How To Build A Armillary Sphere

An armillary sphere is a model of the Ptolemaic, Earth-centered universe that is at least 2,000 years old. It consist of a globe of the Earth as it was known at the time, surrounded by a series of fixed bands that represented important celestial tracks, such as the equator, the zodiac, the paths of the sun and moon and the positions of important constellations. "Armillary" comes from an old word that means "bracelets" — the bands encircling the globe apparently suggested bracelets to someone.

Step 1

Paint the central globe to represent the earth. For authenticity, make America and Asia one continent. Most areas of the world can be inaccurate, but the Mediterranean must be accurate. It is a good idea to include sea serpents and dragons, as these are always present in any medieval map. The real armillary spheres had globes that were etched to show the continental outlines. You can simulate this with metallic paint over raised – or depressed — outlines.

Step 2

Support the bands with short sections of the dowel rod. Cut the dowels to be half the difference between the diameters of the bands and the globe. For example, if the globe is 6 inches in diameter and the bands are 10 inches in diameter, the dowels will be 2 inches long because 1/2(10 – 6) = 2. Spray paint the dowels. Find three or four places around the equator that do not interfere with an interesting feature, like the Mediterranean, to glue the first dowels. Glue on the equatorial band. This band should have the word "Equator" written on it in old fashion script and the band should be painted like the rest of the armillary sphere.

Step 3

Glue in place the Tropic of Cancer and Tropic of Capricorn bands parallel to the equatorial bands and half way from the equator and the poles. The paths of the sun, moon and zodiac – always included in armillary spheres are roughly the same and make a 20 to 30 degree angle to the equatorial band. This angle changes with the time of year. It is traditional to divide the zodiac band up with 12 vertical bars and put the appropriate symbol in each section. Add one or two other bands at artistically pleasing angles. Attach the pedestal, if there is one, to the South Pole.