The
Independent: The two men boarding the Eurostar to Paris
this Wednesday will be unremarkable, save for the metallic
suitcase they keep in their sight at all times. Their fellow
passengers could be forgiven for shuffling away as they eye the
words DO NOT DROP in red on the side of the case.Far from
transporting some doomsday device, the two British scientists
will be carrying a kilogram of harmless metal. But not just any
kilogram: it is the UK standard kilogram, used as the ultimate
reference for everything from the accuracy of a grocer's scales
to the ingredients in a pill.Actually, it weighs a fraction
more than a kilogram. And that is a problem: as the years go
by, it is gaining weight. Scientists from
Britain's National Physical
Laboratory (NPL) hope that cleaning the weight with a
revolutionary new method, invented in the UK, will bring it
back closer to its true mass. Long-term comparisons suggest
that other nations' benchmark kilos are also gaining weight
compared with the prototype in Paris â the
definitive kilo based on the weight of a litre of water at 4C
â which was cast in 1879.
