The History of Sundials

Sundial InscriptionsThe history of sundials dates back many thousands of  years and a true date could not be truly established. Like the wheel there was no eureka moment and it was probably commonplace for a stick to be pushed into the ground and the shadow used for moments in the day that were important such as meal times or for prayer. But it is generally accepted that 3000 to 5000 years BC would see the start of their development.
Once the Greek mathematicians had established trigonometry things started to develope rapidly in the field of astronomy. It was Eratosthenes who calculated that the Earth was tilted on its axis so giving us the seasons, he also calculated the Earth’s circumference and distance from the sun. These calculations  were to be found very accurate .

It was soon realised that the angle of the gnomon, the pointer that cast’s the shadow was critical for accurate time keeping . For the a sundial to keep time the gnomons angle would need to run parallel to the Earth’s axis. So the angle should correspond to the angle of latitude at which the sundial is sited. A sundial sited in London would have a gnomon angled from from the sundial plate of 51.5 degrees. as the latitude of London is 51.5 degrees North.

On many old churches around the UK one can find sundials within the stonework. These are  known as Mass Dials or Scratch Dials. They are  usually a semicircle with lines  scratched into a stone with a hole bored in them to hold  the  gnomon which would be a stick of wood. The original gnomons are long gone with just the hole remaining.
During the renaissance and Tudor periods sundials started to become more accurate and  sophisticated. There development  has left a legacy that remains with us today, with most prestigious buildings and country houses  displaying an elaborate sundial.