ESS11
Prof. Jin-Yi Yu
Solar Flux Density Reaching Earth
q Solar Constant (S)
    The solar energy density at the mean distance of      Earth from the sun (1.5  x 1011 m)
    
        S = L / (4 p d2)
           = (3.9 x 1026 W) / [4 x 3.14 x (1.5  x 1011 m)2]
           = 1370 W/m2