BİRİNCİ FEN · ÜÇÜNCÜ BÂB · DÖRDÜNCÜ FASIL · İkinci Madde
**Article Two**
Concerning the states of dawn, twilight, and shadows.
Know, esteemed one, that philosophers and astronomers unanimously declare: The occurrence of morning and the breaking of dawn are specific to this lower sphere of air. Their explanation is as follows: Because the body of the sun’s orb is, according to the measure explained in previous articles, greater than half the earth's circumference, it perpetually illuminates more than half of the earth while leaving less than half in darkness. Its shadow forms a cone, with one tip extending to the star Venus. The head of this conical shape, as mentioned above, always remains tangent to the zodiacal sphere. The time when this aforementioned conical shadow is beneath the horizon is daytime. The time when it is above the horizon is nighttime.
As the source of greatest light, the sun, being below the earth’s surface, approaches the eastern horizon, its inclined conical shadow moves across the earth's surface towards the western horizon. Until the rays encompassing the conical shadow appear on the western side. At this point, the near portion of the dawn rises considerably from the east and appears white. The space between it and the horizon remains dark.
For, from the observer’s position, the triangle formed by the white area and the horizon direction, with the angle between the observer and the white area arising from the rays of the eye, is assumed to be originating from the surface of the shadow and lies upon the line drawn by the sun's rays touching the earth and the ground. This angle is shorter and closer than the angle between the observer and the horizon; thus, sunlight appears first from it. Subsequently, as the sun approaches the horizon a little further—that white area—begins to spread.
Though its light is faint, it appears weak. People call this spreading whiteness "false dawn" (fecr-i kazib), believing it to be transient and illusory. Yet, that whiteness does not truly vanish or pass; rather, it increases as time goes on. Indeed, as the sun draws closer to the horizon, the spread of this whiteness expands towards the horizon, its light strengthens, and brightness never fades again. This is what people call "true dawn" (fecr-i sadik). After that, when the sun is very close to the horizon, this whiteness spreads everywhere, and the point where the sun first rises (matla'-i kamer) appears red. Following this, the sun’s course emerges from the horizon, marking the beginning of the first hours of the day. Such is the formation and operation that occurs at dawn, which we have explained in its truth.
As for the states of twilight, its position is precisely opposite to the order described above pertaining to dawn. For after the sun's course sets below the horizon, marking the end of daylight, the point where the sun sets (magrib-i shams) becomes intensely red. Then a spreading whiteness appears, and it is subsequently believed that this whiteness disappears; yet, it expands outwards and rises. Experience demonstrates that when the sun descends eighteen degrees below the horizon, it marks the beginning of false dawn (subh-i kazib) and the end of twilight. At forty-eight and a half degrees latitude, when the radiant sun reaches the summer solstice (munkalib-i sayfî), twilight ends abruptly and merges directly into false dawn, leaving no interval for evening prayer (diya bir şey ortada). For, when the radiant sun is at the aforementioned summer solstice, it does not descend more than eighteen degrees below the horizon of forty-eight and a half degrees latitude.
Concerning shadows, they are divided into two categories: The first is called the "primary shadow" (zill-i evvel). It is also termed the “reflected shadow” (zill-i ma’kus) or the “inverted shadow” (zill-i menkus). This shadow is that of a rod erected perpendicular to the horizon line. For example, it is like the shadow cast by a rod driven into a flat surface. The second shadow is called the "secondary shadow" (zill-i sani). It is also termed the “flat shadow” (zill-i mustawi) or the “extended shadow” (zill-i mebsut). This is the shadow visible from a rod erected vertically on a flat surface. For example, it is like the shadow of a rod driven upright into level ground.
“We praise God, who cleaves the darkness and brings forth dawns,” [524] and creates shadows that are likenesses of bodies; He is free from all imperfection.” [525]