class37a - Wednesday, Nov. 26 Syllabus, class notes, and...

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Wednesday, Nov. 26 Syllabus, class notes, and homeworks are at: www.as.utexas.edu courses AST 301, Lacy Reading for this week: chapter 17 We won’t have a help session this week. Today: the greenhouse effect
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Topics for this week How can we use the concept of thermal equilibrium to calculate the temperature of the surface of a rock orbiting the Sun? How does the result depend on the distance of the rock from the Sun? How does the Earth’s atmosphere affect the surface temperature of the Earth? Why do Venus and Mars have such different surface temperatures? How are we changing the Earth’s atmosphere, and how do we think this will affect the surface temperature?
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ABCD Quiz The temperature of the surface of a planet is determined by an equilibrium between heating and cooling. For the Earth, the heating of the surface is dominated by: A. radioactive decay of Uranium inside of the Earth B. absorption of visible light from the Sun C. absorption of ultraviolet light from the Sun D. infrared (blackbody) radiation
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ABCD Quiz The cooling of the surface of the Earth is dominated by: A. emission of infrared radiation B. reflection of sunlight by the surface C. evaporation of water D. conduction of heat into the air (During the day, heat is conducted into the air, but at night the heat flows from the air into the ground.)
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ABCD Quiz The greenhouse effect causes an increase in the temperature of the surface of the Earth by: A. preventing the radiation of infrared radiation by the ground B. preventing the infrared radiation from the ground from getting out to space C. preventing convection from removing heat from the ground D. heating the atmosphere so it can emit infrared radiation which adds to the heating of the ground I would accept answer B on a test, although D is better. C is important in real greenhouses.
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Calculating the rock’s temperature To calculate the temperature of the rock orbiting the Sun, we need to write down the formulas for the energy going into the rock and the energy going out each second. Power going in is the flux of sunlight multiplied by the area
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class37a - Wednesday, Nov. 26 Syllabus, class notes, and...

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