Paris Observatory

Already the Greeks, some two centuries BC, had invented the first meridian lines. Later, there were many of them, which obviously created confusion when it came to navigation. The Paris Meridian exists officially since 1634. The Paris Observatory was built 1667-71 – a few years before the Royal Greenwich Observatory - on a hill where since then the centre of the building is crossed by the Paris Meridian in a perfect North-South direction. The Paris Observatory was then outside the city borders in a calm area, today it’s in the middle of the city.
The architect was Claude Perrault (brother of Charles Perrault, who wrote “Little Red Riding Hood”, “Puss in Boots”, “Cinderella”…). For that time it was a very simple building with hardly any decorative elements, but the quality of the stones and how perfectly well they are fitted together, is amazing – hardly any concrete needed.

The basic activity of the Observatory was of course to study the sky. Telescopes and other optical instruments were, to start with, installed in the central hall of the building, which had very high windows. In this hall was also installed the way to check exact hours and dates (summer and winter solstice, autumn and spring equinox) by help of the sun, a little hole in the wall and a line (the meridian) on the floor. (The same can be seen elsewhere, in Paris e.g. in the Sainte Sulpice Church (see previous post).) 

Later, with larger telescopes, special buildings were added to house the instruments – there are a number of cupolas in the surrounding garden.  

One of the cupolas is to be found on the top of the building, added during the 19th century. Today all these installations are just historical. Visual sky observation is not done here anymore, but elsewhere, and the Paris Observatory is today only a leading scientific and educational centre. 

You have the impression that the Meridian runs through the middle of the Luxembourg Palace (see previous post) and I, also, mistakenly believed so. However, not quite. The Palace was of course built some 50 years before the Observatory.

It seems to be admitted that cartography in its modern sense originated at the Paris Observatory. This led also later to the invention of the meter – defined as one ten millionth of the distance between the North Pole and the Equator. The metric system became the official system of measurement in France in 1795 (also involving litres, kilogrammes…).

In 1884 an International Meridian Conference decided that the Greenwich Meridian should be the standard for the zero degree longitude. France (of course) voted against and got as a “compensation” that the British would adopt the metric system - finally launched a bit later, in 1965, with an official metric program. Today, the only major country which has not adopted the metric system is the USA (see the map of countries which have not adopted the metric system.).

Standing on the roof top, you have of course some nice views of Paris.


Julie said...

One of the things that I appreciate about the Paris skyline, Peter, is that it's relatively uniform height enables the more notable buildings yo be identified, as in your final two shots. I am trying, from memory, to work out which departmente your photos were taken in. You say once outside the city walls, but now in the centre. Well 4450 years will do that. But the two images of famous buildings might be more a clue. Invalides on left, Sacre Coeur in mid, Pantheon more right ... so perhaps 15th? ... but not so when I google, as the 14th is "Observatoire". Perrault wrote such ever-lasting tales. My grand-daughter adores LRRH, but I am banned from reading it to her as she does NOT like that wolf.

Fasinating post. I did not realise that the English were metric. Took them only 300+ years ... typical.

Alain said...

En mer, on mesure de préférence par miles (1852 mètres)ce qui correspond à une minute d'arc. Assez curieusement cette unité n'a pas de sous multiple, mais, comme le mètre, elle est basée sur les dimensions de la terre. On se souviens que le méridien de Paris a joué des tours au capitaine Haddock, pourtant, le professeur Tournesol lui disait : "Un peu plus à l'ouest"...

Starman said...

Actually, the US did try to go to the metric system, but the dim people of the US just could grasp the fundamentals.

claude said...

Je passe vite fait car moi ya n'a pas le temps ce matin et encore moins demain.
A plus !

Olivier said...

c'est magnifique

lyliane six said...

j'y suis allée une fois, mais hélas c'était fermé! Après ton post,je vais y retourner mais me renseigner pour les horaires.

Christine said...

Another interesting post - lots of us in England still talk 'old money' asking for a yard of material we get the extra 3ins of the metre.
Is it possible to visit the Observatory?
We will be coming to Paris in April and are looking for somewhere 'different' to visit and, as the DH has just taken up Astronomy, this would be really interesting.
thank you for sharing.

Thérèse said...

J'ai pense que tu allais nous parler de Jules Vernes en voyant la premiere image apparaitre.
Je viens d'avoir droit a une petite lecon supplementaire de la part de ma moitie qui ajoute que le metre en platine/iridum original se trouve a Sevres. J'espere que c'est vrai je n'ai pas verifie...

Amanda said...

A definitively interesting place to visit. Thank you for the history too, Peter! Europeans changed to the Euros without too much of a problem (though it did take a while), there is no reason why the US cannot embrace the metric system too.

PeterParis said...

Christine >
Yes visits can be arranged, but I think rather by groups. To make a request / reservation, here is an adress:

PeterParis said...

Thérèse >
Ta moitié a raison, mais aujourd'hui ce plutôt une pièce de musée. Je crois que le mètre aujourd'hui est défini comme on peut trouver sur Wikipedia:

"En 1960, la 11e Conférence générale des poids et mesures (CGPM) redéfinit le mètre comme 1 650 763,73 longueurs d'onde d'une radiation orangée émise par l'isotope 86 du krypton10.
La 17e CGPM de 1983 redéfinit la vitesse de la lumière dans le vide absolu à 299 792 458 m/s, ce qui a pour effet de réviser la valeur du mètre comme étant la distance parcourue par la lumière dans le vide en 1/299 792 458 seconde.
La vitesse de la lumière dans le vide étant la même en tous points (résultat établi par la relativité restreinte), la définition de 1983 est plus précise que l'antérieure car la seconde est l'unité du Système international (SI) qui est mesurée avec la plus faible incertitude." :-)

Studio at the Farm said...

Another most fascinating post, Peter, full of interesting bits of information and wonderful photos! And now I know who wrote some of my favorite fairy tales. :) Thank you, Peter!

Synne said...

I remember that we talked about the meridians on one of our walks!
I love cogs and lenses and instruments like these. The observatory looks magical!

Anne in Oxfordshire said...

Hi Peter , another very interesting post. If we can visit , I am sure I could get my husband to Paris ,, he would love this, he really wants to go to The Louvre , I said well then we have to book our tickets!!

I sometimes ask the men on our market for a KILO of this and that, they look at me in surprise. Take care Anne