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Earth

Also called Blue planet. It is 5th Largest planet in our solar system. It rotates in a direction from West to East or in counter clockwise direction. It has only one Satellite-Moon. It has an axial tilt of 23.5 degrees. It is because of this tilt that the seasons change.
There are 2 types of movements that the Earth undergoes:
i. Rotation
ii. Revolution

Earth completes 1 rotation about its axis in about 24 hours. It is because of rotation of the earth that day and night occurs.
Earth completes 1 revolution around the Sun in about 365 and one quarter days. There are 2 positions in the path of revolution of Earth at which it is nearest and farthest from the sun-Perihelion and Aphelion. During Perihelion earth is nearest to Sun and during Aphelion it is farthest. The length of day and night depends on the position of earth in its path of revolution around the sun. Taking reference of Northern Hemisphere:

i. Longest Day is experienced on 21st or 22nd June and is known as Summer Solstice. 
ii. Longest Night is experienced on 21st or 22nd December and is known as Winter Solstice.
iii. Equal length of day and night is experienced at 2 instances 20th or 21st March known as Vernal Equinox and 22nd or 23rd September known as Autumnal Equinox.

For Southern Hemisphere dates are reversed i.e. 21st or 22nd June will become Winter Solstice and 21st or 22nd December will become Summer Solstice.
Image result for earth revolution

Composition of Earth:
1. Most abundant elements on Earth's Crust:
Oxygen>Silicon>Aluminium>Iron>Calcium>Sodium>Potassium>Magnesium>Others

2. Most abundant elements on Earth as a whole:
Iron>Oxygen>Silicon>Magnesium>Nickel>Sulphur>Calcium>Aluminium>Others










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