The Royal Observatory and the Greenwich meridian

The Royal Observatory in Greenwich, on the hill overlooking Greenwich Park in south-east London, is the place from which time and longitude are measured for the whole world. Here runs the Greenwich Meridian, the zero line that divides the Earth into eastern and western hemispheres, and from here comes "Greenwich Mean Time", GMT. Founded in 1675, the observatory is now a museum devoted to astronomy and navigation, with a planetarium and one of the best views of London.

History

In the 17th century the most serious problem in navigation was calculating longitude, a ship's east-west position on the open sea. Errors caused shipwrecks and the loss of thousands of lives. In 1675 King Charles II founded the observatory to study the stars and find a solution. The main building, Flamsteed House, was designed by Christopher Wren, the architect of St Paul's Cathedral, and named after the first Astronomer Royal, John Flamsteed.

The solution came thanks to a self-taught carpenter and clockmaker, John Harrison, who in the 18th century built marine timekeepers accurate enough to keep exact time even on rolling seas. In 1884 an international conference in Washington chose the Greenwich meridian as the world's prime meridian. Harrison's story is told compellingly in Dava Sobel's book Longitude.

What to see

The meridian

In the courtyard, a metal line marks the prime meridian: everyone takes a photo with one foot in the eastern hemisphere and the other in the western. At night a green laser projects the line of the meridian across the London sky.

Flamsteed House and Harrison's clocks

In Flamsteed House you can visit the Astronomer Royal's apartments and the splendid Octagon Room, designed by Wren for observing the sky. The heart of the museum is Harrison's marine timekeepers, H1 to H4: marvellous machines, some still working, that changed the history of navigation. On the roof, the red time ball rises and drops every day at exactly 1 pm, as a signal to ships on the Thames since 1833.

The great telescope and the planetarium

Under the onion dome is the Great Equatorial Telescope, the largest refracting telescope in the United Kingdom. The Peter Harrison Planetarium, London's only planetarium, offers shows about the sky and the universe. The astronomy galleries tell the story of how stars and planets are born, with a real meteorite you can touch.

Practical information

The meridian area and Flamsteed House require a ticket, while some astronomy galleries are free; the planetarium has a separate ticket. The observatory is part of Royal Museums Greenwich. It is best to book online, especially at weekends. Opening times and prices are published on the official website.

Getting there

• By train or DLR: to Greenwich or Cutty Sark, then about 15 minutes' uphill walk through the park.
• By boat: on the Thames riverboats from central London to Greenwich Pier, a pleasant trip.
• By air: London City Airport is a few minutes away. See also London's airports.

Nearby

• The clipper ship Cutty Sark, the National Maritime Museum and the Queen's House by Inigo Jones.
• The Old Royal Naval College, with the magnificent Painted Hall.
• Greenwich Park, one of London's royal parks. See also London's museums.

Tips

• How long: two to three hours for the observatory, a full day for all of Greenwich.
• When to go: all year round; arrive before 1 pm to see the time ball drop.
• A tip: walk up to the viewpoint by the statue of General Wolfe: the view of the Canary Wharf towers and the City is extraordinary.

Royal Observatory (Greenwich) on the map

Nearby