History of the Paris Observatory

It is the oldest observatory still serving. In 1665 the physicist and astronomer Auzout convinced Colbert and Louis XIV to construct `l'Observatoire Royale'. It is built without wood (to avoid fire) or metal (to avoid magnetic disturbances). In the summer solstice of 1667, the orientation (north-south) is traced in its place by members of the Académie Royale.

Claude Perrault (the architect of the Louvre Colonnade) projected the building and directed its construction. It was finished in 1672. It is a large rectangle (31 m x 29 m) with its four faces oriented with the cardinal points of the compass. The latitude of the south face defines the Paris latitude (48deg 50' 11''). The meridian line passing through its center defines the Paris longitude.

The foundations are as deep (27 m) as high is the building itself. In this deep basement is the Bureau Internationale de l'Heure (International Time Bureau) who sets the coordinated universal time (UTC) with 10**-6sec. of accuracy. Since 1933, the speaking clock (tel. 3699) gives the accurate time. The basement is connected with the Paris catacombs (visits forbidden). The catacombs consist of 65 km of underground galleries.

The first Director of the Observatoire de Paris was Jean-Dominique Cassini (Cassini I), born in Italy in 1625. It was followed as Director by his son Jacques (Cassini II), his grand-son César-François and his grand-grand-son Jean-Dominique .

We find among the better known directors Pierre Simon de Laplace, Joseph Jerôme Lefrançois de Lalande, Jean-Baptiste Delambre, François Arago (1843-1853), Urbain Le Verrier (1854-1870 and 1873-77).

One can mention as principals scientific works made in the Observatoire:

The map of the moon by Cassini I that was the best till the photography was invented.
The discovery of the gap in the Saturne rings by Cassini I and the table of the Jupiter movements that allowed the danish astronomer Olaüs Römer to compute the speed of light for the first time in 1675 while he was working here.
Jacques Cassini discovered the proper motion of Arcturus, showing the first that the stars were not fixed.
César-François and Jean-Dominique (IV) Cassini made the first modern map of France from 1750 to 1790.
The units of mass (gramme) and length (meter) were defined following measurements and researches made at the Observatoire. Lavoisier worked here on the mass unit.
Arago introduced here the photography in astronomy. In 1845 Hyppolite Fizeau and Léon Foucault obtained the first daguerreotype of the sun.
Foucault in 1850-51 showed manifestly the rotation of the earth with his pendulum hanging in the `grande salle' .
The works by Le Verrier lead to the discovery of Neptune. His tables of sun and planets positions were used for more than one century. Discrepancies remarked by him between calculated and observed orbits were only solved with the advent of general relativity.

At present the Observatoire de Paris owns three campuses: Paris, the Meudon astrophysics section and the radioastronomy station at Nançay. More than 700 scientists and technicians work there.

Nearby Historic Monuments

The Observatory Fountain (1873) by Davioud is known for its decoration of the four quarters of the globe by Carpeaux (Oceania was omitted for symmetry reasons).

Before the Closerie des Lilas café stands the statue of Marshal Ney by François Rude (1853). Ney was shot nearby in 1815 for his support of Napoleon. Rodin said that this was the nicest statue in Paris.

Inside the Baudelocque Maternity (123, boulevard Port Royal) remain some buildings from the Port Royal abbey. There is the nuns chapel (constructed by Le Pautre, 1646-47), the cloister (1652-55) and the hôtel d'Atry. The benedictian nuns of Saint Bernard were there from 1626 till 1664 when Louis XIV dispersed them due to their jansenist ideas. Afterwards Visitandins nuns stay there till the french revolution. It become then a prison (Lavoisier was jailed here) and a Maternity since 1818.

In the middle of the place Denfert-Rochereau is a small bronze version of Bartholdi's Lion in commemoration of colonel Denfert-Rochereau successful defence of Belfort against the prussians in 1870-71.

In 1, Place Denfert-Rochereau there is the entrance of the Paris Catacombs. Several million skeletons are stored inside. The headquarters of the Résistance - F.F.I. (Interior French Forces) of the Ile-de-France commanded by colonel Henri Rol-Tanguy were here, inside the catacombs during the liberation of Paris in August 1944.

The elegant and vast hôtel Massa, (38, rue du Faubourg Saint-Jacques) was built in 1784 on the Champs-Elysées at the present location of the Virgin Megastore. The duke of Richelieu, the count Marescalchi and the duke of Massa lived there. In 1928 was moved here. It belongs to the Men of Letters Society.

Honoré de Balzac lived from 1829 to 1834 at the house in 6, rue Cassini. He wrote there `Eugénie Grandet', `Le Père Goriot' and may be `La Peau de Chagrin'.