Royal Observatory and the Prime Meridian
Why is it significant?
Catch your breath at the top of the hill and look at the courtyard of the Royal Observatory: a metal line runs across the stones, and people queue to stand with one foot on either side of it, one in the eastern hemisphere, one in the western.
Key Facts
| Place | Royal Observatory and the Prime Meridian |
|---|---|
| Address | Blackheath Avenue, London SE10 8XJ, United Kingdom |
| Geo Coordinates | 51.47740, -0.00080 |
| Part of Walk | Under the Thames to Longitude Zero: Maritime Greenwich, London |
| Generated | Generated |
Catch your breath at the top of the hill and look at the courtyard of the Royal Observatory: a metal line runs across the stones, and people queue to stand with one foot on either side of it, one in the eastern hemisphere, one in the western. This is the Prime Meridian, longitude zero, the line from which the whole planet measures east and west.
The observatory was founded by Charles the Second in 1675 for one urgent purpose: to help sailors find their longitude at sea, where a wrong guess could put a ship on the rocks. Christopher Wren, himself an astronomer before he was an architect, designed the first building, Flamsteed House, named after John Flamsteed, the first Astronomer Royal. Wren said it was built for the observer's habitation and a little for pomp.
Now look up at the red ball on the mast above the building. That is the Time Ball, installed in 1833. Every day it rises halfway, then to the top, and at exactly one o'clock it drops. Ships' officers on the Thames watched for it to set their chronometers, and it is one of the earliest public time signals in the world.
Why Greenwich, and not Paris? In 1884 delegates from twenty-five nations met in Washington for the International Meridian Conference. Most of the world's shipping already used charts based on Greenwich, so the vote went twenty-two to one, with San Domingo against and France and Brazil abstaining. France kept the Paris meridian for its own clocks until 1911. And the twist: the line at your feet follows George Airy's telescope of 1851, but satellite measurements place zero longitude about a hundred metres to the east, out on the grass of the park.
Beside the observatory, on the edge of the slope, a bronze soldier gazes out over London: General James Wolfe, a gift from Canada unveiled in 1930, his pedestal still pitted by bomb splinters from the Second World War. Wolfe's family home stood at the far side of the park, so follow the avenue south, then bear right along the park's western edge, to the red-brick house where the walk ends.