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Nothing Weighs What It Used to Weigh!
Wait, did you see this horrifying thing on the kilogram, a measure of weight (yes, yes it is) that is actually tied to a real object? (Which affects the "pound," as the pound is now basically defined as 0.45359237 kilograms!)
Familiarly known as Le Grand K and held in a vault just outside of Paris under three bell jars, it dates back to the 1880s, when it was forged by the British metallurgist George Matthey from an alloy of nine-tenths platinum and one-tenth iridium. As a metric unit, the kilogram is “equal to the mass of the international prototype,” according to the official definition. In other words, as metrologists like to point out, it has the remarkable property of never gaining or losing mass. By definition, any physical change to it alters the mass of everything in the cosmos…. But comparisons since the 1940s have revealed a troublesome drift. Relative to the témoins and to the national standards, Le Grand K has been losing weight—or, by the definition of mass under the metric system, the rest of the universe has been getting fatter.
Systems! Mass! Concepts gone wrong! The Earth-centric conflation of mass and weight! Entropy! DARK MATTER! ISOTOPE DRIFT! THE END OF TIME! LET'S GO BACK TO BED. (via)
Finally, vindication! I knew learning metric was a waste of time.
Also, isn't it interesting that it's the kilogram, and not the gram, that's the fundamental unit? The other base units aren't like that!
@boyofdestiny setting internashunul standarz: ur doin it wrong
@boyofdestiny a very complicated topic. "Metric" actually encompasses a couple of different measurement systems. The current system – "SI" (from the French for "International System"), is "kms", or kilogram-meter-second… meaning all the other units are based on these. For example, the energy unit in SI is the joule: which is defined in kilogram meter^2/second^2. But before this they used the cgs system, for centimeter-gram-second. The energy unit in this system is the erg: gram centimeter^2/second^2. The bottom line: they settled on SI because it produced subordinate units that were convenient in size – in the case of energy, for example, it takes a really large number of ergs to describe processes of even ordinary energy, and when you're talking about, say, an earthquake, the numbers get absurdly huge.
@SeanP Ummm, physics major here, in case it wasn't obvious.
@SeanP : Oh good, you can check my math down below. (I was using "standard diameter of the Earth = 12756000 m")
@SeanP And yet astronomers still often use cgs, which makes me laugh. I guess when things are such large scale 10^(n+2) cm is just as absurdly huge as 10^(n) m and so you may as well get the advantage of cleaner E&M.
does this prototype make my ass look big?
@roboloki
Yes
I'm just heartened that the universe has decided to take up Michelle Obama's cause.
Does this mean our microwave ovens don't work anymore?
God's revenge for vanity sizing.
This is all just a centuries-long Knights Templar conspiracy to… to commit a sort of gentle prank on society, I guess. They just shave off a little of the kilogram every few months! For decades!
@deepomega Sounds like someone's been working on a spec script for National Treasure 3!
God. Does every article today have to be about Chris Christie??
/nerd on
Actually, the kilogram has theoretically been redefined as a certain number of carbon atoms (since there's a measurement, the mole, which is defined as "the number of atoms in 12 grams of carbon-12", you can theoretically put together that number of atoms to create 12 grams, and then size that up to a kg). If you could count out that amount of carbon atoms, you'd have a reference kilogram. Of course, counting out a big lump of a certain number of atoms is impractical, so the next-best theoretical method would be to take an existing lump of a completely pure element and carve it into a perfect sphere — basic math would allow us to determine the size of the sphere based on how many atoms we wanted in it. Interestingly, this is actually doable, and the practical realization of this method is in its final stages right now : it's a silicon-28 sphere of almost perfect roundness (they chose silicon because it's more stable, among other reasons). The "almost perfect" bit is "within a single layer of atoms" (~.3 nm on its radius). Since the nominal diameter of a 1kg Si sphere is 93.6 mm, a back-of-the-envelope calculation (not guaranteed accurate: please refute) reveals that the .3nm error in a sphere that size is roughly equivalent to a 4cm error in a sphere the size of the Earth. So there's your more stable reference kilogram, carved out of pure silicon to an extraordinary degree of accuracy.
/nerd off
tl;dr : New reference kilogram made out of a very very very close-to-perfect sphere of silicon. "Platinum supplanted by silicon" is definitely a sign of our modern age.
@Gef the Talking Mongoose As a fellow nerd, I found this interesting! I didn't know they were working on a new kg definition. (Aside: Do you love that the meter is now defined so that the speed of light is exactly 299792458 m/s? I do!)
@Alibi Jones : As with many things, Wikipedia is a. pedantic, b. exhaustive, and c. fascinating on the subject. I like that the meter has become another measurement that's very difficult to actually, uh, measure. Three cheers for laser interferometers!
WTF? It's metric. Who gives a shit? It's like weighing things in "stone." If it can't be parsed in sides of bacon, it's meaningless. You may as well do something in base twelve for all I'm going to use it.
Some of my favorite copy from a catalog was a 1990 or so era J Crew catalog that said their khakis were "the standard, like the platinum-iridium kilogram."
Christ, what a masshole!
Under THREE bell jars??? UNDER THREE BELL JARS?!?!?! Fucking French!
@kneetoe : Sylvia Plath = super jealous.