‘To calculate the amount of sunlight reaching the ground, both the elliptical orbit of the Earth and the attenuation by the Earth’s atmosphere have to be taken into account. The extraterrestrial solar illuminance (Eext), corrected for the elliptical orbit by using the day number of the year (dn), is:
![E_{\rm ext}=E_{\rm sc}\left[1+0.034 \cdot \cos\left(2\pi\frac{{\rm dn}-3}{365}\right)\right],](http://upload.wikimedia.org/math/6/a/8/6a8589e762b2a6e4d54cbb5b16fd2067.png)
where dn=1 on January 1; dn=2 on January 2; dn=32 on February 1, etc. In this formula dn−3 is used, because in the modern times Earth’s perihelion, the closest approach to the Sun and therefore the maximum Eext, occurs around January 3 each year.’
We gonna make it baby
So step inside
And if we make it baby
We’re gonna ride into the sun
Just ride into the sun
Burn it up
We’re gonna cruise
Kick down
Nothin’ to lose
When you’re ridin’
Ride into the sun