Outside In | The end for ‘Le Grand K’, but let’s not forget the importance of correct measurement
Measurement provides structure, removes chaos, reduces waste, ensures open and fair markets, supports precision where required, and saves lives, money and time
After 138 years of rule from inside a triple-locked vault in Sevres outside Paris, “Le Grand K” seems about to be retired. The arcane world of metrology is afire. I for one will be sad. At the very least it is the end of measurement as we know it. At worst it feels like measurement gone mad.
For those unfamiliar with the fastidious world of metrology, Le Grand K is a little lump of platinum-iridium alloy that was forged in 1879 to provide the world with the definitive measure of a kilogram.
Since it was forged – and benchmarked against six official copies – Le Grand K has been allowed out of its vault only four times, for a quick but careful clean, and to be compared against its six copies.
And here is the crisis: when last allowed out in 1991, it was found to be 50 micrograms lighter than the average of its copies. That, by the way, is about the weight of a fly’s wing.
Le Grand K’s guardians are not sure if it is Le Grand K that has slimmed, or whether its comparators have gained weight. But for the world of measurers, this was not good news, and something had to be done about it.
