Meridian of Greenwich

The Meridian of Greenwich is the meridian that passes on the locality of Greenwich (in the Real Astroroof, in the outskirts of London, the United kingdom) and that, for convention, divides the globe in ocidente and has guided, allowing to measure the longitude. George Biddell Airy in 1851 was established by Sir. Defined, for international agreement in 1884, as the first meridian, serves of reference to calculate distances in longitudes and to establish the hourly spindles. Each hourly spindle corresponds to a band of fifteen degrees of width longitude, being the greenwich time called Greenwich Mean Teams (GMT).

The Meridian of Greenwich crosses two continents and seven countries. (in the Europe: The United kingdom, France and Spain; e in Africa: Algeria, Mali, Burkina Faso and Gana).

Its antimeridian is meridian 180, that it coincides fugazmente with the irregular International Line of Date, crosses a part of Russia in the strait of Bering and one of the islands of the archipelago of Fiji, in the Pacific Ocean.

Nor always the meridian of Greenwich was used for the counting of the longitude degrees. Balbi thus historiou the subject, in its Treated one to Universal Geographia, Physica, Historical and Politics (1858):

“… not thus the longitude degrees, therefore that counting itself of a convention meridian, the one that call first meridian it has two ways counting of them, namely: or until 360º starting of the first meridian for the eastern part until finding for the part occidental person, or until 180º for the eastern part, and until others 180º for the occidental person, and in case such is necessity that if it declares express if the longitude is eastern or occidental person.
The old geógrafos, and still today the Germans, had always followed the first way counting of them; as generally it was adapted by the modern, and in particular for the Frenchmen and English.
How much to the meridian of convention or first meridian, it agrees to know, that Ptolomeu adaptou of the islands Afortunadas or Canary Islands, for if finding in the limit occidental person of the countries at that time known; that Luis XIII, king of France, determined for decree to the French geógrafos to relate the longitudes to the meridian of the Island of Iron, that is more the occidental person of that archipelago; that the dutches adaptaram of Pico de Tenerife; that Gerardo Mercator, celebrates geógrafo, chose of the Island of the Crow in the archipelago of the Açores, because in it in its time the needle to get dizzy did not suffer no declination; that however, lately, almost all the nations adaptaram the meridians of its respective astroroofs. The Frenchmen refer it the meridian of the astroroof of Paris, the English to the one of Greenwich, the Spaniard to the one of Cádis, the Portuguese to the one of Coimbra or to the one of Lisbon. “
In Portugal, at the beginning of century XIX the Average Solar Time was adopted (always 24-hour days, when in the reality they present variations between more 16 or less 14 minutes throughout the year), simplifying the determination of the Legal Hour. Later, from 1878, the Astronomical Astroroof of Lisbon (OAL) started to function as only meridian zero for all the domestic territory. In 1912, with the adhesion of the country to the system of hourly spindles, the legal hour of Continental Portugal started to be of the meridian of Greenwich and the clocks had had that to be advanced in 36m and 44,68s, that is, the difference enters the meridians of the OAL and of Greenwich.

After Greenwich

. Although the confusion in relation to the prime meridian, no longer year of 1884 more than one two terços of the ships used the Meridian of Greenwich as longitude reference. In the month of October of that year, under the auspices of Chester. the Arthur, then president of the United States, 41 commission agents of 25 nations if had found in Washington, DC for the International Conference of the Meridian. This Conference selected the Meridian of Greenwich as prime meridian due to its popularity. They had voted for the Meridian of Greenwich the Austrohungarian Empire, Chile, Colombia, Costa Rica, Germany, the United kingdom, Guatemala, the Hawaii, Italy, Japan, the Libéria, Mexico, the Netherlands, Paraguay, Russia, Spain, Sweden, Switzerland and Turkey. Brazil and France, however, had abstained it vote (per some decades still, the French maps had remained using the Meridian of Paris as meridian zero) and the Dominican Republic voted against. The representatives of the United States, Venezuela and El Salvador had lacked to the voting.