The four seasons on Earth | Why the Earth has seasons?

Many people think Summers occur when the Earth is closer to the Sun. This is not true. In fact, when there are summers in the Northern Hemisphere, Southern Hemisphere experiences Winter and vice-versa. So what causes the seasons? Let’s read.

The seasons on Earth (or any other planet) occur due to its axial tilt. Earth’s axis is an imaginary line passing through the geographic North Pole and the geographic South Pole around which it rotates. The axis is tilted at an angle of 23.5° with respect to Earth’s orbital axis.

Earth’s Axial tilt

When the North Pole tilts towards the Sun, Northern Hemisphere experiences summer. This is because the Northern Hemisphere receives more direct sunlight. On the contrary, the Southern Hemisphere experiences winter as it receives less direct sunlight.

Summer in Northern Hemisphere
Summer in Northern Hemisphere

Summer

During the summer season, temperatures rise and the days are longer. Mid-summer in the Northern Hemisphere is the time when the North Pole has the maximum tilt towards the Sun. This is also the time of mid-winter in the Southern Hemisphere.

Mid-summer (summer solstice) in Northern Hemisphere = mid-winter (winter solstice) in Southern Hemisphere = around 21 June

Seasons

Winter

During the winter season, temperatures are low and the days are shorter.

Mid-winter in Northern Hemisphere = mid-summer in Southern Hemisphere = around 21 December

Spring

Spring is the season when the flowers blossom. It is basically the transformation phase from winter to summer.

Autumn

Autumn is the season when the trees shed their leaves. It is basically the transition phase from summer to winter.

Equinox and solstice

Equinox is the time of the year when the durations of day and night are approximately equal. It occurs twice a year. Once during the spring and once during the autumn season. Spring equinox in Northern Hemisphere (also Autumn equinox in Southern Hemisphere) occurs around 20 March. Autumn equinox in Northern Hemisphere (also spring equinox in Southern Hemisphere) occurs around 22 September.

Solstice is the time of the year when the Poles have maximum tilt towards or away from the Sun. Summer solstice in Northern Hemisphere (also Winter solstice in Southern Hemisphere) occurs around 21 June. Winter solstice in Northern Hemisphere (also summer solstice in Southern Hemisphere) occurs around 21 December.

Seasons at the poles

The Poles have very cold winters and cool summers. During winters there is no sunlight (even no twilight) for the entire 24 hours of the day. On the contrary, during summers, there is continuous sunlight for the entire 24 hours.


Quick question

Perihelion is the nearest point in an object’s orbit from the Sun.


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Answer to quick question

True


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