Changes

==Origin==

==Origin==

[http://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)

*[http://en.wikipedia.org/wiki/14th_century 14th Century]

*[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 [http://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.

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 [http://en.wikipedia.org/wiki/Celestial_sphere celestial sphere] that is directly opposite the [http://en.wikipedia.org/wiki/Nadir nadir] and vertically above the [[observer]] — see [http://en.wikipedia.org/wiki/Azimuth azimuth] illustration

*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 [http://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 [http://en.wikipedia.org/wiki/Nadir nadir].

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.

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 [http://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 [http://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 [http://en.wikipedia.org/wiki/Celestial_pole celestial poles].

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]]