Dusk

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Landers, California at astronomical dusk (20-second exposure) Desert Dusk.jpg
Landers, California at astronomical dusk (20-second exposure)

Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall. [1] 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), such lighting is required to read outside. [2] The term dusk usually refers to astronomical dusk, or the darkest part of twilight before night begins.

Contents

Technical definitions

Civil, nautical, and astronomical twilight. Dusk is the darkest part of evening twilight. Twilight subcategories.svg
Civil, nautical, and astronomical twilight. Dusk is the darkest part of evening twilight.

The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the night sky sets in, or may be thought of as the darkest part of evening twilight. [4] However, technically, the three stages of dusk are as follows:

Media

Dusk can be used to create an ominous tone and has been used as a title for many projects. One instance of this is the 2018 first person shooter Dusk (video game) by New Blood Interactive whose setting is in a similar lighting as the actual time of day.

See also

Related Research Articles

<span class="mw-page-title-main">Afterglow</span> Whitish or rosy light during twilight or after sunset

An afterglow in meteorology are several atmospheric optical phenomena, with a general definition as a broad arch of whitish or pinkish sunlight in the twilight sky, consisting of the bright segment and the purple light. Purple light mainly occurs when the Sun is 2-6° below the horizon, from civil to nautical twilight, while the bright segment lasts until the end of the nautical twilight. Afterglow is often in cases of volcanic eruptions discussed, while its purple light is discussed as a different particular volcanic purple light. Specifically in volcanic occurrences it is light scattered by fine particulates, like dust, suspended in the atmosphere. In the case of alpenglow, which is similar to the Belt of Venus, afterglow is used in general for the golden-red glowing light from the sunset and sunrise reflected in the sky, and in particularly for its last stage, when the purple light is reflected. The opposite of an afterglow is a foreglow, which occurs before sunrise.

Generally, a day is roughly the time of one rotation of the Earth or one rotation of other large astronomical objects. In everyday life, the word "day" often refers to a solar day, which is the length between two solar noons or times the Sun reaches the highest point. The word "day" may also refer to daytime, a time period when the location receives direct and indirect sunlight. On Earth, as a location passes through its day, it experiences morning, noon, afternoon, evening, and night. The effect of a day is vital to many life processes, which is called the circadian rhythm.

A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September.

<span class="mw-page-title-main">Green flash</span> Meteorological optical phenomenon

The green flash and green ray are meteorological optical phenomena that sometimes occur transiently around the moment of sunset or sunrise. When the conditions are right, a distinct green spot is briefly visible above the upper rim of the Sun's disk; the green appearance usually lasts for no more than two seconds. Rarely, the green flash can resemble a green ray shooting up from the sunset or sunrise point.

<span class="mw-page-title-main">Sunrise</span> Time of day when the sun appears above the earth

Sunrise is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects.

<span class="mw-page-title-main">Sunset</span> Daily falling of the Sun below the horizon

Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth, the equinox Sun sets due west at the moment of both the spring and autumn equinoxes. As viewed from the Northern Hemisphere, the Sun sets to the northwest in the spring and summer, and to the southwest in the autumn and winter; these seasons are reversed for the Southern Hemisphere.

<span class="mw-page-title-main">Dawn</span> Time that marks the beginning of the twilight before sunrise

Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's horizon. This morning twilight period will last until sunrise, when direct sunlight outshines the diffused light.

<span class="mw-page-title-main">Sky</span> A view upward from the surface of the Earth

The sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space.

<span class="mw-page-title-main">Night</span> Period of darkness during a 24-hour day

Night is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends on the location and varies throughout the year, based on factors such as season and latitude.

<span class="mw-page-title-main">Midnight sun</span> Natural phenomenon when daylight lasts for a whole day

The midnight sun is a natural phenomenon that occurs in the summer months in places north of the Arctic Circle or south of the Antarctic Circle, when the Sun remains visible at the local midnight. When the midnight sun is seen in the Arctic, the Sun appears to move from left to right, but in Antarctica the equivalent apparent motion is from right to left. This occurs at latitudes from 65°44' to 90° north or south, and does not stop exactly at the Arctic Circle or the Antarctic Circle, due to refraction.

<span class="mw-page-title-main">Maghrib prayer</span> First prayer of the day in Islam

The Maghrib Prayer is one of the five mandatory salah. As an Islamic day starts at sunset, the Maghrib prayer is technically the first prayer of the day. If counted from midnight, it is the fourth prayer of the day.

<span class="mw-page-title-main">Twilight</span> Illumination of the atmosphere when the sun is not directly visible because it is below the horizon

Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs.

<span class="mw-page-title-main">Night sky</span> Appearance of the sky in a clear night

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.

<span class="mw-page-title-main">Polar night</span> Night lasting for more than 24 hours

The polar night is a phenomenon where the nighttime lasts for more than 24 hours that occurs in the northernmost and southernmost regions of Earth. This occurs only inside the polar circles. The opposite phenomenon, the polar day, or midnight sun, occurs when the Sun remains above the horizon for more than 24 hours.

<span class="mw-page-title-main">Evening</span> Period of the day

Evening is the period of a day that starts at the end of the afternoon and overlaps with the beginning of night. The exact times when evening begins and ends depend on location, time of year, and culture, but it is generally regarded as beginning when the Sun is low in the sky and lasting until the end of twilight. Depending on the speaker, it may start as early as 6 p.m. and to last until night. It may be used colloquially to include the last waning afternoon shortly before sunset.

<span class="mw-page-title-main">Blue hour</span> Period of twilight in the morning or evening

The blue hour is the period of twilight when the Sun is at a significant depth below the horizon. During this time, the remaining sunlight takes on a mostly blue shade. This shade differs from the colour of the sky on a clear day, which is caused by Rayleigh scattering.

<span class="mw-page-title-main">Sky brightness</span> Visual perception of the sky and how it scatters and diffuses light.

Sky brightness refers to the visual perception of the sky and how it scatters and diffuses light. The fact that the sky is not completely dark at night is easily visible. If light sources were removed from the night sky, only direct starlight would be visible.

<span class="mw-page-title-main">Daytime</span> Period of a day in which a location experiences natural illumination

Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.

<span class="mw-page-title-main">Rayleigh sky model</span>

The Rayleigh sky model describes the observed polarization pattern of the daytime sky. Within the atmosphere, Rayleigh scattering of light by air molecules, water, dust, and aerosols causes the sky's light to have a defined polarization pattern. The same elastic scattering processes cause the sky to be blue. The polarization is characterized at each wavelength by its degree of polarization, and orientation.

<span class="mw-page-title-main">Earth's shadow</span> Shadow that Earth itself casts through its atmosphere and into outer space

Earth's shadow is the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period, the shadow's visible fringe – sometimes called the dark segment or twilight wedge – appears as a dark and diffuse band just above the horizon, most distinct when the sky is clear.

References

  1. The Random House College Dictionary, "dusk".
  2. 1 2 "Rise, Set, and Twilight Definitions". USNO.
  3. Van Flandern, T.; K. Pulkkinen (1980). "Low precision formulae for planetary positions". Astrophysical Journal Supplement Series. 31 (3): 391. Bibcode:1979ApJS...41..391V. doi:10.1086/190623.
  4. "Full definition of Dusk".
  5. "Dusk – Definition and Meaning". www.timeanddate.com.