Royal Greenwich Observatory

The original site of the Royal Greenwich Observatory (RGO), which was built as a workplace for the Astronomer Royal, was on a hill in Greenwich Park in Greenwich, London, overlooking the River Thames. The Prime Meridian, to which longitude refers, went through the observatory. It is marked by a brass strip in the courtyard and, since December 16, 1999, a powerful green laser shining north across the London night sky.

Chronology

• 1675 Royal Observatory founded.
• 1924 Hourly time signals (Greenwich Time Signal) from the Greenwich Observatory were first broadcast on February 5.
• 1948 Astronomer Royal moves to Herstmonceux.
• 1957 Royal Observatory completes its move to Herstmonceux, becoming the Royal Greenwich Observatory (RGO). The Greenwich site becomes the Old Royal Observatory.
• 1990 RGO moves to Cambridge.
• 1998 RGO closes. Greenwich site becomes the Royal Observatory, Greenwich, and is part of the National Maritime Museum.