The atmosphere, a thin shell of gases surrounding the Earth, is a very effective protective shield that reflects and absorbs harmful radiation and objects like meteorites.
The atmosphere protects the Earth from receiving too much radiation from the Sun.
The Sun is a vast ball of exploding gases - mostly hydrogen that is converted to helium through a nuclear reaction.
At its surface, the Sun reaches a temperature of 6,000°C at the surface.
The Sun's heat and light travel almost 150 million kilometers (93 million miles) passing Mercury and Venus, until reaching the Earth's atmosphere.
An extremely important layer in the atmosphere lies between 25 and 50 kilometers (15 and 31 miles) above the ground. This is rich in a gas called ozone. The ozone layer filters out ultraviolet light from the Sun.
Below this, the atmosphere becomes much more mixed.
The air that we breathe is made up of 78.09 percent nitrogen, 20.95 percent oxygen, 0.93 percent argon, with the remaining 0.03 percent consisting of carbon dioxide and many other gases.
The progress of this energy coming from the Sun is hampered even further in the 10 kilometers (6 miles) just above the Earth's surface - the area in which our weather exists.
Clouds, water surfaces, snow and ice reflect energy back from the Earth.
Ultimately, only one in every 2,000 million parts of the Sun's energy reaches the Earth.
Without an atmosphere, the Earth would be extremely hot during the day and extremely cold at night. It has been calculated that if the Earth's atmosphere disappeared, temperatures at the equator would reach 80°C during the day and fall to -140°C at night.