Greenwich - Thames Yacht Charters

Erected in 1833, the Greenwich Time Ball was one of the world's first visual time signals. The ball, which drops daily at 1300, was used to check marine chronometers by sailors on the Thames.Charles II, and was built specifically to do work which would help to solve the problem of finding longitude - one's exact position east and west - while at sea and out of sight of land.

Charles II appointed John Flamsteed as his first Astronomer Royal in March 1675. The 28-year old clergyman was instructed 'to apply himself with the most exact care and diligence to the rectifying the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much-desired longitude of places for the perfecting the art of navigation.'

Longitude was then impossible to calculate at sea and Flamsteed began his observations in 1676 to solve the longitude problem once and for all.

The Royal Observatory, Greenwich is also the source of the Prime Meridian, longitude 0° 0' 0''.
Until the 19th century, each country tended to keep its own zero meridian. The Prime Meridian for the world was adopted in 1884, at the International Meridian Conference in Washington DC. Twenty five countries were represented and voted to adopt the Meridian at Greenwich as the Prime Meridian for the world. It was also agreed that longitude would be measured in two directions from the Prime Meridian, 'east longitude being plus and west longitude being minus.'