base element (hydrogen, helium, carbon 12 something like that). Sort of like time based on radiation emissions or the like. The problem is both precisely and accurately measuring it, and agreeing on what base element. The actual details are fairly simple, you probably want something with the minimum of unstable isotopes that occur in the minimum quantities possible. It's a matter then of finding something suitable (that you can either separate out the isotope easily, or that is naturally acceptable).

Sort of by definition what you said is that no one has come up with a way of doing the above, so they stick with the official masses. There's nothing circular about basing it on some fixed elemental composition. One could even define based on a fixed number of moles of platinum/iridium isotopes to make the current masses 'official'. The issue is whether or not it can be reconstructed exactly from only the definition, which presently it cannot, and under some other system it should be. Yes, the original definition is always going to be arbitrary, that's equally true of time. There's no fundamentally natural reason why our base unit of time needs to have the length of a second, or why we should use the kilogram specifically. There are conveniences associated with it, but it's not like there's some perfect 1 second pulse from the sun or perfect gram that is naturally occurring.

Re:Get rid of the artifact? (0)

Anonymous Coward | more than 3 years ago | (#34066940)

Last I heard, nobody had come up with a way to define mass without referring to an artifact

E=mc^2

Re:Get rid of the artifact? (0)

Anonymous Coward | more than 3 years ago | (#34066942)

Every other unit was defined by our understanding of the fundamental forces involved. Basically, time is defined by the speed of light (ie. electromagnetic force), therefore speed of light is constant, by definition. There is no insight into the phenomenon of "mass", therefore it remains an artifact. How else do you define it? 1/12 of the Avagadro's number of C12 atoms in their ground state? Sorry, but we do not "easily" deal with these numbers. And defining Avagadro's number is like defining PI, at least at our current understanding of mass.

http://en.wikipedia.org/wiki/Avogadro%27s_number

So, understand the nature of mass first, then define a unit based on that understanding. Not the other way around.

Re:Get rid of the artifact? (2, Informative)

goodmanj (234846) | more than 3 years ago | (#34067004)

The goal is to use a single atom as the artifact. Atoms (of a specific isotope) are always *exactly* the same, so there's no concern about variations in the weight of the artifact over time.

So all you've got to do is build an object with a mass as close to 1 kilogram as possible, precisely count the number of atoms it contains, and then make a definition like:

"A Kilogram is defined as the mass of 5.018451 x 10^22 atoms of Carbon 12".

The difficulty is precisely counting the number of atoms in a macroscopic object: the Avogadro Project has been working on this for years.

This is similar to how a second is defined, as "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:Get rid of the artifact? (4, Interesting)

kenj0418 (230916) | more than 3 years ago | (#34067070)

Last I heard, nobody had come up with a way to define mass without referring to an artifact. It seems easy but they all turn out to be circular.

kilogram: the amount of mass required to deflect a proton by X degrees at a distance of Y meters.

I'm guessing X and/or Y would have to be quite small.

BASE16 (5, Funny)

AmigaHeretic (991368) | more than 3 years ago | (#34066712)

Death to KILLograms!
Ounces and pounds were way a head of the time and are becoming even more useful with the advent of computer systems and the common use of base16.

16 ounces in a Pound is not just coincidence.

F=15 ounces
10 = a pound

We can all agree, I am sure, it's easier to look at 89 and go, 8 pounds 9 ounces. With metric I have to keep moving the decimal place around and remember how many 0s there were in huge words like kilogram, milligram, centigram.

Re:BASE16 (1, Informative)

Yvan256 (722131) | more than 3 years ago | (#34066740)

Computers use base 2, humans use base 10.

Re:BASE16 (2, Informative)

morgan_greywolf (835522) | more than 3 years ago | (#34066882)

You're almost right. Base 16 (hexadecimal) happens to be a convenient way for humans to do base 2 math. Any programmer worth his salt can do hex math in his head. ;)

Re:BASE16 (1)

man_of_mr_e (217855) | more than 3 years ago | (#34066986)

Yes, but 16 is easier to carve up into smaller pieces using fractions.

10 is divisible by itself, 5, 2, and 1.
16 is divisible by itself, 8, 4, 2, and 1

12 is even better than 16
12 is divisble by itself, 6, 4, 3, 2, and 1

.

Re:BASE16 (2, Funny)

Anonymous Coward | more than 3 years ago | (#34067012)

CPUs use base 2 and many Computer "Systems" use base 16.

I'm human and I use base 8. Worked in a knife sharpening factory as a kid. :(

Whoosh! (1)

AmigaHeretic (991368) | more than 3 years ago | (#34066910)

Jesus people it was a joke as to the headline of the article, "US objects to Kilogram" and how we still insist on using the pound over the kilogram.

Obviously base16 would be retardedly hard for every day measure for most people.

How many pounds is FCA again grandma?

Re:BASE16 (1)

bluefoxlucid (723572) | more than 3 years ago | (#34066978)

The Chinese Suan Pan had 5 earth beads and 2 heaven on each rod, with each heaven bead being 5. You counted 1, 2, 3, 4, then zero'd the Earth and shifted a Heaven bead for 5; 6, 7, 8, 9, then zero'd and shifted a Heaven bead to make 10; then 11, 12, 13, 14, and then finally used that last Earth bead to make 5 + 10 = 15. Then 1 on the next rod meant 16. This is because there were 16 liang to 1 jin.

Re:BASE16 (1)

BurningTyger (626316) | more than 3 years ago | (#34066984)

Sure. Please do the following calculation in your head (you can use your fingers too)

Let's say a bag of wood weighs 8 pound 9 ounces, and you want to buy 3 bags. What is the total weight in pound and ounces?
Versus, you have 8.9kg of wood, and you want to buy 3 bags, what is the total weight in kg?

I am sure you'd be able to multiply in BASE16 if you are trained for it, and memorize the BASE16 multiplication table when you were a kid. But for the rest of us, BASE10 is what we learned and used to.

Weight a minute... (1, Insightful)

Anonymous Coward | more than 3 years ago | (#34066730)

The US cares that much why? Its only a trade matter, as we still use primitave imperial measurements. Maybe if we had switched to metric like they had told us we were going to every year in grade school this would be a big deal, but right now, who cares?

Re:Weight a minute... (4, Interesting)

XanC (644172) | more than 3 years ago | (#34066742)

Because this prototypical kilogram is what the definition of the pound is currently based on.

Re:Weight a minute... (4, Interesting)

sexconker (1179573) | more than 3 years ago | (#34066766)

The US cares that much why? Its only a trade matter, as we still use primitave imperial measurements. Maybe if we had switched to metric like they had told us we were going to every year in grade school this would be a big deal, but right now, who cares?

Because prices, taxes, tariffs, etc. care about pounds and kilograms. We still have a department of weights and measures, and they still do extremely important work. The fact that you don't ever notice any problems means they're doing their jobs.

Re:Weight a minute... (0)

Anonymous Coward | more than 3 years ago | (#34066798)

I like how $arbitrary_measurement_unit_1 is more "primitave" than $arbitrary_measurement_unit_2. This amuses me greatly.

Now, if it were "less sensible" or "part of a system that makes less sense", maybe that wouldn't make me laugh as much at your attempt at a comment.

Re:Weight a minute... (2, Interesting)

Wyatt Earp (1029) | more than 3 years ago | (#34066980)

The US was one of the original signatories to the treaty that defined the meter and started the BIPM which lead to the SI.

All US weights and measures, no matter what standard they are on, come from the National Bureau of Standards which standardized on the metric system, as has the USGS (since the early 19th century).

THe NBS has standard meter and kilograms that are copies of the originals kept in Paris, so the US has a valid reason to wonder about the new kilogram definition.

Re:Weight a minute... (0)

Anonymous Coward | more than 3 years ago | (#34067018)

The US cares that much why? Its only a trade matter, as we still use primitave imperial measurements.

There are scientists in the US and, mostly, they use standard units of measurement. So they care.

Re:Weight a minute... (1)

blair1q (305137) | more than 3 years ago | (#34067074)

It's hardly a trade matter as no shipment of anything (other than platinum-iridium reference cylinders) has ever depended on that level of accuracy.

It's an anal-retentive comparative science matter. The only people who could care are those who come up with different answers because their nearest reference cylinder was not the same exact mass as someone else's.

Re:Weight a minute... (1)

goodmanj (234846) | more than 3 years ago | (#34067094)

Because a pound [wikipedia.org] is defined as exactly 0.45359237 kilogram, by international agreement since 1959. D'oh! We've secretly been using the filthy metric system all along!

Did the OP even read the NIST doc? (5, Informative)

walmass (67905) | more than 3 years ago | (#34066758)

It clearly states this is an international effort, and the objection is not the the unit 'kilogram' but rather to using a decaying (however slowly) object as the reference mass.

Re:Did the OP even read the NIST doc? (0)

Anonymous Coward | more than 3 years ago | (#34067048)

Is there anything in this universe that doesn't decay over time? Unobtanium maybe?

old, and not just the US (5, Interesting)

Imabug (2259) | more than 3 years ago | (#34066764)

seriously, this is pretty old. physicists working in metrology have been working to redefine the kilogram for at least the last few decades

Re:old, and not just the US (0, Flamebait)

blair1q (305137) | more than 3 years ago | (#34067100)

If it takes any of them more than 30 seconds to find the solution, they're suck for physicists.

Best of Both Worlds (4, Funny)

Anne_Nonymous (313852) | more than 3 years ago | (#34066772)

We have American pints and British pints; the imperial tone, the short ton, and the tonne; why not have an American kilogram and traditional kilogram as well? That should really simplify things for NASA/EUA coordination.

Re:Best of Both Worlds (4, Funny)

pyser (262789) | more than 3 years ago | (#34066810)

That's it! Define a kilogram in terms of pints. Now, the quandary: ale or lager?

It makes as much sense to define a kilogram as some huge number of moles of banana pudding or something like that.

Re:Best of Both Worlds (4, Funny)

rjstanford (69735) | more than 3 years ago | (#34066928)

Wouldn't a mole made out of banana pudding degrade pretty quickly itself?

And how could it burrow?

Solution fail. Tasty, tasty solution fail...

Re:Best of Both Worlds (1)

Wyatt Earp (1029) | more than 3 years ago | (#34067040)

On 7 April 1795, the gram was decreed in France to be equal to “the absolute weight of a volume of water equal to the cube of the hundredth part of the meter, at the temperature of melting ice.”

So why not switch that to beer? Lager, Porter or Bock is a better question than Ale or Lager.

Nyuk (1, Funny)

Anonymous Coward | more than 3 years ago | (#34067118)

Of course it only makes sense to use guacamole, not banana pudding. Then the conversion is a simple computation based on Avocado's number.

Speaking as a metric man (3, Interesting)

Max Romantschuk (132276) | more than 3 years ago | (#34066776)

Funnily enough I never ever think of a kilogram as the weight of some standard weight in a vault somewhere. The only way I ever think about the kilogram is the weight of one liter of water. Also comes in handy when I'm calculating how much liquids I can afford to buy when shopping groceries, given that I often go to the store on foot for the exercise and have to make sure I can manage the haul back.

So, um, does this all really matter? In practice, that is.

Re:Speaking as a metric man (5, Funny)

Anonymous Coward | more than 3 years ago | (#34066828)

then how do you define a liter?

OH I JUST BLEW YOUR MIND

Re:Speaking as a metric man (0, Troll)

guruevi (827432) | more than 3 years ago | (#34066944)

The amount of pure water under regulated conditions that fits in a cubic decimeter. The meter is derived from the speed of light in a vacuum (Wikipedia or Google the exact amount).

You guys really needed to have paid better attention in your 4th grade physics classes, this is quite basic (a good question for "Are you smarter than a 5th grader?"). Oh, you're American, never mind then.

Who cares? (5, Funny)

tarsi210 (70325) | more than 3 years ago | (#34066784)

It's the US of A -- we don't use the kilogram anyway. Change it as you like.

That being said, keep your filthy hands off my hogshead.

Re:Who cares? (5, Funny)

paranoid123 (633401) | more than 3 years ago | (#34066830)

I think the American Association of Cocaine Dealers would object to arbitrarily getting rid of the kilogram!

Re:Who cares? (1)

rjstanford (69735) | more than 3 years ago | (#34066950)

If you're dealing in kilos rather than grams, I think you can hire people to figure it out. So do what you will with the kilogram - just don't change the gram, and we're all good!

Re:Who cares? (5, Insightful)

cool_arrow (881921) | more than 3 years ago | (#34067010)

Without cocaine and weed so many american kids would know absolutely nothing about the metric system. Think of the children!

It's true... (4, Funny)

N0Man74 (1620447) | more than 3 years ago | (#34066916)

I'm not even sure we even use Imperial units anymore...

From reading the news, I believe our units are:
- Hairs
- Stories
- Football Fields
- Libraries of Congress

Re:Who cares? (0)

Anonymous Coward | more than 3 years ago | (#34066962)

It's the US of A -- we don't use the kilogram anyway. Change it as you like.

But we do. The pound is defined as 0.45359237 kilograms, exactly.

Re:Who cares? (1)

geekoid (135745) | more than 3 years ago | (#34066996)

Please, it's used i a lot of places. My kids learn metric in grade school. In fact, just the other day my son referred to a distance a centimeters. in casual conversation.

It's not just the Kilogram (-1, Troll)

Anonymous Coward | more than 3 years ago | (#34066792)

The US seems to object to pretty much the entire Metric system, not just the Kilogram.

The difficulty of standard artifacts (4, Funny)

Homburg (213427) | more than 3 years ago | (#34066802)

"There is one thing of which one can say neither that it is one metre long, nor that it is not one metre long, and that is the standard metre in Paris." - Wittgenstein, Philosophical Investigations

US != SI (-1, Redundant)

Anonymous Coward | more than 3 years ago | (#34066806)

Why USA care about the definition of kilograms since they use imperial units ?

I think I need more coffee (1, Funny)

Anonymous Coward | more than 3 years ago | (#34066814)

I read the title as "US Objects To the Klingon". @.@

I suspect that all the fuss... (2, Insightful)

Slutticus (1237534) | more than 3 years ago | (#34066832)

..is about a decimal place in which the instuments available to most of us can't even touch (precicion-wise...) But by all means, carry on.

Re:I suspect that all the fuss... (1)

SydShamino (547793) | more than 3 years ago | (#34067016)

No, but every NIST-traceable instrument eventually gets back to those standards. Sure, there are a very small number (probably a dozen or so) weights directly calibrated against the original articles. But then those are used to calibrate a few hundred weights at metrology labs, which are used to calibrate weights for thousands of customers around the world. Each step introduces uncertainty, but uncertainty around a precise value can be accounted for. Uncertainty around the wrong value renders the instrument useless.

The same is true for other standard units. I have instruments at my desk that are calibrated and NIST-traceable for time and voltage.

What? (1)

rdg55 (751418) | more than 3 years ago | (#34066836)

--Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is.-- I scoffs @ the writers grammer.

Re:What? (0)

Anonymous Coward | more than 3 years ago | (#34066890)

--Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is.--
I scoffs @ the writers grammar.

FTFY

Re:What? (1)

kenboldt (1071456) | more than 3 years ago | (#34067042)

--Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is.-- I scoffs @ the writers grammer.

I'm sure you meant writer's grammar with the appropriate apostrophe in writer's and an "a" in grammar and not an "e"

Why the sensationalism ? (0)

Anonymous Coward | more than 3 years ago | (#34066842)

It is just a scientific opinion from a group of scientist who happen to work for an institution funded by federal dollars. Nothing to do with the adoption of SI units by the US - which of course is a sensational.

Shitty Fox Article (0, Troll)

dcollins (135727) | more than 3 years ago | (#34066850)

That is one super-shitty Fox article that's been chosen to base the headline here on.

FTA: "...now NIST plans submit what amounts to a formal complaint at next October's General Conference on Weights and Measures -- along with a proposal to define a new kilogram according to something called a Planck value... Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is. But all you need to know is, they're using it to determine the mass of one mole of silicon atoms."

Yeah: Bullshit and more bullshit.

No more gold standard (5, Funny)

countertrolling (1585477) | more than 3 years ago | (#34066856)

We're going to let the kilogram "float" and put it on the commodities market. It should triple the value of the gram

Say what? (1)

mark-t (151149) | more than 3 years ago | (#34066860)

Why is the US objecting to a standard that it has not ever taken the time to actually use? Talk about anything in metric to most anyone from the US and they go "what's that in English?" Argh!!!!

That said, I am compelled to agree with the reasons for the change... hopefully the new value is close enough to the old that not too much should require updating (I'm thinking the most likely candidates for updates are books in astrophysics).

Re:Say what? (1)

dondelelcaro (81997) | more than 3 years ago | (#34067098)

Why is the US objecting to a standard that it has not ever taken the time to actually use?

Anyone in the US who actually does quantitative research uses the metric system. I can't remember the last time I attempted to mass something in pounds.

I wonder why american scientists care (1)

MouseR (3264) | more than 3 years ago | (#34066880)

...given the bulk of the population doesn't even know what metric is and that they measure distances in football field lengths.

Not quite as retarded as calculating weight in stones, but it`s only a foot away from that.

WHy does America care (0)

Anonymous Coward | more than 3 years ago | (#34066912)

They don't even use the Metric system
Shit I am surprised they even know that a kg exists and now that they know it is a french thing they are not going to change

um, it's been a while since I took physics (0)

Anonymous Coward | more than 3 years ago | (#34066932)

but unless my 40+ yr old brain is deteriorating a lot faster than I realize a kilogram has NEVER "weighed" a kilogram - pretty sure a kilogram weighs 9.8 NEWTONS (and that's only at sea level)

am I seriously the 1st /.-er to point this out?

Hey, Space Nutters (-1, Troll)

Anonymous Coward | more than 3 years ago | (#34066960)

Care to explain what materials you plan to use to colonize the galaxy when materials seem to lose substance over small time frames like 130 years? Wishes, dreams and delusions don't cut it in the real world.

MASS not WEIGHT! (0)

Anonymous Coward | more than 3 years ago | (#34066974)

If this whole discussion is about the WEIGHT of one kilogram, as the post suggests, it won't get far.

kilogram is a unit of mass, not weight.

Kilogram is a mass not a weight (4, Informative)

MConlon (246624) | more than 3 years ago | (#34067014)

Newton is a weight. The summary (and the Fox article) are incorrect, while the NIST article correctly refers to the reference mass.

MJC

Headline is sensationalist (5, Informative)

starseeker (141897) | more than 3 years ago | (#34067036)

and misses the point. The variability of the kilogram standard is a scientific and engineering concern, not a political one.

Wikipedia discusses the issue: http://en.wikipedia.org/wiki/Kilogram#Proposed_future_definitions [wikipedia.org]

In a nutshell - in order to create 1 kilogram physical standard masses, you have to first know what a kilogram IS. The physical standards referred to in the article do not appear to have retained constant mass over time. You can't define a constant based on something that is variable, so the current masses are (as I understand it) acknowledged to be an inadequate basis for the definition of the unit. The problem arises when you try to pick something to define it with that is both stable (i.e. a fundamental property of the natural laws of the universe) and practical (can actually create one to use as a practical mass standard against which you can prepare working standards.)

From articles that have popped up about this over the years, my guess is they will have to pick something as a basis and then work on various practical techniques to get as close to that ideal as possible - the question is what specifically to pick. N Carbon atoms? N Si atoms? What are the pros and cons when trying to physically create something that represents those numbers? How stable will a standard created according to a chosen standard be over time? (I.e., how often to we have to make new master standards? It's an important question - obviously the existing masses were not chosen with the expectation that their mass would vary with time, so how do we know to trust a given solution?)

So it's not the US objecting to the kilogram as a unit, but rather concern over the methods used to DEFINE the unit. That's something quite rational, not specific to the USA, and of scientific interest. Editors, how about changing the title to "US to Propose New Method of Defining a Standard Kilogram" instead?

Ben Stein? (0)

Anonymous Coward | more than 3 years ago | (#34067090)

If you look at the NIST release... note whose name is given for the press contact.

I guess they really do have Clear Eyes (TM) in the government. :-)

Calculate decay (0)

Anonymous Coward | more than 3 years ago | (#34067102)

I suppose those great physicists could always calculate how much the decay means and figure out how much weight the item lost. But somebody please tell me, is this even noticeable ?

Americans missing the point (1)

chargersfan420 (1487195) | more than 3 years ago | (#34067104)

First and foremost, it must be said that the kilogram is a unit of MASS, not weight. It refers to the amount of space that an object takes up, not its gravitational force. See here. [wikipedia.org]

Second, I don't care what the experts say, a kilogram is equal to the mass of one litre of water, which is equal to 1000 cubic centimetres of water, or a 10cm x 10cm x 10cm box full of water.

It is this way because it makes sense, like the rest of the metric system. Unfortunately, somehow it became more common to refer to it as a weight, which just confuses people.
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