Rotation and revolution of earth Upsc

Rotation and revolution of earth

Earth has two types of Motions. They are Rotation and Revolution. Rotation is the movement of the earth on its axis. Earth takes 24 hours for one rotation around its axis. This period of rotation is known as Earthday.

Revolution is the movement of the earth around the sun in a fixed path or orbit. Earth motion around the sun in its orbit, which the earth takes 365 days which is measured as 1 year. Also, 6 Hours is ignored for convenience.

These 6 Hours are saved every year to make one day (24 Hours) and this extra day is added to the month of February. Thereby every 4th year there will be 29 days instead of 28 days. The year with 366 days is called a leap year.

The Axis of the Earth is an imaginary line, which makes an angle of 66° with its orbital plane. An Orbital Plane is a plane formed by orbit.

Effects of Motion of Earth

The earth receives sunlight from the sun. Only half side of the earth receives sunlight at one point and the other of the earth does not receive sunlight.

The side that receives sunlight is the Day, the side which does not receive Sunlight is the night. This is because of the Spherical shape of the earth.

The circle of Illumination is the circle which divides the day from night on the Sphere of Earth (Globe). This circle does not coincide with the axis.

Seasons of Earth

The season in the Earth is caused by the inclination of the earth in the same direction and revolution around the sun in an elliptical orbit. Every year is divided into Summer, winter, spring, and autumn seasons.

The change of season is because of the earth’s position around the Sun.

Summer Solstice

The Northern Hemisphere is tilted towards the sun on 21st June. The Sunrays fall directly on the Tropic of Cancer, the areas near the Tropic of Cancer receive more heat.

The regions near the Poles receive less heat are the Sun rays fall of Poles are Slanting. The North Pole which is inclined towards the Sun and the areas beyond the Arctic circle experiences continuous daylight for six months.

The Summer occurs North of the equator, as the large portion of the Northern Hemisphere is getting Sunlight. At these places, on June 21, the longest day and the shortest night occurs.

In the Southern Hemisphere, this condition is opposite, where the Southern Hemisphere has winter, where the Nights are longer than the days. The above-mentioned points are all the characteristics of Summer Solstice.

Winter Solstice

On 22nd December, the Tropic of Capricorn receives direct rays of the Sun. This is because the South Pole is tilted towards the Sun.

As the result, the rays of the Suns fall vertically at the Tropic of Capricorn which is 23° S and by this Southern Hemisphere receives more sunlight. Therefore, it is Summer in Southern Hemisphere and Winter in Northern Hemisphere.

The Days in the Southern Hemisphere is longer than the Nights. This position of the earth is called Winter Solstice. Australia is a good example for Winter Solstice, and it has Summer during December and celebrates the Christmas festival in the Summer Season.


During Equinox, the direct Sun Rays fall on the equator. At this position, neither the North Pole and the south pole is tilted towards the Sun. As a result, the whole earth experiences equal days and equal nights.

This position of the earth is called the Equinox. It happens on 21st March and September 23.

On September 23, it is Spring season in the Southern Hemisphere and Autumn in the Northern Hemisphere. On March 21, it is Spring season in the Northern Hemisphere and Autumn in the Southern Hemisphere.


* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.
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