Sunset 190933 225559329 2008-07-14T08:54:18Z NickEfron121 7429215 {{otheruses}} {{redirect|Sundown}} '''Sunset''', also called '''sundown''' in some [[American English]] [[dialect]]s, is the instant when the trailing edge of the [[sun]]'s disk disappears below the [[horizon]] in the [[west]]. It should not be confused with [[dusk]], which is the point at which [[night|darkness]] falls, some time after the beginning of [[twilight]] when the sun itself sets. [[Image:Miamisunset2004.jpg|thumb|right|250px|Typical sunset in [[Miami, Florida|Miami]]]] [[Image:Nightfall europe-and-afrika 20050507-184500.jpg|thumb|right|250px|A composite image showing the [[Terminator (solar)|terminator]] dividing night from day, running across Europe and Africa. Observers on the surface of the earth along this terminator will see a sunset.]] The sunset is often more brightly colored than the [[sunrise]],{{Fact|date=March 2008}} 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 particular [[geography|geographical]] features of the location from which they are viewed. For example, on a west-facing [[coastline]], sunset occurs over water while sunrise occurs over land. ==Occurrence== The timing of sunset varies with the time of year and the [[latitude]] of the location from which it is viewed. The timing also varies in [[local time]] within a given time zone, determined by each location's precise [[longitude]]. Changes in timing of sunset are driven by the [[axial tilt]] of Earth, the spherical shape of the Earth, and the planet's movement in its annual orbit around the sun. Some apparent anomalies exist however, the main one caused by the Earth's axial tilt and the Earth's elliptical orbit. In the [[Northern Hemisphere]], the earliest sunset does not fall on the winter [[solstice]] around [[December 21]]<sup>st</sup>, but instead it occurs earlier in December. Likewise, the latest sunset does not fall on the summer solstice around [[June 21]]<sup>st</sup>, but instead it happens later in June or in early July, depending on your latitude. The same phenomenon exists in the [[Southern Hemisphere]] except with the respective dates being some time ''before'' June 21<sup>st</sup> in winter and some time ''after'' December 21<sup>st</sup> in summer, possibly in January of the following year. 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]].<ref>[http://www.starrynight.com/sntimes/2007/01/ Starry Night&reg; Times - January 2007] (explains why Sun appears to cross slow before early January)</ref><ref>[http://www.analemma.com/Pages/framesPage.html the analemma], elliptical orbit effect. 'July 3rd to October 2nd the sun continues to drift to the west until it reaches its maximum "offset" in the west. Then from October 2nd until [[January 2]], the sun drifts back toward the east'</ref> [[Image:Sunset_in_AUS.JPG|thumb|right|225px|Typical sunset in [[Australia]]]] Due to Earth's axial tilt, the direction of sunset in the northern hemisphere 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. Sunsets occur precisely due west on the March and September equinoxes. The sunrise and sunset times for a 12 hr day and 12 hr night do not fall on the "equinox" (equal night), since the timing of sunrises and sunsets, and hence, the lengths of day and night vary with each viewer's particular latitude. 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]]. ==Colors== [[Image:2000-08-supersti-sunset.jpg|thumb|200px|Arizona sunset]] [[Image:Full Image Sunset Bates College Lewiston Maine July 3 2008 8.30PM.JPG|thumb|left|200px|Colors of a sunset in [[Maine]].]] [[Image:Sunset over Bates College in Lewston Maine on July 3ed 2008.JPG|thumb|left|200px|Same image [[Cropping|cropped]] and [[zoom]]ed to show the colors]] The [[red]] and orange [[hue]]s of the sky at sunset and [[sunrise]] are caused by scattering of sunlight off of dust particles, soot particles, other solid aerosols, and liquid aerosols floating in the earth's atmosphere. The enhanced red and orange colors at sunset and [[sunrise]] are mathematically explained by [[Mie theory]] or the [[discrete dipole approximation]]. The brilliance and intensity of the colors of sunsets are typically greater than sunrises, since there are generally more particles in the evening air than in the morning air. Nightime air is usually cooler and less windy which allows the dust and soot particles to settle out of the atmosphere, reducing the amount of Mie Scattering and the amount of [[red]] and orange scattered light at [[sunrise]]. [[Sunrise]] color intensities can however exceed sunset's intensities when there are nighttime fires, volcanic eruptions or emissions, or dust storms to the east of the viewer. 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. <ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/redsun.html Red Sunset, Green Flash]</ref><ref>Selected Papers on Scattering in the Atmosphere, edited by Craig Bohren ~SPIE Optical Engineering Press, Bellingham, WA, 1989</ref><ref>[http://ucsu.colorado.edu/~kuesterm/RTweb/startRT.html Science Made Simple]</ref> ==Sunsets on other planets== [[Image:Sunset on Mars.jpg|thumb|Sunset on Mars]] Sunsets on other planets appear different because of the differences in the distance from the planet to the sun and in different atmospheric compositions. Because Mars is farther from the Sun than the Earth is, the Sun appears only about two-thirds the size that it appears in a sunset seen from the Earth.<ref>http://photojournal.jpl.nasa.gov/catalog/PIA07997 This article incorporates text from this source, which is in the public domain.</ref> Although Mars lacks oxygen and nitrogen, it is covered in red dust frequently hoisted into the atmosphere by fast but thin winds.<ref name=apod>http://apod.nasa.gov/apod/ap050620.html This article incorporates text from this source, which is in the public domain.</ref> At least some Martian days are capped by a sunset significantly longer and redder than typical on Earth.<ref name=apod/> One study found that for up to two hours after twilight, sunlight continued to reflect off Martian dust high in the atmosphere, casting a diffuse glow.<ref name=apod/> ==See also== *[[Sunrise]] *[[Sunrise equation]] *[[Day length]] *[[Diffuse sky radiation]] *[[Twilight]] *[[Afterglow]] *[[Astronomy on Mars]] ==References== {{reflist}} ==External links== {{commons|Sunset}} {{commonscat|Sunset on Mars}} * [http://commons.wikimedia.org/wiki/Sunset#Sunsets_on_other_planets Sunsets on other planets] (Wikimedia Commons gallery) * [http://www.sunrisesunset.com/ Sunrise and sunset calculator] * [http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html Full physical explanation in simple terms] * [http://www.ecy.wa.gov/programs/eap/models/twilight.zip Excel workbook] with VBA functions for sunrise, sunset, solar noon, twilight (dawn and dusk), and solar position (azimuth and elevation); by [http://www.ecy.wa.gov/programs/eap/models.html Greg Pelletier], translated from NOAA's online calculators for [http://www.srrb.noaa.gov/highlights/sunrise/azel.html solar position] and [http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html sunrise/sunset] * [http://sun.exnatura.org sun.exnatura.org] Online sunrise/sunset calendar with interactive location finder [[Category:Solar phenomena]] [[Category:Earth phenomena]] [[Category:Symbols]] [[Category:Parts of a day]] [[ar:غروب]] [[an:Escurexito]] [[ay:Jayp'u]] [[bg:Залез]] [[ca:Ocàs]] [[cs:Soumrak]] [[da:Solnedgang]] [[de:Sonnenuntergang]] [[myv:Чивалгома (пертпельксэнь вал)]] [[es:Ocaso]] [[fr:Coucher de soleil]] [[gl:Ocaso]] [[it:Tramonto (giorno)]] [[he:שקיעה]] [[la:Sol occidens]] [[lv:Riets]] [[lt:Saulėlydis]] [[mr:सूर्यास्त]] [[nl:Zonsondergang]] [[no:Solnedgang]] [[nn:Soleglad]] [[pl:Zachód Słońca]] [[pt:Pôr-do-sol]] [[qu:Inti yaykuy]] [[ru:Закат]] [[simple:Sunset]] [[sk:Západ slnka]] [[sv:Solnedgång]] [[chr:ᏭᏕᎵᎬ]] [[bat-smg:Saulielėidis]] [[zh:日落]]