Armillary Sphere

The Armillary Sphere is an earth-centered model of the universe developed and used extensively in the medieval period. The model the earth in the center because medieval societies believed the earth was the center of the universe.

An armillary sphere was used to tell the time of year (like a sundial was used to tell the time of day) by the positions on the horizon where the sun would rise and set. This helped medieval communities know when to plant, harvest, hunt, expect certain phenomenons of weather (for example seasonal rains, floods, and extremes of temperature) celebrate festivals associated with these yearly occurences.

Even though we now know that we live in a sun-centered universe, this is still an accurate and interesting model. It allows us to "speed up" time and see how the path of the sun, moon and planets (the ecliptic) moves both through the course of the day and through the course of the year.