Editing Light pollution (section)

==Types==

[[File:Skybeamer-uniqema-640.jpg|thumb|upright|A light pollution source, using a broad spectrum [[metal halide lamp]], pointing upward at Uniqema factory, [[Gouda, South Holland|Gouda]], the Netherlands]]

===Light trespass===

Light trespass occurs when unwanted light enters one's property, for instance, by shining over a neighbour's fence. A common light trespass problem occurs when a strong light enters the window of one's home from the outside, causing problems such as [[sleep deprivation]]. A number of cities in the U.S. have developed standards for outdoor lighting to protect the rights of their citizens against light trespass. To assist them, the [[International Dark-Sky Association]] has developed a set of model lighting ordinances.<ref name="International Dark-Sky Association">[https://web.archive.org/web/20081122040258/http://www.darksky.org/programs/model-lighting-ordinance.php International Dark-Sky Association]. darksky.org</ref>

The [[International Dark-Sky Association|Dark-Sky Association]] was started to reduce the light going up into the sky which reduces the visibility of stars (see Skyglow below). This is any light that is emitted more than 90° above [[nadir]]. By limiting light at this 90° mark they have also reduced the light output in the 80–90° range which creates most of the light trespass issues.
[[File:Phoenix Lights from afar.jpg|thumb|The city of Phoenix, seen from {{convert|55|mi}} away in [[Surprise, Arizona]]]]

U.S. federal agencies may also enforce standards and process complaints within their areas of jurisdiction. For instance, in the case of light trespass by white [[strobe]] lighting from communication towers in excess of [[Federal Aviation Administration|FAA]] minimum lighting requirements<ref>{{cite web| title = AC 70/7460-1K Obstruction Marking and Lighting| date = 2007-02-01| url = http://wireless.fcc.gov/antenna/documentation/faadocs/7460-1K.pdf| access-date = 2009-07-04| archive-url = https://web.archive.org/web/20100527213109/http://wireless.fcc.gov/antenna/documentation/faadocs/7460-1K.pdf| archive-date = 2010-05-27}}</ref> the [[Federal Communications Commission]] maintains an Antenna Structure Registration database<ref name="FCC Antenna Structure Registration">{{cite web|title = FCC Antenna Structure Registration|url = http://wireless.fcc.gov/antenna/index.htm?&job=home|access-date = 2009-07-04|archive-url = https://web.archive.org/web/20090207035625/http://wireless.fcc.gov/antenna/index.htm?&job=home|archive-date = 2009-02-07}}</ref> information which citizens may use to identify offending structures and provides a mechanism for processing citizen inquiries and complaints.<ref name="fcc.gov">{{cite web|title = FCC Consumer & Governmental Affairs Bureau|url = http://www.fcc.gov/cgb/cgb_offices.html#CICD|publisher = U.S. Federal Communications Commission|date = March 2011|access-date = 2006-12-03|archive-date = 2010-08-10|archive-url = https://web.archive.org/web/20100810191544/http://www.fcc.gov/cgb/cgb_offices.html#CICD|url-status = live}}</ref> The [[U.S. Green Building Council]] (USGBC) has also incorporated a credit for reducing the amount of light trespass and sky glow into their environmentally friendly building standard known as [[Leadership in Energy and Environmental Design|LEED]].

Light trespass can be reduced by selecting light fixtures that limit the amount of light emitted more than 80° above the nadir. The [[Illuminating Engineering Society of North America|IESNA]] definitions include full cutoff (0%), cutoff (10%), and semi-cutoff (20%). (These definitions also include limits on light emitted above 90° to reduce sky glow.)

===Over-illumination===

[[File:HPS-lamps.jpg|thumb|An office building is illuminated by [[sodium lamp|high-pressure sodium (HPS)]] lamps shining upward. Much light goes into the sky and neighboring apartment blocks, causing light pollution.]]Over-illumination is the excessive and unnecessary use of light.<ref name="Chepesiuk-2009">{{Cite journal |last=Chepesiuk |first=Ron |date=1 January 2009 |title=Missing the Dark: Health Effects of Light Pollution |journal=Environmental Health Perspectives |language=en |volume=117 |issue=1 |pages=A20-7 |doi=10.1289/ehp.117-a20 |issn=0091-6765 |pmc=2627884 |pmid=19165374}}</ref>

A large and overabundant amount of electricity is required to support light consumption in the United States. U.S homes consumed 81 billion kilowatthours (kWh) of electricity for lighting in 2020 according to the U.S. Energy Information Administration's (EIA).<ref name="www.eia.gov">{{Cite web |title=Frequently Asked Questions (FAQs) - U.S. Energy Information Administration (EIA) |url=https://www.eia.gov/tools/faqs/faq.php?id=99&t=3#:~:text=According%20to%20the%20most%20recent%20CBECS%2C%20in%202018%2C%20electricity%20consumption,consumption%20by%20U.S.%20commercial%20buildings. |access-date=29 March 2024 |website=www.eia.gov |archive-date=29 March 2024 |archive-url=https://web.archive.org/web/20240329024520/https://www.eia.gov/tools/faqs/faq.php?id=99&t=3#:~:text=According%20to%20the%20most%20recent%20CBECS%2C%20in%202018%2C%20electricity%20consumption,consumption%20by%20U.S.%20commercial%20buildings. |url-status=live }}</ref> Additionally, the EIA reported that 208 billion kWh and 53 billion kWh of electricity were used for commercial and manufacturing buildings respectively in 2018.<ref name="www.eia.gov" />

Light use is not excessive in all developed countries. Amongst developed countries there are large variations in patterns of light use. American cities emit three to five times more light to space per capita compared to German cities.<ref>{{cite journal |last1=Kyba |first1=Christopher |last2=Garz |first2=Stefanie |last3=Kuechly |first3=Helga |last4=de Miguel |first4=Alejandro |last5=Zamorano |first5=Jaime |last6=Fischer |first6=Jürgen |last7=Hölker |first7=Franz |date=23 December 2014 |title=High-Resolution Imagery of Earth at Night: New Sources, Opportunities and Challenges |journal=Remote Sensing |volume=7 |issue=1 |pages=1–23 |bibcode=2014RemS....7....1K |doi=10.3390/rs70100001 |doi-access=free}}<!--|access-date=8 March 2015--></ref>

Over-illumination stems from several factors:

* Consensus-based standards or norms that are not based on vision science;<ref>{{cite journal |last1=Fotios |first1=S |last2=Gibbons |first2=R |date=9 January 2018 |title=Road lighting research for drivers and pedestrians: The basis of luminance and illuminance recommendations |journal=Lighting Research & Technology |volume=50 |issue=1 |pages=154–186 |doi=10.1177/1477153517739055 |doi-access=free}}</ref>
* Improper design, by specifying higher levels of light than needed for a given visual task;<ref name="EcoSky2">{{cite journal |last1=Kyba |first1=Christopher C. M. |last2=Mohar |first2=Andrej |last3=Pintar |first3=Gašper |last4=Stare |first4=Jurij |date=20 February 2018 |title=Reducing the environmental footprint of church lighting: matching façade shape and lowering luminance with the EcoSky LED |journal=International Journal of Sustainable Lighting |volume=19 |issue=2 |pages=132 |doi=10.26607/ijsl.v19i2.80 |doi-access=free}}</ref>
* Incorrect choice of fixtures or [[light bulbs]], which do not direct light into areas as needed;<ref name="EcoSky2" />
* Improper selection of hardware to utilize more energy than needed to accomplish the lighting task;
* Incomplete training of building managers and occupants to use lighting systems efficiently;
* Inadequate lighting maintenance resulting in increased [[stray light]] and energy costs;
* "Daylight lighting" demanded by citizens to reduce crime or by shop owners to attract customers;<ref name="ReferenceB2">Over-illumination can be a design choice, not a fault. In both cases target achievement is questionable.</ref>
* Substitution of old lamps with more efficient [[LED|LEDs]] using the same electrical power; and
* Indirect lighting techniques, such as illuminating a vertical wall to bounce light onto the ground.
* Institutions who illuminate their buildings not to improve navigation, but "to show that its empire is inescapable".<ref name="The New Yorker-2023">{{Cite magazine |date=2023-02-20 |title=Is Artificial Light Poisoning the Planet? |url=https://www.newyorker.com/magazine/2023/02/27/darkness-manifesto-book-johan-eklof |access-date=2023-02-21 |magazine=The New Yorker |language=en-US |archive-date=2023-02-21 |archive-url=https://web.archive.org/web/20230221001754/https://www.newyorker.com/magazine/2023/02/27/darkness-manifesto-book-johan-eklof |url-status=live }}</ref>
** Lighting is less for the benefit of seeing at night, and more for institutions to push working hours beyond natural daylight hours. An economic and financial gain as opposed to a necessity.<ref name="The New Yorker-2023" />

Most of these issues can be readily corrected with available, inexpensive [[technology]], <ref>{{Cite arXiv |last1=Raki |first1=Gholamreza Fardipour |last2=Khakzad |first2=Mohsen |date=2024 |title=Silicon-Photomultiplier (SiPM) Protection Against Over-Current and Over-Illumination |class=hep-ex |eprint=2404.07875}}</ref> and with the resolution of landlord/tenant practices that create barriers to rapid correction of these matters. Most importantly, public awareness would need to improve for industrialized countries to realize the large payoff in reducing over-illumination. <ref>{{Cite journal |last1=Kim |first1=Kyung Hee |last2=Choi |first2=Jae Wook |last3=Lee |first3=Eunil |last4=Cho |first4=Yong Min |last5=Ahn |first5=Hyung Rae |date=2015 |title=A study on the risk perception of light pollution and the process of social amplification of risk in Korea |url=http://link.springer.com/10.1007/s11356-015-4107-5 |journal=Environmental Science and Pollution Research |language=en |volume=22 |issue=10 |pages=7612–7621 |doi=10.1007/s11356-015-4107-5 |pmid=25649389 |bibcode=2015ESPR...22.7612K |issn=0944-1344|url-access=subscription }}</ref>

In certain cases, an over-illumination lighting technique may be needed. For example, indirect lighting is often used to obtain a "softer" look, since hard direct lighting is generally found less desirable for certain surfaces, such as skin. The indirect lighting method is perceived as cozier and suits bars, restaurants, and living quarters. It is also possible to block the direct lighting effect by adding softening filters or other solutions, though intensity will be reduced. <ref>{{Cite arXiv |last1=Miguel |first1=De |last2=Sánchez |first2=Alejandro |date=2022-09-05 |title=Pros and cons of gaussian filters versus step filters for light pollution monitoring |class=astro-ph.IM |language=en |eprint=2209.02100}}</ref>

===Glare===

<!-- This section is linked from [[Solar power]]. -->
{{Main|Glare (vision)}}

Glare can be categorized into different types. One such classification is described in a book by Bob Mizon, coordinator for the British Astronomical Association's Campaign for Dark Skies, as follows:<ref>Mizon, Bob (2001) ''Light Pollution: Responses and Remedies''. Springer. {{ISBN|1-85233-497-5}}</ref>
* ''Blinding glare'' describes effects such as that caused by staring into the Sun. It is completely blinding and leaves temporary or permanent vision deficiencies.
* ''Disability glare'' describes effects such as being blinded by oncoming car lights, or light scattering in fog or in the eye, reducing contrast, as well as reflections from print and other dark areas that render them bright, with a significant reduction in sight capabilities.
* ''Discomfort glare'' does not typically cause a dangerous situation in itself, though it is annoying and irritating at best. It can potentially cause fatigue if experienced over extended periods.

According to Mario Motta, president of the [[Massachusetts Medical Society]], "...{{nbsp}}glare from bad lighting is a public-health hazard—especially the older you become. Glare light scattering in the eye causes loss of contrast and leads to unsafe driving conditions, much like the glare on a dirty windshield from low-angle sunlight or the high beams from an oncoming car."<ref name="Motta-2009">{{cite web| last = Motta| first = Mario| title = U.S. Physicians Join Light-Pollution Fight| work = news| publisher = Sky & Telescope| date = 2009-06-22| url = http://www.skyandtelescope.com/news/48814012.html| access-date = 2009-06-23| archive-url = https://web.archive.org/web/20090624203356/http://www.skyandtelescope.com/news/48814012.html| archive-date = 2009-06-24}}</ref> In essence bright and/or badly shielded lights around roads can partially blind drivers or pedestrians and contribute to accidents.

The blinding effect is caused in large part by reduced contrast due to light scattering in the eye by excessive brightness, or to the reflection of light from dark areas in the field of vision, with luminance similar to the background luminance. This kind of glare is a particular instance of disability glare, called veiling glare. (This is not the same as loss of accommodation of [[night vision]] which is caused by the direct effect of the light itself on the eye.)
===Light clutter===

[[File:Las Vegas Strip.png|thumb|The [[Las Vegas Strip]] displays excessive groupings of colorful lights. This is a classic example of light clutter.]][[File:San Tan Mountain Lights.jpg|thumb|View of the Phoenix metro area from the top of Goldmine Trail in the San Tan Mountains]]

Light clutter refers to excessive groupings of lights. Groupings of lights may generate confusion, distract from obstacles (including those that they may be intended to illuminate), and potentially cause accidents. Clutter is particularly noticeable on roads where the street lights are badly designed, or where brightly lit advertisements surround the roadways. Depending on the motives of the person or organization that installed the lights, their placement and design can even be intended to distract drivers, and can contribute to accidents.<ref name="Kaushik-2022">{{Cite journal |last1=Kaushik |first1=Komal |last2=Nair |first2=Soumya |last3=Ahamad |first3=Arif |date=September 2022 |title=Studying light pollution as an emerging environmental concern in India |url=http://dx.doi.org/10.1016/j.jum.2022.05.012 |journal=Journal of Urban Management |volume=11 |issue=3 |pages=392–405 |doi=10.1016/j.jum.2022.05.012 |issn=2226-5856|hdl=10419/271475 |hdl-access=free }}</ref>

=== Sky glow ===
[[Skyglow|Sky glow]] is the bright haze above cities that is produced from excessive artificial lighting at night.<ref name="Chepesiuk-2009" /> This type of light pollution is created from artificial light reflecting in the sky and bouncing around the different types of particles that reside in the atmosphere<ref>{{Cite journal |last1=Kaushik |first1=Komal |last2=Nair |first2=Soumya |last3=Ahamad |first3=Arif |date=September 2022 |title=Studying light pollution as an emerging environmental concern in India |url=http://dx.doi.org/10.1016/j.jum.2022.05.012 |journal=Journal of Urban Management |volume=11 |issue=3 |pages=392–405 |doi=10.1016/j.jum.2022.05.012 |issn=2226-5856 |hdl-access=free |hdl=10419/271475}}</ref> The effect of sky glow can be harmful in [[astronomy]] and on the health of many organisms. It worsens the visibility of the stars, the [[Milky Way]], and significantly increases the natural light levels at night.<ref>{{Cite journal |last1=Kyba |first1=Christopher C. M. |last2=Tong |first2=Kai Pong |last3=Bennie |first3=Jonathan |last4=Birriel |first4=Ignacio |last5=Birriel |first5=Jennifer J. |last6=Cool |first6=Andrew |last7=Danielsen |first7=Arne |last8=Davies |first8=Thomas W. |last9=Outer |first9=Peter N. den |last10=Edwards |first10=William |last11=Ehlert |first11=Rainer |last12=Falchi |first12=Fabio |last13=Fischer |first13=Jürgen |last14=Giacomelli |first14=Andrea |last15=Giubbilini |first15=Francesco |date=2015-02-12 |title=Worldwide variations in artificial skyglow |journal=Scientific Reports |language=en |volume=5 |issue=1 |pages=8409 |doi=10.1038/srep08409 |pmid=25673335 |pmc=5389131 |bibcode=2015NatSR...5.8409K |issn=2045-2322}}</ref>

===From satellites===
{{main|Satellite flare}}
[[File:Eso2004a.jpg|thumb|upright|Visibility of satellites during twilight marked green and red. 30° above the horizon is where most astronomical observations take place. In Earth's shadow, represented by the darker area on the left, satellites become practically invisible.]]
Also contributing to light pollution are [[artificial satellites]]. With increasing numbers of [[satellite constellation]]s such as [[OneWeb#Concerns|OneWeb]] and [[Starlink]], members of the astronomical community, notably the [[International Astronomical Union|IAU]], fear that light pollution will increase significantly, one of many concerns reported in the media regarding satellite overcrowding.<ref name="iau">{{cite web |title=IAU's statement on satellite constellations |url=https://www.iau.org/news/announcements/detail/ann19035/ |website=International Astronomical Union |access-date=3 June 2019 |archive-date=27 May 2020 |archive-url=https://web.archive.org/web/20200527073625/https://www.iau.org/news/announcements/detail/ann19035/ |url-status=live }}</ref><ref>{{cite web|url=http://www.astronomy.com/news/2019/06/light-pollution-from-satellites-will-get-worse-but-how-much|title=Light pollution from satellites will get worse. But how much?|date=2019-06-14|access-date=2019-11-07|website=astronomy.com|archive-date=2021-04-28|archive-url=https://web.archive.org/web/20210428172415/https://astronomy.com/news/2019/06/light-pollution-from-satellites-will-get-worse-but-how-much|url-status=live}}</ref><ref>{{cite web|url=https://www.theverge.com/2019/5/29/18642577/spacex-starlink-satellite-constellation-astronomy-light-pollution|date=2019-05-29|title=SpaceX Starlink satellite constellation astronomy light pollution|archive-date=2020-11-29|archive-url=https://web.archive.org/web/20201129020343/https://www.theverge.com/2019/5/29/18642577/spacex-starlink-satellite-constellation-astronomy-light-pollution}}</ref> Public discourse surrounding the continuing deployment of satellite constellations includes multiple petitions by astronomers and citizen scientists,<ref>{{cite web|url=https://astronomersappeal.wordpress.com/|title=Appeal by Astronomers|first=Stefano|last=Gallozzi|date=2020-01-09|archive-url=https://web.archive.org/web/20201129001704/https://astronomersappeal.wordpress.com/2020/01/09/astronomers-appeal/|archive-date=2020-11-29}}</ref><ref>{{cite web|url=https://www.astro.princeton.edu/~gbakos/satellites/index.html|title=Light pollution from Satellites|archive-url=https://web.archive.org/web/20201129023557/https://www.astro.princeton.edu/~gbakos/satellites/index.html|archive-date=2020-11-29|first=Gaspar|last=Bakos}}</ref> and has raised questions about which regulatory bodies hold jurisdiction over human actions that obscure starlight.<ref>{{cite web|title=SpaceX's Starlink satellites are about to ruin stargazing for everyone|url=https://theconversation.com/spacexs-starlink-satellites-are-about-to-ruin-stargazing-for-everyone-149516|date=2020-11-17|first=Samantha|last=Lawler|archive-url=https://web.archive.org/web/20201129000433/https://theconversation.com/spacexs-starlink-satellites-are-about-to-ruin-stargazing-for-everyone-149516|archive-date=2020-11-29}}</ref><ref>{{cite web|url=https://www.rcinet.ca/en/2020/11/18/astronomers-vs-tech-giants-in-space/|title=Astronomers vs tech giants in space|first=Marc|last=Montgomery|date=2020-11-18|archive-url=https://web.archive.org/web/20201129000829/https://www.rcinet.ca/en/2020/11/18/astronomers-vs-tech-giants-in-space/|archive-date=2020-11-29}}</ref><ref>{{cite press release|url=https://www.darksky.org/why-do-mega-constellations-matter-to-the-dark-sky-community/|title=Why do mega constellations matter to the Dark Sky community|date=2019-12-27|archive-url=https://web.archive.org/web/20201117232230/https://www.darksky.org/why-do-mega-constellations-matter-to-the-dark-sky-community/#webpage|archive-date=2020-11-17}}</ref><ref>{{cite web |url=https://aas.org/satellite-constellations-1-workshop-report|title=Satellite Constellations 1 Workshop Report |website=American Astronomical Society |date=2020-08-25|archive-url=https://web.archive.org/web/20201129021515/https://aas.org/satellite-constellations-1-workshop-report|archive-date=2020-11-29}}</ref><ref>{{cite press release|url=https://noirlab.edu/public/announcements/ann20011/|date=2020-08-21|title=Media advisory: Press Conference to Unveil Conclusions from Satellite Constellations 1 (SATCON1) Workshop|archive-url=https://web.archive.org/web/20201129021144/https://noirlab.edu/public/announcements/ann20011/|archive-date=2020-11-29}}</ref><ref>{{cite arXiv|eprint=2001.10952|title=Concerns about ground based astronomical observations: A step to Safeguard the Astronomical Sky|first1=Stefano|last1=Gallozzi|first2=Marco|last2=Scardia|first3=Michele|last3=Maris|date=2020-02-04|class=astro-ph.IM}}</ref>