Monday, August 24, 2015

Locating the Sun Whenever

At around dusk on a recent evening, I came to a logical conclusion while staring up at the half moon in the blue sky.  The Sun was hidden by this time, but I was able to draw a conclusion about its whereabouts.  I just needed to use the Moon as a guide.

First, let vector v1 point from you to the center of the Moon.  Second, let vector v2 point from the center of the Moon to the vertex of the lit up part (as shown below):

Vectors v1 and v2 form a plane.  The center of the Sun lies in that plane.  Think about it.