360The Royal Observatory is founded at Greenwich
On 22 June 1675, King Charles II of England signed a warrant to build an observatory at Greenwich, near London, to chart the stars and help sailors find their longitude at sea. John Flamsteed became the first Astronomer Royal. Two centuries later, the line through Greenwich became the world's Prime Meridian, longitude zero.
In the 1670s, sailors could find their latitude from the Sun and stars, but not their longitude, their position east or west. Ships were lost because navigators did not know where they were.
On 22 June 1675, King Charles II signed a royal warrant to found an observatory to solve the problem by mapping the positions of the stars with new precision. The building, on a hill in Greenwich Park, was designed by Sir Christopher Wren and finished in 1676.
John Flamsteed was appointed the first Astronomer Royal. Over more than 40 years he measured the positions of about 3,000 stars, producing the most accurate star catalogue of his age.
The longitude problem was finally solved in the 18th century, with accurate sea clocks built by John Harrison and with tables of the Moon's motion calculated at Greenwich.
In 1884, delegates from 25 nations met in Washington and chose the meridian through Greenwich as the world's Prime Meridian, longitude zero. Greenwich Mean Time became the basis of the world's time zones. Today the observatory is a museum, and visitors can stand with one foot in each hemisphere.
- 1675
- Charles II founds the Royal Observatory
- 1676
- The observatory building is completed
- 1725
- Flamsteed's star catalogue is published
- 1884
- Greenwich is chosen as the Prime Meridian
Sources: Royal Museums Greenwich · Britannica.