Bureau des Longitudes
Encyclopedia
The Bureau des Longitudes is a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nautical navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

, standardisation of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

-keeping, geodesy
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...

 and astronomical observation. During the 19th century, it was responsible for synchronizing
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...

 clocks across the world. It was headed during this time by François Arago
François Arago
François Jean Dominique Arago , known simply as François Arago , was a French mathematician, physicist, astronomer and politician.-Early life and work:...

 and Henri Poincaré
Henri Poincaré
Jules Henri Poincaré was a French mathematician, theoretical physicist, engineer, and a philosopher of science...

. The Bureau now functions as an academy
Academy
An academy is an institution of higher learning, research, or honorary membership.The name traces back to Plato's school of philosophy, founded approximately 385 BC at Akademia, a sanctuary of Athena, the goddess of wisdom and skill, north of Athens, Greece. In the western world academia is the...

 and still meets monthly to discuss topics related to astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

.

The Bureau was founded by the National Convention
National Convention
During the French Revolution, the National Convention or Convention, in France, comprised the constitutional and legislative assembly which sat from 20 September 1792 to 26 October 1795 . It held executive power in France during the first years of the French First Republic...

 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 Grégoire
Henri Grégoire , often referred to as Abbé Grégoire, was a French Roman Catholic priest, constitutional bishop of Blois and a revolutionary leader...

 had brought to the attention of the National Convention France's failing maritime power and the naval mastery of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, 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
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...

 and all other astronomical establishments throughout France. The Bureau was charged with taking control of the seas away from the English
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 and improving accuracy when tracking the longitudes of ships through astronomical observations and reliable clocks.

The ten original members of its founding board were:
  • Geometers:
    • Joseph-Louis Lagrange;
    • Pierre-Simon Laplace
      Pierre-Simon Laplace
      Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...

      ;
  • Astronomers:
    • Joseph Jérôme Lefrançais de Lalande;
    • Pierre Méchain
      Pierre Méchain
      Pierre François André Méchain 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:...

      ;
    • Jean Baptiste Joseph Delambre;
    • Dominique, comte de Cassini
      Dominique, comte de Cassini
      This article is about the French astronomer. For his Italian-born great-grandfather, see Giovanni Domenico Cassini.Jean-Dominique, comte de Cassini was a French astronomer, son of César-François Cassini de Thury....

      ;
  • Jean-Charles de Borda
    Jean-Charles de Borda
    Jean-Charles, chevalier de Borda was a French mathematician, physicist, political scientist, and sailor.-Life history:...

    , who carried out work related to the mechanics
    Mechanics
    Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....

     of fluid
    Fluid
    In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

    s and precursor of Carnot
    Lazare Carnot
    Lazare Nicolas Marguerite, Comte Carnot , the Organizer of Victory in the French Revolutionary Wars, was a French politician, engineer, and mathematician.-Education and early life:...

     because of his insights on thermodynamics
    Thermodynamics
    Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...

    ;
  • Jean-Nicolas Buache, geographer
    Geographer
    A geographer is a scholar whose area of study is geography, the study of Earth's natural environment and human society.Although geographers are historically known as people who make maps, map making is actually the field of study of cartography, a subset of geography...

    ;
  • Louis Antoine de Bougainville
    Louis Antoine de Bougainville
    Louis-Antoine, Comte de Bougainville was a French admiral and explorer. A contemporary of James Cook, he took part in the French and Indian War and the unsuccessful French attempt to defend Canada from Britain...

    , celebrated navigator
    Navigator
    A navigator is the person on board a ship or aircraft responsible for its navigation. The navigator's primary responsibility is to be aware of ship or aircraft position at all times. Responsibilities include planning the journey, advising the Captain or aircraft Commander of estimated timing to...

    ; and
  • Noël Simon Caroché, manufacturer of telescopes.


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 Paris Observatory
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...

, separating it from the Bureau, and focused the efforts of the Bureau on time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 and astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

. 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
French colonial empire
The French colonial empire was the set of territories outside Europe that were under French rule primarily from the 17th century to the late 1960s. In the 19th and 20th centuries, the colonial empire of France was the second-largest in the world behind the British Empire. The French colonial empire...

 by determining the length of time for a signal to make a round trip to and from a French colony
Colony
In politics and history, a colony is a territory under the immediate political control of a state. For colonies in antiquity, city-states would often found their own colonies. Some colonies were historically countries, while others were territories without definite statehood from their inception....

.

The French Bureau of Longitude established a commission in the year 1897 to extend the metric system
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...

 to the measurement of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

. They planned to abolish the antiquated division of the day into hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...

s, minute
Minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...

s, and second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

s, and replace it by a division into tenths, thousandths, and hundred thousandths of a day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...

. This was a revival of a dream
Dream
Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, philosophical intrigue and religious...

 that was in the minds of the creators of the metric system at the time of the French Revolution
French Revolution
The French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...

 a hundred years earlier. Some members of the Bureau of Longitude commission introduced a compromise
Compromise
To compromise is to make a deal where one person gives up part of his or her demand.In arguments, compromise is a concept of finding agreement through communication, through a mutual acceptance of terms—often involving variations from an original goal or desire.Extremism is often considered as...

 proposal, retaining the old-fashioned hour as the basic unit of time and dividing it into hundredths and ten thousandths. Poincaré 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. Since 1998, practical work has been carried out by the Institut de mécanique céleste et de calcul des éphémérides.

Publications

  • Connaissance des temps
    Connaissance des Temps
    The Connaissance des temps is an official astronomical yearly publication in France.- History :Connaissance des temps is the oldest such publication in the world, published without interruption since 1679 , after the astronomer Jean Picard obtained from the King the right to create the journal...

    , astronomical ephemerides, published annually since 1679;
  • Annuaire du Bureau des longitudes, almanac
    Almanac
    An almanac is an annual publication that includes information such as weather forecasts, farmers' planting dates, and tide tables, containing tabular information in a particular field or fields often arranged according to the calendar etc...

     and calendar
    Calendar
    A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...

    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.

External links

  • Official website (in French)
  • IMCCE Institut de Mecanique Celeste et de Calcul des Ephemerides - This institute hosts ephemeris calculations formerly hosted by the BDL.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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