BİRİNCİ FEN · İKİNCİ BÂB · DÖRDÜNCÜ FASIL · Üçüncü Madde
Article Three
It describes the epicycle of the Jupiter star, along with its movements and structure.
O Noble One! Know that astronomical scholars, in explaining the conditions of this Jupiter star, do not suffice with previously determined and ordained knowledge, but have proven the existence of another small sphere not included within the earth, and they have named it an Epicycle (epicyclic orbit). The aforementioned epicycle is a small sphere, not included within the earth, which is a sphere of common purpose for the Jupiter star. Its form is incorporated into and embedded in the inclined belt of the second sphere that carries the star and is eccentric; so much so that the diameter of the two surfaces of the carrying sphere and its surface rotation are tangent to the carrying sphere.
The epicycle is a spherical body, completely filled and surrounded by a single surface. Within its own space and on the inclined orbit’s body, it rotates eastward without ceasing with its own specific movement, rotating Jupiter along with itself, which remains fixed on one side. The movement of this sphere around its own center, directed westward, advances Jupiter approximately one degree from its three hundred sixty-degree belt in a day and night. That is to say, it moves it by the average amount that the sun moves, completing its cycle once per year. This movement is what they call the star’s differing motion ( *hareket-i ihtilaf-ı kevkeb*) and the star's specific motion (*hareket-i hasa-i kevkeb*). The Jupiter star itself is a spherical body surrounded by a single surface; it is filled within and luminous.
It is embedded in the body of the carrying sphere in such a way that it touches the epicycle at a common point on the belt located between the two poles of the carrying star [43/b]. That is, this star is entirely within the epicycle, its surface being tangent to its surface. On one side of the carrying sphere, just as the epicycle rotates around its own center, it is constantly rotating around its own center, which many astronomers (*erbâb-ı irsâd*) have observed and said: “There is no stationary body in the heavens.”