Nadir Nadir The nadir (, ; from / ALA-LC: "naẓīr", meaning "counterpart") is the direction pointing directly "below" a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there. Since the concept of "being below" is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location. The direction opposite the nadir is the zenith. Nadir is
Overhead line Overhead line An overhead line or overhead wire is used to transmit electrical energy to trams, trolleybuses or trains. It is known variously as: In this article, the generic term "overhead line" is used, as used by the International Union of Railways. An overhead line is designed on the principle of one or more overhead wires (or rails, particularly in tunnels) situated over rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals. The feeder stations are usually fed from a high-voltage electrical grid. Electric trains that collect their current from overhead lines use