On the outskirts of Paris, in a locked vault to which only three people have the key, lies a treasure worth more than its weight in gold. It's even worth more than its weight in platinum and iridium, ...

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We’ve long known that there were some issues with France’s ‘Le Grand K’, the international prototype for what a kilogram really is. Made in 1879 from platinum and iridium alloy, it is the perfect ...

Contaminants have made the standard kilogram weigh slightly more than it originally did, but a careful cleaning method may slim it down. Sophie Bushwick reports How do you define one kilogram? Easy: ...

France holds the world’s standard for the kilogram weight. It’s a cylinder-shaped object that has dictated all other kilogram weights for 130 years now. As it’s made from platinum-iridium though, the ...

More than a century ago, a small metal cylinder was forged in London and sent to a leafy suburb of Paris. The cylinder was about the size of a salt shaker and made of an alloy of platinum and iridium, ...

Since 1889, Le Grand K, a sleek cylinder of platinum-iridium metal, has ruled from its underground vault in Paris. An absolute monarch, it was the very definition of 1 kilogram of mass. Scientists ...

One of the most illuminating high school courses no doubt for many readers as much as for your scribe, was the series of physics lessons during which the SI units were explained. That glorious sense ...

Hackers, advanced hobbyists, makers, and hands-on physics experimenters are always looking for their next great project, and I think this is a good one: an apparatus to establish the “standard” ...

How do you define one kilogram? Easy: it's the exact mass of a metal cylinder called the International Prototype Kilogram, IPK for short, kept in controlled conditions in France. But the standard ...