In broad terms, the zenith is the direction pointing directly above a particular location (perpendicular, orthogonal). Since the concept of being above is itself somewhat vague, scientists define the zenith in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (for example, meteorology), the zenith at a given point is the local vertical direction pointing away from direction of the force of gravity at that location. For reference, the vertical direction at the give… (More on Zenith)