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
Related Stories
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.
(Score: 3, Insightful) by Snotnose on Saturday November 17 2018, @03:29AM (2 children)
Simply set it so that 1.000 kilograms is the same as 1.000 pounds. Think of all the problems that will solve.
/ I would attribute the original author on this
// except I have no idea who that was
/// Satisfy yourself with I did not come up with this and don't remember who did
When the dust settled America realized it was saved by a porn star.
(Score: 4, Funny) by coolgopher on Saturday November 17 2018, @03:40AM
xkcd [xkcd.com].
(Score: 2) by Snotnose on Monday November 19 2018, @12:12AM
Who the hell would mod this insightful? Get out of bed, spend 30 minutes on the internet, some 10 hours later see this and remember a joke I read 10 hours ago, but not the source.
Insightful? I should downmod my own post.
When the dust settled America realized it was saved by a porn star.
(Score: 1, Informative) by Anonymous Coward on Saturday November 17 2018, @03:35AM (7 children)
For the vast majority of us, filling a measuring cylinder with distilled water at the right temperature would do just fine. This is only going to affect people who are looking for as much precision as possible, and they'll be able to cook up their own standard kg and then base precisely calibrated lab weights off of that. Not that it isn't important, but it isn't going to change the way we weigh everything. All the old brass weights for your scale will still be good, and I bet even most fine analytical balances in labs will still be OK.
(Score: 5, Interesting) by MostCynical on Saturday November 17 2018, @04:44AM (6 children)
For some, it will mean less precision - the new definition sets Planck's Constant to an exact value of 6.62607015×10^-34 kg⋅m^2/s. This will cause Kilogram measurements to be inexact, as Planck's Constant varies slightly, depending on when and where it's measured.
"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 Saturday November 17 2018, @10:12AM (2 children)
Given that it's called Planck's constant and there's no big campaign to have it renamed, is it that the value itself varies, or is it just that our measuring devices are not reliably consistent to a sufficient level of accuracy?
Also, [citation needed]
(Score: 3, Informative) by MostCynical on Saturday November 17 2018, @10:51AM
https://physicsworld.com/a/can-gps-find-variations-in-plancks-constant/ [physicsworld.com]
https://www.researchgate.net/post/Is_the_Plancks_constant_really_a_constant [researchgate.net]
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 4, Funny) by Bot on Saturday November 17 2018, @03:36PM
> planck's constant ain't constant
what do you expect, it's physics, the systemd of knowledge.
Account abandoned.
(Score: 3, Funny) by khallow on Saturday November 17 2018, @03:52PM (2 children)
Not when it is set to exactly 6.62607015×10^-34 kg⋅m^2/s.
(Score: 0) by Anonymous Coward on Sunday November 18 2018, @01:35AM (1 child)
uhm ... but you just used "kg" to define plank constant?
it's the strangest think in the world:
some cave dwellers come to the insight that understanding the world together requires to agree on a arbitrary measuring unit and the go about measuring shit and recording the results in this unit.
later on laws are discovered that yield a constant. then the constant becomes the new foundation and the arbitrary "cave man" unit goes out the window.
so in way this is good, you can send plans of a device to aliens and it can tell them kg. bad because someone cannot just make an appointment and copy "cave man" kg anymore via bar-scale but needs to pay and build a complicated setup ...
(Score: 1) by khallow on Sunday November 18 2018, @01:18PM
No, "I used it" to define "kg⋅m^2/s" which is a different thing. Combined with definitions for the speed of light and a second and you can pull out the kilogram.
(Score: 2) by jmorris on Saturday November 17 2018, @04:59AM (6 children)
This isn't really going to change much.
The Metric System was a fairly well thought out thing for the time but eventually we should probably do another rip and replace. One final rethink in another hundred or two years. This time base it on deeply embedded aspects of physical reality instead of things common on Earth at a particular moment or based even on Humans. Work hard on a system that interlocks such that as many arbitrary constants either disappear in equations or become very simple. Of course it might never actually be worth the disruption to jack with units like the second because pretty much everything would get screwed up but it would probably be needed to simplify everything else. If giving everything a total rework would it even be worth it to rethink base 10 being so deeply tied to the system of measurements?
Look at electronics for an example. E=IR. Ohm's Law. No constants. Capacitance, Inductance, Impedence, still tend to work without arbitrary constants littering the equations. Because really clever people put a lot of thought into selecting units that all worked together because they were all derived from a few common phenomena. Of course they had to also tie it to existing units like the second for the RC constant as does the Hz tie back to seconds.
Obviously you can't eliminate all constants, especially the irrational ones like Pi and e. At least not at our level of knowledge of math, and aliens doing it would be some scary crap to pick up on a transmission.
(Score: 2) by suburbanitemediocrity on Saturday November 17 2018, @10:04AM (1 child)
For all but a very small number of people, nothing will change at all
(Score: 5, Funny) by Bot on Saturday November 17 2018, @03:39PM
Are you kidding my AI? about 4 billion meatbags of the female variety are in this very moment anxiously asking around "will this new kilogram make me gain weight, or lose it?"
Account abandoned.
(Score: 0) by Anonymous Coward on Saturday November 17 2018, @10:19AM
The next system should be based on units that can be derived empirically using ordinary tools and methods, with female bodies as reference. Recognizing that there may be some variance from one to the next, practitioners will be advised to measure as many as possible and average the results to obtain robust results.
(Score: 2) by Unixnut on Sunday November 18 2018, @11:02AM (2 children)
> The Metric System was a fairly well thought out thing for the time but eventually we should probably do another rip and replace.
Yes, because since metric was created in the 1800s, we've managed to switch everyone over to one single standardised system, right?
Apparently it is not enough that we just ended up with two systems. In addition to SI units, I have to keep track of Imperial units (and even better, USA Imperial is slightly different to UK/Commonwealth Imperial).
What is really missing in this quagmire is a third system, to really add to the confusion. /s
(Score: 1) by khallow on Sunday November 18 2018, @01:19PM
(Score: 2) by Tara Li on Friday December 14 2018, @03:05PM
Actually, physicists use this all the time - they call it "natural units" - https://en.wikipedia.org/wiki/Natural_units [wikipedia.org]
Unfortunately, the XKCD strip still applies - there's a number of ways to get sets of "natural units". The most commonly used set is based around the Planck constant, but there are others...
(Score: 1) by Sulla on Saturday November 17 2018, @08:49AM (9 children)
Call it whatever you want, measure it however you want, there are two systems of measurement easily available. One of them got us to the moon and the other is metric, some fancy ass ceremony wont change that, unless of course they rename the gram the moonlander.
Ceterum censeo Sinae esse delendam
(Score: 0) by Anonymous Coward on Saturday November 17 2018, @09:02AM (1 child)
One of them got US to the moon and the other got everyone else to Moon and Mars
(Score: 0) by Anonymous Coward on Saturday November 17 2018, @02:38PM
So why is it then that the ones who got to the Moon are the only ones who can land on Mars?
(Score: 1, Insightful) by Anonymous Coward on Saturday November 17 2018, @10:37AM
One got you to the moon and very nearly screwed everything up to hell and gone.
Try again.
(Score: 3, Insightful) by bzipitidoo on Saturday November 17 2018, @02:58PM (2 children)
We got to the moon in spite of the crappy, antiquated, confusing mess of a measurement system, you mean.
At least one Mars mission failed thanks to confusion between measurement systems.
(Score: 2) by hemocyanin on Saturday November 17 2018, @04:47PM (1 child)
It's also worth noting that when true precision is desired using inches as a foundation, the preferred fractional unit is the thousandth of an inch -- a base ten value.
(Score: 0) by Anonymous Coward on Sunday November 18 2018, @04:37AM
And because it's not confusing enough, I give you the following from Wikipedia, emphasis mine:
That's right, the common verbal shorthand for the millimetre is also used, in north america, as a verbal shorthand for a thousandth of an inch.
/headdesk.
(Score: 2) by linkdude64 on Sunday November 18 2018, @01:54AM
" One of them got us to the moon and the other is metric"
Fuckin' BOO-YAH.
(Score: 1) by DrXenos on Sunday November 18 2018, @02:58AM
You're a fucking idiot.
(Score: 1) by zzarko on Sunday November 18 2018, @09:36PM
I'm sorry to bust your bubble, but metric got you to the moon:
https://www.doneyles.com/LM/Tales.html [doneyles.com]
"Inside the computer we used metric units, at least in the case of powered-flight navigation and guidance. At the operational level NASA, and especially the astronauts, preferred English units. This meant that before being displayed, altitude and altitude-rate (for example) were calculated from the metric state vector maintained by navigation, and then were converted to feet and ft/sec."
C64 BASIC: 1 a=rnd(-52028):fori=1to8:a=rnd(1):next:fori=1to5:?chr$(rnd(1)*26+65);:next
(Score: 2) by darkfeline on Monday November 19 2018, @06:43PM
Why doesn't the summary include the most important bit of information, what the new definition is?
tl;dr using new technologies, the Planck constant was measured more accurately and then declared as a constant by fiat using the average of multiple measurements. The Planck constant can be expressed as kg, m, and s, and m and s are both well-defined, et voila.
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