Sphere two poles is called the axis of rotation. Circles on the sphere that are parallel to the equator are lines of latitude. This terminology is also used for such approximately spheroidal astronomical bodies as the planet Earth (see geoid). Any plane that includes the center of a sphere divides it into two equal hemispheres. Any two intersecting planes that include the center of a sphere subdivide the sphere into four lunes or biangles, the vertices of which all coincide with the antipodal points lying on the line of intersection of the planes. The antipodal quotient of the sphere is the
Sublunary sphere - the idea usually going hand in hand with geocentrism and the concept of a spherical Earth. Avicenna carried forward into the Middle Ages the Aristotelian idea of generation and corruption being limited to the sublunary sphere. Medieval scholastics like Thomas Aquinas - who charted the division between celestial and sublunary spheres in his work "Summa Theologica" - also drew on Cicero and Lucan for an awareness of the great frontier between Nature and Sky, sublunary and aetheric spheres. The result for medieval/Renaissance mentalities was a pervasive awareness of the existence, at the Moon, of what C.S. Lewis called 'this