The Invention of the Sundial merges with the history of two ancient civilizations, Egypt and Mesopotamia. Taken up later by the Romans and the Greeks, this tool was very useful for administrative and especially religious organizations, the latter often punctuating daily activities. Today there are still many sundials from these periods, in various shapes:spherical, concave, convex, hemispherical...
The invention of the sundial
It is the Greek historian Herodotus (v. 484-v. 420 BC. ) which was the first to mention the ancestor of the sundial, called the gnomon, invented by the Babylonians. One can advance the idea that the gnomon is used a long time before this first mention. The principle is simple:a stick planted in the ground casts its shadow on a plane on which one can determine, following previously established observations, the hours of the day and the periods of the year. The invention was passed on to the Egyptians who created the real vertical sundial in the 20th century BC. At the same time, the Mesopotamians invented the polo shirt where the shadow of the style is projected on a hollow half-sphere.
A sundial is made up of two parts:the gnomon and the plane of the sundial. The gnomon usually consists of a metal rod called a style, parallel to the axis of the Earth and pointing towards the celestial pole. The plane of the dial is the surface on which the twenty-four meridians, or hour lines, are traced. A sundial must be adapted to the latitude. Tables are used to calculate universal time from solar time, because solar time is irregular, since the apparent speed of the Sun varies during the year. Sundials were used before the use of clocks and watches spread, as early as the 18th century.
To go further
- 30,000 years of Thomas Craughwell inventions. Gründ, 2009.
- The 1001 inventions that changed the world by Jack Challoner. Flammarion, 2010.