Short answers, pulled from the story.
Charles Maurice de Talleyrand-Périgord stood before the French National Assembly and proposed a radical new system of measurement. He suggested replacing centuries of chaotic local weights with a single decimal standard based on nature itself.
Scientists defined the metre as one ten-millionth of the distance from the North Pole to the Equator through Paris by 1791. This definition tied human measurement directly to planetary dimensions rather than royal decrees or arbitrary customs.
Authorities adopted a new definition for the kilogram based on the Planck constant in May 2019. That metal artifact served as the global standard until that date when scientists replaced the natural reference with a platinum-iridium cylinder stored in Pavillon de Breteuil near Saint-Cloud, France.
The United States stands out as a notable exception that continues using different systems despite occasional metric usage. By 2019, maps showed nearly every nation had embraced SI except for specific sectors within American industry.
Giovanni Giorgi resolved electromagnetic anomalies in 1901 by adding an electrical unit to create MKSA structures. These variants coexisted before SI unified them under a single coherent international standard adopted in 1960.