The team achieved its result using a Kibble Balance purchased from the UK’s National Physical Laboratory in 2008. The Kibble Balance allows an object to be weighed by balancing it against an electromagnetic force, rather than against an artifact such as the standard kilogram.
The work is said to have brought the international system of units (SI) to the point where, within a year, all basic units will be calculated mathematically – something scientists have been working towards for 30 years.
Barry Wood, an NRC Fellow, said: “While some aspects of every scientific breakthrough can be attributed to luck, our achievement stems from continually improving each and every component through perseverance.”
For more on the NPL's work on replacing the standard kilogram, click here.