Nadir Nadir NER Class T3 Category="Arabic words"Category="Spherical astronomy"

: For other uses, see Nadir (disambiguation).

The nadir (from Arabic nazir, opposite) is the astronomical term for the point in the sky directly below the observer, or more precisely, the point in the sky with an altitude of -90°.

Geometrically, it is the point on the Celestial sphere intersected by a line drawn from your location on the Earth's surface through the center of the Earth. The point opposite the nadir is the Zenith.

By association, nadir is also used to mean the lowest point, or time of greatest adversity.

Nadir also refers to the remote sensing of the atmosphere by a satellite viewing directly down through the atmosphere.