02/11/2014

The Kilogram moves from Platinum/Iridium to a Plank

In October the Kilogram turned 125 and the current International Prototype Kilogram based on a 4cm rod of Platinum and 10 Iridium is going to be phased out in favour of a new Kilogram based on a fundament constant of nature.

The IPK is based at the International Bureau of Weights in Sevres, France with 6 copies spread across the world, but time is having an effect and the weights do not agree with each other and the disagreements are increasing (each time measurements are taken the IPK has to be handled).

The new Kilogram will be based on the Plank, which will be measured using a watt balance (in a vacuum, developed by the National Physics Laboratory in Teddington) and is worked out by measuring how much current is required to move the balance, this will also mean redefinition of the ampere (which will be based on the charge carried by a single proton), but if gravity is known at the measuring point, it all works out from there.

This won't happen overnight and assuming all goes well the new standard will come into force (sic) in 2018.

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