The Royal Observatory, Greenwich
'…the very centre of Time and Space.' Nathaniel Hawthorne, 'Our Old Home', 1863
| King Charles II. © NMM|
This was founded by Charles II in 1675 for the advancement of navigation and astronomy, especially finding a way to calculate longitude at sea.
Developing the site
Sir Christopher Wren designed the original building, which was built in 1675 on the foundations of Duke Humphrey's Tower (Greenwich Castle). This was soon called Flamsteed House, after John Flamsteed, who lived there as first Astronomer Royal from 1676 until his death in 1719.
|The Royal Observatory. © NMM|
Flamsteed did most of his work in a quadrant house in the garden (now reconstructed). Later additions from the 18th century up to 1857 make up what is now called the Meridian Building.
Here, the Airy Transit Circle of 1851 defines the position of Longitude 0°, the modern Greenwich Meridian and baseline of world time.
National Maritime Museum
|The Royal Observatory at Greenwich. © NMM|
The Observatory has been part of the National Maritime Museum since the early 1950s and fully open to the public since 1967.
Much of the original instrumentation is still there together with the Museum's related astronomical and time-keeping collections.
|The 28-inch refracting telescope. © NMM|
These include John Harrison's pioneering marine chronometers and the 28 - inch (71 cm) Greenwich refracting telescope, which is the eighth largest in the world.
The South Building, completed in 1899, was previously the New Physical Observatory. It is due to become the Museum's modern astronomy centre by 2006.
| Sir George Biddell Airy, Astronomer Royal 1835-1881. © NMM|
Since Earth turns on its axis once every 24 hours, there has to be a baseline where each day begins. That line is Longitude 0°, the Universal Prime Meridian fixed at the Royal Observatory, Greenwich.
Meridians - lines of longitude joining the north and south poles - can only be accurately calculated from timing the 'transit', or passage, of stars overhead.
In 1851 the seventh Astronomer Royal, (Sir) George Biddell Airy, installed a new transit telescope at the Observatory. Its position defined his new 'Greenwich meridian', just east of several others dating back to 1676.
Also in 1851, Airy began using the electric telegraph to broadcast Greenwich time based on this new meridian, to Britain and the world. This transformed 'Greenwich time' from a nautical and scientific idea to a fully public one.
| The Meridian Building, Royal Observatory.|
In 1884 the International Meridian Conference in Washington DC agreed that Greenwich time should be the world standard. This was largely because most sailors used British sea-charts (with 'longitude zero' at Greenwich).
World timekeeping is now co-ordinated in Paris and is based on atomic clocks. But each 'universal day' still begins on the Greenwich meridian.