Scientists to update definition of the kilogram

The unit of mass is currently defined by a lump of metal stored in France

Kilogram, weight
(Image credit: Wikimedia Commons)

Scientists are preparing to officially update the definition of a kilogram after using an old metal prototype as the global reference for almost 130 years.

Since 1889, the exact mass of one kilogram has been based on an object known as Le Grand K, a cylinder of platinum and iridium, which sits under three glass bell jars in a locked vault outside Paris.

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