Why are there four seasons: spring, summer, autumn and winter?

There are tropics, frigid zones and temperate zones on the earth. There are only rainy and dry seasons in tropical areas, while there is ice and snow all year round in cold areas. Only temperate regions have obvious four seasons: spring, summer, autumn and winter. The four seasons are divided as follows: in the temperate zone of the northern hemisphere, according to the revolution of the earth, June with the longest sunshine time is divided into spring and summer, and June with the shortest sunshine time is divided into autumn and winter, which is a cycle. According to the change of temperature, the four seasons are divided.

Because there is a certain angle between the earth's rotation axis and the public rotation circle, that is to say, the earth revolves around the sun obliquely. Of course, the situation that the sun shines on a certain area of the earth will not be constant all the time, but it will show certain regularity, that is, the "four seasons"

Netizen's point of view: Because the earth's movement has rotation and revolution, these two factors combine to cause the cold and hot changes in different seasons of spring, summer, autumn and winter. However, this change is not because the distance between the sun and the earth is very small (about 500&; 127; 10 thousand kilometers), but because of whether the sun shines directly or obliquely on the ground in different seasons and the length of sunshine time. For us, that is, for people in the mid-latitude region of the northern hemisphere, around the summer solstice, the sun shines almost vertically on the ground, while around the winter solstice, the sun shines very obliquely on the ground at noon. The size of the irradiation angle determines how much heat the earth receives, thus causing the temperature. In addition, around the summer solstice, the sun rises in the northeast and sets in the northwest, and the sun stays above the horizon for a long time. This situation of long days and short nights makes the ground in long-term light, which further aggravates the rise of ground temperature; On the contrary, around the "winter solstice", the sun rises in the southeast and sets in the southwest, and the sun stays above the horizon for a short time. This situation of short days and long nights further aggravated the cooling of the ground. So it is hot in summer and cold in winter. Around the vernal equinox and autumnal equinox, the angle of sunlight is between the above two situations. The sun rises near due east and sets near due west. The length of day and night is almost the same, and it is also between the summer solstice and the winter solstice, so the spring and autumn seasons are formed.

It is precisely because of the change of the sun's exposure angle and the length of sunshine time that the four seasons change. These two factors are caused by the rotation and revolution of the earth.

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