September 10, 2007

Prime Meridian (French version)

Before the agreement to use Greenwich as Prime Meridian – in 1884, there were several other meridians which of course led to confusion, especially at sea. A major competitor to Greenwich was the French version. During the different conferences that were held to decide on a global common meridian, the French accepted to give up theirs on one condition; to have the meter accepted as a universal measurement - not yet quite achieved!

The French meridian was officialised in 1667 and has its starting point at the Observatoire (Paris 14th), finished in 1672 (three years before Greenwich!). The building which is exactly in a north-south axe had as architect, Claude Perrault, brother of Charles Perrault (author of Little Red Riding Hood, Sleeping Beauty, Puss in Boots, Cinderella, Bluebeard, Hop o’ My Thumb…). It’s the world’s oldest still active observatory. I have not found a clear explanation for the choice of the place of the Observatoire. It’s interesting to see that it’s exactly in the axe of the then already exisiting Palais de Luxembourg, built on the initiative of Marie de Medici (Henry IV’s widow), who was much interested in astrology. You find the same north-south axe around the Invalides, built at the same period as the Observatoire.The “Da Vinci Code” refers to this axe, the “Rose Line”. Actually the French meridian passes well the Louvre, but not exactly where the pyramid is, whereas the St. Sulpice church is well out of the axe.To find the trace of the axe, the “Da Vinci Code” refers to the 135 “Arago plates”, 12 cm (= 4,7 inches, - the meter is not yet adapted all over) bronze disks which were placed along the axe in 1994. You still find most of them along the streets – but some have disappeared; nice pieces of collection.(Arago was a 19th century French astronomer and politician.) The axe is in Paris also visualised in the park just behind the Observatoire and by the so called “mires”, one at Montmartre (north) and one in the Montsouris Park (south). You can read that they were erected in 1806 during the reign of….- the name of Napoleon has disappeared.The meter was “invented” by the French Academy of Sciences in 1793, based on researches made at the Observatory, as being one ten-millionth of the length of the meridian. (Nowadays it’s equal to the distance traveled by light in vacuum during a time interval of 1/299 792 458 of a second or something similar!)

The Greenwich Mean Time (GMT) is today officially replaced by an international time reference, UTC, maintained by a number of atomic clocks around the world.

35 comments:

Marantita said...

I didn't really understand why those plates were in the floor. I had an idea, but not really. And of of course I didn't know they were in the same line as the observatory and the gardens.

I guess the observatory was placed there because in that time that placewas considered as the outskirts of the city. Nobody would think so nowadays...

Azer Mantessa said...

yes i watched 'the da vinci code' and yes, there are scenes on the meridian ... i was intrigued ... now i know there were others besides greenwich ... tq

Annie said...

I read the story you told about the meridian line and the markers and then, when I came to the end I learned something I had been trying to figure out for a while. I learned what UTC meant. Thanks, Peter.

alice said...

Crois-tu que dans d'autres pays, l'idée de ce genre de "collection" puisse venir à l'esprit de certains...?

Olivier said...

je suis impressionné chaque jour par tes posts. je ne connaissais pas du tout ce premier Méridien.
Tres bonne idee ce plan et cette ballade, tu dois passer ton temps dans les bibliotheques parisiennes pour trouver tous ces renseignements

hpy said...

C'est intéressant. Je suppose qu'on devrait trouver quelque part - mais où - la raison d'implanter l'Observatoire là où il se trouve. Bon courage pour tes futures recherches!

MONA said...

this is quite an enlightening post! I never knew about the French meridian and that it was there before the Greenwich!

You Do learn new things in blogland :)

delphinium said...

Comme le dit Olivier, on apprend tellement de choses ici. Moi non plus, je n'étais pas au courant de l'existence de ce méridien. Me voilà donc moins ignare pour ce lundi 10 septembre. J'espère que vous avez passé un bon WE. Je suis allée à la montagne et j'ai fait quelques belles photos que je mettrai quand j'aurai un peu d'inspiration sur mon blog. Bon début de semaine, je vous embrasse!

ruth said...

Ah, another point of contention between the British and the French I didn't know about. Some great info here.

We have a meridian going through our community, in fact my son's band is named "Meridian." I like how it's local and global at the same time. But for the life of me, I can't find out what the number/degree of this meridian is! Maybe I should put you onto it, Peter. You are the history/geography guru!

Leena said...

Oh,oh -we should be more hours a day,
your posts are taking too much time from other posts ;), but your, I could say articles, are brilliant.
Special thanks for them!

Peter said...

marantita:
Yes, I guess you are right; hte place was certainly then outside the city limits. It proves however somehow that the north-south axe had been taken into account already when the Luxembourg Palace was built a few decades earlier.

azer:
Yes the Da Vinci Code is fascinating, but we know that there are some inexact details in the story. The real questions about what happened to Maria Magdalena, Jesus, the Holy Grail... are still there! But it made us more curious!

Pleased to see that you at least learnt something!

Matritensis said...

As always a very very interesting post.

Peter said...

annie:
My last remark on the comment at 12:36 was intended for you!

alice:
Oui, je pense. La photo du trou vide a été prise à la Cité Universitaire.

olivier:
Content de voir que tu as appris quelque chose! Non, je ne passe pas mon temps à la bibliothèque; internet m'aide bien!

hpy:
J'esperai de l'aide de ta part!

Peter said...

mona:
Good if your learnt something. I also learn a lot from your blog, unfortunately sometimes terrifying things!


delphinium:
Merci! L'inspiration ne semble pas manquer, déjà dans les commentaires! (Je n'oublerai jamais les commentaires sur le vin et Balzac!!)

ruth:
At least, the British seem now to slowly go for the metric system and for Celsius temperatures! How about the States???

leena:
I'm sorry, but when I start looking into these things, I have a problem to limit myself. I will try to make shorter! ... but no promise!

matritensis:
Thanks!

Keshi said...

Peter hows u? :)

**Louvre

I wanna be there some day..


I havent seen The Da Vinci Code...only cos there was so much controversy ard it I got bored with it :)


Nice post..great info!

Keshi.

Neva said...

You continute to enlighten and inspire! I love all the facts you know....and thanks for the nice compliment....maybe I just have good genes!

Peter said...

keshi:
So YOU are the one who hasn't read or seen the da Vinci Code! Thanks for your comments (here and elsewhere today)!

neva:
Lucky you are!

Olivier said...

juste un petit oubli ;o) pourquoi Arago ? bon j'ai fait un tour sur Wikipedia et j'ai appris que c'etait un hommage à François Arago ( c'etait un astronome, physicien et un homme politique français, dans les années 1810 )

Peter said...

olivier:
Merci. Je n'ai pas voulu faire trop long, mais j'ai pourtant mentionné (entre paranthèses) que Arago était un astronome et homme politique due 19éme/

April said...

An excursion in 'time'. What interesting things you discover! If I'd ever see one in Paris next time, I will know what they mean.

That reminds me of the square plaquettes all over Cologne. I will upload one soon and explain what it means.

Chuckeroon said...

Well, Peter..up until 1884 another meridian line actually ran through Richmond at the Kew observatory (our friend Karl Moritz actually put his foot on it, but I did not take a photo - he and I were talking about other things). In 1884 it was shifted to Greenwich.

The Kew line was there to set "the King's Time".

For a while there were several "meridians", and as you know George 111 co-operated enthusiastically with France to establish mapping precedures.
It seems that England and France raced neck and neck to establish these very important measuring points and systems. I once read somewhere that "in the case of France and England success in one drives the other into an absolute frenzy of competition to do better". The important thing here is "....better" provided it is for a "common better", isn't it?

Peter said...

april:
They are not easy to find, but as you know know where the French Meridian goes, it may make it easier for you! If you need a guide...!

Looking forward to the Cologne plates!

chuckeroon:
I read about a lot of Meridians, but I missed the Kew version. Thanks!
I appreciate a lot your comments about efforts leading to common understanding!

oldmanlincoln said...

Interesting. I like the information which I did not know. Thanks for that.

Ash said...

French Meridien ? Never knew about that! Wow - thanks for sharing.

Olivier said...

desole, j'ai lu trop vite, ou mal traduit (mon anglais, mon anglais est vraiment nul)

Tient, a quand une version bi : anglais/français ;o))

SusuPetal said...

I think you learn us too much, Peter! I don't have the capacity of digesting every piece of information you give!

But, as always, your post and the photos delight me!

Peter said...

oldmanlincoln:
I'm happy I can still teach you something, old man!

ash:
My pleasure!

olivier:
Déjà avec tout le temps que je passe avec le blog et les textes qui sont (trop) longs, tu veux une traduction? La réponse est clairement NON!

susupetal:
I'm sure you can digest! But, I know, I should shorten a bit. It's an old bad habit of mine not to write short!

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Anonymous said...

Hey you all. I suggest to you to go and see "Sainte Croix" or Saint-Colomban church in town of Quimperle in Bretagne, France.

For all the readers of Da Vinci Code this church will offer many very interesting details.

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Wow! Really a nice work and I saw all these things in the movie "Da Vinci Code" itself. It was fantastic!