Securely tucked away inside a French vault is a lump of metal known as the International Prototype. A mixture of platinum and iridium, it was made in the 1880s to define the mass of a kilogram.But work by a team of Australians could help pave the way for the retirement of this century- old prototype, as weight and measurement experts across the globe work towards a more scientific definition of the kilogram.
CSIRO's optical engineers will form two perfect spheres from a 20-centimetre cylinder of exceptionally pure silicon that arrived in Australia last night. The silicon, which has taken three years to produce, was made in Russia and grown into a near-perfect crystal in Germany.
Scientists will use the spheres to determine how many silicon atoms make up a kilogram, and this will be used as the new definition — bringing the kilogram into line with other base units such as the meter and the second, which are all defined by physical constants.
This means the diameter of the sphere varied by an average of only 35 millionths of a millimeter, making it a top contender for the title of the roundest object in the world.
Link & Image: The Age
Tags: Silicon Sphere | Measurement | Kilogram | Mass
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