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Metre Convention signatories | |
The treaty created the International Bureau of Weights and Measures (BIPM), an intergovernmental organization, under the authority of the General Conference on Weights and Measures (CGPM) and the supervision of the International Committee for Weights and Measures (CIPM). These organizations coordinate international metrology and the development of internationally recognized systems of measurement.
The Metre Convention established a permanent organizational structure for member governments to act in common accord on all matters relating to units of measurement. The governing organs of the BIPM are:
Initially the scope of the Metre Convention covered only units of mass and length. In 1921, at the sixth meeting of the CGPM, convention was amended to its scope to other fields in physics. In 1960, at the eleventh meeting of the CGPM, its system of units was named the International System of Units (Système international d'unités, abbreviated SI).
The Metre Convention provides that only nations can be members of the BIPM. In 1999, the CGPM created in the status of associate, to allow non-member states and economic entities to participate in some activities of the BIPM through their national metrology institutes (NMIs).
, the CGPM had 64 members and 37 associates.
Membership in the CGPM requires payment of substantial fees. Being in arrears with these payments over a span of years has led to expulsion of some former members.
Some of Charlemagne's units of measure, such as the pied du Roi (the king's foot) remained virtually unchanged for about a thousand years, while others, such as the aune (ell – used to measure cloth) and the livre (pound) varied dramatically from locality to locality. By the time of the revolution, the number of units of measure had grown to the extent that it was almost impossible to keep track of them.
In England in 1215, clause 25 of Magna Carta required that the same standards of measurement be applied throughout the realm. The wording of the clause emphasized that "There is to be a single measure ... throughout our realm".
Five centuries later, when in 1707 England and Scotland were united into a single kingdom, the Scots agreed to use the same units of measure that were already established in England., Article 3 During the eighteenth century, in order to facilitate trade, Peter the Great, Czar of Russia adopted the English system of measure.
From 1668 to 1776 the French standard of length was the Toise of Châtelet which was fixed outside the Grand Châtelet in Paris. In 1735 two geodetic standards were calibrated against the Toise of Châtelet. One of them, the Toise of Peru was used for the French Geodesic Mission to the Equator. In 1766 the Toise of Peru became the official standard of length in France and was renamed Toise of the Academy ().
Profusion of units of measures was a practical problem of importance before the French Revolution and its reform was one of the items on the agenda of National Assembly. In 1799, after the remeasurement of the Paris meridian arc () between Dunkirk and Barcelona by Delambre and Mechain, the metre was defined as a quarter of a 10-millionth of the Earth circumference or 3 (French feet) and 11.296 (lines) of the Toise of the Academy. Talleyrand, an influential leader of the Assembly invited British and American participation in the establishment of a new system, but in the event, the Assembly went it alone and introduced the metre and the kilogram which were to form the basis of the metric system, manufacturing prototypes which, in 1799, were lodged with Archives.
Between 1840 and 1870, a number of countries definitively adopted the metric system as their system of measure including France, Spain, many South American republics and many of the Italian and German states (the Netherlands had adopted the system in 1817).
In 1863, the International Postal Union used grams to express permitted weights of letters. In the 1860s, inspections of the prototype metre revealed wear and tear at the measuring faces of the bar and also that the bar was wont to flex slightly when in use.
In 1816, Ferdinand Rudolph Hassler was appointed first Superintendent of the Survey of the Coast. Trained in geodesy in Switzerland, France and Germany, Hassler had brought a standard metre made in Paris to the United States in October 1805. He designed a baseline apparatus which instead of bringing different bars in actual contact during measurements, used only one bar calibrated on the Committee meter, an authenthic copy of the Mètre des Archives, and optical contact. In 1830, Hassler became head of the Office of Weights and Measures, which became a part of the Survey of the Coast. He compared various units of length used in the United States at that time and measured coefficients of expansion to assess temperature effects on the measurements. In 1834, Hassler, measured at Fire Island the first baseline of the Survey of the Coast, shortly before Louis Puissant declared to the French Academy of Sciences in 1836 that Jean Baptiste Joseph Delambre and Pierre Méchain had made errors in the Arc measurement, which had been used to determine the length of the metre., in canton of Bern, Switzerland in 1880.]] In 1855, the Dufour map (French: Carte Dufour), the first topographic map of Switzerland for which the metre was adopted as the unit of length, won the gold medal at the Exposition Universelle. However, the baselines for this map were measured in 1834 with three toises long measuring rods calibrated on a toise made in 1821 by Jean Nicolas Fortin for Friedrich Georg Wilhelm von Struve. The Spanish standard, a geodetic measuring device calibrated on the metre devised by Carlos Ibáñez e Ibáñez de Ibero and Frutos Saavedra Meneses, was also displayed by Jean Brunner at the Exhibition. Carlos Ibáñez e Ibáñez de Ibero recognized that the end standards with which the most perfect devices of the eighteenth century and those of the first half of the nineteenth century were still equipped, that Jean-Charles de Borda or Friedrich Bessel simply joined measuring the intervals by means of Calipers or glass wedges, would be replaced advantageously for accuracy by microscopic measurements, a system designed in Switzerland by Ferdinand Rudolph Hassler and Johann Georg Tralles, and which Ibáñez ameliorated using a single standard with lines marked on the bar. Regarding the two methods by which the effect of temperature was taken into account, Ibáñez used both the bimetallic rulers, in platinum and brass, which he first employed for the central base of Spain, and the simple iron ruler with inlaid mercury thermometers which was used in Switzerland. On the sidelines of the Exposition Universelle (1855) and the second Congress of Statistics held in Paris, an association with a view to obtaining a uniform decimal system of measures, weights and currencies was created in 1855. Under the impetus of this association, a Committee for Weights and Measures and Monies (French: Comité des poids, mesures et monnaies) would be created during the Exposition Universelle (1867) in Paris and would call for the international adoption of the metric system.
Egyptian astronomy has ancient roots which were revived in the 19th century by the modernist impetus of Muhammad Ali who founded in Sabtieh, Boulaq district, in Cairo an Observatory which he was keen to keep in harmony with the progress of this science still in progress. In 1858, a Technical Commission was set up to continue cadastral surveying inaugurated under Muhammad Ali. This Commission suggested to Viceroy Mohammed Sa'id Pasha to buy geodetic devices which were ordered in France. While Mahmud Ahmad Hamdi al-Falaki was in charge, in Egypt, of the direction of the work of the general map, the viceroy entrusted to Ismail Mustafa al-Falaki the study, in Europe, of the precision apparatus calibrated against the metre intended to measure the geodesic bases and already built by Jean Brunner in Paris. Ismail Mustafa had the task to carry out the experiments necessary for determining the expansion coefficients of the two platinum and brass bars, and to compare the Egyptian standard with a known standard. The Spanish standard designed by Carlos Ibáñez e Ibáñez de Ibero and Frutos Saavedra Meneses was chosen for this purpose, as it had served as a model for the construction of the Egyptian standard. In addition, the Spanish standard had been compared with Borda's double-toise N° 1, which served as a comparison module for the measurement of all geodesic bases in France, and was also to be compared to the Ibáñez apparatus. In 1954, the connection of the southerly extension of the Struve Geodetic Arc with an arc running northwards from South Africa through Egypt would bring the course of a major meridian arc back to land where Eratosthenes had founded geodesy.
In the second half of the 19th century, the creation of the Central European Arc Measurement () would mark, following Carl Friedrich Gauss, Friedrich Wilhelm Bessel and Friedrich Georg Wilhelm von Struve examples, the systematic adoption of more rigorous methods among them the application of the least squares in geodesy. It became possible to accurately measure parallel arcs, since the difference in longitude between their ends could be determined thanks to the invention of the electrical telegraph. Furthermore, advances in metrology combined with those of gravimetry have led to a new era of geodesy. If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs and all determinations of the gravitational acceleration by means of pendulum.Carlos Ibáñez e Ibáñez de Ibero, Discursos leidos ante la Real Academia de Ciencias Exactas Fisicas y Naturales en la recepcion pública de Don Joaquin Barraquer y Rovira, Madrid, Imprenta de la Viuda e Hijo de D.E. Aguado, 1881, p. 78
In 1866, an important concern was that the Toise of Peru, the standard of the toise constructed in 1735 for the French Geodesic Mission to the Equator, might be so much damaged that comparison with it would be worthless, while Bessel had questioned the accuracy of copies of this standard belonging to Altona and Koenigsberg Observatories, which he had compared to each other about 1840. In fact, the length of Bessel's Toise, which according to the then legal ratio between the metre and the Toise of Peru, should be equal to 1.9490348 m, would be found to be 26.2·10-6 m greater during measurements carried out by Jean-René Benoît at the International Bureau of Weights and Measures. It was the consideration of the divergences between the different toises used by geodesists that led the European Arc Measurement ( ) to consider, at the meeting of its Permanent Commission in Neuchâtel in 1866, the founding of a World Institute for the Comparison of Geodetic Standards, the first step towards the creation of the International Bureau of Weights and Measures.Guillaume, Charles-Édouard (1927). La Création du Bureau International des Poids et Mesures et son Œuvre ''The. Paris: Gauthier-Villars. p. 129-130. Spain joined the European Arc Measurement at this meeting. In 1867 at the second General Conference of the European Arc Measurement held in Berlin, the question of international standard of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth. The conference recommended the adoption of the metric system (replacing Friedrich Bessel's toise) and the creation of an International Metre Commission.
In July 1870, two weeks before the conference was due to start, the Franco-Prussian War broke out. Although the delegates did meet (without a German delegation), it was agreed that the conference should be recalled once all the delegates (including the German delegation) were present. Following the war, which resulted in Napoleon III's exile, Germany and Italy, now unified nations, adopted the metric system as their national system of units, but with the prototype copy of the kilogram and metre under the control of the French Third Republic. In 1872 the new republican government reissued the invitations and the same year scientists from thirty European and American countries met in Paris.
When the International Metre Commission was reconvened in 1872, it was proposed that new prototype metre and kilogram standards be manufactured to reproduce the values of the existing artifacts as closely as possible. Indeed, since its origin, the metre had kept a double definition; it was both the ten-millionth part of the quarter meridian and the length represented by the Mètre des Archives. The first was historical, the second was metrological. There was much discussion, considering the opportunity either to keep as definitive the units represented by the metre and kilogram standards of the Archives, or to return to the primitive definitions, and to correct the units to bring them closer to them. The first solution prevailed, in accordance with common sense and in accordance with the advice of the French Academy of Sciences. Abandoning the values represented by the standards, would have consecrated an extremely dangerous principle, that of the change of units to any progress of measurements; the Metric system would be perpetually threatened with change, that is to say with ruin. The Commission decided the maintenance of new international standards rather than using French existing standards which, at that time, were 70 years old and which, through wear and tear, might not be exactly the same as when they had been adopted in 1799. Thus the Commission called for the creation of a new international prototype metre which length would be as close as possible to that of the Mètre des Archives and the arrangement of a system where national standards could be compared with it.
While the German astronomer Wilhelm Julius Foerster along with the Russian and Austrian representatives had boycotted the Permanent Committee of the International Metre Commission in order to prompt the reunion of the Diplomatic Conference of the Metre and to promote the foundation of a permanent International Bureau of Weights and Measures, Adolphe Hirsch, delegate of Switzerland at this Diplomatic Conference in 1875, conformed to the opinion of Italy and Spain to create, in spite of French reluctance, the International Bureau of Weights and Measures in France as a permanent institution at the disadvantage of the Conservatoire national des arts et métiers.
In 1875, the Permanent Commission of the European Arc Measurement would also hold its reunion in Paris and decide the creation of an international geodetic standard for baselines' measurement calibrated against the metre. French Empire had hesitated for a long time before giving in to the demands of the European Arc Measurement, which asked the French geodesists to take part in its work. It was only after the Franco-Prussian War, that Charles-Eugène Delaunay represented France at the Congress of Vienna in 1871. In 1874, Hervé Faye was appointed member of the Permanent Commission of the European Arc Measurement presided by Carlos Ibáñez e Ibáñez de Ibero who was collaborating with the French on the extension and remeasurement of the meridian arc of Delambre and Méchain since 1853.
Spain notably supported France for these outcomes and the first president of the International Committee for Weights and Measures, the Spanish geodesist, Carlos Ibáñez e Ibáñez de Ibero received the Grand Officer medal of the Légion d'Honneur for his diplomatic role on this issue and was awarded the Poncelet Prize for his scientific contributions to metrology and geodesy. Indeed, Carlos Ibáñez e Ibáñez de Ibero, first president of the International Geodetic Association, played a pivotal role in reconciling French and German interests.
The comparison of the new prototypes of the metre with each other involved the development of special measuring equipment and the definition of a reproducible temperature scale. The BIPM's thermometry work led to the discovery of special alloys of iron–nickel, in particular invar, whose practically negligible coefficient of expansion made it possible to develop simpler baseline measurement methods, and for which its director, the Swiss physicist Charles Édouard Guillaume, was granted the Nobel Prize in Physics in 1920. Guillaume's Nobel Prize marked the end of an era in which metrology was leaving the field of geodesy to become an autonomous scientific discipline capable of redefining the metre through Technology applications of physics. On the other hand, the foundation of the United States Coast and Geodetic Survey by Ferdinand Rudolph Hassler paved the way to a new definition of the metre, with Charles Sanders Peirce being the first to experimentally link the metre to the wavelength of a spectral line. Albert A. Michelson soon took up the idea and improved it.
The prototype metre was retained as the international standard until 1960 when the metre was redefined in terms of the wavelength of the orange-red line of krypton-86. The current definition of the metre is "the length of the path travelled by light in vacuum during a time interval of 1/ of a second".
On 16 November 2018, the 26th General Conference on Weights and Measures (CGPM) voted unanimously in favour of revised definitions of some SI base units, in particular the kilogram. The new definitions came into force on 20 May 2019, but did not change the metre. "Decision CIPM/105-13 (October 2016)" . The day is the 144th anniversary of the Metre Convention.
The structure may be compared to a corporation, the CIPM is analogous to a board of directors, and the CGPM to a shareholders' meeting.
Initially it had a staff of 9, falling to 4 once the initial batch of prototypes had been distributed;Convention of the Metre (1875), Appendix 1 (Regulation), Article 6 in 2012 it had a staff of over 70 people and an annual budget of over €10 million.
The director of the BIPM is ex-officio a member of the CIPM and a member of all consultative committees.
The French government offered the treaty members the Pavillon de Breteuil in Saint-Cloud to house the BIPM. The Pavillon was originally built in 1675 on the estate of the Château de Saint-Cloud which was home to, amongst others, Napoleon III. The château was all but destroyed during the Franco-Prussian War (1870–1) and the Pavillon badly damaged.
The Pavillon has been fully restored and, as headquarters of an intergovernmental organization enjoys privileges and immunities.
In 1901 Giovanni Giorgi published a proposal for building a coherent set of units based on four base units – the metre, kilogram, second and one electrical unit (ampere, volt or ohm). In 1921 the convention was extended to permit the promotion of standards relating to any physical quantity which greatly increased the scope of the CIPM's remit and implicitly giving it freedom to exploit Giorgi's proposals. The 8th CGPM (1933) resolved to work with other international bodies to agree to standards for electrical units that could be related back to the international prototypes.
This was agreed in principle by the International Electrotechnical Commission at its congress in Brussels in 1935 subject to the choice of the fourth unit being agreed with, amongst others, the appropriate consultative committee of the CIPM.
In 1948, three years after the end of World War II and fifteen years after the 8th CGPM, the 9th CGPM was convened. In response to formal requests made by the International Union of Pure and Applied Physics and by the French Government to establish a practical system of units of measure, the CGPM requested the CIPM to prepare recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention.
At the same time the CGPM formally adopted a recommendation for the writing and printing of unit symbols and of numbers.
The recommendation also catalogued the recommended symbols for the most important MKS and CGS units of measure and for the first time the CGPM made recommendations concerning derived units.
The CIPM's draft proposal, which was an extensive revision and simplification of the metric unit definitions, symbols and terminology based on the MKS system of units, was put to the 10th CGPM in 1954. In the proposal the CIPM recommended that the ampere be the base unit from which electromechanical standards would be derived. After negotiations with the CIS and IUPAP, two further base units, the degree kelvin and the candela were also proposed as base units.
The full system and name "Système international d'unités" were adopted at the 11th CGPM.
During the years that followed the definitions of the base units and particularly the mise en pratique
to realize these definitions have been refined.
The formal definition of International System of Units (SI) along with the associated resolutions passed by the CGPM and the CIPM are published by the BIPM on the Internet and in brochure form at regular intervals. The eighth edition of the brochure Le Système international d'unités – The International System of Units was published in 2006.
International trade is hampered by one country not recognising the quality controls in place in other countries – often due to standards being different or being incompatible with each other. At the 20th CGPM (1995), it was recognized that although ad-hoc recognition of instrument calibration between cooperating countries had been taking place for a hundred years, a need had arisen for a more comprehensive agreement. Consequently, the CIPM was mandated to investigate the setting up of a Mutual Recognition Agreement in respect of instrument calibration. Any such agreement would require the keeping of records that could demonstrate the traceability of calibrations back to the base standards. Such records would be recorded within an ISO 9000 framework. Four years later, in 1999 the text of the CIPM-MRA was agreed at the 21st CGPM.
The CIPM-MRA scheme is to catalogue the capabilities of National Measurement Institutes (NMIs) such as NIST in the United States or the National Physical Laboratory in Britain whose calibration procedures have been peer-assessed. The essential points of CIPM-MRA are:
Subsequent to launch of the CIPM MRA and in response to a European Community directive on in vitro medical devices, the Joint Committee for Traceability in Laboratory Medicine (JCTLM) was created in 2002 through a Declaration of Cooperation between the International Committee of Weights and Measures (CIPM), the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), and the International Laboratory Accreditation Cooperation (ILAC).
The joint committee provides a forum for the harmonization of standards of the various participants.
Independently of this drift having been identified, the Avogadro project and development of the Kibble balance promised methods of indirectly measuring mass with a very high precision. These projects provided tools that enabled alternative means of redefining the kilogram.
A report published in 2007 by the Consultative Committee for Thermometry to the CIPM noted that their definition of temperature had proved to be unsatisfactory for temperatures below 20 K and for temperatures above 1300 K. The committee was of the view that the Boltzmann constant provided a better basis for temperature measurement than did the triple point of water, as it overcame these difficulties.
Over the next few years the support for natural constants grew and details were clarified,
until in November 2018, the 26th General Conference on Weights and Measures voted unanimously in favour of revised definitions of the SI base units.
The 2019 revision of the SI came into force on the 144th anniversary of the convention, 20 May 2019.
On 20 May 1875 representatives from seventeen of countries that attended the Conference of the Metre in 1875, signed the Convention of the Metre.Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, German Empire, Italy, Peru, Portugal, Russian Empire, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States and Venezuela. In April 1884 HJ Chaney, Warden of Standards in London unofficially contacted the BIPM inquiring whether the BIPM would calibrate some metre standards that had been manufactured in Britain. Broch, director of the BIPM replied that he was not authorized to perform any such calibrations for non-member states. On 17 September 1884, the British Government signed the convention.
This number grew to 21 in 1900, 32 in 1950, and 49 in 2001. , the General Conference membership was made up of 64 member states, 37 associate states and economies and four international organizations as follows (with year of partnership between brackets):
International organization
General Conference on Weights and Measures
International Committee for Weights and Measures
Secretariat of the BIPM
Headquarters, language and protocol
Post-1875 developments
Extensions to the treaty (1921) and development of the SI
Mutual Recognition Arrangements (CIPM-MRA)
Coordination of International Atomic Time
New SI
Membership
Member states
Argentina 1877 Australia 1947 Austria 1875 Joined originally as Austria-Hungary Belarus 2020 Belarus was previously an Associate member since 2003 Belgium 1875 Brazil 1921 Bulgaria 1911 Canada 1907 Chile 1908 China 1977 Colombia 2013 Costa Rica 2022 Croatia 2008 Czech Republic 1922 Joined originally as part of Czechoslovakia Denmark 1875 Ecuador 2019 Ecuador was previously an Associate member since 2000 Egypt 1962 Estonia 2021 Finland 1923 France 1875 Germany 1875 Joined originally as the German Empire Greece 2001 Hungary 1925 India 1957 Indonesia 1960 Iran 1975 Iraq 2013 Ireland 1925 Joined originally as the Irish Free State Israel 1985 Italy 1875 Japan 1885 Kazakhstan 2008 Kenya 2010 Lithuania 2015 Malaysia 2001 Mexico 1890 Montenegro 2018 Morocco 2019 Netherlands 1929 New Zealand 1991 Norway 1875 Joined originally as part of Sweden and Norway Pakistan 1973 Poland 1925 Portugal 1876 Romania 1884 Russian Federation 1875 Joined originally as the Russian Empire Saudi Arabia 2011 Serbia 1879 Joined as the Principality of Serbia in 1879, as the Kingdom of Yugoslavia in 1929, and as the Federal Republic of Yugoslavia in 2001 Singapore 1994 Slovakia 1922 Joined originally as part of Czechoslovakia Slovenia 2016 South Africa 1964 South Korea 1959 Spain 1875 Sweden 1875 Joined originally as part of Sweden and Norway Switzerland 1875 Thailand 1912 Tunisia 2012 Turkey 1875 Joined originally as the Ottoman Empire Ukraine 2018 United Arab Emirates 2015 United Kingdom 1884 United States 1878 Uruguay 1908
Associates
International organizations
Former member states
See also
Notes
Further reading
External links
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