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Standard Kilogram Gains Weight
mrbluze writes "The standard kilogram weights used by countries around the world for calibration have variably increased in mass by tens of micrograms. This poses a threat to the precision and comparability of measurements in science, engineering and trade. The problem is due to surface contamination, but a safe method of cleaning the weights has only recently been devised by the use of ozone and ultraviolet light (abstract). 'The ultraviolet light-ozone treatment removes hydrocarbon contamination that has built up on the metal surface, gunk that comes from the emissions of an industrial society. Cumpson suspects that because the kilos living in national labs have been retrieved and handled more frequently than the international kilo, more carbon-containing contaminants have built up on them over time. Incubating the kilograms with a set amount of ozone and ultraviolet light "gently breaks up the carbonaceous contamination at the surface."'"
its a matter of record keeping
if you know it weighed X in 2000, and it weighs Y in 2013 whats the problem, it grew shit or dorito boy finger fucked it 30 feet away from the ocean
the whole idea seems backwards, there are changes we can not control, but instead we change the thing we actually can?
Your error: " the American "pound-weight" has mostly been defined in terms of the kilogram"
Sorry, you fail. The US Govt maintains a standard "pound", a standard "foot", etc. These units are precisely defined mathematically and also there are standard objects in their facilities that match the definitions and (for units of mass) are made of a metal that is not decaying (sorry, I don't recall what metal they used but you can probably google it). Any US measuring device that is sold as a "calibrated instrument" has documentation showing its "traceability" back to those standards. The "closer" an instrument is to the NIST standard (in other words: somebody calibrated something to the actual "standard" at NIST, and then used THAT to calibrate other things, which were then used to calibrate other things etc), the more accurate it is presumed to be.
Your error is that you apparently misunderstood that the US Govt has defined a set of standard conversions which are acceptable to use to mathematically convert from things like meters to feet, or kilograms to pounds where such conversions are more practical and where the user understands what he is doing