The metric system, a decimal-based measurement system with origins dating back to the French Revolution, is the standard in global trade and is used worldwide, with the United States, Liberia, and Myanmar remaining notable exceptions by not fully adopting it.
However, before the French Revolution, a vast array of units of weights and measures were used by different countries. There was little standardization within countries or even within regions. In France, for example, there were over 250,000 distinct units of measurement. During the Enlightenment, revolutionaries sought to radically transform society by discarding traditional systems of the ancien régime (or “old order”) and creating new ones based on reason and the natural world.
In 1791, the French Academy of Sciences took on this task, defining the meter as one ten-millionth of the distance from the North Pole to the Equator. Through the mathematical process of triangulation, they determined the length of the meter along the Paris meridian, which runs through the Paris Observatory.
By the end of the 18th century, the units of the metric system had all been derived from the meter. Metric units included the kilogram for mass, the second for time, the kelvin for temperature, the ampere for electric current, the mole for amount of substance, and the candela for luminous intensity.
Despite the confusion caused by the huge number of measurement systems previously in use, the introduction of the metric system in France faced resistance. People were slow to adopt the new system, preferring their familiar, traditional methods. Authorities in Paris even instructed police to check that marketplaces were using the metric system. In 1812, Napoleon abolished the metric system, but it continued to be taught in schools and was reinstated in 1840. Now, some two centuries later, the metric system in its modern form, the International System of Units (or SI, from the French Système international d'unités), is consistently used across France and in over 95% of the world.
The meter and more:
- *The word meter is derived from the Greek metron, meaning “measure.”
- *Located in a suburb of Paris, the International Bureau of Weights and Measures is home to the original kilogram. To keep it safe, the circular weight is stored in an underground vault under three bell jars that are opened using three unique keys, each in the possession of a different individual.
- *One of the traditional French units of length was the toise, which was said to be based on the distance between the fingertips of the outstretched arms of a man, roughly equivalent to 1.949 meters, or 6.395 feet.
- *Although the United States continues to use U.S. customary units such as the pound, gallon, and foot, SI units such as grams, liters, and meters are widely used in commerce, science, technology, and industry. And, of course, we tell time using a metric unit—the second!