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Meteorology. Why did they pick a name that sounds like a term from astronomy to mean study of the weather?
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Meteorology • Why did they pick a name that sounds like a term from astronomy to mean study of the weather? • The term ‘meteor’ means the streak of light in the sky caused by debris from outer-space burning up in earth’s atmosphere. Since it happens in the sky, the term was closely associated with study of the sky.
Why does earth have an atmosphere? • Scientists think that volcanic eruptions were very abundant when earth was first forming and emitted large volumes of gas. • Gas emissions from collisions with comets may have also played a role. Picture from: http://www.ccsf.edu/Departments/History_of_Time_and_Life/images/VolcanoOutgassing.jpg
Why did those gases remain around the earth? Gravity is a force where mass attracts mass. Since the gases have mass, they are pulled toward the center of earth by gravity.
What is weight? The FORCE of gravity pulling on an object.
So, what is atmospheric pressure? • The FORCE of the air molecules that results from the weight of the air. • (Remember, weight is simply the force of an object pulled to the surface by gravity)
Classic mercury barometer Aneroid Barometer How can you measure atmospheric pressure?
See if you can solve this: • Marnie and Deanna are collecting air pressure readings for a science fair project. Marnie is recording her data near sea level and Deanna chose to hike to the top of a nearby mountain. Who would experience more atmospheric pressure? 1) Marnie 2) Deanna
Marnie experiences greater atmospheric pressure since there is more air above her, thus there is more weight force of the air. Source: http://vathena.arc.nasa.gov/curric/weather/adptcty/elvation.html
Figure 1: Change in average atmospheric pressure with altitude. Source: http://www.physicalgeography.net/fundamentals/7d.html How does pressure change with Altitude? 90% of all air is below 16 km 50% of all air is below 5.6 km
WHAT DO YOU THINK? How does atmospheric pressure play a role in each of these situations? • A mountain climber going to the top of mountain brings an oxygen tank with him. • Airplanes pressurize the cabin during take-off. • Athletes who train at higher altitudes can have an advantage over those who train at sea-level.
Homework: Read about atmospheric pressure on this website: http://kids.earth.nasa.gov/archive/air_pressure/index.htmland answer the following questions: 1) What causes atmospheric pressure on earth? 2) Which location would have more atmospheric pressure (on average), sea-level or on a mountain top? Explain. 3) Why do your ears pop when you go up a mountain? 4) What factors related to atmospheric pressure have caused baseball statistics to be skewed for the Colorado Rockies' home games?