Why are there four seasons in a year? Why are there four seasons in a year?

The Earth's axis is tilted, resulting in sunlight not being able to project evenly on the Earth, the Earth spares the Sun once a year, and the Earth's surface "Northern Hemisphere and Southern Hemisphere" regularly approaches away from the Sun, and the angle of incidence of sunlight changes regularly, forming the four seasons.

Classification of spring, summer, autumn and winter.

There is little frost in the late year of the law, and the grass and trees in the world know when spring arrives". Since ancient times, there have been many studies and records on the division of the four seasons by the people of our country, and the following four types are introduced:

The first is the solar term method. Astronomy, the spring equinox, summer solstice, autumn equinox, and winter solstice are the beginning of the four seasons. In ancient China, the beginning of spring, summer, autumn and winter were the beginning of the four seasons. This is all based on the position of the Earth in orbit.

The second is the lunar calendar law. Spring is from January to March, summer from April to June, autumn from July to September, and winter from October to December.

The third is the solar calendar. In meteorology, the solar calendar usually refers to spring from March to May, summer from June to August, autumn from September to November, and winter from December to February of the following year.

The fourth is phenological method. The willows are spreading their leaves, the peach blossoms are blooming, and spring is coming; The trees are shady, the red sun is scorching, and summer has arrived; The leaves of the fruit trees fall, the water is clear and the dew is cold, and the time sequence is autumn; The grass and flowers are withering, the north wind is howling, and the years are in winter.

The scientific division method is to quantify the fourth method, which is to use the average temperature of 5 days as an indicator to divide the four seasons: the average temperature is stable below 10, which is called winter, stable above 22, called summer, and stable between 10 and 22, that is, spring or autumn. He who.

To be in the human world is to live in the world defined by man. There are some things that don't have to be at the root of the matter. There are many similar questions: why 24 hours a day, why an hour and 60 minutes ?..Just get used to it, and too much knowledge will make you even more.

A natural phenomenon, nothing to say about hunger.

There are four seasons in a year, mainly because of the results of the earth's rotation, in the process of the earth's rotation around the sun, according to the distance from the sun, as well as the declination angle of the earth's rotation, the earth's surface is alternated between cold and hot north and south, resulting in the appearance of the four seasons on the earth's surface, but due to the declination of the earth's rotation, in the same season, the earth will also appear different squirting phenomenon.

In astronomy, the four seasons begin with the spring equinox, summer solstice, autumn equinox, and winter solstice, but the seasons divided in this way cannot fully reflect the phenological signs of each season in each place. Therefore, our ancestors divided the year into 24 solar terms, each of which was divided into 3 seasons. The climate is also divided into four seasons by the average temperature of the weather (5 days for each weather).

The average temperature of 10 is winter; 22 o'clock is summer; The average temperature is between October and 22 o'clock in spring and autumn.

Causes of formation. How the seasons are formed.

There is an angle (23°26) between the Earth's axis of rotation and the Earth's orbit around the Sun (the ecliptic plane), so when the Earth revolves around the Sun, the position of the Sun directly on the Earth changes, from 23°26 S (Tropic of Capricorn) to 23°26 N (Tropic of Cancer). When the sun is directly shining, the heat obtained by the earth's surface is high, and the temperature is high, which is summer;

Conversely, when the sun is obliquely shining, the heat gained from the earth's surface is low, which is winter. When the sun shines directly into the Northern Hemisphere, it is summer in the Northern Hemisphere and winter in the Southern Hemisphere; Conversely, when the sun shines directly into the Southern Hemisphere, it is summer in the Southern Hemisphere and winter in the Northern Hemisphere.

When the sun reaches the Tropic of Capricorn, the winter solstice (around December 22) and the summer solstice (around June 22) are respectively. When the sun reaches the equator, the spring equinox (around March 21) and the autumn equinox (around September 21) are respectively.

There are four seasons in a year, mainly because of the result of the earth's revolution, in the process of the earth's rotation around the sun, according to the distance from the sun, as well as the declination angle of the earth's rotation, resulting in the alternation of cold and hot north and south on the earth's surface, resulting in the appearance of the four seasons on the earth's surface, but due to the declination of the earth's rotation, in the same season, different phenomena will appear on the earth.

The alternation of the four seasons is related to the tilt of the earth, it is precisely because the earth is inclined to revolve around the sun, so that the direct sunlight of the sun is centered on the equator, with the Tropic of Cancer as the boundary of the north and south sweeping, once a year, the cycle continues, thus forming the phenomenon of the four seasons on the earth, alternating in order.

There are four seasons in a year, mainly because of the result of the earth's revolution, in the process of the earth's rotation around the sun, according to the distance from the sun, as well as the declination angle of the earth's rotation, resulting in the alternation of cold and hot north and south on the earth's surface, resulting in the appearance of the four seasons on the earth's surface, but due to the declination of the earth's rotation, in the same season, different phenomena will appear on the earth.

The alternation of the four seasons is related to the tilt of the earth, it is precisely because the earth is inclined to revolve around the sun, so that the direct sunlight of the sun is centered on the equator, with the Tropic of Cancer as the boundary of the north and south sweeping, once a year, the cycle continues, thus forming the phenomenon of the four seasons on the earth, alternating in order.

Extended Materials. The law of the four seasons:

From the spring equinox through the summer solstice to the autumn equinox, the northern hemisphere is in the summer half and the southern hemisphere is in the winter half. During this period, the days are longer and the nights are shorter in the Northern Hemisphere, and the days are shorter and the nights are longer in the Southern Hemisphere; The North Pole is in the polar day, and the South Pole is in the polar night; The height of the Sun north of the Tropic of Cancer is always greater than the mean and south of the Tropic of Cancer is less than the average.

North of the Tropic of Capricorn, the sun rises over the horizon circle in the northeast and sets on the horizon circle in the northwest. On the equinox, the sun rises due east and sets due west all over the world.

From the autumnal equinox through the winter solstice to the spring equinox, the northern hemisphere is in the winter half of the year, and the southern hemisphere is in the summer half. During this period, the length of day and night, polar day and night, and solar altitude in the northern and southern hemispheres were reversed. North of the Tropic of Capricorn, the sun rises over the horizon circle in the southeast and sets on the horizon circle in the southwest.

From the summer solstice through the autumn equinox to the winter solstice, the northern hemisphere changes from summer to winter, and the southern hemisphere changes from winter to summer. During this period, the days in the Northern Hemisphere became shorter, the nights became longer, and the polar diurnal zone gradually shrank. In the Southern Hemisphere, the days are getting longer, the nights are getting shorter, and the polar night zone is shrinking. The height of the Sun decreases north of the Tropic of Cancer and increases south of the Tropic of Capricorn.

North of the Tropic of Capricorn, the rising direction of the sun changes from northeast to southeast, and the direction of falling changes from northwest to southwest. The autumnal equinox rises due east and sets due west.

From the winter solstice through the spring equinox to the summer solstice, the northern hemisphere changes from winter to summer, and the southern hemisphere changes from summer to winter. The variations in the length of day and night, polar day and night, and solar altitude in the northern and southern hemispheres are reversed. North of the Tropic of Capricorn, the direction of the sun rises from southeast to northeast, and the direction of setting changes from southwest to northwest.

From the winter solstice to the vernal equinox and from the summer solstice to the autumnal equinox, the length of the day is approaching the average (12 hours) around the world, and the range of polar day and night is gradually decreasing. The height of the Sun north of the Tropic of Cancer and south of the Tropic of Cancer is approaching the mean. North of the Tropic of Capricorn, the sun rises in a direction that gradually approaches due east and sets in a direction that is close to due west.

From the spring equinox to the summer solstice and from the autumn equinox to the winter solstice, the length of day and night is changing to extremes around the world, and the range of polar day and night is gradually expanding. The height of the Sun north of the Tropic of Cancer and south of the Tropic of Cancer also tends to be extreme. The direction of the rising and setting of the sun north of the Tropic of Cancer moves northeast, southeast, northwest and southwest, respectively.

The generation of the four seasons is closely related to the rotation of the earth, but the decisive condition is that the earth must revolve obliquely around the sun, and obliquely revolve around the sun to make the direct sunlight of the sun take the equator as the center, and sweep north and south with the Tropic of Cancer as the boundary, once a year, and the cycle continues, thus forming the four seasons on the earth.

Although the change of the seasons is related to the rotation of the earth, the decisive condition is that the earth must revolve diagonally around the sun, that is, the existence of the angle between yellow and red.

If there is no yellow and equatorial angle, the earth rotates vertically around the sun, and the sun's rays will always shine directly near the earth's equator, and the angle between the sun's rays and the earth's plane in other places will never change, and there will be no change of seasons on the earth.

The presence of the yellow-red angle causes the direct solar point to move back and forth between 23 ° 26 s and 23 ° 26 n. Therefore, the amount of heat received by the surface of the earth changes with time and space from moment to moment.

This is because the Earth's orbit around the Sun is elliptical and has an angle to the plane of the Earth's rotation. When the earth is in different positions of the orbit, each place receives different sunlight and receives different solar heat, so there are seasonal changes and differences in hot and cold.