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Question: Why do you chew gum when you are going down in altitude on a plane?
The answer involves an understanding of air pressure and human anatomy. The air around us is composed of invisible gas molecules in constant motion. They create pressure as they bounce off of solid and liquid matter like the surface of the Earth and our bodies. As you get father away from the Earth's surface, air molecules are less concentrated so air pressure decreases. In order to make airplane rides possible, modern aircraft are designed to keep the pressure inside close to the pressure on the ground. If pressure gets too low inside the airplane, you would suffer or even die.
The airport you start from is likely to be at a different altitude than the airport your arrive at. Even airports at the same altitude are likely to have different air pressure since it changes with the local weather. The air pressure control system in the airplane gradually changes the pressure in the cabin during your flight. For most of your body this in not a problem. One part for your body, however, contains a closed column of air. It is called the eustachian (yoo stay' shun) tube. You have two, and they go from inside your nose to your middle ear. Their purpose is to keep the pressure inside your ear equal to the pressure outside your body. This prevents painful earaches and hearing loss. Normally these tubes are closed. As the pressure changes outside, these tubes need to open to keep the pressure in your middle ear equal to the surrounding air pressure. This happens when you open your mouth wide like when you yawn. Chewing gum, or anything else causes them to open, and so can swallowing. When they open and pressure equalizes, you are likely to hear a pop.
Airplanes aren't the only place where this happens. If you drive in the mountains, pressure will decrease as you go up. If you start to feel the pressure build up in your ear, be sure to do what it takes to open your eustachian tubes. If you dive far enough under water, the pressure of the water will cause the same problem, so be ready.
So chewing gum can help avoid earaches and some temporary hearing loss while flying, but you don't have to be a gum chewer. For diagrams and pictures of these important parts of your anatomy, enter this address in your internet browser: http://bit.ly/HvcpF2
Dr. Doug Green blogs at DrDougGreen.com for educators and parents who don't have as much time to read and surf as he does.
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