Difference between revisions of "Zenith"
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==Origin== | ==Origin== | ||
[https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] ''cenyth'', ''senyth'', from Middle French ''cenit'', from Medieval Latin, from Old Spanish ''zenit'', ''modification'' of Arabic ''samt'' (''al-ra's'') way (over one's head) | [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] ''cenyth'', ''senyth'', from Middle French ''cenit'', from Medieval Latin, from Old Spanish ''zenit'', ''modification'' of Arabic ''samt'' (''al-ra's'') way (over one's head) | ||
| − | *[ | + | *[https://en.wikipedia.org/wiki/14th_century 14th Century] |
| − | The word "zenith" derives from the inaccurate [[reading]] of the Arabic expression سمت الرأس (samt ar-ra's), meaning "[[direction]] of the head" or "[[path]] above the head", by Medieval Latin scribes in the [ | + | The word "zenith" derives from the inaccurate [[reading]] of the Arabic expression سمت الرأس (samt ar-ra's), meaning "[[direction]] of the head" or "[[path]] above the head", by Medieval Latin scribes in the [https://en.wikipedia.org/wiki/Middle_Ages Middle Ages] (during the 14th century), possibly through Old Spanish. It was reduced to 'samt' ("[[direction]]") and miswritten as 'senit'/'cenit', as the "m" was misread as an "ni". Through the Old French 'cenith', 'zenith' first appeared in the 17th century. |
==Definitions== | ==Definitions== | ||
| − | *1: the point of the [ | + | *1: the point of the [https://en.wikipedia.org/wiki/Celestial_sphere celestial sphere] that is directly opposite the [https://en.wikipedia.org/wiki/Nadir nadir] and vertically above the [[observer]] — see [https://en.wikipedia.org/wiki/Azimuth azimuth] illustration |
*2: the highest [[point]] reached in the heavens by a celestial body | *2: the highest [[point]] reached in the heavens by a celestial body | ||
*3: [[culminating]] [[point]] : [[acme]] <at the zenith of his powers — John Buchan> | *3: [[culminating]] [[point]] : [[acme]] <at the zenith of his powers — John Buchan> | ||
==Description== | ==Description== | ||
| − | The '''zenith''' is an [[imaginary]] point directly "above" a particular location, on the imaginary [ | + | The '''zenith''' is an [[imaginary]] point directly "above" a particular location, on the imaginary [https://en.wikipedia.org/wiki/Celestial_sphere celestial sphere]. "Above" means in the [[vertical]] direction opposite to the apparent [[gravitational]] force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the [https://en.wikipedia.org/wiki/Nadir nadir]. |
The term ''zenith'' is sometimes used to refer to the highest [[point]] reached by a celestial body during its apparent [[orbit]] around a given point of [[observation]]. This sense of the word is often used to [[describe]] the location of the [[Sun]] ("The sun reached its zenith..."), but to an [[astronomer]] the sun doesn't have its own zenith, and is at the zenith only if it is directly overhead. | The term ''zenith'' is sometimes used to refer to the highest [[point]] reached by a celestial body during its apparent [[orbit]] around a given point of [[observation]]. This sense of the word is often used to [[describe]] the location of the [[Sun]] ("The sun reached its zenith..."), but to an [[astronomer]] the sun doesn't have its own zenith, and is at the zenith only if it is directly overhead. | ||
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In a scientific [[context]], the zenith is the direction of [[reference]] for measuring the zenith angle, the angle between a direction of interest (e.g., a star) and the local zenith. | In a scientific [[context]], the zenith is the direction of [[reference]] for measuring the zenith angle, the angle between a direction of interest (e.g., a star) and the local zenith. | ||
| − | In [[astronomy]], the altitude in the [ | + | In [[astronomy]], the altitude in the [https://en.wikipedia.org/wiki/Horizontal_coordinate_system horizontal coordinate system] and the zenith angle are [[complementary]] [[angles]], with the [[horizon]] perpendicular to the zenith. The astronomical [https://en.wikipedia.org/wiki/Meridian_(astronomy) meridian] is also determined by the zenith, and is defined as a circle on the celestial sphere that passes through the zenith, nadir, and the [https://en.wikipedia.org/wiki/Celestial_pole celestial poles]. |
Zenith is also used to determine the time of Dhuhr (midday) prayer by Muslims which is when the sun passes the zenith. | Zenith is also used to determine the time of Dhuhr (midday) prayer by Muslims which is when the sun passes the zenith. | ||
[[Category: Astronomy]] | [[Category: Astronomy]] | ||
Latest revision as of 02:42, 13 December 2020
Origin
Middle English cenyth, senyth, from Middle French cenit, from Medieval Latin, from Old Spanish zenit, modification of Arabic samt (al-ra's) way (over one's head)
The word "zenith" derives from the inaccurate reading of the Arabic expression سمت الرأس (samt ar-ra's), meaning "direction of the head" or "path above the head", by Medieval Latin scribes in the Middle Ages (during the 14th century), possibly through Old Spanish. It was reduced to 'samt' ("direction") and miswritten as 'senit'/'cenit', as the "m" was misread as an "ni". Through the Old French 'cenith', 'zenith' first appeared in the 17th century.
Definitions
- 1: the point of the celestial sphere that is directly opposite the nadir and vertically above the observer — see azimuth illustration
- 2: the highest point reached in the heavens by a celestial body
- 3: culminating point : acme <at the zenith of his powers — John Buchan>
Description
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the nadir.
The term zenith is sometimes used to refer to the highest point reached by a celestial body during its apparent orbit around a given point of observation. This sense of the word is often used to describe the location of the Sun ("The sun reached its zenith..."), but to an astronomer the sun doesn't have its own zenith, and is at the zenith only if it is directly overhead.
In a scientific context, the zenith is the direction of reference for measuring the zenith angle, the angle between a direction of interest (e.g., a star) and the local zenith.
In astronomy, the altitude in the horizontal coordinate system and the zenith angle are complementary angles, with the horizon perpendicular to the zenith. The astronomical meridian is also determined by the zenith, and is defined as a circle on the celestial sphere that passes through the zenith, nadir, and the celestial poles.
Zenith is also used to determine the time of Dhuhr (midday) prayer by Muslims which is when the sun passes the zenith.
