The International Prototype of the Kilogram in three nested bell jars
(Photo: BIPM)
Did you gain a bit of weight after the holidays? Take heart, you’re not
the only one – even the kilogram itself has put on weight:
Using a state-of-the-art Theta-probe XPS machine — the only one of
its kind in the world — the team have shown the original kilogram is
likely to be tens of micrograms heavier than it was when the first standard
was set in 1875. […]The original kilogram — known as the International Prototype Kilogram
or the IPK — is the standard against which all other measurements of
mass are set. Stored in the International Bureau of Weights and Measures
in Paris, forty official replicas of the IPK were made in 1884 and distributed
around the world in order to standardise mass. The UK holds replica
18 at the National Physical Laboratory (NPL).But despite efforts to protect the IPK and its duplicates, industrialisation
and modern living have taken their toll on the platinum-based weights
and contaminants have built up on the surface.
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