__NOTOC__ The ''Bureau des Longitudes'' () is a French scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nautical

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navig ...

standardisation Standardization (American English) or standardisation (British English) is the process of implementing and developing technical standards based on the consensus of different parties that include firms, users, interest groups, standards organiza ...

time Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...

-keeping,

geodesy Geodesy or geodetics is the science of measuring and representing the Figure of the Earth, geometry, Gravity of Earth, gravity, and Earth's rotation, spatial orientation of the Earth in Relative change, temporally varying Three-dimensional spac ...

and

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

observation. During the 19th century, it was responsible for synchronizing

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

s across the world. It was headed during this time by

François Arago Dominique François Jean Arago (), known simply as François Arago (; Catalan: , ; 26 February 17862 October 1853), was a French mathematician, physicist, astronomer, freemason, supporter of the Carbonari revolutionaries and politician. Early l ...

and

Henri Poincaré Jules Henri Poincaré (, ; ; 29 April 185417 July 1912) was a French mathematician, Theoretical physics, theoretical physicist, engineer, and philosophy of science, philosopher of science. He is often described as a polymath, and in mathemati ...

. The Bureau now functions as an

academy An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of tertiary education. The name traces back to Plato's school of philosophy, founded approximately 386 BC at Akademia, a sanctuary of Athena, the go ...

and still meets monthly to discuss topics related to

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

. The Bureau was founded by the

National Convention The National Convention () was the constituent assembly of the Kingdom of France for one day and the French First Republic for its first three years during the French Revolution, following the two-year National Constituent Assembly and the ...

after it heard a report drawn up jointly by the Committee of Navy, the Committee of Finances and the Committee of State education.

Henri Grégoire Henri Jean-Baptiste Grégoire (; 4 December 1750 – 28 May 1831), often referred to as the Abbé Grégoire, was a French Catholic priest, constitutional bishop of Blois and a revolutionary leader. He was an ardent slavery abolitionist and sup ...

had brought to the attention of the National Convention France's failing maritime power and the naval mastery of

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

, proposing that improvements in navigation would lay the foundations for a renaissance in naval strength. As a result, the Bureau was established with authority over the

Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...

and all other astronomical establishments throughout France. The Bureau was charged with taking control of the seas away from the English and improving accuracy when tracking the

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

s of ships through astronomical observations and reliable clocks. The ten original members of its founding board were: *

Joseph-Louis Lagrange Joseph-Louis Lagrange (born Giuseppe Luigi LagrangiaPierre-Simon Laplace Pierre-Simon, Marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French polymath, a scholar whose work has been instrumental in the fields of physics, astronomy, mathematics, engineering, statistics, and philosophy. He summariz ...

, geometer; *

Joseph Jérôme Lefrançais de Lalande Joseph is a common male name, derived from the Hebrew (). "Joseph" is used, along with " Josef", mostly in English, French and partially German languages. This spelling is also found as a variant in the languages of the modern-day Nordic count ...

, astronomer; *

Pierre Méchain Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was bo ...

, astronomer; *

Jean Baptiste Joseph Delambre Jean Baptiste Joseph, chevalier Delambre (19 September 1749 – 19 August 1822) was a French mathematician, astronomer, historian of astronomy, and geodesist. He was also director of the Paris Observatory, and author of well-known books on the ...

, astronomer; *

Dominique, comte de Cassini Jean-Dominique, comte de Cassini (30 June 174818 October 1845), also called Cassini IV, was a French astronomer, son of César-François Cassini de Thury and great-grandson of Giovanni Domenico Cassini. Cassini was born at the Paris Observato ...

, astronomer; *

Jean-Charles de Borda Jean-Charles, chevalier de Borda (4 May 1733 – 19 February 1799) was a French mathematician, physicist, and Navy officer. Biography Borda was born in the city of Dax to Jean‐Antoine de Borda and Jeanne‐Marie Thérèse de Lacroix. In 17 ...

, Navy officer; *Jean-Nicolas Buache,

geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" a ...

; *

Louis Antoine de Bougainville Louis-Antoine, Comte de Bougainville (; 12 November 1729 – 31 August 1811) was a French military officer and explorer. A contemporary of the British explorer James Cook, he served in the Seven Years' War and the American Revolutionary War. B ...

, Navy officer; *Noël Simon Caroché,

manufacturer Manufacturing is the creation or Production (economics), production of goods with the help of equipment, Work (human activity), labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary se ...

telescopes A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

. By a decree of 30 January 1854, the Bureau's mission was extended to embrace geodesy, time standardisation and astronomical measurements. This decree granted independence to the

, separating it from the Bureau, and focused the efforts of the Bureau on

and

. The Bureau was successful at setting a universal time in Paris via air pulses sent through pneumatic tubes. It later worked to synchronize time across the

French colonial empire The French colonial empire () comprised the overseas Colony, colonies, protectorates, and League of Nations mandate, mandate territories that came under French rule from the 16th century onward. A distinction is generally made between the "Firs ...

by determining the length of time for a signal to make a round trip to and from a French

colony A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their ''metropole'' (or "mother country"). This separated rule was often orga ...

. The French Bureau of Longitude established a commission in the year 1897 to extend the

metric system The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...

to the measurement of

. They planned to abolish the antiquated division of the day into

hour An hour (symbol: h; also abbreviated hr) is a unit of time historically reckoned as of a day and defined contemporarily as exactly 3,600 seconds ( SI). There are 60 minutes in an hour, and 24 hours in a day. The hour was initially establis ...

minute A minute is a unit of time defined as equal to 60 seconds. It is not a unit in the International System of Units (SI), but is accepted for use with SI. The SI symbol for minutes is min (without a dot). The prime symbol is also sometimes used i ...

s, and

second The second (symbol: s) is a unit of time derived from the division of the day first into 24 hours, then to 60 minutes, and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of U ...

s, and replace it by a division into tenths, thousandths, and hundred-thousandths of a

day A day is the time rotation period, period of a full Earth's rotation, rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, ...

. This was a revival of a

dream A dream is a succession of images, ideas, emotions, and sensation (psychology), sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around ...

that was in the minds of the creators of the metric system at the time of the French Revolution a hundred years earlier. Some members of the Bureau of Longitude commission introduced a

compromise To compromise is to make a deal between different parties where each party gives up part of their demand. In arguments, compromise means finding agreement through communication, through a mutual acceptance of terms—often involving variations fr ...

proposal, retaining the old-fashioned hour as the basic unit of time and dividing it into hundredths and ten-thousandths.

Poincaré Poincaré is a French surname. Notable people with the surname include: * Henri Poincaré Jules Henri Poincaré (, ; ; 29 April 185417 July 1912) was a French mathematician, Theoretical physics, theoretical physicist, engineer, and philos ...

served as secretary of the commission and took its work very seriously, writing several of its reports. He was a fervent believer in a universal metric system. But he lost the battle. The rest of the world outside France gave no support to the commission's proposals, and the French government was not prepared to go it alone. After three years of hard work, the commission was dissolved in 1900. Since 1970, the board has been constituted with 13 members, 3 nominated by the

Académie des Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

. Since 1998, practical work has been carried out by the ''Institut de mécanique céleste et de calcul des éphémérides''.

Publications

*'' Connaissance des temps'', astronomical ephemerides, published annually since 1679; *''Annuaire du Bureau des longitudes'',

almanac An almanac (also spelled almanack and almanach) is a regularly published listing of a set of current information about one or multiple subjects. It includes information like weather forecasting, weather forecasts, farmers' sowing, planting dates ...

and

calendar A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A calendar date, date is the designation of a single and specific day within such a system. A calendar is ...

for public and civil use, published annually since 1795; *''Éphémérides nautiques'', (from 1889) for marine navigation; *''Éphémérides aéronautiques'', (from 1938) for civil and military aerial navigation.
Procès-verbaux du Bureau des longitudes

References

Bureau Des Longitudes
(French) * Galison, Peter Louis (2003). ''Einstein's Clocks, Poincaré's Maps: Empires of Time''. Hodder & Stoughton. . *Dyson, Freeman J. (November 6, 2003)
Clockwork Science
''The New York Review of Books'' 50 (17)

(French)

External links

Official website (in French)IMCCE
Institut de Mécanique Céleste et de Calcul des Éphémérides - This institute hosts ephemeris calculations formerly hosted by the BDL. {{Authority control Geodesy organizations Astronomy organizations 1795 establishments in France Scientific organizations established in 1795 Astronomy in France Meridians (geography) Navigation organizations

Publications

See also

References

External links