The Sphere of the World

...is called the motion of the first mover original: "primi mobilis"; the outermost sphere of the medieval universe which imparts motion to all other spheres. This refers to the ninth sphere, or the final heaven, which moves from the east through the west and returns again to the east. This is also called the rational motion Medieval thinkers believed the rotation of the highest heaven mirrored the "orderly" movement of human reason, following the likeness of the movement of reason within the microcosm literally "little world"; the human being seen as a reflection of the entire universe. That is to say, just as human contemplation starts with the Creator, moves through the study of created things, and returns to rest in the Creator. The second motion, which belongs to the firmament and the planets, is contrary to this: it moves from the west through the east and returns again to the west. This is called the irrational or sensual motion, following the likeness of the movement of the microcosm which goes from corruptible things toward the Creator and returns again to corruptible things. Therefore, the "belt" of the first motion is so named because it girds or divides the first mover—that is, the ninth sphere—into two equal parts, sitting equidistant from the poles of the world.

In this regard, it should be noted that the pole of the world which is always visible to us is called the northern, arctic, or boreal pole. It is called Septentrional original: "septentrionalis" from the septentrio, which is the Lesser Bear; the name comes from septen [seven] and trion [ox], because the seven stars in that constellation move slowly like oxen, being so close to the pole. Others say those seven stars are called septentriones as if they were teriones [threshers], because they "tread" original: "terunt" the parts around the pole. It is called Arctic from the word arctos, which means the Greater Bear, as it is situated near the Greater Bear. Finally, it is called Boreal because it is in that region from which the Boreas the North Wind blows. The opposite pole is called the Antarctic, placed as if "against the arctic." It is also called the Meridional pole, because it is in the direction of the south literally "midday," the direction of the sun at noon, and it is also called the Austral pole, because it is in the region from which the Auster the South Wind blows. These two stable points in the firmament are called the poles of the world because they terminate the axis of the sphere, and the world revolves around them; one of them is always visible to us, while the other is always hidden. Thus Virgil Publius Vergilius Maro (70–19 BC), the Roman poet; this quote is from his Georgics, a poem on agriculture and nature says in the first book of the Georgics:

On the zodiac circle.

¶ There is another circle in the sphere which intersects the equinoctial the celestial equator and is intersected by it into two equal parts. One half of it inclines toward the north, and the other toward the south. This circle is called the zodiac, from the word zoe Greek for "life"...