The concept of meridian can have several applications in our language.
Maximum circle of the celestial sphere that passes through the poles and that determines the time zone
At the behest of Astronomy, a meridian it is each great circle of the celestial sphere that passes through the poles.
They are used to determine the time zones of each region of planet earth, since they will vary in each meridian or as a consequence of the rotation of the earth.
The time zone comprises each of the twenty-four longitudinal zones into which our planet is divided.
These zones are between two semicircle-shaped Meridans that are united at the north and south poles. Meanwhile, since the earth rotates only once every twenty-four hours on its axis, twenty-four time zones have been established.
The areas that are in the same region will coincide in the time zone and will share noon, that is, they will have the same hour of sun.
It is the Greenwich meridian that defines the time zones. Those who are to the east of this will have to add an hour as it passes to another meridian, and those who are to the west must subtract one hour.
Geographically speaking, the meridians are the imaginary maximum semicircles, the circle is completed with the Antimeridian, mapped out cartographically, that pass through the two poles, the North Pole and the South Pole, therefore, they follow a North-South direction, with an extension of twenty thousand km. approximately.
The Greenwich Meridian
The Prime Meridian, also designated Greenwich Meridian (the 0 ° meridian), is the only meridian that has a specific name and is in charge of dividing our planet earth into the western hemisphere, west of the meridano and the eastern hemisphere, east of it. The rest of the meridians, parallel to the one of origin and perpendicular to the Equator, are also measured in degrees always in relation to Greenwich.
Both the parallels (latitude) and the meridians (longitude) make up what could be called a network of geographic coordinates, which, at their intersection, determine the location of any point within the earth's surface. All those points that are located on the same meridian will have the same length, although what will vary is their length.
Associate at noon
Also, another common use of the term is to refer to that linked to the noon hours.
“ The meridian heat it is doing is unbearable.”
At noon the sun is very close to the zenith (highest point in the sky). This implies that the sun at this moment is just above our heads if we become observers of it.
The shadow will be minimal at this point and will point north in the northern hemisphere, and south in the southern hemisphere.
Generally, this time of day is associated with 12 o'clock, although some extend it a little more and consider it between 11 and 1 o'clock.
During the midday various activities are usually carried out, especially it is at this time when people have lunch. You will stop doing daily activities for a moment and sit down to lunch.
It is also an ideal time to go outside, especially in winter because the sun beats down and you can feel the cold much less.
On the contrary, at this time in the summer, it is better to stay in a cool place.
Something luminous
On the other hand, the term meridian is also used to refer to something extremely diaphanous, clear and bright, in relation to the clarity of noon. " Juan's explanation of the matter was crystal clear.”
From an example just given, we realize that this meaning has especially a symbolic application.
When something is said to be a meridian, it will be because it appears very clear and sharp to the senses. If it is something that can be seen, it will be manifested with the naked eye, and if it is something that must be understood or solved, it will be characterized by being lucid so that everyone can understand it or, failing that, it can be solved.
And at the behest of the Geometry, the meridian is the line of intersection of a surface of revolution with a plane passing through its axis.
