Le Kilogramme is to walk the Planck.
International boffins are mounting a determined diplomatic push to end the practice of measuring mass by reference to a 130-year-old metal cylinder kept in France, saying that the French ingot is no longer up to the job. The Consultative Committee for Units, whose chairman is Blighty's Professor I M Mills FRS, and which counts …
The reason we use a 360 degree circle and 60 seconds in a minute are because of the factors you can get from this. A base 12 measurement system gives you more factors to work with than base ten, which gives you five, two and... ten. With base 12 you get five, two, ten, six and three, which is easy to understand when you're working with fractional mathematics. Fractions, I find, are more intuitive than decimal maths. Get a decimal point on the wrong place and you're out by an increasingly large factor. Get a fraction wrong and it's obvious immediately.
By curious coincidence the length of a yard, and a foot (and consequently an inch) can be derived using nothing more than a time standard and the motion of the stars. Despite popular belief these measurements aren't based on some sovereign's oversized foot, which is why they're remained so constant for so many thousands of years (tens of thousands if you count the megalithic yard).
This is the best page I could find describing the process:
Now, the problem with imperial measurements isn't an inherent one: they lack standardisation, which isn't a flaw of the units but of the people using them. Many were derived from the existing basic units for use in agriculture, and others were modified to fit that use (the mile used to be 5000 feet long, the same distance as used by the Romans, but was modified under Elizabeth the first for some reason). The solution would be standardisation, which was never actually tried on anything other than an ad-hoc and contradictory basis (most of the criticism of imperial measurements is how ad-hoc they appear, which is true if you take the entire gamut of measurements grouped together under "imperial", many of which were taken from informal measures for various things but which aren't actually related to the basic units). If you go back and work from the basic measurement of the inch, foot and yard you could create a set of standard measures for weight, volume and length that would be far more versatile than base ten metric. It would be rather revolutionary.
On the other hand metric can be converted between units counting on your fingers, if you're willing to give up some flexibility and a few useful factors. It's all about what you want to do with it.
Advocacy over. :)
I agree with all of that and I would add that the current metric measures also lead to unwieldy amounts like 498 ml cans of stuff which might have been measured imperially using single digits.
Metric measures may be easier to calculate with arithmetically (being based on units of 10) but they don't actually make for handy numbers in real life..
"A base 12 measurement system gives you more factors to work with than base ten, which gives you five, two and... ten. With base 12 you get five, two, ten, six and three, which is easy to understand when you're working with fractional mathematics."
Copy-paste fail, one presumes? But I have to ask... what were you hoping to save time on?
The metric system is the only one that can be used for accurate microscopic measurement. Also, the metric system is MUCH more intuitive since division by ten is easier than divisions by 12. You think the Imperial system is more intuitive only because it is the one you have been using. Try to measure the larvae of bed bugs on my laboratory using the Imperial system and you will never use it again in your life.
Have said that, there is a reason why the Imperial system lacks standartisation: It is based on a very old method of measurement that has not evolved because it has no precision for scientific application. No reason to have two systems imo.
"The metric system is the only one that can be used for accurate microscopic measurement"? Bullshit. Just like you can measure a billionth of a metre, you can measure a billionth of a yard. Your problem is simply that your tools are set up to provide easy access to SI units.
@ Graham :
Surely multiples of 12 aren't used much in Imperial weight systems (unless you're talking the 12 troy oz in a troy pound) - 12 is more commonly used in money calculations (12 pence in a shilling, 240 in £1) ?
The main multipliers in the Avoirdupois weights system are 8 and 7 (16 oz in a pound, and 14 pounds in a stone - hence everything upwards is neatly divisible by 7 and 8). Why ? ~ because there are 7 days in the week, and the Roman army unit was eight men (as the British Army unit still is).
So a hundredweight (112 lb) of wheat, for example, easily breaks down into 1 stone per man; if it has to last them a fortnight, they each have exactly 1 pound per day. One pound of meat = 2 oz per man, etc. That's where the metric system really falls down, just try splitting a ton of horse feed into 7 equal parts.
(Also - IIRC - there is a theory that the Mesopotamians - from whom we get our 360 degrees & 60 minutes - used base 60 because they counted using each joint on each finger, not because they knew it could easily be broken down into factors. Though they may just have been clever bastards.)
If only the author of Genesis had decided that god creating the world in 8 days instead of 7, we'd all be working on a base-2 system. 64 minutes in an hour, 16 ounces to a pound, 128 pounds to a hundredweight...
And who wants to be a millionaire would be satisfyingly binary all the way up.
Heh. The Mesopotamians and Babylonians also started western astrology. Most people are familiar with the 12 signs of the Zodiac. However, each sign (or house) was divided into three decans (because there are three signs ruled by each of the four elements, natch) and each decan was graduated into 10 degrees (for accurate recording of the positions of the planets - do keep up). 12 houses make 36 decans make 360 degrees. Simples! So much nicer than those dreary new grads, too.
If it's ease of use (and factorization) that you want, I'd say go for a binesimal system: divide the circle in half, then keep halving the divisions until they come out small enough, like with a compass rose. How does a 512-degree circle (and a 128-degree right angle) sound? 'Cause, as any physicist will tell you, the only measure of angle that's scientifically meaningful is the radian, and I can't really see Joe Public getting to grips with that.
...if someone breaks in there and slices a bit off, will everything weigh more? It sounds like some crazy villain's plot to take over the world - when the kilogram weighs less he'll be able to get into some bank vault because the pressure sensors calibrated to 50 kilograms won't work anymore, etc etc...
"Elaborate precautions are taken to ensure that the kilogramme doesn't change mass - a complicated official cleaning procedure is carried out to remove atmospheric oxidants from the surface. "
This is ridiculous. All they need to do is give it two coats of epoxy varnish and the problem is solved.
He wouldn't need to get into some bank vault by devious means, accessing it in the conventional manner will do.
1) Deposit 100 kilos of gold ingots in bank vault. Get receipt for same.
2) Saw 30% off the standard kilo.
3) Withdraw 100 kilos of gold from bank vault.
4) Wait for new kilo definition issue to be resolved.
> the measurement should be a gramme, not 1000 grammes
The choice is somewhat arbitrary; just because gram doesn't have a prefix doesn't mean it is the basis for the unit. After all, a liter isn't really a base unit either, being a volume of 1 /1000 of a cubic meter... What determines the basis for the set is really just convenience.
There are two basic SI 'sets' of units, the MKS set (meter, kilogram and second) and CGS (centimeter, gram and second). The MKS set is the most common, as it is a good set for 'ordinary' things such as cars, factories,etc. The CGS set is preferred typically by the nuclear boffins, as the smaller unit set aligns more closely with the smaller scales involved.
Metric building/engineering plans are almost always in mm, even for "big things" like houses, cars and the like.
Nuke boffinss will likely be dealing with far smaller units than mm. As soon as you start using exponents then you use metres: 55x10^18m. Nobody uses exponents with mm.
Centimetres are just a low-brow measurement for "something about the same magnitude as an inch". Use them in any professional capacity (building trade, science, etc and you'll be marked as an impostor).
or of course an american, they do love their centimetre. dolts
even better than that, in some states some utilities use imperial and others use metric, giving rise to such wonderful questions/statements as 'our 110kV cable runs 85m alongside the road, 3m from the kerbline, the 9 inch watermain joins out route 54 feet from one end and runs 12 feet 6 from the kerbline... so when we energise will there be a bang?
metic is the only rational system, I had endless arguments with my old man about factors of this that and the other, and roman soldiers getting their bread for a fortnight. it's all bollocks.
Any measurment system can me useful so long as there are human scale units in there - microfortnight, attoparsecs, or indeed the bulgarian airbag all work. though with a rational system you dont need to remember millions of factors to convert between them eg feet per second into miles per hour etc etc etc
more interesting question is _why_ is THE kilo gaining weight whe compared to al lthe witnesses?
If a bunch of spanner-wielders want to use something else, then fine, but the SI units of meter, second, second, ampere etc. and the derived quantities, like the Newton, were agreed on by the scientific community in 1960. They are defined by physicists and it isn't going to change.
The CGS units are not SI units by the way. It may be an alternative metric unit, but SI it is not.
Isn't the Pound (1 lb) odd enough, considered along with its siblings: grains, ounces, stones, hundredweights, tons, and you really don't want to know about its cousins. Oh, you do? Well google "Imperial Units of weight"
The centihundredweight (or cCwt?) might be amusing: cancelling, you get exactly one weight. (1 wt.)
In passing, why do the French use tonnes, when clearly they ought to use megagrammes?
They're pretty unreactive elements so unlikely to accumulate mass by grabbing oxygen atoms from the atmosphere. The iridium is probably there to harden the platinum.
There is a project to calculate the kilogram as the mass of a certain number of atoms of a crystalline substance such as silicon:
The other reason they use the platinum iridium alloy is it is also very dense. The smaller the volume, the smaller the error introduced during measuring from it's buoyancy (i.e., the amount of air it displaces). It may not seem like much, but when you're worried about fractions of a microgram, it becomes important. If you still doubt it, consider the complications of weighing (in air) the standard kilogram if it was defined as a the mass of certain volume of helium...
One of the contaminants that they found on it just before the official polisher retired was mercury. They wondered where the hell it came from and then realised that people were breathing it out from their fillings.
I think I am never going to breathe in through my mouth again; mercury poisoning is not very nice!
Disbelief have I.
More likely that the Mercury came from the gills of all the fish in the atmosphere.
Mercury in good old British fillings is already bonded with silver quite tightly.
Unless, of course, this is evidence of yet another French Innovation: Silver-free amalgam fillings.
I've had "dangerous" amalgam fillings in my head for nearly 50 years and it hasn't harmed me.
Major Frisnit le Boeuf en Croute (Mrs).
That's only one of several competing contenders for an updated definition.
One idea that I tend to like is to simply count the number of atoms of a certain isotope, and define Avogadros constant at the same time. A kilogram would then simply be defined as the weight of a certain number of Carbon-12 atoms.
and that it varied depending upon your location in space...? I'm as thick as one though - a plank, that is - so may be feeling the sword point at my back.
Perhaps it is adequately specific and accurate for local purposes but then again so may be the mass in Paris.
Sound like a lot of effort for nothing dramatically important. Or have I missed the fundamental point at debate here? Is this the most important 'Standards' issue or just the one that will catch the most headlines and earn the most grants?
However, looking into this, I see that its value is rather contentious after about 9 significant figures, which makes one wonder whether these microgramme variations in the kilogramme standard are really much to be worrying about, and whether the Planck solution is actually any more reliable.
If Planck's constant is constant, then even if we don't know it to more than 9 sig fig today, any definition of the kilogram based on it would be reproducible to whatever level of experimental accuracy we are capable of in the future. It's that reproducibility that matters here. We're not trying to measure the mass of that cylinder, we're trying to compare other masses with it and hoping to get the same results as other people who are also trying to compare other masses with it.
If Planck's constant varies, then either it varies on a cosmological timescale, which wouldn't bother us in the near future, or we've discovered some exciting new physics. I doubt any physicist would consider the latter to be a problem.
Lastly, although I haven't looked at this particular issue, it wouldn't surprise me if there are reasons why we can be certain of the constancy of Planck's constant to rather more sig figs than we can be certain of its actual value.
As I heard it, there's one elderly bloke allowed to do this. Apparently he knows how to do it without rubbing off any of the actual kilo.
Personally I find the fact that you can currently put a serious crimp in the laws of physics using only Vim and a Brillo pad rather amusing.....
Back in my undergraduate days, we used to joke about it being the Planck Very-Nearly-Constant. Oh, we were a laugh-an-aeon, I can tell you.
In all seriousness, Planck's Constant will (likely) vary over cosmological time, so we may have to come up with a new measure by the time the sun burns out, or we get flying cars, whichever comes first.
"But it is compared from time to time with other exact copies held by other nations, and it is known that in reality slight changes on the order of microgrammes - a billionth of a kilo - do occur"
And how do they know it is not the "exact copies" that have changed mass ? (and clearly they can't be exact copies!)
And how do they do the measurement ? Which "unit" do they take to the other to do the comparison, and would this "transportation" of one unit not introduce substantial risk of change (e.g., when it gets X-rayed at the airport, could the x-rays knock off a few atoms, thus changing the weight)
"All the scientists do - as well as most engineers etc"
They don't all use metric. Britain's martian probe burned up on entry because the Brits specified something in metric and the US space boffins in charge of transporting it read the figures as whatever passes for Imperial in the US. Are those guys just engineers, or is it rocket science?
I must be about 45 years younger than I thought: as a schoolboy in England in the sixties, doing sciences actually, as well as the usual maths, we definitely used the metric system. I do remember the usual mental arithmetic questions in the mid to late 1950's (how much does a dozen eggs cost at 3 farthings an egg .... Absolutely invaluable skill now). I even recall my first physics laboratory lesson, working out that one inch is 2.54 centimetres.
Actually, I think UK was metric for scientific matters much longer than that.
As for the US, apart from short-changing most of the world in most things, they even short-change themselves in liquid matters - took the wrong measuring bucket with them when they invaded the place, apparently.
> US : which DOES NOT use SI
The US imperial system is specified in SI base units much longer than the UK one. Stronger even, some of the so called Founding Fathers already made a case for SI (because they could get better standards info from their ally France than from the Brits that were still fumigating because of some lost tea).
IIRC the American Imperial System is defined in SI base units since the 1870s. Like the UK, it is the plebs that can't deal with it.
I hope I have this right, but I seem to recall from school that 1g is the mass of 1cm^3 of water (I assume there's a specified temperature applicable here, but who knows what that is). I also recall the school had a rather nice heavy wooden weapon^H^H^H^H teaching aid that was a 10x10x10cm cube.
Shirley then, all you need to do is fill the bath to the top, lob the block in and weigh the water that pours out. Platinum-iridium chamfered cylinder? Has the world gone mad? (Or just the French?)
Another subtlety is whether gravitational mass (commonly known as weight) is the same as inertial mass. It's been shown to very high accuracy that the two are equivalent for everyday forms of matter. But is the inertial mass of a kilogramme of electrons the same as that of a kilogramme of protons or a kilogramme of neutrons?
The US has always been metric, when they had their little tantrum over the tea in Boston harbour we wouldn't let them into the houses of parliament to compare their yard against the real one.
So the french lent them a metre ruler - but they didn't quite do the sums right which is why a US inch and a proper inch used to be slightly different - until we compromised on the international inch.
the thing I found most fascinating about the article is wondering how these fumbling fucks get paid. you want to hold a kilo of platinum (if it were pure, you're looking at around 35 grand for a hunk that big) in several nested boxes polished by some geriatric frenchman who probably has no other job, in some specially constructed little room of wonder?
how much does this anachronistic bullshit cost us versus just defining it via non-corporeal means? hell, if you'd put the price points in and shown us how The British Taxpayer Pays for French billion-dollar paperweight, the Daily Fail woulda picked this shit up in a heartbeat.
mines the one with the quarter of bonfire toffee. mmmn. toffee.
"Although it was later determined that the first prototype metre bar was short by a fifth of a millimetre because of miscalculation of the flattening of the Earth, this length became the standard. The circumference of the Earth through the poles is therefore slightly more than forty million metres."
Can we just define the mole as exactly 6 x 10e23 and round off all those other nasty constants? Let's face it, does anyone really care if a mole is about 0.37% off it's old number? I thought not, daltons are still daltons and the kilogram has been defined in more absolute terms; at least until something ionizes but who cares as long as they keep their hands off our bulgarian airbags.
Kinda like the Mel Brooks "History of the World, Part 1", where Moses comes down from the mountain and says: "Here are the 15 [drops one tablet] ooops, 10 commandments". Changing kilogram, might happen so, if it changes, will my body mass index change as well, and the government charge me more for my medical insurance if it goes the wrong way?
As for the US being on the SI system. Yes, it has been for many years. All our units are defined in terms of metric units. Like an inch IS 2.54 cm.
As for Troy ounces, Linux's units command yields that they are 31.1... grams. So when you see the late night ads for "gold leaf coins" that have 31 milligrams of gold on them, that is 1/1000 of a troy ounce, or about $1.34 or so, or not very much!
I'd far rather 'they' spent money educated people about SI prefixes.
I'm fed up with people who whine because they 'only' have a 4MB/s internet connection.
Or people who boast because they have a 50mb/s connection.
There's also no such thing as a 1tb disk. If there were it wouldn't store much data.
A liter of water (at 277K and 1*10^6Pa) is indeed 1kg, but try varying the temperature or ambient pressure a bit and you'll be sufficiently off to throw any semblance of precision out the window. And precision counts in definitions. So anything that doesn't rely on other measurements is to be preferred: [large_number of stable_atoms] is quite a bit better than [amount of fluid that goes in a container of some size at this temperature and that pressure]
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