[colloque] The new kilogram definition in the revised SI

by Sebastien Merlet

Tuesday 19 Mar 2019, 11:00 → 12:00 Europe/Paris

Grand Amphi (LPSC)

A revised International System of Units was voted during the 26th Conférence Générale des Poids et Mesures (CGPM) in November 2018. The definition of the kilogram, previously based on an artifact (the International Prototype of the Kilogram), is now defined from the fixed numerical value of the Planck constant. The definition had not changed since the 1st CGPM in 1889. In my presentation I will explain how such a definition evolved, since the origin in 1791 to its application in May 2019. I will first present the (current) SI and the world metrology organisation to explain why a change was possible, needed, and how it occurs. For that purpose, I will take example of other units and we will see that since 1889 no definition was found to be better than the original definition of the kilogram despite knowing that it was not totally suitable. Not only the kilogram definition but the revised SI has other consequences that I will present before concluding the seminar showing its consistency, advantages and the possible future evolutions.

Transparents 2019_03_21_kg_in_rev_SI_-_seminaire_LPSC.pdf