Париж меридианы және метр жүйесінің тарихы

Meridian line running through the Paris Observatory in Paris, France

The Paris meridian is a meridian line running through the Paris Observatory in Paris, France – now longitude 2°20′14.02500″ East. It was a long standing rival to the Greenwich meridian as the prime meridian of the world. The "Paris meridian arc" or "French meridian arc" (French: la Méridienne de France) is the name of the meridian arc measured along the Paris meridian. French cartographers would use it as their prime meridian for more than 200 years. Old maps from continental Europe often have a common grid with Paris degrees at the top and Ferro degrees offset by 20 at the bottom. The application of the telescope to angular instruments was an important step. He was the first who in 1669, with the telescope, using such precautions as the nature of the operation requires, measured a precise arc of meridian (Picard's arc measurement). He measured with wooden rods a baseline of 5,663 toises, and a second or base of verification of 3,902 toises; his triangulation network extended from Malvoisine, near Paris, to Sourdon, near Amiens. The angles of the triangles were measured with a quadrant furnished with a telescope having cross wires. The difference of latitude of the terminal stations was determined by observations made with a sector on a star in Cassiopeia, giving 1° 22′ 55″ for the amplitude. The terrestrial degree measurement gave the length of 57,060 toises, whence he inferred 6,538,594 toises for the Earth's diameter. Four generations of the Cassini family headed the Paris Observatory. In 1783 the French Academy of Science presented his proposal to King George III. Between 1792 and 1798 Pierre Méchain and Jean Baptiste Delambre surveyed the Paris meridian arc between Dunkirk and Barcelona (see meridian arc of Delambre and Méchain). They extrapolated from this measurement the distance from the North Pole to the Equator which was 5,130,740 toises. As the metre had to be equal to one ten millionth of this distance, it was defined as 0,513074 toises or 443,296 lignes of the Toise of Peru (see below) and of the double toise N° 1 of the apparatus which had been devised by Lavoisier and Borda for this survey at specified temperatures. In the early 19th century, the Paris meridian's arc was recalculated with greater precision between Shetland and the Balearic Islands by the astronomer François Arago, whose name now appears on the plaques or medallions tracing the route of the meridian through Paris (see below). Biot and Arago published their work as a fourth volume following the three volumes of "Bases du système métrique décimal ou mesure de l'arc méridien compris entre les parallèles de Dunkerque et Barcelone" (Basis for the decimal metric system or measurement of the meridian arc comprised between Dunkirk and Barcelona) by Delambre and Méchain. In the second half of the 19th century, Carlos Ibáñez e Ibáñez de Ibero directed the survey of Spain. From 1870 to 1894 the Paris meridan's arc was remeasured by Perrier and Bassot in France and Algeria. The triangulation of France was then connected to those of Great Britain, Spain and Algeria and thus the Paris meridian's arc measurement extended from Shetland to the Sahara. The fundamental co ordinates of the Panthéon were also obtained anew, by connecting the Panthéon and the Paris Observatory with the five stations of Bry sur Marne, Morlu, Mont Valérien, Chatillon and Montsouris, where the observations of latitude and azimuth were effected. To combine the measurements it was necessary to compare the geodetic standards of length used in the different countries. Alexander Ross Clarke and Henry James published the first results of the standards' comparisons in 1867. The first president of the International Committee for Weights and Measures was the Spanish geodesist Carlos Ibáñez e Ibáñez de Ibero. He also was the president of the Permanent Commission of the Europäische Gradmessung from 1874 to 1886. In 1883 the General Conference of the Europäische Gradmessung proposed to select the Greenwich meridian as the prime meridian in the hope that Great Britain would accede to the Metre Convention.

The United States passed an Act of Congress on 3 August 1882, authorizing President Chester A. Arthur to call an international conference to fix on a common prime meridian for time and longitude throughout the world. Before the invitations were sent out on 1 December, the joint efforts of Abbe, Fleming and William Frederick Allen, Secretary of the US railways' General Time Convention and Managing Editor of the Travellers' Official Guide to the Railways, had brought the US railway companies to an agreement which led to standard railway time being introduced at noon on 18 November 1883 across the nation. Although this was not legally established until 1918, there was thus a strong sense of fait accompli that preceded the International Meridian Conference, although setting local times was not part of the remit of the conference. In 1884, at the International Meridian Conference in Washington DC, the Greenwich meridian was adopted as the prime meridian of the world. San Domingo, now the Dominican Republic, voted against. France and Brazil abstained. The United Kingdom acceded to the Metre Convention in 1884 and to the International Geodetic Association in 1898. The meridian line, dubbed the "Rose Line" by author Dan Brown, appeared in the novel The Da Vinci Code.