Why is there 4 seasons in a year?

Why is a year on Earth divided into 4 seasons: spring, summer, autumn and winter? How important are the seasons on human life on Earth? Why does the weather change between seasons? The article below will answer for you.

About 4.5 billion years ago, an asteroid the size of Mars collided with Earth. As a result, layers of dust and rock gradually coalesced to form the moon. It also tilts the Earth slightly as it orbits the Sun.

It is because of that tilt that at any given time, the amount of sunlight in the Northern Hemisphere and the Southern Hemisphere will be opposite. This cycle varies with the Earth’s seasons.

The Earth moves in an elliptical orbit around the Sun and at the same time rotates along an axis that is tilted relative to the surface of the orbit . That means different hemispheres enjoy different volumes of sunlight over the course of a year. Because, the Sun is our source of light and energy, the change in intensity and concentration of the sun’s rays has caused the change and appearance of the seasons of the year: Winter, spring, summer and summer. collect.

Why is there 4 seasons in a year?

The seasons are marked by the solstices (one of two times a year when the sun is furthest north or south of the equator) and the Spring and Autumnal equinoxes – concepts cosmologically related to tilt of the Earth.

The solstices mark the points at which the North Pole or South Pole has been tilted at its maximum toward or away from the Sun. That is the time when the difference between the hours of the day and the hours of the night is most pronounced. The solstices occur each year on June 20 or 21 (Summer solstice) or December 21 or 22 (Winter solstice) and specify the official beginnings of summer and winter. The Spring and Fall equinoxes mark the beginning of spring and autumn.

In the Northern Hemisphere , the start and end times of the seasons of the countries according to the solar calendar and some countries that are used to using the lunar – solar calendar in Asia are not the same. The countries according to the solar calendar in the Northern hemisphere take four days: Spring equinox (March 21), Summer Solstice (June 22), Autumn equinox (September 23) and Winter Solstice (December 22) are the four starting days of the lunar calendar. four Seasons.

In the Southern Hemisphere , the four seasons take place opposite to the Northern Hemisphere. That is to say, on March 21 every year, the Northern Hemisphere gradually reaches the Spring equinox and enjoys the signs of spring; At that time, the winds brought cold to the Southern Hemisphere because it had reached the autumn equinox. Another equinox of the year appears on September 23, when summer fades in the North, the cold of winter begins to give way to spring in the South.

In particular, our country and some Asian countries are used to using the lunar – solar calendar, the time to start the seasons is calculated 45 days earlier.

Why is there 4 seasons in a year?
The Earth’s orbit around the Sun is elliptical. (Photo: Internet source).

Especially each season of the year does not have to be rounded by the number of days a year divided by 4. Spring starts from the Spring Equinox (January 23) to the Summer Solstice (June 21) , which is about 92 days and 19 hours. Summer starts from the summer solstice to the autumn equinox (September 23) about 93 days and 15 hours long. Autumn lasts from the autumn equinox to the winter solstice (December 22) for about 89 days and 19 hours. The winter from the winter solstice to the spring equinox is only 89 days long. Thus, summer is 4 days and 15 hours longer than winter.

This short-term problem concerns the distance between the Earth and the Sun at any given time, far or near. Summer, when the Earth is furthest from the Sun, the Sun’s attraction to it is weakest, so the Earth rotates the slowest and the summer is longest in a year. In contrast, winter, when the Earth is closest to the Sun, the sun’s gravity acts on it the strongest, so the Earth rotates quickly and it is the shortest season of the year. Spring and autumn are two intermediate seasons.

Another feature that also affects the formation of the four seasons is that the Earth’s orbit around the Sun is not circular but elliptical , leading to different distances from the Earth to the Sun (if rotating). in a circular orbit, the distances are equal). This results in a different amount of heat received from the Sun and produces different hot and cold temperatures depending on the season.