Why is the Prime Meridian located at the Greenwich, London? How was it chosen?
Currently the measurement for the prime meridian is based on a decision in 1884. The decision was greatly influenced by shipping lines that already had marked the prime meridian as such. The modern Greenwich Meridian, based at the Royal Observatory, Greenwich, 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 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 Greenwich Meridian 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. The Greenwich Meridian is now marked at night by a laser beam emitted northwards from the observatory.
