1. http://www.youtube.com/watch?v=jmQ8FWn M0fA

2. Feeling pressured?... Air pressure is all around us. Air pressure is the force exerted on you by the weight of tiny particles of air known as air molecules. Although these molecules are invisible they still have weight and take up space. Why doesn't all that pressure squash you? Remember that you have air inside your body too, that air balances out the pressure outside so you stay nice and firm and not squishy.

3. Weather forecasters measure air pressure with a barometer. Barometers are used to measure the current air pressure.

4. Air pressure can tell us about what kind of weather to expect as well. If a high pressure system is on its way, often you can expect cooler temperatures and clear skies. If a low pressure system is coming, then look for warmer weather, storms and rain. http://www.theweathernetwork.com/weather /canada/alberta/edmonton

5. A high pressure system is represented as a big, blue H. A low pressure system is represented as a big, red L.

6. What Happens if Air Pressure Changes? Why do my ears pop? If you've ever been to the top of a tall mountain, you may have noticed that your ears pop and you need to breathe more often than when you're at sea level. As the number of molecules of air around you decreases, the air pressure decreases. This causes your ears to pop in order to balance the pressure between the outside and inside of your ear. Since you are breathing fewer molecules of oxygen, you need to breathe faster to bring the few molecules there are into your lungs to make up for the deficit.