from the weighty-subject-has-mass-appeal dept.
The future of the kilo: a weighty matter
First, the platinum-iridium cylinder is rubbed with a chamois that has been soaked in alcohol and ether. Then it is steam rinsed using boiling, double-distilled water. Finally, the 1kg cylinder is returned, carefully, to its resting place. Such reverence for a lump of metal is unusual, but has a purpose. The pavilion houses the International Bureau of Weights and Measures and that piece of platinum-iridium alloy is its holiest relic. It is the defining mass against which all other kilograms are measured. This is the international prototype of the kilogram. The IPK, in short.
Dozens of copies of this carefully calibrated piece of metal have been made. They are stored around the world and used to standardise individual nations' weights and measures systems. Britain's copy is kept at the National Physical Laboratory (NPL) at Teddington, near London. But the Parisian version is the king of the kilograms. "All mass measurements, anywhere on the planet, are traceable to that one unit in the Pavillon de Breteuil," says NPL scientist Tim Prior.
But the days of le grand K, as it is known, are numbered. Later this month, at the international General Conference on Weights and Measures, to be held in France, delegates are expected to vote to get rid of this single physical specimen and instead plump to use a fundamental measurement – to be defined in terms of an electric current – in order to define the mass of an object. The king of kilograms is about to be dethroned.
[...] In replacing the Paris kilogram with units measured in terms of Planck's constant, scientists have had to push technology to its limits, though in one sense they are merely catching up with all the other methods now used to define the other basic units with which we measure our existence, such as time and length. These are determined today in terms of fundamental processes.
Also at Inverse and Physics World.
Related Stories
From PBS:
The kilogram — anywhere in the world, for any purpose — is based on the exact weight of a golf-ball-sized chunk of platinum and iridium stored under three glass bell jars in a vault in an ornate building outside of Paris. Accessing the vault requires three people with three separate keys and the oversight of the Bureau Internationale des Poids et Mesures, the international organization that oversees the International System of Units.
Despite all of this security, in the 129 years since the International Prototype of the Kilogram was forged, polished and sanctioned as an artifact of measurement, it seems to have lost a tiny amount of material.
[...] On Friday, metrologists — people who study the science of measurements — and representatives from 57 nations will gather in a conference room in Versailles, France to redefine the kilogram. In other words: the way we weigh the world is about to change.
Also at Smithsonian, New Atlas, and Nature.
Related: International Prototype of the Kilogram Soon to Become Obsolete
(Score: 1, Informative) by Anonymous Coward on Tuesday November 06 2018, @01:30AM (7 children)
That means at least one animal sacrificed its life for the kg: https://en.m.wikipedia.org/wiki/Chamois_leather [wikipedia.org]
How are vegans ok with this?
(Score: 4, Funny) by black6host on Tuesday November 06 2018, @01:53AM (3 children)
Who do you think is behind the change? Bwahahahahaha!
(Score: 2) by MostCynical on Tuesday November 06 2018, @02:19AM (2 children)
Vegetarians? Vegans?
What about the electicity needed to now create a reference? Unless it is only from renewable energy, climate change will ill the animals anyway!
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 3, Touché) by Nuke on Tuesday November 06 2018, @09:38AM (1 child)
It will kill humans too, so makes it OK.
(Score: 3, Funny) by Gaaark on Tuesday November 06 2018, @04:21PM
If I go to the electric chair, tell them I want 12kg of electricity put through me.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by PiMuNu on Tuesday November 06 2018, @09:48AM
It's okay, the kilogram is a French unit. I pity the poor Republicans who are *forced* at school to study a *socialist* unit of mass. Something must be done!
(Score: 2) by c0lo on Tuesday November 06 2018, @12:30PM
ChamWoW!
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Touché) by mcgrew on Tuesday November 06 2018, @05:49PM
Why should I care about what a vegan cares about? Which reminds me, it's lunchtime and there are ribs waiting for me. S.E.P.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 5, Funny) by PartTimeZombie on Tuesday November 06 2018, @02:00AM
I have managed to maintain my weight at 75 kilograms. The kilograms are a lot bigger than they used to be though.
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @02:08AM (6 children)
Was the mystery about why all the cylinder's weights were no longer matching ever solved? Or was that the impetus for the move?
(Score: 2, Funny) by Anonymous Coward on Tuesday November 06 2018, @02:24AM (1 child)
I guess I can confess now. That was me. I snuck in and did things with le grand K. Terrible things. Unspeakable things. Things that just wouldn't wash off.
It's good that it is being replaced. Good for all of mankind.
(Score: 2) by Gaaark on Tuesday November 06 2018, @04:38PM
Shouldn't you have ended that with #MAGA, Donald?
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 3, Interesting) by MostCynical on Tuesday November 06 2018, @02:31AM
from the BBC [bbc.co.uk]
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @02:38AM
Could you elaborate on that, please?
(Score: 2) by mcgrew on Tuesday November 06 2018, @05:53PM (1 child)
It's no mystery. Every time you touch it a few molecules come off. Over a century it adds up.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @07:11PM
Except some of the national standards (which are handled much more frequently) have gained mass relative to their initial calibration against the IPK, so a loss of mass due to handling does not, by itself, explain the observations.
However that's not actually important. The real problem is that, since the IPK defines the results of virtually all mass measurements, there is no way to measure whether the national standards have gotten more/less massive, whether the IPK has gotten more/less massive, or whether it is some combination of both.
(Score: 2) by Walzmyn on Tuesday November 06 2018, @02:34AM (3 children)
I'm really suprised this hasn't already been done. the others are all based on something that can be calculated anywhere. Mass was compared to one object, like wheat sellers in a bazaar with a balance scale.
(Score: 3, Informative) by Anonymous Coward on Tuesday November 06 2018, @02:49AM
The problem was the proposals for replacing it with something defined in fundamental constants is that the constants necessary (e.g. Planck's constant, or perhaps the number of atoms in a kilogram of some substance) could not be determined with precision greater than these physical kilogram objects (even with their inaccuracies).
In the past few years, we've finally got the necessary precision in constants to create a new definition.
(Score: 3, Interesting) by driverless on Tuesday November 06 2018, @05:01AM
It's already being done now with a Watt balance, which measures the mass of an object using a precisely-defined current and voltage, that being the amount required to move a one kilogram mass a certain distance. Then you have Watt balances all the way down to define your base unit.
(Score: 2) by FatPhil on Tuesday November 06 2018, @04:32PM
https://www.nist.gov/si-redefinition/kilogram-silicon-spheres-and-international-avogadro-project
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2, Insightful) by Anonymous Coward on Tuesday November 06 2018, @02:44AM (6 children)
I for one hope they keep a few backup kilo standards around. Never know when civilization might collapse and take down the ability to use sophisticated methods. Keep some of the antique beam balances too, they work just fine (for any common application) and don't need any electricity/computers/PhDs to operate.
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @03:03AM
Best to keep a physical backup because: constants aren't, variables don't. You never know if next week the LHC won't redefine another constant in physics.
But now with the kilogram going virtual, we need it to be blockchained so people's virtual weightloss can be tracked and verified. I'm not fat, this "weight" is all virtual!
(Score: 2, Informative) by agr on Tuesday November 06 2018, @04:50AM
Standard masses will still be kept for day to day use in measuresment, but they can now be tested against the new definition in terms of Plank’s Constant, h = 6.626 070 15 × 10^−34 J s, when needed.
(Score: 3, Touché) by maxwell demon on Tuesday November 06 2018, @09:02AM (3 children)
When society collapses, the simple approximation "one kilogram is the weight of one liter of water" will be sufficient.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by bob_super on Tuesday November 06 2018, @04:51PM
"One kilogram is what my little friend M1A1 and I say it is."
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @06:03PM (1 child)
And one liter is as we all know just one Faradays Fluxcapacitor filled up to brim with Ö-quarks, while of course maintaining a negative azimuthal Z-load.
(Score: 2) by maxwell demon on Tuesday November 06 2018, @09:25PM
One liter is the volume of a cube with a side length of 10 cm. And given the large amount of low-tech measurement instruments for measuring centimeters in reasonable accuracy, there's no danger of that going lost.
Well, except maybe in America. But Americans don't care about the kilogram anyway. :-)
The Tao of math: The numbers you can count are not the real numbers.
(Score: 1, Interesting) by Anonymous Coward on Tuesday November 06 2018, @03:51AM (5 children)
All the other base units don't have a prefix!
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @04:26AM
Perhaps the French have an MKS sort of culture?
(Score: 2) by Bot on Tuesday November 06 2018, @01:02PM (3 children)
A gram would be more sensitive to measuring errors and the impact of degradation I guess.
Account abandoned.
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @04:27PM (2 children)
Um, where you use X or 1/1000 of X, your error is the same.
(Score: 2) by bob_super on Tuesday November 06 2018, @05:04PM
In theory.
In practice, humans are not ant-sized, so our tools favor handling and measuring a kilogram easier than a gram or a ton.
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @06:24PM
Not necessarily, because instrument noise (independent of X) may be an insignificant fraction of X but is a thousand times more significant when compared to X/1000. That can be a problem.
To a point you can solve this by rel-ing out the error (first measure without the object under test, then measure the object, and use the difference as the measurement result) but as the value being measured becomes smaller then your instrument error will eventually become more significant than the thing you are measuring and you can't usefully rel it out anymore. At that point (probably before) you need a different instrument and/or a different measurement technique.
(Score: 4, Funny) by Anonymous Coward on Tuesday November 06 2018, @05:27AM (2 children)
All these years and it never got out of beta? It's still a damn prototype!?
(Score: 2) by All Your Lawn Are Belong To Us on Tuesday November 06 2018, @03:52PM
No, now they're out of beta and releasing on time.
Nobody thought to ask what computer system the master copy of the new standard will be archived to. Let's just say you'll be glad to be Still Alive.
This sig for rent.
(Score: 2) by bob_super on Tuesday November 06 2018, @04:58PM
You gotta applaud the fact that some manager said "it's good enough, just keep it like that", and that stood for two hundred years (over a hundred for the copy, the IPK).
They fired the marketing guy who kept trying to add more features.
Can I hire that team?
(Score: 3, Funny) by Gaaark on Tuesday November 06 2018, @04:42PM
When the shit hits the fan, no one will be able to tell what a kg really is without that bar, or as Asimov surmised, some day a janitor will be teaching mathematicians how to do math without a calculator.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by linkdude64 on Tuesday November 06 2018, @06:17PM
"The Origins of Precision"
https://www.youtube.com/watch?v=gNRnrn5DE58 [youtube.com]