The Royal Observatory, Greenwich (also known as the Royal Greenwich Observatory) is on the prime meridian where Greenwich Mean Time (GMT) is set. This museum of astronomy and time is where you can see the time-ball and working telescopes and visit the adjoining planetarium.
King Charles II commissioned the observatory in 1675 with Sir Christopher Wren choosing the site and the building was completed just a year later in 1676. The primary purpose of the Royal Observatory was to accurately calculate longitude to aid navigation.
The Greenwich Meridian (0º longitude) passes through the buildings of the Royal Observatory. The meridian is marked by a stainless steel strip (originally a brass strip) in the Observatory’s courtyard, and since 16 December 1999, the Greenwich Meridian is also marked by a green laser.
Greenwich Mean Time (GMT) is also based at the Royal Observatory and until 1954 the official time was based on observations made from the observatory; however, the Royal Observatory moved to Herstmonceux in the 1950s and the site in Greenwich is now used solely as a museum.
The time ball at the Royal Observatory drops at precisely 1pm every day, and many people rely on this to synchronise their watches.
The observatory buildings are now an important museum of timekeeping, astronomy and navigation. Since 2007, the museum has featured a 120-seat planetarium.
Visiting Royal Observatory, Greenwich
Greenwich is less than 10 minutes by train from London Bridge station with trains running every ten minutes. Most people combine a visit with the nearby National Maritime Museum and the Cutty Sark. The observatory is around a 15-minute walk from Greenwich station.
Admission is free with a London Pass and visitors with the National Art Pass are eligible for a 50% discount on the admission price.
Wheelchair access to the Royal Observatory is limited to the Meridian line, the ground floor of the Meridian building, Astronomer’s Garden and Camera Obscura but the older Grade I-listed buildings including Flamstead House and the Great Equatorial telescope are not accessible. The main walking path to the observatory is rather steep and wheelchair users are recommended to take the longer – less steep – path.
The Royal Observatory has the Astronomy Café and Terrace plus a gift shop.