In the balance: scientists vote on first change to kilogram in a century

The weight is defined by a lump of metal in a Paris vault - which could make Earth 'laughing stock of universe'

For the band of specialists in the much-overlooked arena of metrology, it will be the most profound moment in more than a century. Since 1889, one of the pillars of the science, the kilogram, has been defined by a lump of metal held in a triple-locked vault in a lab on the outskirts of Paris. It is the one true kilogram in the world.

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