Bastille Day and the Metric System

The metric system was born during the French Revolution, formalised in 1795. The metre was defined as one ten‑millionth of the quarter meridian from the North Pole to the Equator. The kilogram was the mass of one litre of water. Decimalisation applied to all units, replacing hundreds of local measures. The revolutionaries also introduced decimal time (10 hours per day, 100 minutes per hour) – it failed. The metric system is now the global standard (except for the USA, Liberia, and Myanmar). All science uses SI units.