The Royal Observatory, Greenwich
You can stand with one foot in the east and one in the west, but the real story of Greenwich is how a king's astronomer helped sailors find their way home.
Published
Quick Facts
- Location
- Greenwich Park, south-east London
- Founded
- 1675, by order of Charles II
- Designed by
- Sir Christopher Wren, with Robert Hooke
- First Astronomer Royal
- John Flamsteed
- Famous line
- The Prime Meridian, longitude 0°, fixed in 1884
- Famous clock
- Harrison's marine timekeepers, including H4 (1759)
- Telescope
- The 28-inch refractor, installed 1893 and among the largest of its type in the UK
- Status
- Part of the Maritime Greenwich UNESCO World Heritage Site, inscribed 1997
The building that was ordered to find the sea
The Royal Observatory exists because of a very practical problem: ships were getting lost. In the 17th century, sailors could work out latitude fairly well, but longitude was guesswork, and mistakes wrecked fleets and cost lives. In 1675 Charles II founded the observatory and created the post of Astronomer Royal. The job was to map the stars and the Moon's movements precisely enough to help navigators fix their position at sea. The king's choice of site was the hilltop in Greenwich Park, with wide views over the Thames and the sky. Sir Christopher Wren designed the original building, now known as Flamsteed House, and Robert Hooke was involved too. It was built quickly and on a modest budget, with some materials reportedly reused from other sources.
Flamsteed, the stargazer who had to pay for his own instruments
John Flamsteed, the first Astronomer Royal, was given a salary and a building, but not much else. He famously had to buy many of his own instruments. Over decades he compiled a huge catalogue of star positions, far more accurate than anything before it. His relationship with Isaac Newton and Edmond Halley turned sour when they arranged for an unauthorised edition of his observations to be printed without his approval. Flamsteed was furious, and later reportedly burned copies he got hold of. His careful work all the same laid the foundations for the observatory's reputation.
The great longitude race and the clockmaker who won it
The big prize was a way to measure longitude. Astronomers hoped to do it by watching the Moon and stars. A carpenter-turned-clockmaker from Yorkshire, John Harrison, had a different idea: a clock that kept accurate time at sea. His marine timekeepers, H1 to H4, are now displayed at the observatory. H4, finished in 1759, looks like an oversized pocket watch, and it performed superbly on sea trials. If you know the time at Greenwich and the local time on board, the difference tells you how far east or west you have travelled. Harrison's struggle to win recognition under the Board of Longitude is one of the great stories of British science, and you can see the clocks that made it happen.
Why the world's time starts in a London park
Greenwich became the home of zero longitude partly through habit. British charts used it, and by the 19th century a huge share of the world's shipping relied on them. In 1884 delegates at the International Meridian Conference in Washington voted to adopt the Greenwich meridian as the world's prime meridian. Greenwich Mean Time became the basis for global time zones. Today a brass strip in the courtyard marks the line, and visitors queue to straddle the eastern and western hemispheres for a photograph. Other markers of the meridian have been used over time. The line used for modern satellite navigation, the one GPS relies on, actually lies slightly east of the brass strip, a fact that surprises many people.
The red ball that drops at one o'clock
Look up at the roof of Flamsteed House and you will see a red time ball. Installed in 1833, it rises halfway up its mast shortly before 1pm and drops at exactly 1pm each day. It was designed so that ships on the Thames could set their chronometers by eye. It is thought to be one of the oldest public time signals of its kind in the world, and it still works. On the gate outside is the 24-hour Shepherd Gate Clock, which shows Greenwich Mean Time and was one of the first clocks to show time distributed by an electric signal.
What to look for when you visit
Start with the courtyard, the meridian line and the views over the Queen's House, the Old Royal Naval College and Canary Wharf. It is one of the best panoramas in London. Inside, seek out Harrison's clocks, Flamsteed's octagonal room and the rooms that show how astronomers lived and worked. The 28-inch refractor telescope sits under a distinctive onion-shaped dome, and the nearby Peter Harrison Planetarium brings the night sky indoors. The climb up through the park is steep, so take your time. The walk is part of the experience, because the hill was chosen for the view.
Notable people
- Charles II
- Sir Christopher Wren
- Robert Hooke
- John Flamsteed
- Edmond Halley
- Isaac Newton
- John Harrison
Test yourself
Play the UK quizMore to see nearby
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