Prime meridian (Greenwich)
A prime meridian, based at the Royal Observatory, Greenwich, in London, was established by Sir George Airy in 1851. By 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps. In October of that year, at the behest of U.S. President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., USA, for the International Meridian Conference. This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity. However, France abstained from the vote and French maps continued to use the Paris meridian for several decades. In the 18th century, London lexicographer, Malachy Postlethwayt published his African maps showing the 'Meridian of London' intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.
The prime meridian passes through the Airy transit circle () of the Greenwich observatory. It was long marked by a brass strip in the courtyard, now upgraded to stainless steel, and, since 16 December 1999, has been marked by a powerful green laser shining north across the London night sky.
The Greenwich meridian passes through:
- United Kingdom,
- Burkina Faso,
- Queen Maud Land in Antarctica.
- ROG Learing Team (23 August 2002). "The Prime Meridian at Greenwich". Royal Museums Greenwich. Royal Museums Greenwich. Retrieved 14 June 2012.
- Malachy Postlethwayt. (1774) Universal Dictionary of Trade and Commerce. (4th edition) London: W. Strahan, J. & F. Rivington. Vol. 1 "A New and Correct Map of the Coast of Africa"
- Calvert, Carl (1999). "The Greenwich Meridian in the Space Age". Retrieved 7 July 2011.
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