zenith

Dictionary: ze·nith   (zē'nĭth)

1. The point on the celestial sphere that is directly above the observer.
2. The upper region of the sky.
3. The highest point above the observer's horizon attained by a celestial body.
4. The point of culmination; the peak: the zenith of her career. See synonyms at summit.

[Middle English senith, from Old French cenith, from Medieval Latin, from Arabic samt (ar-ra’s), path (over the head), from Latin sēmita, path.]

The point in the sky directly above an observer. If the observer is at a pole, then the observer's zenith is a celestial pole; but for observers at midlatitudes the zenith is a point in the sky that corresponds to a changing right ascension but a constant declination as the sky rotates overhead. The point directly below the observer is the observer's nadir, and is 180° in longitude and in latitude from the observer's zenith.

The zenith distance of an object in the sky is the angle across the sky from the zenith to the object. The zenith distance is 90° minus the altitude of an object above the horizon. See also Astronomical coordinate systems; Celestial sphere.

noun

The highest point or state: acme, apex, apogee, climax, crest, crown, culmination, height, meridian, peak, pinnacle, summit, top. Informal payoff. Medicine fastigium. See high/low.

Definition: top
Antonyms: bottom, nadir

An Australian medium-woolled (21.5 to 23 microns), dual-purpose, polled sheep, produced by crossing sheep of Merino and Lincoln breeds.

n.

The point in the heavens directly overhead to a man standing or a growing cabbage. A man in bed or a cabbage in the pot is not considered as having a zenith, though from this view of the matter there was once a considerably dissent among the learned, some holding that the posture of the body was immaterial. These were called Horizontalists, their opponents, Verticalists. The Horizontalist heresy was finally extinguished by Xanobus, the philosopher-king of Abara, a zealous Verticalist. Entering an assembly of philosophers who were debating the matter, he cast a severed human head at the feet of his opponents and asked them to determine its zenith, explaining that its body was hanging by the heels outside. Observing that it was the head of their leader, the Horizontalists hastened to profess themselves converted to whatever opinion the Crown might be pleased to hold, and Horizontalism took its place among fides defuncti.

May indicate aspiration and culmination of achievement in the world.

For other uses, see Zenith (disambiguation).

Diagram showing the relationship between the Zenith, the Nadir, and different types of Horizon. Note that the Zenith is opposite the Nadir.

In general terms, the zenith is the direction pointing directly "above" a particular location (perpendicular, orthogonal). The concept of "above" is more specifically defined in astronomy, geophysics and related sciences (e.g., meteorology) as the vertical direction opposite to the force of gravity at a given location. The opposite direction, i.e. the direction of the gravitational force is called the nadir. The term zenith is also used to represent the highest point reached by a celestial body during its apparent orbit around a given point of observation.^[1] This sense of the word is often used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and impossible for latitudes outside the tropics.

Strictly speaking, the zenith is only approximately contained in the local meridian plane because the latter is defined in terms of the rotational characteristics of the celestial body, not in terms of its gravitational field. The two coincide only for a perfectly rotationally symmetric body. On Earth, the axis of rotation is not fixed with respect to the planet (for example due to constant displacements of its fluid components) so that the local vertical direction, as defined by the gravity field, is itself changing direction in time (for instance due to lunar and solar tides).

Contents 1 Origin 2 Relevance and Use 3 See also 4 References

Origin

The word zenith derives from the inaccurate reading of the Arabic word Zeenath as samt ('beauty of the direction/path'), pronounced sent, by scribes in the Middle Ages (during the 14th century), in the expression samt arrâs ('path above the head'). The Arabic word for Zenith is Zawâl, meaning "decline", that is, when the sun ceases to rise and starts to decline.

Relevance and Use

Only between the tropics is it possible for the Sun to be at the zenith.

The zenith is used in the following scientific contexts:

• It serves as the direction of reference for measuring the zenith angle, which is the angular distance between a direction of interest (e.g., a star) and the local zenith, relative to the point for which the zenith is defined.
• It defines one of the axes of the horizontal coordinate system in astronomy.

See also

• Geodesy
• History of geodesy
• Midheaven
• Nadir
• Subsolar point
• Vertical deflection
• Zenith distance

References

1. ^ http://www.merriam-webster.com/dictionary/zenith

• Huschke, Ralph E. (1959) Glossary of Meteorology, American Meteorological Society, Boston, Second printing-1970.
• McIntosh, D. H. (1972) Meteorological Glossary, Her Majesty's Stationery Office, Met. O. 842, A.P. 897, 319 p.
• Picoche, J. (1992) Dictionnaire Etymologique du Français, Le Robert, Paris, ISBN 2-85036-458-4.

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Dansk (Danish)
n. - zenit, toppunkt, højdepunkt

Nederlands (Dutch)
toppunt, zenit

Français (French)
n. - (Astron) zénith, (fig) zénith, apogée, faîte

Deutsch (German)
n. - Zenit, Scheitelpunkt, Höhepunkt

Ελληνική (Greek)
n. - ζενίθ, αποκορύφωμα

Italiano (Italian)
culmine, picco, punto più alto, zenit

Português (Portuguese)
n. - apogeu (m), a parte mais alta no céu acima de sua cabeça

Русский (Russian)
зенит, расцвет

Español (Spanish)
n. - cenit, apogeo, punto culminante

Svenska (Swedish)
n. - zenit, höjdpunkt, topp

中文（简体）(Chinese (Simplified))
顶点, 天顶, 顶峰

中文（繁體）(Chinese (Traditional))
n. - 頂點, 天頂, 頂峰

한국어 (Korean)
n. - 천정, 정점, 극도

日本語 (Japanese)
n. - 天頂, 頂点

العربيه (Arabic)
‏(الاسم) سمت, اوج, ذروة‏

עברית (Hebrew)
n. - ‮קטע הרקיע הנמצא ישר מעל ראשו של הצופה בו, נקודת-קודקוד, שיא, פסגה, גולת-הכותרת, זנית‬

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