Nadir


Nadir
Diagram showing the relationship between the zenith, the nadir, and different types of horizon. The nadir is opposite the zenith.

The nadir (from Arabic: نظير / ALA-LC: naẓīr; meaning "opposite") 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 of the nadir is the zenith.

Nadir also refers to the downward-facing viewing geometry of an orbiting satellite,[1] such as is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing an EVA.

This diagram depicts a satellite observing backscattered sunlight in the nadir viewing geometry.

The word is also used figuratively to mean the lowest point of a person's spirits,[2] or the quality of an activity or profession.[3]

The term nadir can also be used to represent the lowest point reached by a celestial body during its apparent orbit around a given point of observation. This can be used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The sun is said to be at the nadir at a location when it is at the zenith at the location's antipode.

See also

References



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  • nadir — nadir …   Dictionnaire des rimes

  • nadir — [ nadir ] n. m. • 1556; nador 1361; ar. nâdir « opposé (au zénith) » ♦ Astron. Point de la sphère céleste diamétralement opposé au zénith, et qui se trouve sur la verticale de l observateur. ● nadir nom masculin (arabe naẓīr, opposé au zénith)… …   Encyclopédie Universelle

  • nadir — NADÍR s.n. (Astronom.) Punct de pe bolta cerească, opus zenitului, situat la intersecţia verticalei locului la care ne referim cu emisfera cerească inferioară. – Din fr. nadir. Trimis de ana zecheru, 13.09.2007. Sursa: DEX 98  nadír s. n. Trimis …   Dicționar Român

  • Nadir — Na dir (n[=a] d[ e]r), n. [F., Sp., & It. nadir; all fr. Ar. naz[=i]ru s samt nadir, prop., the point opposite the zenith (as samt), in which naz[=i]r means alike, corresponding to. Cf. {Azimuth}, {Zenith}.] 1. That point of the heavens, or lower …   The Collaborative International Dictionary of English

  • Nadir — Nadir, Fußpunkt, dem Zenith oder Scheitelpunkte entgegengesetzt, der untere Pol des Horizontes, eine Linie, verlängert durch die Erde bis an ihre entgegengesetzte Himmelskugel gedacht. Auf jedem Punkte der Erde hat man demnach seinen eigenen… …   Damen Conversations Lexikon

  • Nadir [1] — Nadir oder Fußpunkt ist der Punkt der Sphäre, in dem sie von der Lotlinie[558] des Beobachtungsorts zu Füßen des Beobachters geschnitten wird, diametral gegenüberliegend dem Zenitpunkt oder Scheitelpunkt. Nadirlinie ist die Richtung des Lotfadens …   Lexikon der gesamten Technik

  • nadir — (n.) late 14c., in astronomical sense, from M.L. nadir, from Arabic nazir opposite to, in nazir as samt, lit. opposite of the zenith, from nazir opposite + as samt zenith (see ZENITH (Cf. zenith)). Transferred sense of lowest point (of anything)… …   Etymology dictionary

  • nadir — (Del ár. clás. naẓīr, homólogo). m. Astr. Punto de la esfera celeste diametralmente opuesto al cenit. nadir del Sol. m. Astr. Punto de la esfera celeste diametralmente opuesto al que ocupa en ella el centro del astro …   Diccionario de la lengua española

  • Nadir — Nadir, 1) Punkt am scheinbaren Sternenhimmel, auf welchen eine von dem eigenen Standort auf der Erde durch den Mittelpunkt der Erde hindurch gezogene Linie treffen würde; ist der Gegenpunkt des eigenen Zeniths (s.d.); 2) N. der Sonne, bei den… …   Pierer's Universal-Lexikon

  • Nâdir — Nâdir, Schah von Persien, geb. 1688 in Chorasan als Sohn eines turkmenischen Befehlshabers, nahm in Chorasan Militärdienste, stellte sich aber sodann an die Spitze einer ihm ergebenen Schar, mit der er den von der Regierung verdrängten… …   Meyers Großes Konversations-Lexikon

  • Nadir — (Fußpunkt), s. Zenit …   Meyers Großes Konversations-Lexikon


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