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### Theory:

Earth (Prithvi) is the only planet where life is known to exist. Earth has only one natural satellite, called Moon. Some environmental conditions are mainly responsible for the existence of life on Earth.

Earth

Conditions responsible for life on Earth:
• The right distance from the Sun,
• Right temperature range,
• Presence of water,
• Suitable atmosphere, and
• A blanket of ozone.
Earth's atmosphere

Appearance:
The Earth appears blue and green from space. This appearance is due to the reflection of light from the water and the landmass on the Earth surface.

Axis of the Earth:
The Earth's axis is tilted to a side by $$23.5\ degrees$$, and it is not perpendicular to the plane of its orbit. This tilted axis is responsible for the cycle of seasonal changes on Earth.

Position of Earth around the Sun

Rotation of Earth on a tilted axis:
The Equatorial plane is the plane of the equator, and the orbital plane is the plane in which the Earth revolves around the Sun.
The equatorial plane is inclined to the orbital plane at an angle of $$23.5\ degrees$$. Thus, the Earth's axis is inclined to its orbital plane at an angle of $$66.5\ degrees$$.

Earth's equatorial and orbital plane

Earth completes its rotation from west to east in $$24\ hours$$, and the period of revolution is $$365.25\ days$$.

Important!
Fun fact
A person at the age of $$20$$ years would have gone around the Sun $$20$$ times.
Reference:
https://cdn1.photostockeditor.com/c/1904/space-outer-space-photography-of-earth-earth-earth-image.jpg
https://live.staticflickr.com/65535/48322498346_e743933560_b.jpg