Crunch time for the kilogram [News]

K50 is going on a trip. Sometime soon, the golf-ball-size cylinder of platinum and iridium, which makes its home in Ottawa, will be carefully packed up and hand carried by a member of Canada's diplomatic corps on a plane to France, with special instructions that its case not be opened by customs or airport security. This precious cargo will join a small clutch of similar objects that will trickle into Paris in the coming weeks. Their destination: the International Bureau of Weights and Measures (BIPM) just outside the city, where they'll be compared with one another to see just how well their estimated masses match up.