The French Revolution not only toppled a king—it also forged the metric system

As revolution raged in the 1790s, French scientists replaced a chaotic system of weights and measures with an unified way to calibrate and calculate.

Citizens use France’s new metric measures in this detail of a 1795 color engraving. Carnavalet Museum, Paris
BRIDGEMAN/ACI

Mathematician and author, the Marquis de Condorcet (1743-1794) was an aristocrat who nevertheless embraced the early stage of the French Revolution. Even as the Jacobins hunted him down during the Reign of Terror—he was a moderate and opposed putting King Louis XVI to death—he wrote the Sketch for a Historical Picture of the Progress of the Human Mind, expressing his faith in a future guided by science and reason. Two days after his arrest, he killed himself in prison rather than face execution.

Condorcet’s ideals live on, however, in the way most of the world measures things: the metric system. He believed a universal and standard system would allow people to calculate their own best interests, “without which they cannot be really equal in rights . . . nor really free.”

At the time of the French Revolution in 1789, Paris was the global capital of science, whose leading lights, the savants (wise ones), made lasting contributions to physics, chemistry, and biology. (A century earlier, France was also the dueling capital of Europe.)

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