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Information about Sunset

“Sundown” redirects here. For other uses, see Sundown (disambiguation).


Sunset, also called sundown in some American English dialects, is the time at which the Sun disappears below the horizon in the west. It should not be confused with dusk, which is the point at which darkness falls, some time after the beginning of twilight when the Sun itself sets.
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A composite image showing the terminator dividing night from day, running across Europe and Africa. Observers on the surface of the earth along this terminator will see a sunset.
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A fiery sunset over Miami, FloridaPhoto: Marc Averette
The red hues of the sky at sunset and sunrise are caused by Mie Scattering, not Rayleigh Scattering. The colours of the sky throughout the day and at sunrise and sunset, are explained by the phenomena of both Rayleigh Scattering and Mie Scattering. The colour of the sky described by Rayleigh Scattering applies to the hues of blue, violet and green, not to the reds, oranges, peaches and purples of sunrise and sunset. Rayleigh Scattering is scattering of shorter wavelength light (e.g. blue & violet) by air atoms and molecules (not statistical variations in density of the Earth's atmosphere). The magnitude or strength of Rayleigh Scattering varies by the reciprocal of the wavelength raised to the fourth power, and hence does not explain the beautiful variations of reds, purples, oranges and peachy colours. The latter colours arise from Mie Scattering, low angle scattering of light off dust, soot, smoke and (ash) particles. Mie Scattering (producing the colours of sunset and sunrise) is beautifully recognizable down-wind of and after dust storms, forest fires and volcanic eruptions that inject large quantities of fine particulate matter into the atmosphere. A number of eruptions in recent times, such as those of Mount Pinatubo in 1991 and Krakatoa in 1883, have been sufficiently large to produce remarkable sunsets and sunrises all over the world. Sometimes just before sunrise or after sunset a green flash can be seen.

The sunset is often more brightly coloured than the sunrise, with the shades of red and orange being more vibrant. The atmosphere responds in a number of ways to exposure to the Sun during daylight hours. In particular, there tends to be more dust in the lower atmosphere at the end of the day than at the beginning. During the day, the Sun heats the surface of the Earth, lowering the relative humidity and increasing wind speed and turbulence, which serves to lift dust into the air. However, differences between sunrise and sunset may in some cases depend more on the geographical particulars of the location from which they are viewed. For example, on a west-facing coastline, sunset occurs over water while sunrise occurs over land.

The timing of sunset varies with the time of year and the latitude of the location from which it is viewed. The timing can also vary in local time, with the location's precise longitude. Changes in timing of sunset are generally driven by the axial tilt of Earth and the planet's movement around its orbit, but some differences exist. For example, in the Northern Hemisphere, the earliest sunset is not at the winter solstice around December 21, but instead it occurs earlier in December. Likewise, the latest sunset is not at the summer solstice around June 21, but later in June or in early July. The same phenomenon exists in the Southern Hemisphere except with the dates swapped. For one or two weeks surrounding both solstices, both sunrise and sunset get slightly later or earlier each day. Even on the equator, sunrise and sunset shift several minutes back and forth through the year, along with solar noon. This effect is plotted by an analemma.

Due to Earth's axial tilt, the direction of sunset is always to the northwest from the March equinox to the September equinox, and to the southwest from the September equinox to the March equinox.

As sunrise and sunset are calculated from the leading and trailing edges of the Sun, and not the centre, this slightly increases the duration of "day" relative to "night". Further, because the light from the Sun is bent by the atmospheric refraction, the Sun is still seen after it is below the horizon. This effect is a daily illusion along with sunrise. The sun also appears larger on the horizon, which is another optical illusion, similar to the moon illusion.

As a visual motif, sunset is often associated with summer, and (particularly when paired with a coconut palm) beach living and surfing culture. This may be due in the first instance to people spending more time outdoors in the evening during summer than during winter, and also because pictures of sunsets over the sea are often more spectacular than daytime beach scenes (see images below). Sunset is also a symbol of west, old age, ending, and closure.

See also

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Sundown may refer to:
  • Sunset, the time of the day
  • Sundown, Manitoba, A small hamlet in South Eastern Manitoba
  • Sundown (album), a 1974 album by Gordon Lightfoot
  • "Sundown (song)", a hit single from the Sundown

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American English (AmE, AE, AmEng, USEng, en-US), also known as United States English or U.S. English, is a set of dialects of the English language used mostly in the United States.
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For dialects of programming languages, see .


A dialect (from the Greek word διάλεκτος, dialektos) is a variety of a language characteristic of a particular group of the language's speakers.
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time.

One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence, and time itself is something that can be measured.
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The Sun

Observation data
Mean distance
from Earth 1.4961011 m
(8.31 min at light speed)
Visual brightness (V) −26.74m [1]
Absolute magnitude 4.
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horizon (Ancient Greek ὁ ὁρίζων, /ho horídzôn/, from ὁρίζειν, "to limit") is the line that separates earth from sky.
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WEST can refer to:
  • Western European Summer Time
  • WEST (AM), an AM radio station located in Easton, Pennsylvania
''This article refers to the cardinal direction; for other uses see West (disambiguation).

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Dusk or civil dusk is the time at which the sun is 6 degrees below the horizon in the evening. At this time objects are distinguishable and some stars and planets are visible to the naked eye.
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Night or nighttime is the period of time when the sun is below the horizon. The opposite of night is day (or "daytime" to distinguish it from "day" as used for a 24-hour period). Time of day varies based on factors such as season, latitude, longitude and timezone.
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Twilight is the time before sunrise or after sunset when sunlight scattered in the upper atmosphere illuminates the lower atmosphere and the surface of the Earth is between light and dark.
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Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 625–750 nm.
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Hue is one of the three main attributes of perceived color, in addition to lightness and chroma (or colorfulness). Hue is also one of the three dimensions in some colorspaces along with saturation, and brightness (also known as lightness or value).
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Sunrise is the time at which the first part of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the (variously defined) point at which the sky begins to lighten, some time before the sun itself appears, ending twilight.
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Mie theory, also called Lorenz-Mie theory or Lorenz-Mie-Debye theory, is a complete analytical solution of Maxwell's equations for the scattering of electromagnetic radiation by spherical particles (also called Mie scattering).
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Rayleigh scattering (named after Lord Rayleigh) is the scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. It can occur when light travels in transparent solids and liquids, but is most prominently seen in gases.
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Color or colour[1] (see spelling differences) is the visual perceptual property corresponding in humans to the categories called red, yellow, blue, black, etc.
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For other uses, see Daylight (disambiguation).
Daylight or the light of day is the combination of all direct and indirect sunlight outdoors during the daytime (and perhaps twilight).
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Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.
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Smoke is the airborne solid and liquid particulates and gases emitted when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass.
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Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. Ash is created when solid rock shatters and magma separates into minute particles during explosive volcanic activity.
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Volcano:
1. Large magma chamber
2. Bedrock
3. Conduit (pipe)
4. Base
5. Sill
6. Branch pipe
7. Layers of ash emitted by the volcano
8. Flank 9. Layers of lava emitted by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14.
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Mount Pinatubo is an active stratovolcano located on the island of Luzon in the Philippines, at the intersection of the borders of the provinces of Zambales, Tarlac, and Pampanga. Ancestral Pinatubo was a stratovolcano made of andesite and dacite.
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KRAKATOA is a modular explosive device used for explosive ordnance disposal (EOD) or demolitions. It was developed by the British company Alford Technologies and has been featured during the second season of Discovery Channel's Future Weapons television series.
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Green flashes and green rays are rare optical phenomena that occur shortly after sunset or before sunrise, when a green spot is visible for a short period of time above the sun, or a green ray shoots up from the sunset point.
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Relative humidity is a term used to describe the amount of water vapor that exists in a gaseous mixture of air and water.

Definition

The relative humidity of an air-water mixture is defined as the ratio of the partial pressure of water vapor in the mixture to the
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turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time.
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Geography - (from the Greek words Geo (γη) or Gaea (γαία), both meaning "Earth", and graphein (γράφειν) meaning "to describe" or "to write"
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coast is defined as the part of the land adjoining or near the ocean. A coastline is properly a line on a map indicating the disposition of a coast, but the word is often used to refer to the coast itself.
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equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator.
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time zone is a region of the Earth that has adopted the same standard time, usually referred to as the local time. Most adjacent time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC (see also Greenwich Mean Time).
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