View source for Skyglow

{{Short description|Diffuse luminance of the night sky}}
{{About|night sky luminance from artificial light|the natural atmospheric phenomenon|airglow|the interplanetary phenomenon|zodiacal light|the wider environmental impacts of artificial light|light pollution}}
[[File:México City at Night 2005.jpg|thumb|right|[[Mexico City]] at night, showing skyglow]]
[[File:Light pollution europe.jpg|thumb|A map from 1996 to 1997 showing the extent of skyglow over Europe]]

'''Skyglow''' (or '''sky glow''') is the diffuse [[luminance]] of the [[night sky]], apart from discrete light sources such as the [[Moon]] and visible individual [[star]]s. It is a commonly noticed aspect of [[light pollution]]. While usually referring to luminance arising from artificial [[lighting]], skyglow may also involve any [[light scattering by particles|scattered light]] seen at night, including natural ones like [[starlight]], [[zodiacal light]], and [[airglow]].<ref name="The Light of the Night Sky">{{cite book |last1=Roach |first1=Franklin E. |title=The Light of the Night Sky |last2=Gordon |first2=Janet L. |publisher=D. Reidel |year=1973 |location=[[Dordrecht]] and Boston, Massachusetts |author-link=Franklin E. Roach |name-list-style=amp}}</ref><ref>{{cite journal |url=https://skyandtelescope.org/astronomy-resources/rate-your-skyglow/#Natural |title=Rate Your Skyglow |last=Flanders |first=Tony |date=December 5, 2008 |journal=[[Sky & Telescope]] |publisher=[[American Astronomical Society|AAS]] Sky Publishing |access-date=2020-02-26}}</ref>

In the context of light pollution, skyglow arises from the use of artificial light sources, including electrical (or rarely [[gas lighting|gas]]) lighting used for illumination and advertisement and from [[gas flare]]s.<ref>{{cite web |title=Oil Boom Means Sky Watchers Hoping for Starlight Just Get Stars, Lite |first=Emily |last=Guerin |url=https://www.npr.org/2015/11/05/454341141/oil-boom-means-sky-watchers-hoping-for-starlight-just-get-stars-lite |publisher=[[NPR]] |date=5 November 2015 |access-date=2016-04-24}}</ref> Light propagating into the [[atmosphere of Earth|atmosphere]] directly from upward-directed or incompletely shielded sources, or after reflection from the ground or other surfaces, is partially [[backscatter|scattered back]] toward the ground, producing a [[photon diffusion|diffuse glow]] that is visible from great distances. Skyglow from artificial lights is most often noticed as a glowing dome of light over cities and towns, yet is pervasive throughout the [[developed country|developed world]].

==Causes==
[[File:suburban night sky.jpg|thumb|upright=1.2|In this 10-second exposure, facing south toward [[Sagittarius (constellation)|Sagittarius]], three forms of light pollution are present: skyglow, [[glare (vision)|glare]], and [[light pollution#Light trespass|light trespass]].]]

Light used for all purposes in the outdoor and indoor environments contributes to the artificial skyglow. In fact, both intentional and unintentional usage of light such as lampposts, fixtures, and buildings illumination contribute to the scattering of the light into the atmosphere and represent one of the most detrimental effects of light pollution at night. 

Part of this artificial light at night interacts with the air molecules and aerosols, and it is absorbed and scattered depending on the optical characteristics of the surrounding environment (see {{section link||Mechanism}}) thus creating skyglow. Whether clouds are present, this effect is amplified by the interaction with water droplets.<ref>{{cite journal |vauthors= |title= Imaging and mapping the impact of clouds on skyglow with all-sky photometry|journal= Scientific Reports|volume= 7|issue= |pages= 6741|doi= 10.1038/s41598-017-06998-z |first1=Andreas |last1=Jechow |first2=Zoltán |last2=Kolláth |first3= Salvador J.|last3=Ribas| first4=Henk|last4=Spoelstra |first5=Franz |last5=Hölker|first6=Christopher C.M.|last6=Kyba |date= 2017|access-date=2024-12-19| url=https://www.nature.com/articles/s41598-017-06998-z|pmc=5532222}}</ref> 

Research indicates that when viewed from nearby, about half of skyglow arises from direct upward emissions, and half from reflected, though the ratio varies depending on details of lighting fixtures and usage, and distance of the observation point from the light source.<ref name=LWW2009>{{cite journal|last1=Luginbuhl|first1=C.|last2=Walker|first2=C.|last3=Wainscoat|first3=R.|title=Lighting and Astronomy|journal=Physics Today|date=2009|volume=62|issue=12|pages=32–37|doi=10.1063/1.3273014|bibcode=2009PhT....62l..32L|doi-access=free}}</ref><ref>{{cite web|title=Outdoor Lighting Codes|url=http://www.flagstaffdarkskies.org/dark-sky-solutions/dark-sky-solutions-2/outdoor-lighting-codes/|website=Flagstaff Dark Skies Coalition|accessdate=17 April 2016}}</ref> In most communities, direct upward emission averages about 10–15%.<ref name=LWW2009 /> Fully shielded lighting (with no light emitted directly upward) decreases skyglow by about half when viewed nearby, but by much greater factors when viewed from a distance.

Skyglow is significantly amplified by the presence of snow, and within and near urban areas when [[clouds]] are present.<ref>{{cite journal |author=Kyba |first1=C. C. M. |last2=Ruhtz |first2=T. |last3=Fischer |first3=J. |last4=Hölker |first4=F. |name-list-style=amp |date=2011 |editor1-last=Añel |editor1-first=Juan |title=Cloud Coverage Acts as an Amplifier for Ecological Light Pollution in Urban Ecosystems |journal=PLOS ONE |volume=6 |issue=3 |pages=e17307 |bibcode=2011PLoSO...617307K |doi=10.1371/journal.pone.0017307 |pmc=3047560 |pmid=21399694 |doi-access=free}}</ref> In remote areas, snow brightens the sky, but clouds make the sky darker.

[[File:Effect of light pollution on clouds.jpg|thumb|upright=1.2|In remote areas on moonless nights clouds appear dark against the sky. In or near developed areas skyglow is strongly enhanced by clouds.]]

==Mechanism==
There are two kinds of light scattering that lead to sky glow: scattering from molecules such as N<sub>2</sub> and O<sub>2</sub> (called [[Rayleigh scattering]]), and that from [[aerosols]], described by [[Mie theory]]. Rayleigh scattering is much stronger for short-wavelength (blue) light, while scattering from aerosols is less affected by wavelength. Rayleigh scattering makes the sky appear blue in the daytime; the more aerosols there are, the less blue or whiter the sky appears. In many areas, most particularly in urban areas, aerosol scattering dominates, due to the heavy aerosol loading caused by modern industrial activity, power generation, farming and transportation.

Despite the strong wavelength dependence of Rayleigh scattering, its effect on sky glow for real light sources is small. Though the shorter wavelengths suffer increased scattering, this increased scattering also gives rise to increased [[extinction (astronomy)|extinction]]: the effects approximately balance when the observation point is near the light source.<ref name=luginbuhl2014>{{cite journal|last1=Luginbuhl|first1=C.|last2=Boley|first2=P.|last3=Davis|first3=D.|title=The impact of light source spectral power distribution on sky glow|journal=Journal of Quantitative Spectroscopy and Radiative Transfer|date=2014|volume=139|pages=21–26|doi=10.1016/j.jqsrt.2013.12.004|bibcode=2014JQSRT.139...21L|doi-access=free}}</ref>

For human visual perception of sky glow, generally the assumed context under discussions of sky glow, sources rich in shorter wavelengths produce brighter sky glow, but for a different reason (see {{section link||Dependence on light source}}).

==Measurement==
Professional astronomers and light pollution researchers use various measures of luminous or radiant intensity per unit area, such as magnitudes per square arcsecond, watts per square meter per steradian,(nano-)Lamberts, or (micro-)candela per square meter.<ref>{{cite journal|last1=Garstang|first1=R.|title=Night-Sky Brightness at Observatories and Sites|journal=Publications of the Astronomical Society of the Pacific|date=1989|volume=101|page=306|doi=10.1086/132436|bibcode=1989PASP..101..306G|doi-access=free}}</ref> All-sky maps of skyglow brightness are produced with professional-grade imaging cameras with [[charge-coupled device|CCD]] detectors and using stars as calibration sources.<ref name="DLM2007" /><ref>{{cite journal|last1=Ashley|first1=A.|last2=Duriscoe|first2=D.|last3=Luginbuhl|first3=C.|title=Measuring the color and brightness of artificial sky glow from cities using an all-sky imaging system calibrated with astronomical methods in the Johnson-Cousins B and V photometric systems|journal=American Astronomical Society, AAS Meeting|date=2017|volume=229|page=236.20|bibcode=2017AAS...22923620P}}</ref> Amateur astronomers have used the [[Bortle Dark-Sky Scale]] to approximately quantify skyglow ever since it was published in ''Sky & Telescope'' magazine in February 2001.<ref>{{cite news | last=Bortle | first=John E. | title=Observer's Log – Introducing the Bortle Dark-Sky Scale | date=February 2001 | work=[[Sky & Telescope]] | url=http://skyandtelescope.com/printable/resources/darksky/article_84.asp | url-status=dead | archive-url=https://archive.today/20060316144447/http://skyandtelescope.com/printable/resources/darksky/article_84.asp | archive-date=2006-03-16 }}</ref> The scale rates the darkness of the night sky inhibited by skyglow with nine classes and provides a detailed description of each position on the scale. Amateurs also increasingly use [[Sky Quality Meter]]s (SQM) that nominally measure in astronomical photometric units of visual ([[UBV photometric system|Johnson]] V) magnitudes per square arcsecond.{{refn|group=note|SQM meters have a notably different spectral response than the human eye, and even from the Johnson V response they nominally use. As a consequence SQM measures are not accurate for tracking visual impressions, particularly as spectral characteristics change from yellow sources such as [[sodium-vapor lamp|HPS]] to white sources such as LED. Likewise, the difference between SQM measures and a true Johnson V measure is dependent on the skyglow spectrum and source(s) of artificial luminance.<ref>{{cite journal|last1=Sánchez de Miguel|first1=Alejandro|last2=Aubé|first2=Martin|last3=Zamorano|first3=Jaime|last4=Kocifaj|first4=Miroslav|last5=Roby|first5=Johanne|last6=Tapia|first6=Carlos|title=Sky Quality Meter measurements in a colour-changing world|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=467|issue=3|pages=2966|date=3 March 2017|doi=10.1093/mnras/stx145|doi-access=free |url=https://academic.oup.com/mnras/article-abstract/467/3/2966/3061573/Sky-Quality-Meter-measurements-in-a-colour?redirectedFrom=fulltext|accessdate=18 April 2017|arxiv = 1701.05019 |bibcode = 2017MNRAS.467.2966S }}</ref>}}

[[File:All-sky_map_of_measured_skyglow_brightness.png|thumb|center|upright=2.8|A calibrated all-sky map in the vicinity of [[Ashurst Lake]], [[Arizona]], showing skyglow brightness, including artificial ([[Phoenix, Arizona|Phoenix]] and [[Flagstaff, Arizona]]) and natural sources ([[airglow]], Milky Way) are visible (U.S. National Park Service).]]

==Dependence on distance from source==
Sky glow brightness arising from artificial light sources falls steeply with distance from the light source, due to the geometric effects characterized by an [[inverse square law]] in combination with atmospheric absorption. An approximate relation is given by

:<math>\text{intensity} \ \propto \ \frac{1}{\text{distance}^{2.5}} \, </math>

which is known as "Walker's Law."<ref name="Walker1977">{{cite journal |last1=Walker |first1=M. F. |date=1977 |title=The Effects of Urban Lighting on the Brightness of the Night Sky |journal=Publications of the Astronomical Society of the Pacific |volume=89 |pages=405 |bibcode=1977PASP...89..405W |doi=10.1086/130142 |doi-access=free}}</ref>

Walker's Law has been verified by observation<ref name=Walker1977 /><ref name="DLM2007">{{cite journal
|last1=Duriscoe|first1=D.
|last2=Luginbuhl|first2=C.
|last3=Moore|first3=C.
|title=Measuring Night-Sky Brightness with a Wide-Field CCD Camera
|journal=Publications of the Astronomical Society of the Pacific
|date=2007
|volume=119|issue=852
|pages=192–213
|doi=10.1086/512069
|arxiv=astro-ph/0702721|bibcode=2007PASP..119..192D|s2cid=53331822
}}</ref> to describe both the measurements of sky brightness at any given point or direction in the sky caused by a light source (such as a city), as well as to integrated measures such as the brightness of the "light dome" over a city, or the integrated brightness of the entire night sky. At very large distances (over about 50&nbsp;km) the brightness falls more rapidly, largely due to extinction and geometric effects caused by the curvature of the Earth.

==Dependence on light source==
{{More citations needed section|date=May 2024}}
{{multiple image
 | align = right
 | direction = vertical
 | width = 200
 | image1 = Sky Glow with HPS Lighting.png
 | image2 = Sky Glow with 4100K CCT LED Lighting.png
 | footer = Sky glow and stars visible with high-pressure sodium lighting (top) and 4100K CCT LED lighting (bottom). Calibrated model of Flagstaff, Arizona, US as viewed from 10 km.
}}

Different light sources produce differing amounts of visual sky glow. The dominant effect arises from the [[Purkinje effect|Purkinje shift]], and not as commonly claimed from [[Rayleigh scattering]] of short wavelengths (see {{section link||Mechanism}}).<ref name=luginbuhl2014 /><ref name=aube2013>{{cite journal|last1=Aubé|author-link=:fr:Martin Aubé|first1=M.|last2=Roby|first2=J.|last3=Kocifaj|first3=M.|title=Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility|journal=PLOS ONE|date=2013|doi=10.1371/journal.pone.0067798|pmid=23861808|pmc=3702543|volume=8|issue=7|pages=e67798|bibcode=2013PLoSO...867798A|doi-access=free}}</ref> When observing the night sky, even from moderately light polluted areas, the eye becomes nearly or completely dark-adapted or [[scotopic vision|scotopic]]. The scotopic eye is much more sensitive to blue and green light, and much less sensitive to yellow and red light, than the light-adapted or [[photopic vision|photopic]] eye. Predominantly because of this effect, white light sources such as [[metal-halide lamp|metal halide]], [[fluorescent lamp|fluorescent]], or white [[light-emitting diode|LED]] can produce as much as 3.3 times the visual sky glow brightness of the currently most-common [[sodium vapor lamp|high-pressure sodium]] lamp, and up to eight times the brightness of low-pressure sodium or amber [[Aluminium gallium indium phosphide]] LED.

{| class="wikitable"
|+ Sky Glow brightness ratios for different lamp types{{refn|group=note|Results for within cities or near the light source, based on work of Luginbuhl et al.<ref name=luginbuhl2014 /> and Aubé et al.<ref name=aube2013 />}}
|-
! Lamp type !! Description !! Sky glow<br/>relative to LPS !! Sky glow<br/>relative to HPS
|- align="center"
| LPS || Low-pressure sodium || 1.0 || 0.4
|- align="center"
| NBA-LED || amber AlGaInP LED || 1.0 || 0.4
|- align="center"
| HPS || High-pressure sodium || 2.4 || 1.0
|- align="center"
| PCA-LED || Phosphor-converted amber LED || 2.4 || 1.0
|- align="center"
| FLED{{refn|group=note|As used on the Big Island of Hawai`i.<ref>{{cite web|last1=Smith|first1=D.|title=Shift to High-Tech Streetlights Saves Dark Skies, Money|url=http://bigislandnow.com/2012/08/28/shift-to-high-tech-streetlights-saves-dark-skies-money/|website=Big Island Now|accessdate=10 April 2016}}</ref>}} || 5000K CCT LED with yellow filter || 3.6 || 1.5
|- align="center"
| LED 2400K CCT || Warm white LED || 4.3 || 1.8
|- align="center"
| LED 3000K CCT || Warm white LED || 5.4 || 2.1
|- align="center"
| LED 4100K CCT || Neutral white LED || 6.4 || 2.7
|- align="center"
| LED 5100K CCT || Cool white LED || 7.9 || 3.3
|}

[[File:Skyglow_brightness_vs._distance_for_several_light_types,_ratio_to_low-pressure_sodium.png|thumb|right|upright=1.3|Skyglow brightness ratio (compared to low-pressure sodium) vs. distance for various lamp types.<ref name=luginbuhl2014 />]]
In detail, the effects are complex, depending both on the distance from the source as well as the viewing direction in the night sky. But the basic results of recent research are unambiguous: assuming equal [[luminous flux]] (that is, equal amounts of visible light), and matched optical characteristics of the fixtures (particularly the amount of light allowed to radiate directly upward), white sources rich in shorter (blue and green) wavelengths produce dramatically greater sky glow than sources with little blue and green.<ref name=fdsc-lslp>{{cite web|last1=Flagstaff Dark Skies Coalition|title=Lamp Spectrum and Light Pollution|url=http://www.flagstaffdarkskies.org/for-wonks/lamp-spectrum-light-pollution/|website=Lamp Spectrum and Light Pollution|accessdate=10 April 2016}}</ref> The effect of Rayleigh scattering on skyglow impacts of differing light source spectra is small.

Much discussion in the lighting industry and even by some dark-sky advocacy organizations (e.g. [[International Dark-Sky Association]]) of the sky glow consequences of replacing the currently prevalent high-pressure sodium roadway lighting systems with white LEDs neglects critical issues of human visual spectral sensitivity,<ref>{{cite journal |last1=Bierman |first1=A. |date=2012 |title=Will switching to LED outdoor lighting increase sky glow? |journal=Lighting Research and Technology |language=en |volume=44 |issue=4 |pages=449–458 |doi=10.1177/1477153512437147 |s2cid=110024170}}</ref> or focuses exclusively on white LED light sources, or focuses concerns narrowly on the blue portion (<500&nbsp;nm) of the spectrum.<ref>{{cite web|last1=Ashdown|first1=I.|title=Light pollution depends on the light source CCT|url=http://www.ledsmagazine.com/articles/print/volume-12/issue-10/features/street-lights/light-pollution-depends-on-the-light-source-cct.html|website=LEDs Magazine|date=20 October 2015 |publisher=PennWell Corporation|accessdate=10 April 2016}}</ref><ref>{{cite web|last1=International Dark-Sky Association|title=Visibility, Environmental, and Astronomical Issues Associated with Blue – Rich White Outdoor Lighting|url=http://darksky.org/wp-content/uploads/bsk-pdf-manager/8_IDA-BLUE-RICH-LIGHT-WHITE-PAPER.PDF|website=International Dark-Sky Association|accessdate=10 April 2016}}</ref> All of these deficiencies lead to the incorrect conclusion that increases in sky glow brightness arising from the change in light source spectrum are minimal, or that light-pollution regulations that limit the CCT of white LEDs to so-called "warm white" (i.e. [[color temperature|CCT]] <4000K or 3500K) will prevent sky glow increases.<ref name=fdsc-lslp /> Improved efficiency (efficiency in distributing light onto the target area – such as the roadway – with diminished "waste" falling outside of the target area<ref>{{cite web|title=Fitted Target Efficacy metric promotes discussion|date=12 October 2009 |url=http://www.ledsmagazine.com/articles/print/volume-6/issue-10/features/fitted-target-efficacy-metric-promotes-discussion.html|publisher=LEDs Magazine|accessdate=18 April 2016}}</ref> and more uniform distribution patterns{{Citation needed|date=April 2016}}) can allow designers to lower lighting amounts.{{Citation needed|date=April 2016}} But efficiency improvement sufficient to overcome sky glow doubling or tripling arising from a switch to even warm-white LED from high-pressure sodium (or a 4–8x increase compared to low-pressure sodium) has not been demonstrated.

==Negative effects==
[[File:Effect of light pollution on sky polarization.jpg|thumb|upright=1.4|Skyglow is mostly unpolarized, and its addition to moonlight results in a decreased polarization signal. Humans cannot perceive this [[pattern]], but some [[arthropod]]s can.]]

Skyglow, and more generally light pollution, has various negative effects: from aesthetic diminishment of the beauty of a star-filled sky, through energy and resources wasted in the production of excessive or uncontrolled lighting, to impacts on birds<ref>[http://www.flap.org Fatal Light Awareness Program] (FLAP)</ref> and other biological systems,<ref name="ECANL Proceedings">
{{cite book |title=Ecological Consequences of Artificial Night Lighting |date=2006 |publisher=Island Press |editor=Rich |editor-first=C. |location=Washington; Covelo; London |language=en |editor2=Longcore |editor-first2=T.}}</ref> including humans. Skyglow is a prime problem for [[astronomer]]s, because it reduces [[contrast (vision)|contrast]] in the [[night sky]] to the extent where it may become impossible to see all but the [[brightest stars]].{{refn|group=note|It is a widely held misunderstanding that professional astronomical observatories can "filter out" certain wavelengths of light (such as that produced by [[Sodium vapor lamp|low-pressure sodium]]). More accurately, by leaving large portions of the spectrum relatively unpolluted, the narrow-spectrum [[emission spectrum|emission]] from low-pressure sodium lamps and to a lesser extent from amber direct emission [[Aluminium gallium indium phosphide]] LED allows more opportunity for astronomers to "work around" the resulting light pollution.<ref name="IAU Symposium 196 article">
{{cite journal 
| title = Why Astronomy Needs Low-Pressure Sodium Lighting
| author = C.B. Luginbuhl
| journal = Preserving the Astronomical Sky, IAU Symposium No. 196
| volume = 196
| editor = R. J. Cohen
| editor2 = W. T. Sullivan III
| pages = 81–86
| date = 2001| bibcode = 2001IAUS..196...81L
}}</ref>  Even when such lighting is widely used, skyglow still interferes with astronomical research as well as everyone's ability to see a natural star-filled sky.}}

Many nocturnal organisms are believed to navigate using the [[Polarization (waves)|polarization]] [[signal (electrical engineering)|signal]] of [[Rayleigh Sky Model|scattered moonlight]].<ref>{{cite journal |last1=Warrant |first1=Eric |last2=Dacke |first2=Marie |date=1 January 2010 |title=Visual Orientation and Navigation in Nocturnal Arthropods |journal=Brain, Behavior and Evolution |language=en |volume=75 |issue=3 |pages=156–173 |doi=10.1159/000314277 |pmid=20733292 |s2cid=22906227}}</ref> Because skyglow is mostly unpolarized, it can swamp the weaker signal from the moon, making this type of navigation impossible.<ref>{{cite journal|last=Kyba|first=C. C. M.|author2=Ruhtz, T. |author3=Fischer, J. |author4=Hölker, F. |title=Lunar skylight polarization signal polluted by urban lighting|journal=Journal of Geophysical Research|date=17 December 2011|volume=116|issue=D24|pages=D24106|doi=10.1029/2011JD016698 |bibcode=2011JGRD..11624106K|s2cid=56378009|doi-access=free}}<!--|accessdate=4 January 2012--></ref> Close to global coastal megacities (e.g. Tokyo, Shanghai), the natural illumination cycles provided by the moon in the marine environment are considerably disrupted by light pollution, with only nights around the full moon providing greater radiances, and over a given month lunar dosages may be a factor of 6 less than light pollution dosage.<ref>{{Cite journal |last1=Smyth |first1=T. J. |last2=Wright |first2=A. E. |last3=Edwards-Jones |first3=A. |last4=McKee |first4=D. |last5=Queirós |first5=A. |last6=Rendon |first6=O. |last7=Tidau |first7=S. |last8=Davies |first8=T. W. |date=2022 |title=Disruption of marine habitats by artificial light at night from global coastal megacities |url=https://doi.org/10.1525/elementa.2022.00042 |journal=Elementa: Science of the Anthropocene |volume=10 |issue=1 |page=00042 |doi=10.1525/elementa.2022.00042 |bibcode=2022EleSA..10...42S |s2cid=254213236 |issn=2325-1026|hdl=10037/28198 |hdl-access=free }}</ref>

Due to skyglow, people who live in or near urban areas see thousands fewer stars than in an unpolluted sky, and commonly cannot see the [[Milky Way]].<ref>{{cite journal|last1=Falchi |display-authors=etal |first1=F.|title=The new world atlas of artificial night sky brightness|journal=Science Advances|date=10 June 2016|volume=2|issue=6|doi=10.1126/sciadv.1600377|pmid=27386582|pmc=4928945|pages=e1600377|arxiv=1609.01041|bibcode=2016SciA....2E0377F}}</ref> Fainter sights like the [[zodiacal light]] and [[Andromeda Galaxy]] are nearly impossible to discern even with telescopes.

==Effects on the ecosystem==
{{More citations needed section|date=May 2024}}
{{seemain|Ecological light pollution}}
The effects of sky glow in relation to the ecosystem have been observed to be detrimental to a variety of organisms. The lives of plants and animals (especially those which are nocturnal) are affected as their natural environment becomes subjected to unnatural change. It can be assumed that the rate of human development technology exceeds the rate of non-human natural adaptability to their environment, therefore, organisms such as plants and animals are unable to keep up and can suffer as a consequence.<ref>{{cite web|last=Saleh|first=Tiffany|title=Effect of Artificial Lighting on Wildlife|url=http://www.wildlandscpr.org/road-riporter/effects-artificial-lighting-wildlife|work=Road RIPorter|publisher=Wildlands CPR|access-date=March 7, 2012|url-status=dead|archive-url=https://web.archive.org/web/20120910192902/http://www.wildlandscpr.org/road-riporter/effects-artificial-lighting-wildlife|archive-date=September 10, 2012}}</ref>

Although sky glow can be the result of a natural occurrence, the presence of artificial sky glow has become a detrimental problem as urbanization continues to flourish. The effects of [[urbanization]], [[commercialization]], and [[consumerism]] are the result of human development; these developments in turn have ecological consequences. For example, lighted fishing fleets, offshore oil platforms, and cruise ships all bring the disruption of artificial night lighting to the world's oceans.<ref>{{Cite journal |last1=Smyth |first1=T. J. |last2=Wright |first2=A. E. |last3=McKee |first3=D. |last4=Tidau |first4=S. |last5=Tamir |first5=R. |last6=Dubinsky |first6=Z. |last7=Iluz |first7=D. |last8=Davies |first8=T. W. |date=2021-12-13 |title=A global atlas of artificial light at night under the sea |url=https://doi.org/10.1525/elementa.2021.00049 |journal=Elementa: Science of the Anthropocene |volume=9 |issue=1 |pages=00049 |doi=10.1525/elementa.2021.00049 |bibcode=2021EleSA...9...49S |s2cid=245169968 |issn=2325-1026|hdl=10037/24006 |hdl-access=free }}</ref>

As a whole, these effects derive from changes in orientation, disorientation, or misorientation, and attraction or repulsion from the altered light environment, which in turn may affect foraging, predator-prey dynamics,<ref>{{cite journal |last1=Rodríguez |first1=Airam |last2=Orozco-Valor |first2=Paula Maiten |last3=Sarasola |first3=José Hernán |title=Artificial light at night as a driver of urban colonization by an avian predator |journal=Landscape Ecology |date=January 2021 |volume=36 |issue=1 |pages=17–27 |doi=10.1007/s10980-020-01132-3|bibcode=2021LaEco..36...17R |hdl=10261/221083 |hdl-access=free }}</ref><ref>{{Cite journal |last1=McMahon |first1=Oak |last2=Smyth |first2=Tim |last3=Davies |first3=Thomas W. |date=2022-03-25 |title=Broad spectrum artificial light at night increases the conspicuousness of camouflaged prey |journal=Journal of Applied Ecology |volume=59 |issue=5 |language=en |pages=1365–2664.14146 |doi=10.1111/1365-2664.14146 |s2cid=247754178 |issn=0021-8901|doi-access=free |bibcode=2022JApEc..59.1324M |hdl=10026.1/18654 |hdl-access=free }}</ref> reproduction,<ref>{{Cite journal |last1=Davies |first1=Thomas W. |last2=Levy |first2=Oren |last3=Tidau |first3=Svenja |last4=de Barros Marangoni |first4=Laura Fernandes |last5=Wiedenmann |first5=Joerg |last6=D’Angelo |first6=Cecilia |last7=Smyth |first7=Tim |date=2023-05-15 |title=Global disruption of coral broadcast spawning associated with artificial light at night |journal=Nature Communications |language=en |volume=14 |issue=1 |pages=2511 |doi=10.1038/s41467-023-38070-y |issn=2041-1723|doi-access=free |pmid=37188683 |bibcode=2023NatCo..14.2511D |pmc=10185496 }}</ref> migration, and communication. These changes can result in the death of some species such as certain [[migratory birds]],<ref>{{cite journal |last1=Rodríguez |first1=Airam |last2=Holmes |first2=Nick D. |last3=Ryan |first3=Peter G. |last4=Wilson |first4=Kerry-Jayne |last5=Faulquier |first5=Lucie |last6=Murillo |first6=Yovana |last7=Raine |first7=André F. |last8=Penniman |first8=Jay F. |last9=Neves |first9=Verónica |last10=Rodríguez |first10=Beneharo |last11=Negro |first11=Juan J. |last12=Chiaradia |first12=André |last13=Dann |first13=Peter |last14=Anderson |first14=Tracy |last15=Metzger |first15=Benjamin |last16=Shirai |first16=Masaki |last17=Deppe |first17=Lorna |last18=Wheeler |first18=Jennifer |last19=Hodum |first19=Peter |last20=Gouveia |first20=Catia |last21=Carmo |first21=Vanda |last22=Carreira |first22=Gilberto P. |last23=Delgado-Alburqueque |first23=Luis |last24=Guerra-Correa |first24=Carlos |last25=Couzi |first25=François-Xavier |last26=Travers |first26=Marc |last27=Corre |first27=Matthieu Le |title=Seabird mortality induced by land-based artificial lights: Seabird Mortality and Artificial Lights |journal=Conservation Biology |date=October 2017 |volume=31 |issue=5 |pages=986–1001 |doi=10.1111/cobi.12900|pmid=28151557 |hdl=10400.3/4515 |hdl-access=free }}</ref> sea creatures,<ref>{{cite journal |last1=Marangoni |first1=Laura F. B. |last2=Davies |first2=Thomas |last3=Smyth |first3=Tim |last4=Rodríguez |first4=Airam |last5=Hamann |first5=Mark |last6=Duarte |first6=Cristian |last7=Pendoley |first7=Kellie |last8=Berge |first8=Jørgen |last9=Maggi |first9=Elena |last10=Levy |first10=Oren |title=Impacts of artificial light at night in marine ecosystems—A review |journal=Global Change Biology |date=September 2022 |volume=28 |issue=18 |pages=5346–5367 |doi=10.1111/gcb.16264|pmid=35583661 |hdl=11568/1165839 |hdl-access=free }}</ref> and nocturnal predators.<ref>{{cite web|last1=Longcore|first1=T.|last2=Rich|first2=C.|title=Ecological Light Pollution|url=http://www.urbanwildlands.org/Resources/LongcoreRich2004.pdf|work=Frontiers in Ecology|publisher=The Ecological Society of America|accessdate=March 3, 2012}}</ref>

Besides the effect on animals, crops and trees are also susceptible to destruction. The constant exposure to light has an impact of the [[photosynthesis]] of a plant, as a plant needs a balance of both sun and darkness in order for it to survive. In turn, the effects of sky glow can affect production rates of agriculture, especially in farming areas that are close to large city centers.{{Citation needed|reason=Affect positively or negatively? By how much? Where can a reader verify and learn more about this claim?|date=June 2021}}

==See also==
*[[Light pollution]]
*[[SKYGLOW]]
*[[Urbanization]]
*[[Polarized light pollution]]
*[[Over-illumination]]
*[[Dark-sky movement]]
*[[International Dark-Sky Association]] (IDA)
*[[Campaign for Dark Skies]] (CfDS)

==Notes==
{{Reflist|group=note}}

==References==
{{Reflist|30em}}

==External links==
*[http://userpage.fu-berlin.de/~kyba/literature/sky_glow.html List of peer reviewed research papers about sky glow]
*[https://web.archive.org/web/20040621173722/http://www.star.le.ac.uk/~dbl/cfds/skyglow.htm Skyglow: the effect of poor lighting] ([[CfDS]]) (examples of skyglow in the [[United Kingdom|UK]])
*[http://www.streetlights.us/ Skyglow across the Great Lakes] (examples of skyglow in the [[United States|US]])
*[https://web.archive.org/web/20050817122717/http://home.earthlink.net/~sac8/SkyglowBits.htm Filtering Skyglow] (from [[Charge-coupled device|CCD]] [[camera]]s)
*[https://web.archive.org/web/20041126100405/http://www.star.le.ac.uk/~dbl/cfdsdisk/cfdsdisk/Towns%20and%20skyglow/ Towns and Skyglow] ([[United Kingdom|UK]] skyglow image collection)
*[https://play.google.com/store/apps/details?id=com.cosalux.welovestars Loss of the Night] an Android app for estimating skyglow by measuring naked eye limiting magnitude
*[http://www.darkskymeter.com/ Dark Sky Meter] an iPhone app for measuring skyglow luminance
*[http://spie.org/newsroom/technical-articles/1015-led-light-pollution?highlight=x2408&ArticleID=x115768 LED light pollution: Can we save energy and save the night?] SPIE Newsroom article on reducing skyglow

[[Category:Light pollution]]
[[Category:Light sources]]
[[Category:Night]]