Prime meridian (Greenwich)

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The Greenwich meridian is a prime meridian, a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. From 1884 to 1974, the Greenwich meridian was the international standard prime meridian, used worldwide for timekeeping and navigation. The modern standard, the IERS Reference Meridian, is based on the Greenwich meridian, but differs slightly from it. This prime meridian (at the time, one of many) was first established by Sir George Airy (in 1851). In 1883, the International Geodetic Association formally recommended to governments that the meridian through Greenwich be adopted as the international standard prime meridian. In October of the following year, at the invitation of the president of the United States, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference. This inter-governmental conference selected the meridian passing through Greenwich as the world standard prime meridian...

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