The Paris Observatory: a Scientific Utopia

On July 16, 1789, the Count of Cassini, director of the Paris Observatory, was worried: a large crowd was pressing up against its doors, persuaded that the building hid immense reserves of gunpowder as well as ammunition. The people wanted to arm and defend themselves in case the army suppressed the Revolution. However, the cellars of this building, completed in 1667, were empty. The insurgents left. Six years later, in 1795, the site became one of the centerpieces of the new Republic’s scientific policy. Attached to the Office of Longitudes, it was used as a place to store, conserve and loan out “all the astronomical instruments that belong to the Nation.” It also had to test the Navy’s instruments to make sure they worked properly. If the Observatory reflects the faith in scientific progress, its mission was also very political: the French Republic was fighting the British monarchy on the high seas.

Overview of the City of Paris Taken from the Top of the Observatory
Overview of the City of Paris Taken from the Top of the Observatory



61 avenue de l’Observatoire


The Catacombs neighborhood
The Catacombs of Paris

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The metric system, a revolution?

During the Ancien Régime, each province had its own weight and measurement system. In 1795, France established the metric system, which only became obligatory much later on. Not only was it more practical, but it also encouraged commercial exchange and removed differences between people: it thereby helped the universal project that the French Republic was trying to spread throughout Europe… while still imposing its own models. It was the Office of Longitudes and the Paris Observatory that were in charge of keeping the instruments making it possible to measure the new meter (e.g. one ten-millionths of the distance between the equator and the north pole). In order to familiarize the French with the meter, it was decided to place standard meters in the streets of cities and villages. In Paris, two of the original 16 remain: one is still visible on the façade of the Ministry of Justice on the Place Vendôme, and the other one under the arcades at 36 rue de Vaugirard.

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