The atmosphere consists of two main components, which represent about 99% of the air, where nitrogen is 78% of the air and oxygen is 21% of the air and the rest are many different gases, the most important of which is carbon dioxide, and the density of gases in this atmosphere increases as we approach the surface of the earth due to the increase in pressure, And it decreases as we move away from the surface of the earth, so that in the upper atmosphere we find very few and light gases such as hydrogen gas and helium.