BİRİNCİ FEN · ÜÇÜNCÜ BÂB · ÜÇÜNCÜ FASIL · Beşinci Madde
Fifth Article
Concerning the unnatural celestial changes occurring within the atmospheric layer surrounding us.
Know, esteemed one, that philosophers have stated: Some of the unusual changes occurring within the atmospheric layer surrounding us are due to celestial causes, and others are due to earthly (natural) causes.
The atmospheric changes dependent on celestial causes are like those brought about by the influence of the stars. For sometimes luminous stars gather in a particular place and come together with the sun, so that when the time arrives, they intensely heat the zenith point or the air of regions near them. At other times, being far from the zenith point, the warming of the air is lessened, and the influences of *musammat* (a period of stillness), the continuation of *musammat*, and proximity are more prominent. [66/b]
As for the causes originating from the earth; some of these are related to the latitude of regions, and others to the elevation or depression (altitude) of the location in which a region is situated. Some are related to mountains, and others to seas. Some depend on winds, and others arise from reasons pertaining to the structure of the soil.
The atmospheric changes occurring due to the latitudes of regions are quite evident. For any region whose northern orbital ascending node is near the Tropic of Cancer and whose southern orbital ascending node is near the Tropic of Capricorn has a summer season that is hotter than the summer season of regions near the equator, and than the summer of regions inclined towards the south and north. The temperament of the air in countries under the circle of the Equator is close to moderation. This is because the celestial cause of warming the air there is the sun’s arrival at the zenith. However, this angle of incidence of the rays does not alone exert a great influence on the climate. Perhaps the continuity of these rays arriving at an oblique angle from the ascending node exerts more influence. Therefore, the intensity of the heat seen in the sun at midday increases considerably before afternoon, and for this reason, when the sun’s ascending node inclines away from Cancer and is somewhat below it, the heat remains intense.
This is because its inclination is located on the common meridian sphere and has not yet reached the ascending node point of Cancer.
For example, when the sun is near the ascending node point of Gemini, its influence on the air is less than when it reaches the ascending node point of Leo. For when the sun is at the ascending node point of Leo, the rays of sunlight arrive at the earth at an oblique angle, and this continues consistently. But in other regions that coincide with the Equator, the sun remains at the ascending node point for only a few days (so that its rays strike the earth at an oblique angle) and quickly moves away from that point. This is because the increase in minor inclination near the equinox point (point of equality) is much greater than the increase in minor inclination located at the solstice point (point of revolution). And the increase in movement at the solstice point is not limited to three or four days. Surely, the sun remains for a while in a nearby location and influences the warming of the air. From all of this, it is known that those countries whose greatest inclination (general inclination) [520] is closest to their latitudes are the hottest regions of the earth.
The next hottest regions are those located fifteen degrees from their poles and on the side facing towards the equator.
Regions situated between the two aforementioned turning points (summer solstice and winter solstice) are also like these.