Arago

In Paris you notice a lot of people who walk around with their head down. This is for a very practical reason ... to avoid stepping in dog do do. Walk around long enough and you will soon see one of these medallions planted in the ground. These one's I found in the Jardin on my morning walk and that is my foot in the picture. What are they you ask?

Well they are markers for what is called the Arago Rose line. The Arago Rose Line is better known as the Paris Meridian, the once challenger to Greenwich as the zero-longitude line.

The Arago Rose Line is named after the French astronomer Francois Arago. His recalculation of the Paris Meridian in the early 19th resulted in greater accuracy of the actual line.

In 1994 the Arago Association and the city of Paris commissioned a Dutch conceptual artist, Jan Dibbets, to create a memorial to Arago. Dibbets came up with the idea of setting 135 bronze medallions (although only 121 are documented in the official guide to the medallions) into the ground along the Paris Meridian between the northern and southern limits of Paris: a total distance of 9.2 kilometres/5.7 miles. Each medallion is 12 cm in diameter and marked with the name ARAGO plus N and S pointers.

In the year 1634, France ruled by Louis XIII and Cardinal Richelieu decided that Ferro's Meridian should be used as the reference on maps, since this island is the most western position of the Old World. It was also thought to be exactly 20 degrees west of Paris.

A French astronomer, Abbé Jean Picard, measured the length of a degree of longitude and computed from it the size of the Earth during 1669-1670. In 1666,Louis XIV authorized the building of an observatory in Paris to measure longitude. Members of the Academy of Sciences traced the future building's outline on a plot outside town near the Port Royal abbey, with Picard's meridian exactly bisecting the site north-south. French cartographers would use it as their prime meridian for more than 200 years.

Old maps often have a common grid with Paris degrees at the top and Ferro degrees offset by 20 at the bottom.

In the early 19th century, the Paris Meridian was recalculated with greater precision by the astronomer Francois Arago, whose name now appears on the plaques or medallions tracing the route of the meridian through Paris.

In 1884, the Greenwich Meridian was adopted as the prime meridian of the world. France and Brazil abstained. The French clung to the Paris Meridian as a rival to Greenwich until 1911 for timekeeping purposes and 1914 for navigation. To this day, French cartographers continue to indicate the Paris Meridian on some maps.

The competition between the Paris and Greenwich Meridians is a plot element in Jules Verne's "Twenty Thousand Leagues Under the Sea", published just before the international decision in favor of the British one.

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