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At the earth, sunlight is 1400 Watts per square meter, if the sun is directly ov

ID: 2200456 • Letter: A

Question

At the earth, sunlight is 1400 Watts per square meter, if the sun is directly overhead. However, since the sunlight side of the earth is a hemisphere, the average is half that, or 700 Watts per square meter.

At equilibrium, we assume that the surface temperature of the earth raises to just that value that will radiate away 700 Watts per square meter. Actually, since sunlight is falling on only one side of the earth, but the night side of the earth also radiates (i.e. heat is spread out to the night side by the atmosphere and fast rotation of earth) lets divide this by two and say that the earth is radiating and average of 350 Watts per square meter over its entire surface.


A. By Stephan

Explanation / Answer

H = AeT^4

T^4 = H/Ae

      =   350/5.67*10^-8

      = 61.7 *10^8 = 2.8 *10^2 = 280 deg

      = 280+ 273.18 = 553.18 K

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