Greenwich Royal Observatory

Greenwich Royal Observatory: The Meridian Line and the Hill Worth Climbing

In 1884, delegates from 25 countries gathered in Washington DC and voted to make Greenwich the world’s Prime Meridian – longitude zero, the reference point from which every time zone on earth is measured. It was not an inevitable choice. Paris wanted the meridian to pass through France; Washington was also proposed. Greenwich won partly because British naval charts already used it and because Britannia’s maritime dominance made that a practical argument. The meridian line on the observatory courtyard is a thin brass strip that attracts more visitors per metre than almost any feature in London.

Entry to the Royal Observatory and Meridian Line costs GBP 18 for adults; buying online avoids the ticket counter queue on busy days. The Planetarium show is included.

The Prime Meridian

Standing with one foot in each hemisphere is a 10-second activity that becomes a 20-minute queue on summer weekends. More interesting than the photograph is the fact that GPS measurements now show the line runs about 100 metres east of the actual meridian as defined by modern geodetic surveying. The observatory’s own exhibits explain this discrepancy – the original line was set by optical instruments pointing at stars; the GPS-derived meridian accounts for the Earth’s gravitational field variations. The old line and the true line diverge visibly when you know where to look.

On clear evenings, a green laser projects the Prime Meridian northward from the observatory, visible from across Greenwich and along the Thames.

Inside the Observatory

The Flamsteed House, the original 1675 building, contains the Longitude Gallery with John Harrison’s four marine chronometers, H1 through H4. These clocks solved the Longitude Problem – the inability of ships to determine their east-west position at sea – a problem that had caused maritime disasters for centuries. The H4 in particular is a pocket-watch-sized brass instrument of extraordinary precision. Harrison spent 43 years building successively accurate versions and fighting the Admiralty for the prize money the Board of Longitude had promised but refused to pay. The full story is one of the better scientific disputes in British history.

The Great Equatorial Telescope in a Victorian onion-domed building behind the main house is the largest refracting telescope in the UK. Evening telescope viewings are scheduled on Friday and Saturday nights (separate booking, GBP 10).

Greenwich Park

The park surrounding the observatory is the oldest Royal Park in London, laid out as a deer park in the 1430s. The steep grass slope below the observatory gives views of the Queen’s House (a Palladian villa by Inigo Jones from 1635), the National Maritime Museum, the Isle of Dogs skyline, and the Thames below. It is one of the best elevated London views you can get without paying for it.

The National Maritime Museum

Immediately below the observatory hill, the National Maritime Museum is free to enter. It has the largest collection of maritime artefacts in the world: Nelson’s uniform from Trafalgar (with the bullet hole visible), original naval charts, ship models at extraordinary scale. Allow 2-3 hours. The Queen’s House attached to the museum building is Inigo Jones’s first completed building and one of the earliest purely classical structures in England.

Getting to Greenwich

DLR from Bank or Tower Gateway to Cutty Sark station takes 20-25 minutes. The Thames Clipper river boat from Embankment, Waterloo, or London Bridge piers to Greenwich Pier takes 30-45 minutes and costs GBP 9 one way – it is slower than the DLR but the views of the Thames at Canary Wharf are worth the extra time if you have it. Both are covered by Oyster or contactless.