Note:  Do not rely on this information. It is very old.


Nadir is the point in the heavens immediately beneath our feet; it is therefore the zenith (q.v.) of a place on the opposite side of the earth. Every place has its own zenith and nadir, these two points forming a straight line with the centre of the earth. Since this straight line is a vertical line for the place in question, and the horizon is a plane perpendicular to it, the zenith and nadir are respectively the upper and lower poles of the horizon.

“Delight yourself in the LORD and he will give you the desires of your heart.”
Psalms 37:4