Scientists vote to kill the kilogram - “a landmark moment in scientific progress”
A historic vote means that the kilogram will no longer be defined by a piece of metal which was first conceived in 1889.
A historic vote means that the kilogram will no longer be defined by a piece of metal which was first conceived in 1889.
On the 16th November, 2018, a historic vote took place at the General Conference on Weights and Measures, in Versailles, which determined that the kilogram will no longer be defined by the international prototype kilogram (IPK), a platinum alloy cylinder fashioned in 1889, now safely stored in Paris. Instead, the kilogram will be defined by Planck’s constant, a number that is deeply rooted in the quantum world.
Whilst the IPK, or Le Grand K, has worked well as a unit of measurement, it has long been 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, whilst its weight can also increase when pollution in the air binds to the surface.
The new measurement system says goodbye to 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, Klaus von Klitzing and Brian Josephson.
However, the kilogram is not the only unit being redefined. Three other base units will also be redefined as a result of the vote. These include the unit for electric current (ampere), temperature (kelvin) and amount of substance (mole).
The other four base units in the International System of Units, including the unit of time (second), the unit of length (metre), and the unit of luminosity (candela) will remain unchanged.
Martin Milton, director of the International Bureau of Weights and Measures, said the redefinition was “a landmark moment in scientific progress”.
Now, weight and see what the Developing Experts team have planned for world metrology day, which falls on the 20th May 2019, to celebrate these historic changes coming into effect.