BİRİNCİ FEN · İKİNCİ BÂB · SEKİZİNCİ FASIL · Birinci Madde
Article One
It describes the sphere of Mercury’s common perigee and the form of its movement.
Know, O esteemed one, that astronomers have said: The sphere of Mercury is counted among the aforementioned eight spheres and is second to the sphere of the Moon. It lies beneath the sphere of Venus and is renowned as [50/a] the “two below” (as-suflayn), being the spheres closest to the sphere of the Moon and situated lower than it. The star of Mercury alone governs this sphere and is known by the name "the commingling" (al-mumtazij). Its sphere, in terms of its position, structure, and components, is in a condition distinct from that of the other planets.
Astronomers have ascertained the existence of three large spheres encompassing the Earth concerning Mercury, and one small sphere not encompassing the Earth; upon this fundamental observation, they have ordered its variations within the four spheres, observing its conditions. The first of the four spheres is the universal sphere. It is the common perigee (al-mumassil) sphere, centered, on the axis, in the belt, at the poles, conforming to the movement of the zodiacal sphere, and is the sphere of common perigee. This sphere, like other spheres of common perigee, encompasses the Earth. And its center is the center of the universe. It is a spherical body surrounded by two parallel surfaces. Its upper side is tangent to the lower surface of Venus situated above it, and its lower side is tangent to the upper surface of the Moon situated below it. And this sphere of common perigee primarily follows the movement appropriate to the daily rapid motion of the greater sphere, like other spheres above and below it, and is compelled to move from east to west around the center of the universe.
Secondly, it proceeds slowly around the center of the universe from west to east with a movement unique to itself, as if it moves by means of the movement of the zodiacal sphere. In this state, its apogee, perihelion, ascending node, and descending node points advance one degree every seventy solar years (according to the aforementioned motion). The apogee of Mercury, located in its directing sphere – which will be explained below – is distinct from the Moon’s apogee – also explained below –, its sphere of common perigee, and its nodal points. For these four do not conform to them and move from east to west.