Themes

what is twilight?

Meaning and Definition of Twilight

According to the dictionary, twilight is a word that can have three meanings , two of them in denotative language and one in connotative or metaphorical language:

  • The little light that precedes dawn;
  • Little light left at the end of the day, just before night falls;
  • The period before something ends.

time of day is called twilight or twilight when there is a gradation between the darkness of night and daylight near the horizon.

During the day there are two twilights :

  • Morning Twilight or  Dawn : It is the moment that precedes the arrival of sunlight, but it is still night; the sky begins to lighten on the horizon;
  • Evening or Evening Twilight : when night begins to fall and the sky begins to darken, gradually turning into the darkness of night.

Twilight Types and Durations

The definition of the type and duration of each twilight depends on the latitude, longitude and is based on the need of each area:

Civil

Civil twilight defines the times when cities need artificial light or not.

Morning Civil Twilight: begins when the sun is at a height of minus six degrees from the horizon and ends when the sun appears;

Nocturnal civil twilight: begins at sunset, in the late afternoon and ends when the sun is also at a height of minus six degrees from the horizon.

The measurement of the position of the sun is made from the center of the solar disk. In the interval when the sun is between zero and minus six degrees, first magnitude stars and planets that are above the horizon line can be seen.

Nautical

Nautical twilight has been a position reference for sailors for centuries. Stars have always served as landmarks for navigators, from the measurement of their heights relative to the horizon, with the use of an instrument called a sextant .

Defines when the horizon begins to be distinguished from the dark sky in the morning and when it begins to merge with the sky at night.

Morning Nautical Twilight: Begins when the center of the solar disk is twelve degrees below the horizon line and ends when the sun appears;

Evening Nautical Twilight: Also begins at sunset (like civil twilight) and ends when the sun is less than twelve degrees from the horizon.

When the position of the sun is between the horizon line and negative twelve degrees (that is, twelve degrees below the horizon line). Nautical stars of first and second magnitude can be seen ; During the nautical twilight, you can see the main constellations that guide ships.

Astronomical

Astronomical twilight is what most clearly distinguishes the period of light from the period of total darkness, night itself.

Astronomical Morning Twilight: Begins with the sun eighteen degrees below the horizon line and ends when the sun appears.

Astronomical Evening Twilight: Begins at sunset and ends when the center of the solar disk exceeds minus eighteen degrees.

With the sun below eighteen degrees relative to the horizon, it is possible to make astronomical observations without interfering sunlight. Stars up to sixth magnitude can be seen with the naked eye.

Twilight Metaphors

In the metaphorical sense, twilight is often used to designate the near end of something , of someone, of a phase. How the twilight of life indicates the transition from youthful life to old age, for example. In general, the meaning used is sad, alluding to a sad ending.

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