Dusk occurs at the darkest stage of

twilight Twilight is daylight illumination produced by diffuse sky radiation when the Sun is below the horizon as sunlight from the upper atmosphere is scattered in a way that illuminates both the Earth's lower atmosphere and also the Earth's surf ...

, or at the very end of astronomical twilight after

sunset Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its Earth's rotation, rotation. As viewed from everywhere on Earth, it ...

and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enough light in the sky under clear conditions may occur to read outdoors without artificial illumination; however, at the end of civil twilight (when Earth rotates to a point at which the center of the Sun's disk is 6° below the local

horizon The horizon is the apparent curve that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This curve divides all viewing directions based on whethe ...

), such lighting is required to read outside. The term ''dusk'' usually refers to astronomical dusk, or the darkest part of twilight before night begins.

Technical definitions

The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the

night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlig ...

sets in, or may be thought of as ''the darkest part of evening twilight''. However, technically, the three stages of dusk are as follows: *At civil dusk, the center of the Sun's disc goes 6° below the horizon in the evening. It marks the end of civil twilight, which begins at sunset. At this time objects are still distinguishable and depending on weather conditions some stars and planets may start to become visible to the naked eye. The sky has many colors at this time, such as orange and red. Beyond this point artificial light may be needed to carry out outdoor activities, depending on atmospheric conditions and location. *At nautical dusk, the Sun moves to 12° below the horizon in the evening. It marks the end of nautical twilight, which begins at civil dusk. At this time, objects are less distinguishable, and stars and planets appear to brighten. *At astronomical dusk, the Sun's position is 18° below the horizon in the evening. It marks the end of astronomical twilight, which begins at nautical dusk. After this time the Sun no longer illuminates the sky, and thus no longer interferes with astronomical observations.

Gallery

File:Scots pine at dusk, Ridley Plain, New Forest - geograph.org.uk - 296737.jpg, Scots pine at early dusk in New Forest, England File:Dusk at the shore, Silverdale - geograph.org.uk - 5042036.jpg, Dusk at the shore File:Eastwards at dusk from Dalvanie - geograph.org.uk - 3406039.jpg, Looking eastwards at dusk File:Sandakan at dusk (10498416104).jpg, Sandakan, Malaysia at dusk File:Beached boats on the Fleet at dusk - geograph.org.uk - 2537423.jpg, Beached boats at dusk File:Jardim Botânico, Curitiba (20240301 185956).jpg,

Curitiba Curitiba () is the capital and largest city in the state of Paraná (state), Paraná in Southern Brazil. The city's population was 1,773,718 , making it the List of cities in Brazil by population, eighth most populous city in Brazil and the larg ...

at dusk, Brazil File:Singapore Marina Bay Dusk 2018-02-27.jpg, Nautical dusk in Marina Bay, Singapore File:Dusk-A330.JPG, Astronomical twilight as seen from a plane window

References

{{Parts of a day Earth phenomena Parts of a day Night

Technical definitions

Gallery

See also

References