BİRİNCİ FEN · İKİNCİ BÂB · BEŞİNCİ FASIL · Birinci Madde
The greatest source of light conveys the properties of the geocentric sphere. O esteemed one! Know that astronomers have said: Beneath the orbit of Mars, in the sixth orbit relative to the orbit of the Moon, there exists a single Sun and it is known as the “Sun orbit.” This immense source of light, this magnificent sultan; it is the sun illuminating our world. Among the stars, it is the most renowned and radiant, and according to the majority of astronomers, it is the largest star; nights and days, months and years are ordered in accordance with its movement. And many great events have occurred due to the rulings taking place within the Sun. It is like a lamp of light amidst the seven planets, and for illuminating those below and above it, its center serves as a station for all of them, so that its orbit has become simpler than the orbits of the other planets.
Two spheres are proven: the geocentric sphere and the eccentric sphere, and all affairs are ordered and explained with them. The center of the Sun’s orbit is also considered the center of the universe, and that great orbit encompasses our earth with two parallel surfaces. It is a spherical body, and the outer surface of its convex side is tangent to the inner convex surface of the orbit of Mars. Its inner convex surface is tangent to the orbit of Venus, which lies beneath it. The Sun’s orbit, like the geocentric spheres of the higher orbits mentioned earlier, is centered, zonal, polar, and in its movement resembles the zodiacal orbit. It is also geocentric. Therefore, it is also called the geocentric (representative) sphere.
The representatives of the other planets located above and below the Sun’s geocentric sphere are primarily subject to the swift motion of the great orbit, and with this compulsory motion they move from east to west around the center of the universe. Secondly, with its own particular movement, it proceeds slowly from west to east around the center of the universe, as much as the slow movement of the zodiacal orbit. It seems to proceed through the influence of the zodiacal orbit’s movement. Consequently, the points of perihelion and aphelion of the Sun’s orbit move one degree every seventy years.
Article Two
It conveys the structure and movements of the radiant sun’s eccentric sphere. O esteemed one! Know that astronomers have said: Observers have noted slowdowns and accelerations in the Sun’s movements, and therefore they have observed the Sun’s body to appear sometimes large and sometimes small. This is because it appears sometimes distant and sometimes near from the earth’s center. To resolve this contradictory appearance, astronomers have accepted that beneath the Sun’s geocentric sphere there exists another eccentric sphere.
The aforementioned second sphere is within the first sphere, encompassing the earth, and its center is two and a half degrees on its own diameter from the center of the universe in the direction of perihelion, surrounded by two parallel surfaces. And the outer convex surface of this sphere is tangent to the outer convex surface of the first sphere at a point which is called perihelion. And within this orbit, the most distant points from the center of the universe are these; when the radiant Sun and its carrier orbit reach this point, it appears very far away and high above from the earth’s center. Similarly, the inner convex surface of the second sphere touches the inner convex surface of the first sphere at a point which is called aphelion. And this point is the closest to the center of the universe; when the Sun, the light of the universe, reaches it with its carrier, it appears very close to the center of the universe and descends most low.
When the eccentric sphere is separated from the geocentric sphere, and the course of the orbits assumes the form described above, two spherical segments remain as a necessity, whose surfaces are not parallel; some parts of these segments are thick and others thin. One has encompassed the second sphere. The other has been encompassed with the second sphere. The thin side of the encompassing sphere is at perihelion, while its thick side is towards aphelion. The situation on the thin side of the encompassed one is exactly the opposite.
When these two spherical segments are added to the second sphere, the first sphere is completed; since all of them are an orbit, one is called the completing outer and the other the completed inner. The radiant Sun itself is surrounded by only one surface and is a spherical body that is full and luminous. And it is fixed between its two poles on its eccentric sphere, so that the diameter of the Sun’s sphere is equal to the thickness of its eccentric sphere; and the outer boundary of the Sun’s encompassing sphere and the outer boundary of this eccentric sphere have touched at a common point.
The Sun’s eccentric sphere within its geocentric sphere has its own center, axis, and poles; that is, with an axis and poles parallel to the axis and poles of the zodiacal orbit, and with its own zonal movement along its tangent zone, it moves from west to east, and during this journey the Sun remains approximately thirty days in each sign. Thus completing its revolution in 365 days and six hours.
The sphere of the Sun, which is never inclined north or south from the surface of the zodiacal belt and always moves with stability on its own belt, traverses steadily upon the surface of the zodiacal orbit, which also carries it. The stars and celestial spheres never cease from motion; each possesses its own particular movement. And each rotates around its center with a different revolution, while the Sun also turns in its place and revolves around its own center, and the zodiacal wheel turns in order.