### Theory:

The atmosphere is the huge envelope of air that covers the earth and extends more than $$800\ kilometres$$ above the earth's surface. This layer is essential for life on our planet as it provides us with oxygen to breathe.
The atmosphere

The atmosphere is a layer held by the Earth's gravity, filtering the harmful rays such as ultraviolet (UV) rays and infrared radiations from the Sun.

Radiations from the Sun

Density of air:
This huge blanket of air is thicker near the Earth's surface. As we move higher above the earth's surface, the air gets thinner. There is a decrease in the force of gravity at high altitudes, which eventually decreases the air density.

Comparison of air column above Mount Everest and the ground

This illustration compares the amount of air present above Mount Everest and the ground. The above diagram clearly shows the air closer to the ground is denser (thicker) due to gravity. As the height (altitude) increases, the air becomes thinner. Mount Everest, the tallest mountain in the world, has an
altitude of $$8848\ metres$$ (around $$9\ km$$). Hence, the air is less dense at such high altitudes.
Layers of the atmosphere:
The atmosphere is made up of five different layers. They are,
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere (or) Ionosphere
5. Exosphere
Layers of the atmosphere