kilograms have been redefined after nearly 130 years
‘The extra accuracy will be a boon to scientist’ –
The wait is finally over, after nearly 130 years the kilogram was first defined by a lump of metal in a vault in Paris. Scientists have voted for a change and a new system that redefines the global measure of mass in terms of a fundamental constant of nature. Following a historic vote at the General Conference on Weights and Measures, in Versailles, 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,” said Stephan Schlamminger, a physicist from the US National Institute of Standards and Technology who has worked on redefining the kilogram for years. “They did a roll call of each country”. One got a sense of how big metrology is. ”The IPK, or Le Grand K, has served the world well but scientists have long known that even though, by definition, it is precisely one kilogram, its weight changes over time. When in use, the tiniest wear makes it lighter, while pollution in the air binds to the surface and over time makes it ever so slightly heavier”.
The new system retires the IPK and instead defines the unit of mass through the electrical force needed to counteract the weight of a kilogram on a machine called a Kibble balance. The electrical force itself is linked to the Planck constant through quantum electric effects described by two Nobel prize winners, Brian Josephson and Klaus von Klitzing. Along with the kilogram, three other base units will be redefined as a result of the vote. 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.
A historic judgment more than 60 nations come together to vote Unanimously for a new system that redefines the kilograms along with three other units, the ampere (electrical current), the Kelvin (thermodynamic temperature) and the mole (amount of a substance). On November 16, 2018, at the General conference in weights and Measures, in Versailles, Paris, the definition of kilograms was changed forever.
1. This November will be a Culmination of a process that began in 1875. That year, dignitaries from 17 nations signed the international Treaty of the matter making the metric system global in scope.
2. The treaty succeeds in creating the first common measurement system for International trade and the global exchange of ideas. The artefact standards on which the system was based were housed on specially designated International Bureau of weights and measures (BIPM) in France.
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