1. Atmosphere Definition A mixture of gases that surrounds the earth – It protects us from the sun’s damaging rays – Prevents us from getting too warm or too cold – Provides us with oxygen and water – Main gases are Nitrogen 78% and Oxygen 21%

2. Air Pressure Our atmosphere is held in place by gravity Gravity pulls on the gas particles and creates air pressure Air pressure increases as you move closer to the Earth because there is more air above you

3. Atmospheric Layers Troposphere Our atmosphere is divided into main layers based on distance from the Earth’s surface Surface of the planet to about 7.5 miles – All life occurs in this layer – All weather occurs in this layer – Densest layer, meaning a lot of gas particles – As you increase altitude, temperature decreases

4. Stratosphere 7.5 miles out to 21 miles – Contains the ozone layer which blocks out large amounts of solar ultraviolet radiation – Commercial airliners travel in this layer

5. Mesosphere Thermosphere 21 miles out to 50 miles – The coldest layer – Satellites can be found here Uppermost layer of the atmosphere – 50 miles out to 200 miles – International Space station can be found in this layer