Paris meridian, Prime meridian at Paris Observatory, France
The Paris meridian is an imaginary line running north to south through the city, connected to the Paris Observatory. A series of 135 bronze medallions are set into the street pavement to mark its exact path.
This line served as the world's reference for measuring longitude beginning in 1678 until 1884, when Greenwich became the international standard. The scientific work on this meridian helped establish the foundations of modern measurement.
The medallions honor astronomer François Arago, whose name appears on each bronze marker scattered throughout the streets. Walking along this path, you notice how the city has made a scientific concept part of its everyday landscape.
You can walk the meridian from Porte de Montmartre in the north to Cité Universitaire in the south by following the brass markers set into the pavement. The medallions are easiest to spot in areas with lighter foot traffic.
The measurement of this line was crucial to creating the metric system in the late 1700s. Scientists used the distance from the North Pole to the equator along this meridian to define what one meter would be.
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