IN A VAULT under a courtyard near Paris lies a small, shiny cylinder of precious metal - and a big scientific embarrassment. Once a year three people gather outside the vault, turn their three keys simultaneously, and open the door. They have come to check that the small, shiny cylinder is still there. Once satisfied that it is, they shut the door, say their farewells and depart - wondering how much longer science must endure this risible ritual.
It may only be 40 millimetres tall, but the cylinder kept under lock and key at the International Bureau of Weights and Measures (BIPM) at Sèvres in France is beyond price. For it is absolutely and utterly unique: the one object in all the Universe that has a mass of exactly 1 kilogram.
That is why teams of scientists around the world are hard at work trying to get rid of it. ...
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