Earth is the only planet where life is known to exist. Earth has only one natural satellite, called Moon.
Conditions responsible for life:
Some environmental conditions are mainly responsible for the existence of life on Earth. They are,
- Right temperature range
- Presence of water
- Suitable atmosphere, and
- A blanket of ozone
Colour of the planet:
The Earth appears bluish-green from space due to the reflection of light from the water and the landmass on the Earth surface.
Rotation and revolution of the planet:
The Earth's axis is tilted to a side by \(23.5\ degrees\), which is responsible for the seasonal changes on Earth.
The seasonal cycle of Earth
Earth completes its rotation from west to east in \(23.93\ hours\) which is approximately \(24\ hours\), and the period of revolution is \(365.25\ days\).
A person at the age of \(20\) years would have gone around the Sun \(20\) times.