Millennium Sundial

           The Millennium Sundial  Photo Credit: Chris Hawkins

A 10-metre diameter sundial was placed on the north side of the boating lake in 1999 to celebrate the Millennium. It is perfectly positioned to capture the sun’s rays and is also at zero degrees longitude. If you cast your eyes towards the Observatory from here, you are following the invisible Meridian Line. 

The sundial was designed by Christopher St. J. H. Daniel, who, after a career at sea, became a curator at the National Maritime Museum in Greenwich. There he studied sundials and became an expert in their form and function. In 1986, he left the museum to concentrate on creating new sundials. Another example of his work can be seen in the grounds of the Royal Observatory, where the tails of two dolphins tell the time. 

The Millennium Sundial is of a relatively simple design, which is most accurate in the summer months. However, it can be confusing to read because it serves two purposes: one to tell the time and the other to tell the sun’s position. 

The dial plate has a large compass in the centre with the hours of the day marked independently around the circumference. The 3-metre-high bronze gnomon, which casts the shadow, is triangular. The shadow shows the position of the sun from the vertical part of the gnomon on the compass dial. To read the time, you must visually extend the shadow from the sloping part of the gnomon out to the clock surrounding the compass. Since it tells the time in Greenwich Mean Time, you also need to add one hour to the time in the summer.