Royal Observatory, Greenwich
Greenwich Park, London SE10

The home of Greenwich Mean Time, the Royal Observatory marks the line of Longitude 0°00’00”. All the time zones of the world are measured from this point.

Founded in 1675 by Charles II, it was the official government observatory until 1948.  The original building, Flamstead House, was designed by Sir Christopher Wren and named after the first Astronomer Royal. 

The building has an unusual octagonal room at the top, topped by two turrets. Above one of the turrets is a ball on a rod.  This ball has been dropped at 1.00 pm every day since 1833 so that makers of chronometers, navigators' clocks and sailors on the Thames could set their clocks by it.

Charles II set the Royal Observatory the task to find a solution to the problem of determining longitude at sea.  A sum of £20,000 was promised and the prize was claimed by the clockmaker, John Harrison, in 1763.  

In 1884, after an international agreement, Greenwich Mean Time became the basis of time measurement for most of the world.  The meridian, 0º longitude, passes through Greenwich at the Royal Observatory and divides the globe into East and West.  A line on the ground outside the buildings marks the position of the meridian, popular to be photographed with a foot in each hemisphere.

In 1948, when the lights of London became too bright, the astronomers moved to darker Sussex and today the Astronomer Royal is based in Cambridge.  

The group of buildings at the Observatory houses exhibitions charting the establishment of Greenwich Mean Time and the zero meridian.   There is also a collection of astronomical instruments, chronometers and clocks, including a rare 24-hour clock. 

The Planetarium is now being refurbished..

The Royal Observatory, set at the top of a hill, has good views over London.   

Planetarium is now Closed for refurbishment - re-opens 2007

Opening Times

Planetarium is now Closed for refurbishment - re-opens 2007
Open: Daily   10.00 am - 5.00 pm (18.00 in summer), seven days a week. Last admissions 30 minutes before closing.Closed 24–26 December. Please enquire for opening on 31 December, 1 January. Tel: 020 8858 4422 Tel: 020 8312 6565 (recorded information line)