Season

If the axis of the earth would be straight then there will be a day at half of the Earth and night at another half of the Earth and there will be no point of seasons.  But we know that it's not true because the Earth is tilted and we have seasons on our planet. In this article, we will talk about seasons, seasonal variation, how seasons occur, reasons, etc.

Why Do Seasons Change? 

The part of the Earth which got sunlight faces day and other parts of the faces night. It happens because of the rotation around the Earth. Seasons occur because of the apparent movement of the sun also. When the sun is directly overhead at one point of the earth, it increases the temperature of that region and leads to summer in that region and winter in another region where the sun is not overhead.

Reasons 

The cycle of seasons is caused due to the following reasons:

• The Earth has a tilted axis at 23.5° at the orbital plane and it revolves around the Sun.

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• Because of the tilt, the Earth has a different angle of incidence with respect to sunlight received from the sun.

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• The apparent movement of the sun also plays a vital role in forming seasons. We have the sun at 23.5°N in June, at 0° in September, 23.5°S in December and again up to March it'll move to 23.5°N. The process continues which is called the apparent movement of the sun. 

How Do Seasons Change

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We experience different seasons on earth because of the revolution of the earth around the sun. With the help of the above two diagrams, we will learn about how seasons occur. For learning about seasons we have to keep in mind the following points:

• The Earth has a tilted axis 

• It revolved around the sun in 365 days approximately

• It is divided into three lines ie. the equator at 0°, the tropic of cancer at 23.5°N,2, and the tropic of Capricorn at 23.5°S.

We'll be explaining the occurrence of the four seasons of the Earth with respect to the Northern Hemisphere and what will happen in the Southern Hemisphere will also be mentioned along with that.

Summer Solstice

If we talk about the Northern Hemisphere, It is the time when the sun is directly overhead on the tropic of cancer and thus this part of the earth experiences the summer season and at the same time, due to the tilted axis of the Earth and the angle of incidence of the sun rays the southern hemisphere does not receive the same sunlight and thus temperature reduces and leads to winter. June 21 is considered as the hottest day. 

• Here, the Northern Hemisphere has summers and Southern Hemisphere winters.

• Days and nights are not equal because days are longer than nights.

• For example, due to this, India experiences ( which is in the northern hemisphere ) summers, and Australia experiences winters ( which is in Southern Hemisphere )

Autumnal Equinox

It is the time during September when the earth experiences the sun directly at the Equator. Due to this, the days and nights are equal. It is the time of the beginning of the autumn season in the Northern Hemisphere which ends with the winter solstice.

During this time, the southern hemisphere experiences the spring season or we can say the vernal equinox.

Winter Solstice

It is the time when the earth is facing the sun rays directly on the Tropic of Capricorn and we know that the region which faces direct rays experiences summers. Thus, the Northern Hemisphere has winters during this time, and summers are there in the Southern Hemisphere. 

• 22 December is considered as the coldest day of the year.

• The Northern Hemisphere has winters and the Southern Hemisphere has summers.

• Days and nights are not equal and Nights are longer than days.

• For example, India has winters during December and Australia has summers during this time.

Vernal Equinox

It is the time when the Earth faces sunlight directly on the Equator and it has equal days and nights. It is the time of March and spring season in the Northern Hemisphere and the season of autumn in the southern hemisphere. 

Did You Know

When the Earth is closest to the Sun i.e on Jan 5,  it is known as Perihelion and when it is away from the Earth i.e on July 5,  it is known as Aphelion and there is no relation of the distance of the Earth from the Sun in forming seasons which is generally presumed to be.