How many joules of sunlight hit Earth per day? I have looked everywhere and can't find an answer!!
The sun emits about 4*10^26 Watt. The flux of solar energy at the Earth is thus about:
F = 4*10^26 Watt/(4 pi R^2)
where R = 149.6*10^9 meters is the Sun-Earth distance:
F = 1422 Watt/m^2
Multiply this by the intercepting cross section of the Earth, which is pi times the square of the radius of the Earth (and *not* 4 pi times radius squared) to obtain the amount of sunlight in joules that hits the Earth per second.
1422 Watt/m^2 * pi (6378*10^3 m)^2 =
1.82*10^17 Joules/second
There are 24*3600 seconds in a day, so about 1.6*10^22 Joules of sunlight hit the Earth per day.
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