BİRİNCİ FEN · ÜÇÜNCÜ BÂB · DÖRDÜNCÜ FASIL · Birinci Madde
The First Article
Concerning the rainbow, halo, mist, frost, and dew (jāle).
O beloved! It is known that philosophers have said: The ebe bow (literally "spider bow") refers to
the rainbow (kavs-i kuzâh), which arises from rain or vapor as small,
bright, pure, and round droplets of water. And these are formed by the
reflection of the light of the radiant sun upon them.
The explanation for the formation of the ebe bow is that the aforementioned
droplets are found in a position directly opposite where the sun's rays strike, so that
the light from the eye is reflected to the sun within each droplet. And this reflection occurs at a time when there is behind these droplets a dense object like masses of dark clouds acting as a mirror. The sun is also near the horizon with very little heat.
A person looking at this scene turns his back to the sun and faces the aforementioned droplets, that is, if he stands somewhere between the sun's course and those droplets,
the light from his eyes will reflect from the droplets to the sun.
In this situation, a person looking there sees the radiance of the sun in each droplet; its shape is not visible. For it has been previously experienced that when a bright object reflected from the eye’s rays is very small, the illuminated object facing it shows only its light and color, but not its shape or form. The aforementioned water droplets appear as a luminous arc less than half of a circle. This arc diminishes as the sun rises; it increases in proportion to how much the sun descends.
Because when the Sun is at the center of that circle, as it rises from the horizon, only less than half of the circle directly opposite it remains above the horizon. As the Sun descends closer to the horizon and approaches it, the angle of the aforementioned incomplete circle increases on both sides towards the horizon. It is then that the light from the eyes reflects from the droplets on either side to the sun.
The esteemed Ibn Sina wrote in his book “Shifa”:
“I was upon a high mountain between Tus and Maward. The sky was dense (kesif). There was a cluster of clouds between the desert and me, right in the middle of the mountain, and the air was quite humid. The sun was at midday. At that time, when I looked at the aforementioned dark cloud, I saw a complete circle in the color of the rainbow. As I descended from the mountain, the complete circular rainbow began to diminish. When I reached the foot of the mountain, it disappeared.”
The reason for the rainbow’s being composed of different colors is that the sun's rays have mixed with clouds of various colors. For the upper part of the clouds is close to the sun, so its brightness prevails and appears red like saffron. The lower part, being farther from the sun, has very little brightness and its redness is slight (orange). The space between these two colors arises from their combination, which appears green like grass. A rainbow with the aforementioned colors appeared clearly adjacent to the horizon in Hizan Castle near Van during the autumn season when the moon was full. Its shape was as indicated in the following diagram.
[69/a]
The halo (Ay ağılı) also consists of small, transparent droplets of water forming a circle, like a winnowing basket around the shape of the moon.
Its explanation is that those who look at the halo are positioned between themselves and the moon (as mentioned above) so that the light from the eye is reflected to the sun in each droplet. When one looks at these droplets, one sees the light of the moon in each one. However, because these droplets are very small, one cannot see the shape or image of the moon within them. They all appear as a complete circle or an incomplete circle. This is the halo. The halo arises from the humidity of the air, and its appearance is considered a sign that rain will fall.
If two clouds with the aforementioned characteristics are found beneath each other, then two halos appear, and the one below appears larger to us because it is closer. If there are more than two such clouds, the number of halos seen corresponds to the number of visible clouds. Seven halos of the radiant moon have been observed.
The circumsolar halo (Züferâ): is the sun's halo – this word is read with the prolongation of the "zı" letter – it is rarely seen. Because as the Sun moves away from the horizon, the effect of its heat becomes intense, causing the fine clouds like those described to dissolve and return to the air.
The esteemed Ibn Sina wrote in his work “Shifa”:
“I have observed a complete halo and an incomplete halo appearing around the radiant sun.”
The author (Erzurumlu Ibrahim Hakkı) says: "The humble one witnessed the complete solar halo that appeared near sunset in the Pasin Plain, towards the end of spring, a year before writing this *Marifatname*. With us at that time was a venerable old man, 142 years old. The elder said: 'I have reached my age and seen many strange things. I have never seen the sun threshing like this before. Now I have witnessed it even now.'"
The material causes of mist (duman), frost, and dew are the rising vapor (as we have detailed above). This is both scant in itself and has weak heat, so it cannot reach the cold layer but remains in its lower layer and begins to descend from there towards the earth. If no coldness affects it during descent, it will encompass the heads of high mountains and then slowly spread outwards from there (like a veil). This is what we call mist (duman). Then this mist turns into air with little heat and disappears.
"We praise the Creator, who possesses wisdom, majesty, and sublimity in His creation, and there is no deity worthy of worship but Allah, the One, the Unique. He is exalted beyond all description; He is free from every imperfection."