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The Future of the Kilo: a Weighty Matter (theguardian.com)
A lump of metal in a building near Paris has long served as the global standard for the kilogram. That's about to change. From a report: 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. And crucially much of the key work that has led to the toppling of the Paris kilogram has been carried out at the National Physical Laboratory where the late Bryan Kibble invented the basic concepts of the device that will replace that ingot in the Pavillon de Breteuil. The Kibble balance works by measuring the electric current that is required to produce an electromagnetic force equal to the gravitational force acting on a mass. A second stage allows the electromagnetic force to be determined in terms of a fundamental constant known as the Planck constant which will, in future, be used to define a kilogram. These machines will provide the standard for weighing objects -- and that means no more dusting of old lumps of alloy to ensure they stay pure and accurate.
[...] "One key reason for doing this work is to provide international security," says Robinson. "If the Pavillon de Breteuil burned down tomorrow and the kilogram in its vaults melted, we would have no reference left for the world's metric weights system. There would be chaos. The current definition of the kilogram is the weight of that cylinder in Paris, after all." [...] Another major motivation for the replacement of le grand K is the need to be able to carry out increasingly more and more precise measurements. "Pharmaceutical companies will soon be wanting to use ingredients that will have to be measured in terms of a few millionths or even billionths of a gram," says Prior. "We need to be prepared to weigh substances with that kind of accuracy." Suggested reading: A thread on Twitter which discusses SI units and the redefinition of the kilogram.
[...] "One key reason for doing this work is to provide international security," says Robinson. "If the Pavillon de Breteuil burned down tomorrow and the kilogram in its vaults melted, we would have no reference left for the world's metric weights system. There would be chaos. The current definition of the kilogram is the weight of that cylinder in Paris, after all." [...] Another major motivation for the replacement of le grand K is the need to be able to carry out increasingly more and more precise measurements. "Pharmaceutical companies will soon be wanting to use ingredients that will have to be measured in terms of a few millionths or even billionths of a gram," says Prior. "We need to be prepared to weigh substances with that kind of accuracy." Suggested reading: A thread on Twitter which discusses SI units and the redefinition of the kilogram.
Drug Lords everywhere will still be able to sell their Kilos.
I have nothing insightful to say except that I've been very interested in metrology for the last years, including the watt balance (now called Kibble balance), and am delighted that there may eventually be a standard of mass that doesn't depend on a physical artifact.
If the Pavillon de Breteuil burned down tomorrow and the kilogram in its vaults melted, we would have no reference left for the world's metric weights system. There would be chaos.
That would absolutely be inconvenient, because it is the master reference.
However, other reference kilograms exist, for example, the US National Institute of Standards and Technology has a kilogram and a meter. These secondary references are sometimes used to compare against the primary reference kilogram to ascertain drift.
It would be an annoyance to lose the master, but not a disaster.
Anyway it will soon be redefined in terms of nonphysical objects so the window of problem is small.
I assumed that it would be an electric scale + gravity measurement and not a balance that would ultimately determine the Kilogram.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
How would you use a device like this to determine the mass if you don't know the exact gravitational constant at the specific location you are at?
Or is there a way to determine it that does not rely on mass?
Originally a kilogram was the weight of one liter of water right at it's freezing point.
They scrapped that because it was too hard to duplicate at the time. I think it would be better to stick to that definition but just make it easier to duplicate. Starting from 100% directly distilled water and following a series of steps or something. Whatever needs to be done.
How do they make this work as the force of gravity is not constant over the surface of the Earth? Does it only work in one place?
The Future of the Kilo: a Massive Matter
With a laser functioning as "optical tweezers" one can isolate single subatomic particles (electron, proton, well-characterized ions ref: https://journals.aps.org/rmp/a... ) set the standard kilogram to the appropriate number of one of those and bid all your metal alloys under bell-jars bye-bye. That is, define the kilogram to be something like 1e30 electron masses or 6e26 proton masses. whichever is more convenient.
Making science great again!
...it's an opportunity to stick one on the French.
"Somebody has stolen the kilogram ingot - the world is about to be thrown into chaos!"
"Never fear Prime Minister, I, Inspector Clouseau am on the case and will find this horrid thief who has stolen this kilogram of nougat!"
"Ingot"
"Zat is what I said!"
OK, I get it, that some drug gets administered in microgram or perhaps even nanogram quantities.
But does a "kee" of that drug need to be measured to one part in 10^9? You could take that quantity of a drug, "cut" it in two, and keep repeat that process 29 more times to get, say, diluted drug doses containing a nanogram of the drug to 7 percent precision?
How precise do you need to administer a nanogram of active ingredient? Certainly not to 9 sig figs, so do you really need to measure out a kilogram to some insane accuracy?
https://www.npr.org/templates/story/story.php?storyId=112003322
Sub-atomic particles are squirrely. Why wouldn't you use a full atom? Lead atoms are huge and relatively easy to work with. They are also pretty damn stable. I'm kind of surprised the reference ingot is made up of an alloy.
There is a much simpler solution than trying to redefine the kilogram.
They should just use pounds instead.
I understand that some journalists from some backward countries used to "pounds" (that are not even well defined enough for precise mass measurements) are confused with words they don't understand, but "The Future of the Kilo" is unspectacular: It continues to be a prefix meaning a factor of exactly 1000. No changes or re-definition planned.
Mod this one up! The pharmaceutical industry don't need this kind of accuracy. Why do we always go to the pharmaceutical industry to try to justify everything? Every Nobel prize is awarded to someone for something that could one day be useful for making better pharmaceuticals. I was kind of hoping the old weights and measures guys wouldn't fall into the same trap.
Officer: Sir, you were going 100 mph in a 35 mph zone.
Me: Officer, I was trying something that one day might help us develop better pharmaceuticals.
officer: Oh, in that case you can go. Drive safely
Kg quantities of a drug do not get made in the development phase. Usually they get made in mg quantities to about a couple of grams. Making drugs from scratch is expensive.
Why would you polish an object kept under two glass bell jars except for the periodic polishing? Where is that dust coming from? Is it made of neutrinos?
"Made up/misattributed quote that makes me look smart. I am on
Mod this one up! The pharmaceutical industry don't need this kind of accuracy. Why do we always go to the pharmaceutical industry to try to justify everything? Every Nobel prize is awarded to someone for something that could one day be useful for making better pharmaceuticals. I was kind of hoping the old weights and measures guys wouldn't fall into the same trap.
Officer: Sir, you were going 100 mph in a 35 mph zone.
Me: Officer, I was trying something that one day might help us develop better pharmaceuticals.
officer: Oh, in that case you can go. Drive safely
Don't be ignorant. Depending on the phase of drug development, sometimes only very small quantities of a drug get made (think 1-10 mg). Making the drug from scratch is horribly expensive. They don't want to make a huge amount only to find out after further research that the drug is too toxic, bioaccumulative, or useless. It's a waste of money. Furthermore, they'd then have to safely dispose of that experimental drug.
How about we take this opportunity to give the kg a new name so the fundamental unit isn't "kilo" something. Call it a kibble maybe. Or make the gram the fundamental one, fine too
Tell me about it. This is like the 54983289th time the Universe gets rebooted because of your damn drugs.
#DeleteFacebook
What about the researchers at the National Institute for Metrology Research, Italy, and the Australian Nuclear Science and Technology Organisation who are working on the silicon-28 sphere to redefine the kilogram in terms of the Planck constant by determining Avogadro’s constant?
Would you like to know more?
Sorry, teleporters just kill you and then make a copy. A perfect, soul-less copy.
You keep using this fundamental units, it doesn't mean what you think it means.
The SI system is a complete clusterfuck of "fundamental units":
* Amp depends on the definition of kg
* candela depends on the definition of kg
* Kelvin depends on the definition of kg
* Mole depends on the definition of kg
These units should be ORTHOGONAL; not dependent on one another.
The metric weight/mass system is based on a house of cards? I thought it was infallible.
And do you need to know whether you have manufactured 1mg or 1mg plus 1pg?
Which is exactly the kind of precision we are speaking about here. Don't mix absolute value with relative precision.
If the Pavillon de Breteuil burned down tomorrow and the kilogram in its vaults melted, we would have no reference left for the world's metric weights system.
It's been a while since I read about this, but I thought there were backup reference weights in London and at NIST. Even so, I always thought this particular metric unit seemed like a bad idea because of all of the issues it entails.
I say Massive.
because where he lives dozens of inconsistent "pounds" have been used as units, and not only for mass, but still today for a currency of decreasing value and relevance.
And I would not be surprised if the next vote there is on re-introducing imperial units, once the Brexit is done.
In non-metric, the velocity of the Earth around the sun is 66,600 miles per hour. Those freaks just love putting their numerology in!
Had those freaks succeeded in converting the USA to the metric system? It'd be "some other value" and wouldn't demonstrate their worship at a satanic altar.
If someone stole the kilogram, we'd have no reference for weight. One could say, we'd be weightless. In other words, gravity would cease to exist. The magnitude of this new found risk is, for all intents and purposes, immeasurable. Mother of God!
Did you hear about the homeopath that didnt take his pill and overdosed?
A good workable definition of pi based on integers is 355/113.
It's so close that it bugs me it isn't used more.
> If the Pavillon de Breteuil burned down tomorrow and the kilogram in its vaults melted, we would have no reference left for the world's metric weights system. There would be chaos.
Bullshit. There are 6 master copies and over 200 certified copies of the kilogram etalon, each country in the UN received at least one, some more (e.g. Hungary has the #16 copy). Their minute deviations from "Le Grande Kilo" are well known and marked down. (Being physical copies they cannot be perfect). In case of LGK loss, their consensus would re-establish the etalon.
> we would have no reference left for the world's metric weights system
Note that the imperial / customary systems of measurement have no reference whatsoever, even without a hypothetical blaze. UK / USA just says the pound is 0.453 kg, the foot 0.3048 is meters and let the frenchies (the SI) do the heavy lifting. So damn convenient...
It's the attempt of kill the metric system in favor of the english imperial system.
Power of 10 is very useful for the metric system thanks to 5+5 fingers of both hands.
The english imperial system is very stupid because it doesn't use the power of 10 for the measures.
Why would you ever consider replacing something simple that works, with something complicated?
You might notice they don't all depend on each other, they are all defined in terms of the kilogram. That means you can know exactly how much a liter of water weighs. Further, that density of water doesn't change as the accuracy of our measurements improves.
The kilogram was originally created by weighing 1 L = 1 dm3 of pure water at the temperature of maximum density (about 4degC), but it turns out that this is a fiendishly difficult measurement. Water is liquid, so you need a container, and it evaporates, its density is affected strongly by temperature and weakly by atmospheric pressure, surface tension does odd things, there's such a thing as "heavy water", and so on.
It's difficult to make this measurement to better than 1 part per million. So if two laboratories (which we for simplicity assume can measure lengths and volumes perfectly) both try to derive mass from volume using water, they will only agree to 6 decimal places.
But comparing standard kilogram metal weights can be done to micrograms, which is a few parts per billion uncertainty.
So I can weigh the metal weights relative to each other to 9 decimal places, but relative to water to only 6 decimal places. It's better for everyone if we use one of the metal weights as the definition, because that will let us weigh other metal weights to 9 digits, without affecting weighings of water (which will still be accurate to 6 places).
Metrology standards are routinely redefined in this way when new technology comes along which permits measurements relative to a new standard more precisely than was possible using the old standard. Some scientists work very very hard to measure the new and old standards relative to each other to a precision greater than any previous measurement relative to the old standard, so that no previous measurement is invalidated by the change.
This has already happened to the kilogram. The water-based definition was decided on in 1795. In 1799, after having spent a few frustrating years weighing water, a platinum kilogram weight was created as the standard to be used from then on. (The "Kilogramme des Archives". Platinum was chosen because it's very dense, minimizing "air bouyancy" corrections, and because it's extremely chemically inert, so doesn't rust or corrode.) But pure platinum is a bit soft, and the "Kilogramme des Archives" was getting dinged during weighings.
So in 1875 a new kilogram (the "international prototype kilogram") was made out of a platinum-iridium alloy, which has all of platinum's advantages and is much harder to damage.
Anyway, although we can measure metal weights relative to each other to 1 part per billion, it turns out that if you take two identical such weights, store them very very carefully under identical conditions for 50 years, and then re-weigh them, the relative weights have changed by up to 50 parts per billion!
This is a big problem. We don't know what is causing that change (one plausible suggestion is carbon soot and mercury pollution in the air has been sticking to the surface of the weights) or how much any single weight has changed (we can only measure they relativechanges), but clearly at least some of the weights have changed by at least 50 ppb over the last half-century.
So that is a fundamental limit on how accurately any past measurement in kilograms has been.
The new definition is actually not as good as 1 ppb in a single day, and we'll continue to use metal weights for day-to-day operations, but has the big advantage that it doesn't change over time, so in 20 years' time we'll still be able to reproduce it to 10 ppb accuracy.
These days, we know the maximum density of water isn't quite 1 kg/L (it's 999.97495 g/L at 3.983035degC when using VSMOW). But it's equal within the accuracy of any measurement made prior to the redefinition of the kilogram in 1799, so the redefinitions hurt nothing (and helped a lot).
Take 50 mcg of sufentanil and get back to us on that.
I don't trust atoms -- they make up stuff.
OK, so let's say they're talking about a specific does. Fentanyl, for example, is lethal to an average human at 3mg, with therapeutic doses as low as 10mcg. In other words, a single does can be a few millionths of a gram.
But nobody's going to be mixing individual doses. A company will be mixing thousands to millions of doses at a time.
Furthermore, nobody manufacturing drugs needs to measure mass that accurately. If your mass standard is 2ppm too high then you'll just end up with 2ppm more drugs than you thought you were getting. It's the ratio that matters, not the absolute mass.
dom
What's the weather like in Moscow today? Miserable, as usual, I am guessing.
This goes beyond a weighty matter, it's a massive issue
Your message title says "Austria", your message body says "Australian". Where are the researchers really based?
Dammit, I just bought a new jar of kilogram polish.
https://www.design-engineering...
This just proves that the English system is better. No worries about kilos, just pounds.
A good workable definition of pi based on integers is 355/113.
FWIW, using gmp and Rmpfr with 200 (binary) digit lengths, comparing 100-digit representation of pi to 355/113 gives an error of 2.7E-7 .
Aren't you glad you asked?
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
Making drugs from scratch is expensive.
Tell that to the meth cooker who does it on the cheap. We can't all be Walter Whites you know!