After almost 130-years, the kilogram which was first defined by a lump of metal in a vault in Paris is going to change as scientists have voted for a new system that redefines the global measure of mass in terms of a fundamental constant of nature.
After a historic vote at the General Conference on Weights and Measures, in Versailles, on Friday the kilogram will no longer be defined by the international prototype kilogram (IPK), a platinum alloy cylinder fashioned in 1889, but by Planck’s constant, a number that is deeply rooted in the quantum world.
“The vote went through unanimously. It was very emotional. They did a roll call of each country. One got a sense of how big metrology is.” Stephan Schlamminger, a physicist from the US National Institute of Standards and Technology was quoted in a report.
Schlamminger worked on redefining the kilogram for years.
Meanwhile, with the kilogram, as a result of the vote, three other base units will be redefined. The units for electric current (ampere), temperature (kelvin) and amount of substance (mole) all become linked to constants of nature, namely the electric charge, the Boltzmann constant and the Avogadro constant respectively.
Director of the International Bureau of Weights and Measures, Martin Milton, called the redefinition as “a landmark moment in scientific progress”.
The redefinition will not affect the was fruit and vegetables are weighed.
The changes will come into effect on 20 May 2019, world metrology day.