The official prototype of the kilogram loses weight

The metal cylinder, which is in custody near Paris, has lost about 50 micrograms, the weight of a fingerprint

Avi Blizovsky
The pound isn't quite what it used to be. A 118-year-old cylinder used as the prototype for the metric system and kept under close guard outside Paris is mysteriously losing weight, albeit at a small rate. Physicist Richard Davies of the International Bureau of Weights and Measures in Sèvres, southwest of Paris, says the reference kilogram has lost about 50 micrograms compared to his dozens of replicas.
"The mystery comes from the fact that they are all made of the same material, and many of them were cast at the same time and under the same conditions, but now, their masses keep changing," he said. "We do not have a good hypothesis as to the reason for this.
The ambiguity regarding the kilogram may affect countries that do not use metric measures - this is the standard for the US customs system, for example, where it is equal to 2.2 pounds. For scientists, the non-constant constant of the meter is a nuisance because it interferes with the calculations of operations such as electricity generation.
They depend on mass measurements and it is not convenient for them to have an exclusion of a kilogram based on some artificial objects," says Davis, who is American by the way.
However, this slight erosion in the weight of the kilogram should not be expected to have a practical effect on those who carefully watch their waist circumference: 50 micrograms is barely equal to the weight of a fingerprint. "To the common man, it means nothing," says Davis, "a kilogram will remain a kilogram."
And on the same subject: the British will be able to continue using English measurements such as the mile, gallon (pint = one-eighth of a gallon) or pound (for weight), despite the long-standing decision that Great Britain and Ireland will align with the metric system with the rest of Europe until 2009.
The European Union allowed the British and Irish to use the imperial system alongside the metric system but not instead. This was decided this week in a decision that the British Guardian calls a U-turn of European policy.
Selling fruit and vegetables by the pound and ounce only has been illegal in the UK since 2000, causing an uproar among traders accustomed to the old system.