A Revolutionary Idea
In 1790, the French National Assembly tasked the French Academy of Sciences with creating a unified, rational system of measurement. The old regime had over 800 different units of measure across France alone—an administrative and economic nightmare.
The Meter
The scientists decided to base the fundamental unit of length on nature itself: one ten-millionth of the distance from the North Pole to the Equator along the meridian passing through Paris.
Two astronomers, Jean-Baptiste Delambre and Pierre Méchain, spent seven years surveying the meridian arc from Dunkirk to Barcelona to calculate this distance—during the French Revolution, no less.
The Kilogram
Originally defined as the mass of one cubic decimeter of water at 4°C, the kilogram was later embodied in a physical platinum-iridium cylinder kept in a vault near Paris. This “International Prototype of the Kilogram” served as the standard until 2019, when it was redefined using the Planck constant.
Global Adoption
The metric system spread gradually:
| Decade | Milestone |
|---|---|
| 1790s | Created in France |
| 1875 | Treaty of the Metre signed by 17 nations |
| 1960 | SI (Système International) formalized |
| 1970s | Most of the world adopts metric |
| 2019 | All SI base units redefined in terms of physical constants |
Today, only three countries have not officially adopted the metric system: the United States, Myanmar, and Liberia.
The Future
The modern SI system defines all units through fundamental physical constants—the speed of light, the Planck constant, the Boltzmann constant—making our measurement system truly universal and reproducible anywhere in the universe.