ASTR-1010 Lecture Notes - Lecture 12: Smog, Northern Hemisphere, Evaporation
19 Nov 2016
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Document Summary
Atmosphere layer of gas that surrounds a planet. Earth"s atmosphere is 10 km thick mostly made of nitrogen and oxygen (n2 and o2) Atmospheric pressure collisions of atoms and molecules causes this pressure. Pressure and density decrease as the altitude increases due to gas being held down by gravity the higher you get the less weight on top of the gas. No clear boundary where the atmosphere ends can extend up to 100 km but most of atmosphere is within 10 km. Without an atmosphere, a planet"s average surface temperature would depend on distance from sun and reflectivity of surface. Reflectivity (albedo) fraction of sunlight that is reflected by the surface. Low reflectivity means the planet absorbs more sunlight which makes the planet hotter. Clouds, snow, and ice reflect 70% of light that hits them, rocks only reflect 20% Rotation also affects temperature faster rotation means less variability between day and night temperatures.
