Dolphin Sundial -- Royal Observatory, Greenwich, London, UK
N 51° 28.667 W 000° 00.113
30U E 708187 N 5707221
An elegant Dolphin Sundial unveiled by Baroness Burke in the Gardens at the national Martitime Museum was moved to the Royal Observatory in 2009
Waymark Code: WMT42R
Location: London, United Kingdom
Date Posted: 09/21/2016
Views: 5
An elegant dolphin sundial presents an interesting lesson on using the sun to tell time in the gardens behind the Royal Observatory in Greenwich.
This artistic scientific instrument was unveiled by Baroness Burke on 5 June 1978 at the National Maritime Museum, but was relocated to the Royal Observatory in 2009.
The sign reads as follows:
"THE DOLPHIN SUNDIAL
Designed by Christopher St. J. H. Daniel;
bronze sculpture by Edwin Russell FRBS
The gnomon, or pointer, of the sundial is formed by the tips of the two Dolphins tales, which almost meet. Details cast a shadow onto the dial plate, which is engraved with thick curved lines representing the hours. Thinner lines indicate 10 min. intervals between each hour.
The dial plate has curved lines rather than straight ones to allow for the variations in the sun's apparent Dailymotion. The plate used in summer shows British Summer Time; that used in winter shows Greenwich Mean Time.
The midpoint between the shadows of the Dolphins tales tips indicates the correct time.
Example: [graph]
The Dolphin Sundial was commissioned by the National Maritime Museum in 1977 to commemorate the Silver Jubilee of Her Majesty Queen Elizabeth II.
It was unveiled on 5 June 1978 by the Baroness Burke, in the main grounds of the Museum. It was moved here in June 2009 during the re-landscaping of this garden, which was made possible by the generosity of the Friends of the National Maritime Museum."
A nearby sign explains the science behind sun dials as follows:
"SUNDIALS AND SOLAR TIME
Clock time and sundial time often appear different. Talk time is based on the assumption that each day lasted for exactly 24 hours all through the year. In contrast, sundial time account for seasonal variations in day length caused by the Earth’s tilted axis and its elliptical orbit around the sun.
When these two effects are combined, we produce the wavy pattern seen in the accompanying figure, known as the equation of time. When the curve is below the horizontal axis, noon on a sundial occurs several minutes after noon on a clock during these months. When the curve is above the horizontal axis, noon on the sundial occurs several minutes before noon on a clock.
The maximum difference between the local solar time and mean (clock) time is 16 min. in this occurs on for November. There are four days in the year when sundials and clocks coincide at noon: 16, April, 15 June, one. September and 25 December."
Original Location: N 51° 28.330 W 000° 00.330
How it was moved: Wheels / Dolly / Truck
Type of move: Inside City
Building Status: Public
Related Website: [Web Link]
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