History of Armillary Spheres

Armillary spheres are without doubt the most visually striking sundials. Modelled on the heavens and earth, armillaries are based on the designs of natural philosophers. Armillary spheres speak of the rich history of astronomical endeavour, from Ptolemy to Copernicus.

Armillaries date from about 225BC, and were devised by the Egyptian astronomer, Eratosthenes. Armillaries were always used as astronomical instruments and never as sundials. Not till the late 17th century were they first used for telling the time.

The name armillary comes from the Latin armilla; for bracelet or amulet; from where we get the word arm (where you put your amulet). They are a sundial in that they use the light from the sun to cast a shadow and hence tell the time.

The concentric rings represent the Equator, the Horizon and the Meridian, and the Gnomon is the shape of an arrow pointing to the pole star.

They could be considered to be one of the purest forms of sundial in that they are a model of the earth - which is the biggest sundial of all!