IPK

From Artifact to Constant – Redefining the Kilogram

In the Saint-Cloud, France facility of the International Bureau of Weights and Measures sits a small platinum-iridium cylinder.  It is stored under two glass bell jars and, is kept under lock and key.  This piece of metal is the International Prototype Kilogram.  Since 1889, it has been the standard against which all other mass values…
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