Why does a kilo weigh more than a kilo? | Chronic

This Monday, May 20, the new official definitions of several units will be implemented, including the kilogram, the kelvin, the ampere and the mole, as agreed last November at the General Conference of Weights and Measures (GFCM) who had Place at Versailles (France).

The date of official adoption of the new International System of Units (SI) by nearly 100 countries – including Argentina – is not a coincidence: this Monday is the World Day of metrology, which celebrates the science of measurement.

The change is seen as a fundamental renewal of the way humanity measures things.

The definition of the kilo hitherto depended on the metal cylinder called "Gran K", the original of which has been preserved since 1889 at the International Bureau of Weights and Measures (BIPM) in Sèvres, a few kilometers away from Paris. West of Paris. .

The kilogram will be derived from this Monday from the Planck constant (h), a fundamental constant of quantum physics.

The definition of the kilo had until then depended on the metal cylinder called "Gran K"

The kelvin, measured until now in water, will be defined by the Boltzmann constant (k), unit linked to the thermal agitation of particles of a body.

The ampere will be measured from the elemental charge (e), the electric charge of a proton, and the mole, a unit mainly used in chemistry, will depend directly on the Avogadro constant (NA).