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 ...

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, ...

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: ...

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Breakthroughs, discoveries, and DIY tips sent every weekday. Terms of Service and Privacy Policy. This week, Sam Kean takes a look at some ridiculously precise ...

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 ...

The kilogram is currently defined by a lump of metal in Paris – but now researchers in the UK, France and Sweden have confirmed a key assumption of a new method of defining the standard based on ...

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 ...

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 ...