Misplaced Pages

#585414

79-418: Light pollution is the result of outdoor lighting that is not properly shielded, allowing light shine into the eyes and night sky . Direct light that shines into the eyes is called glare , and light directed into the night sky above the horizon causes skyglow . Lighting can also cause light trespass when it enters areas where unwanted (e.g. a neighbor's yard and windows). DarkSky was the first organization in

158-449: A Fixture Seal of Approval program. The program provides objective, third-party certification for lighting products that minimize glare, reduce light trespass, and do not pollute the night sky. Light pollution Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting . In a descriptive sense, the term light pollution refers to the effects of any poorly implemented lighting sources, during

237-530: A decade. They tend to be visible only shortly before sunrise or after sunset because those are the times they are close enough to the Sun to show a tail. Clouds obscure the view of other objects in the sky, though varying thicknesses of cloud cover have differing effects. A very thin cirrus cloud in front of the moon might produce a rainbow-colored ring around the moon . Stars and planets are too small or dim to take on this effect and are instead only dimmed (often to

316-558: A distance from other objects because their navigation lights blink. Beside the Solar System objects changing in the course of them and Earth orbiting and changing orbits over time around the Sun and in the case of the Moon around Earth, appearing over time smaller by expanding its orbit, the night sky also changes over the course of the years with stars having a proper motion and changing brightness because of being variable stars , by

395-480: A dome. Orion is among the most prominent and recognizable constellations. The Big Dipper (which has a wide variety of other names) is helpful for navigation in the northern hemisphere because it points to Polaris , the north star. The pole stars are special because they are approximately in line with the Earth's axis of rotation so they appear to stay in one place while the other stars rotate around them through

474-584: A mechanism for processing citizen inquiries and complaints. 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 LEED . Light trespass can be reduced by selecting light fixtures that limit the amount of light emitted more than 80° above the nadir. The 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

553-567: A meeting in 2009 on Circadian Disruption and Cancer. In different wavelengths of light, red light has the least inhibitory effect on melatonin. In June 2009, the American Medical Association developed a policy in support of control of light pollution. News about the decision emphasized glare as a public health hazard leading to unsafe driving conditions. Especially in the elderly, glare produces loss of contrast, obscuring night vision. A new 2021 study published in

632-446: Is a hormone that regulates photoperiodic physiology and behaviour. Some species of frogs and salamanders utilize a light-dependent "compass" to orient their migratory behaviour to breeding sites. Introduced light can also cause developmental irregularities, such as retinal damage, reduced juvenile growth, premature metamorphosis, reduced sperm production, and genetic mutation. Close to global coastal megacities (e.g. Tokyo, Shanghai),

711-528: Is a nine-level measuring system used to track how much light pollution there is in the sky. A Bortle scale of four or less is required to see the Milky Way whilst one is "pristine", the darkest possible. Inspection of the area surrounding Madrid reveals that the effects of light pollution caused by a single large conglomeration can be felt up to 100 km (62 mi) away from the center. Global effects of light pollution are also made obvious. Research in

790-418: 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." In essence bright and/or badly shielded lights around roads can partially blind drivers or pedestrians and contribute to accidents. The blinding effect

869-451: Is about the size of a thumbnail at arm's length, and is readily identified. Over 29.53 days on average, the moon goes through a full cycle of lunar phases . People can generally identify phases within a few days by looking at the Moon. Unlike stars and most planets, the light reflected from the Moon is bright enough to be seen during the day. Some of the most spectacular moons come during the full moon phase near sunset or sunrise. The Moon on

SECTION 10

#1732772392586

948-592: Is also used to refer to artificial light indoors. Adverse consequences are multiple; some of them may not be known yet. Light pollution competes with starlight in the night sky for urban residents, interferes with astronomical observatories , and, like any other form of pollution , disrupts ecosystems and has adverse health effects. Light pollution is a side-effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, outdoor area lighting (such as car parks), offices, factories, streetlights, and illuminated sporting venues. It

1027-446: Is brighter than the stars and often the only "star" visible near sunrise or sunset, depending on its location in its orbit. Because of its brightness, Venus can sometimes be seen after sunrise. Mercury , Mars , Jupiter and Saturn are also visible to the naked eye in the night sky. The Moon appears as a grey disc in the sky with cratering visible to the naked eye. It spans, depending on its exact location, 29–33 arcminutes – which

1106-449: Is caused by inefficient or unnecessary use of artificial light. Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow. A single offending light source often falls into more than one of these categories. Solutions to light pollution are often easy steps like adjusting light fixtures or using more appropriate light bulbs. Further remediation can be done with more efforts to educate

1185-417: 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

1264-475: Is most severe in highly industrialized, densely populated areas of North America, Europe, and Asia and in major cities in the Middle East and North Africa like Tehran and Cairo , but even relatively small amounts of light can be noticed and create problems. Awareness of the harmful effects of light pollution began in the second half of the 19th century, but efforts to address its effects did not begin until

1343-400: Is natural. To precisely measure how bright the sky gets, night time satellite imagery of the earth is used as raw input for the number and intensity of light sources. These are put into a physical model of scattering due to air molecules and aerosoles to calculate cumulative sky brightness. Maps that show the enhanced sky brightness have been prepared for the entire world. The Bortle scale

1422-519: Is no replacement pollinator that would not be affected by the artificial light. This can lead to species decline of plants that are unable to reproduce, and change an area's longterm ecology . Among nocturnal insects, fireflies ( Coleoptera : Lampyridae, Phengodidae and Elateridae) are especially interesting study objects for light pollution, once they depend on their own light to reproduce and, consequently, are very sensitive to environmental levels of light. Fireflies are well known and interesting to

1501-574: 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. Over-illumination stems from several factors: Most of these issues can be readily corrected with available, inexpensive technology , 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

1580-539: Is orchestrated by the natural diurnal patterns of light and dark, so disruption to these patterns impacts the ecological dynamics. Many species of marine plankton, such as Calanus copepods, can detect light levels as low as 0.1 μWm ; using this as a threshold a global atlas of marine Artificial Light at Night has been generated, showing its global widespread nature. Studies suggest that light pollution around lakes prevents zooplankton, such as Daphnia , from eating surface algae , causing algal blooms that can kill off

1659-407: Is required. Twilight is divided in three segments according to how far the Sun is below the horizon in segments of 6°. After sunset the civil twilight sets in, and ends when the Sun drops more than 6° below the horizon. This is followed by the nautical twilight , when the Sun reaches heights of −6° and −12°, after which comes the astronomical twilight defined as the period from −12° to −18°. When

SECTION 20

#1732772392586

1738-597: Is the excessive and unnecessary use of light. 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). Additionally, the EIA reported that 208 billion kWh and 53 billion kWh of electricity were used for commercial and manufacturing buildings respectively in 2018. Light use

1817-479: The IAU , fear that light pollution will increase significantly, one of many concerns reported in the media regarding satellite overcrowding. Public discourse surrounding the continuing deployment of satellite constellations includes multiple petitions by astronomers and citizen scientists, and has raised questions about which regulatory bodies hold jurisdiction over human actions that obscure starlight. Measuring

1896-503: The International Dark-Sky Association has developed a set of model lighting ordinances. The 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

1975-517: The International Space Station (ISS) and Iridium Satellites . Meteors streak across the sky infrequently. During a meteor shower , they may average one a minute at irregular intervals, but otherwise their appearance is a random surprise. The occasional meteor will make a bright, fleeting streak across the sky, and they can be very bright in comparison to the night sky. Aircraft are also visible at night, distinguishable at

2054-457: The Milky Way galaxy. 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,

2133-493: The Solar cycle ) but given optimal conditions, the darkest possible sky has a brightness of about 22 magnitude/square arc second. If a full moon is present, the sky brightness increases to about 18 magnitude/sq. arcsecond depending on local atmospheric transparency, 40 times brighter than the darkest sky. In densely populated areas a sky brightness of 17 magnitude/sq. an arcsecond is not uncommon, or as much as 100 times brighter than

2212-557: The Sun is below the horizon . Natural light sources in a night sky include moonlight , starlight , and airglow , depending on location and timing. Aurorae light up the skies above the polar circles . Occasionally, a large coronal mass ejection from the Sun or simply high levels of solar wind may extend the phenomenon toward the Equator . The night sky and studies of it have a historical place in both ancient and modern cultures. In

2291-516: The backscatter of sunlight by interplanetary dust . Shortly after sunset and before sunrise, artificial satellites often look like stars – similar in brightness and size – but move relatively quickly. Those that fly in low Earth orbit cross the sky in a couple of minutes. Some satellites, including space debris , appear to blink or have a periodic fluctuation in brightness because they are rotating. Satellite flares can appear brighter than Venus, with notable examples including

2370-426: The dark-sky movement , and is currently the largest. DarkSky's principal approach is to raise awareness about the value of dark, star-filled night skies and encourage their protection and restoration through education about the problems and solutions, including outdoor lighting practices that create less light pollution. In 2011, the organization had about 5,000 members in 70 countries. To promote awareness about

2449-425: The rod cells without triggering the cone cells . If it is particularly dark and a particularly faint celestial object is of interest, averted vision may be helpful. The stars of the night sky cannot be counted unaided because they are so numerous and there is no way to track which have been counted and which have not. Further complicating the count, fainter stars may appear and disappear depending on exactly where

DarkSky International - Misplaced Pages Continue

2528-496: The "hidden" harms of LAN, and many other topics. The environmental effects of LAN were mentioned as early as 1897, in a Los Angeles Times article. The following is an excerpt from that article, called "Electricity and English songbirds": Night sky 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

2607-404: The 1950s. In the 1980s a global dark-sky movement emerged with the founding of the International Dark-Sky Association (IDA). There are now such educational and advocacy organizations in many countries worldwide. About 83% of people, including 99% of Europeans and Americans, live under light-polluted skies that are more than 10% brighter than natural darkness. 80% of North Americans cannot see

2686-542: The CfDS handbook "Blinded by the Light?". Chapter 4, "Human health implications of light pollution" states that "...   light intrusion, even if dim, is likely to have measurable effects on sleep disruption and melatonin suppression. Even if these effects are relatively small from night to night, continuous chronic circadian, sleep and hormonal disruption may have longer-term health risks". The New York Academy of Sciences hosted

2765-518: The Southern Economic Journal indicates that light pollution may increase by 13% in preterm births before 23 weeks of gestation. While light at night can be beneficial, neutral, or damaging for individual species , its presence invariably disturbs ecosystems. For example, some species of spiders avoid lit areas, while other species are happy to build their webs directly on lamp posts. Since lamp posts attract many flying insects,

2844-404: The Sun drops more than 18° below the horizon, the sky generally attains its minimum brightness. Several sources can be identified as the source of the intrinsic brightness of the sky, namely airglow , indirect scattering of sunlight, scattering of starlight, and artificial light pollution . Depending on local sky cloud cover, pollution, humidity, and light pollution levels, the stars visible to

2923-453: The U.S. Fish and Wildlife Service of the number of birds killed after being attracted to tall towers range from four to five million per year to an order of magnitude higher. The Fatal Light Awareness Program (FLAP) works with building owners in Toronto , Ontario , Canada and other cities to reduce mortality of birds by turning out lights during migration periods. Another study has found that

3002-526: The U.S. Sky quality in the U.S. ranges from pristine ( Capitol Reef National Park and Big Bend National Park ) to severely degraded ( Santa Monica Mountains National Recreation Area and Biscayne National Park ). The National Park Service Night Sky Program monitoring database is available online (2015). Light pollution in Hong Kong was declared the 'worst on the planet' in March 2013. In June 2016, it

3081-428: The atmosphere 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. Also contributing to light pollution are artificial satellites . With increasing numbers of satellite constellations such as OneWeb and Starlink , members of the astronomical community, notably

3160-705: The blue band. In North America the situation is comparable. There is a significant problem with light pollution ranging from the Canadian Maritime Provinces to the American Southwest. The International Dark-Sky Association works to designate areas that have high-quality night skies. These areas are supported by communities and organizations that are dedicated to reducing light pollution (e.g. Dark-sky preserve ). The National Park Service Natural Sounds and Night Skies Division has measured night sky quality in national park units across

3239-452: The course of a night (or a year). Planets , named for the Greek word for 'wanderer', process through the starfield a little each day, executing loops with time scales dependent on the length of the planet's year or orbital period around the Sun. Planets, to the naked eye, appear as points of light in the sky with variable brightness. Planets shine due to sunlight reflecting or scattering from

DarkSky International - Misplaced Pages Continue

3318-504: The dark adaptation. Star charts are produced to aid stargazers in identifying constellations and other celestial objects. Constellations are prominent because their stars tend to be brighter than other nearby stars in the sky. Different cultures have created different groupings of constellations based on differing interpretations of the more-or-less random patterns of dots in the sky. Constellations were identified without regard to distance to each star, but instead as if they were all dots on

3397-412: The day or night. Light pollution can be understood not only as a phenomenon resulting from a specific source or kind of pollution, but also as a contributor to the wider, collective impact of various sources of pollution. Although this type of pollution can exist throughout the day, its effects are magnified during the night with the contrast of the sky's darkness. It has been estimated that 83 percent of

3476-406: The day, because direction of natural polarization of sun light and its reflection is a source of information for a lot of animals). This form of pollution is named polarized light pollution (PLP). Unnatural polarized light sources can trigger maladaptive behaviors in polarization-sensitive taxa and alter ecological interactions. Lights on tall structures can disorient migrating birds. Estimates by

3555-560: The development and trial of new lighting technologies in the North Sea. In early 2007, the lights were installed on the Shell production platform L15. The experiment proved a great success since the number of birds circling the platform declined by 50 to 90%. Birds migrate at night for several reasons. Save water from dehydration in hot day flying and part of the bird's navigation system works with stars in some way. With city light outshining

3634-598: The direct lighting effect by adding softening filters or other solutions, though intensity will be reduced. 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: According to Mario Motta, president of the Massachusetts Medical Society , "...   glare from bad lighting

3713-416: The effect of sky glow on a global scale is a complex procedure. The natural atmosphere is not completely dark, even in the absence of terrestrial sources of light and illumination from the Moon. This is caused by two main sources: airglow and scattered light . At high altitudes, primarily above the mesosphere , there is enough UV radiation from the sun at very short wavelengths to cause ionization . When

3792-521: The general public (unlike many other insects) and are easily spotted by non-experts, and, due to their sensibility and rapid response to environmental changes, good bioindicators for artificial night lighting. Significant declines in some insect populations have been suggested as being at least partially mediated by artificial lights at night. A 2009 study also suggests deleterious impacts on animals and ecosystems because of perturbation of polarized light or artificial polarization of light (even during

3871-407: The higher layers and thus no appreciable ionization occurs. Apart from emitting light, the sky also scatters incoming light, primarily from distant stars and the Milky Way , but also the zodiacal light , sunlight that is reflected and backscattered from interplanetary dust particles. The amount of airglow and zodiacal light is quite varied (depending, amongst other things on sunspot activity and

3950-563: The highest levels of ALAN reported the highest number of cases of breast cancer. Seoul, which had the highest levels of light pollution, had 34.4% more cases of breast cancer than Ganwon-do, which had the lowest levels of light pollution. This suggested a high correlation between ALAN and the prevalence of breast cancer. It was also found that there was no correlation between other types of cancer such as cervical or lung cancer and ALAN levels. A more recent discussion (2009), written by Professor Steven Lockley, Harvard Medical School, can be found in

4029-403: The horizon benefits from the Moon illusion which makes it appear larger. The Sun's light reflected from the Moon traveling through the atmosphere also appears to color the Moon orange and/or red. Comets come to the night sky only rarely. Comets are illuminated by the Sun, and their tails extend away from the Sun. A comet with a visible tail is quite unusual – a great comet appears about once

SECTION 50

#1732772392586

4108-992: The human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure, and some lighting design textbooks use human health as an explicit criterion for proper interior lighting. Health effects of over-illumination or improper spectral composition of light may include: increased headache incidence, worker fatigue , medically defined stress , decrease in sexual function and increase in anxiety. Likewise, animal models have been studied demonstrating unavoidable light to produce adverse effect on mood and anxiety. For those who need to be awake at night, light at night also has an acute effect on alertness and mood. Outdoor artificial light at night – exposure to contemporary types such as current types of street lighting – has been linked to risks for obesity, mental disorders, diabetes , and potentially other health issues by preliminary studies. In 2007, "shift work that involves circadian disruption"

4187-466: The importance of dark skies". DarkSky describes Urban Night Sky Places as "sites near or surrounded by large urban environs whose planning and design actively promote an authentic nighttime experience in the midst of significant artificial light at night, and that otherwise do not qualify for designation within any other International Dark Sky Places category". To promote the use of responsible outdoor lighting that minimizes light pollution, DarkSky offers

4266-424: The ions collide with electrically neutral particles they recombine and emit photons in the process, causing airglow . The degree of ionization is sufficiently large to allow a constant emission of radiation even during the night when the upper atmosphere is in the Earth's shadow. Lower in the atmosphere all the solar photons with energies above the ionization potential of N 2 and O 2 have already been absorbed by

4345-413: The issues, DarkSky has an International Dark Sky Places program that aims "to encourage communities, parks and protected areas around the world to preserve and protect dark sites through responsible lighting policies and public education". There are currently five types of designation for International Dark Sky Places: DarkSky describes Dark Sky Sanctuaries as "the most remote (and often darkest) places in

4424-424: The lakes' plants and lower water quality. Light pollution may also affect ecosystems in other ways. For example, entomologists have documented that nighttime light may interfere with the ability of moths and other nocturnal insects to navigate. It can also negative impact on insect development and reproduction. Night-blooming flowers that depend on moths for pollination may be affected by night lighting, as there

4503-424: The large payoff in reducing over-illumination. 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

4582-444: The late 1990s showed that the entire area consisting of southern England, Netherlands, Belgium, West Germany, and northern France have a sky brightness of at least two to four times normal. The only places in continental Europe where the sky can attain its natural darkness are in northern Scandinavia and in islands far from the continent. The growth of light pollution on the green band has been 11% from 2012–2013 to 2014–2020, and 24% on

4661-407: The light itself on the eye.) 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

4740-546: The light trespass issues. 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 FAA minimum lighting requirements the Federal Communications Commission maintains an Antenna Structure Registration database information which citizens may use to identify offending structures and provides

4819-462: The lights produced by the Post Tower has affected 25 bird species. As a result, they discovered that decreasing the use of excessive lights increased the survival rate of bird species. Similar disorientation has also been noted for bird species migrating close to offshore production and drilling facilities. Studies carried out by Nederlandse Aardolie Maatschappij b.v. (NAM) and Shell have led to

SECTION 60

#1732772392586

4898-431: 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. Sky glow is the bright haze above cities that is produced from excessive artificial lighting at night. 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

4977-521: 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 dosages. In September 2009, the 9th European Dark-Sky Symposium in Armagh, Northern Ireland had a session on the environmental effects of light at night (LAN). It dealt with bats, turtles,

5056-403: The night sky takes place in the context of observational astronomy . Visibility of celestial objects in the night sky is affected by light pollution . The presence of the Moon in the night sky has historically hindered astronomical observation by increasing the amount of sky brightness . With the advent of artificial light sources, however, light pollution has been a growing problem for viewing

5135-802: The night sky, birds (and also about mammals) no longer navigate by stars. Sea turtle hatchlings emerging from nests on beaches are another casualty of light pollution. It is a common misconception that hatchling sea turtles are attracted to the moon. Rather, they find the ocean by moving away from the dark silhouette of dunes and their vegetation, a behavior with which artificial lights interfere. The breeding activity and reproductive phenology of toads, however, are cued by moonlight. Juvenile seabirds are also disoriented by lights as they leave their nests and fly out to sea, causing events of high mortality. Amphibians and reptiles are also affected by light pollution. Introduced light sources during normally dark periods can disrupt levels of melatonin production. Melatonin

5214-411: The night sky. Optical filters and modifications to light fixtures can help to alleviate this problem, but for optimal views, both professional and amateur astronomers seek locations far from urban skyglow . The fact that the sky is not completely dark at night, even in the absence of moonlight and city lights, can be easily observed, since if the sky were absolutely dark, one would not be able to see

5293-466: The observer is looking. The result is an impression of an extraordinarily vast star field. Because stargazing is best done from a dark place away from city lights, dark adaptation is important to achieve and maintain. It takes several minutes for eyes to adjust to the darkness necessary for seeing the most stars, and surroundings on the ground are hard to discern. A red flashlight can be used to illuminate star charts and telescope parts without undoing

5372-451: The past, for instance, farmers have used the status of the night sky as a calendar to determine when to plant crops. Many cultures have drawn constellations between stars in the sky, using them in association with legends and mythology about their deities . The history of astrology has generally been based on the belief that relationships between heavenly bodies influence or explain events on Earth. The scientific study of objects in

5451-403: The planets' surface or atmosphere. Thus, the relative Sun-planet-Earth positions determine the planet's brightness. With a telescope or good binoculars, the planets appear as discs demonstrating finite size, and it is possible to observe orbiting moons which cast shadows onto the host planet's surface. Venus is the most prominent planet, often called the "morning star" or "evening star" because it

5530-516: The point of invisibility). Thicker cloud cover obscures celestial objects entirely, making the sky black or reflecting city lights back down. Clouds are often close enough to afford some depth perception, though they are hard to see without moonlight or light pollution. On clear dark nights in unpolluted areas, when the Moon appears thin or below the horizon, the Milky Way, a band of what looks like white dust, can be seen. The Magellanic Clouds of

5609-401: The public in order to push legislative change. However, because it is a man-made phenomenon, addressing its impacts on humans and the environment has political, social, and economic considerations. Light pollution is the presence of anthropogenic artificial light in otherwise dark conditions. The term is most commonly used in relation to in the outdoor environment and surrounding, but

5688-424: The silhouette of an object against the sky. The intensity of the sky brightness varies greatly over the day and the primary cause differs as well. During daytime when the Sun is above the horizon direct scattering of sunlight ( Rayleigh scattering ) is the overwhelmingly dominant source of light. In twilight, the period of time between sunset and sunrise, the situation is more complicated and a further differentiation

5767-425: The southern sky are easily mistaken to be Earth-based clouds (hence the name) but are in fact collections of stars found outside the Milky Way known as dwarf galaxies . Zodiacal light is a glow that appears near the points where the Sun rises and sets, and is caused by sunlight interacting with interplanetary dust . Gegenschein is a faint bright spot in the night sky centered at the antisolar point , caused by

5846-508: The spiders that tolerate the light gain an advantage over the spiders that avoid it. This is a simple example of the way in which species frequencies and food webs can be disturbed by the introduction of light at night. Light pollution poses a serious threat in particular to nocturnal wildlife, having negative impacts on plant and animal physiology. It can confuse animal navigation , alter competitive interactions, change predator-prey relations, and cause physiological harm. The rhythm of life

5925-494: The unaided naked eye appear as hundreds, thousands or tens of thousands of white pinpoints of light in an otherwise near black sky together with some faint nebulae or clouds of light. In ancient times the stars were often assumed to be equidistant on a dome above the Earth because they are much too far away for stereopsis to offer any depth cues. Visible stars range in color from blue (hot) to red (cold), but with such small points of faint light, most look white because they stimulate

6004-584: The world whose conservation state is most fragile". DarkSky describes Dark Sky Parks as "publicly- or privately-owned spaces protected for natural conservation that implement good outdoor lighting and provide dark sky programs for visitors". IDA describes Dark Sky Reserves as "dark 'core' zones surrounded by a populated periphery where policy controls are enacted to protect the darkness of the core". DarkSky describes Dark Sky Communities as "legally organized cities and towns that adopt quality outdoor lighting ordinances and undertake efforts to educate residents about

6083-472: The world's people live under light-polluted skies and that 23 percent of the world's land area is affected by skyglow . The area affected by artificial illumination continues to increase. A major side effect of urbanization , light pollution is blamed for compromising health, disrupting ecosystems, and spoiling aesthetic environments. Studies show that urban areas are more at risk. Globally, it has increased by at least 49% from 1992 to 2017. Light pollution

6162-428: Was estimated that one third of the world's population could no longer see the Milky Way, including 80% of Americans and 60% of Europeans. Singapore was found to be the most light-polluted country in the world. Over the past 21 years, China's provincial capital cities have seen a major increase in light pollution, with hotspots along the eastern coastline region. Medical research on the effects of excessive light on

6241-584: Was listed as a probable carcinogen by the World Health Organization's International Agency for Research on Cancer. (IARC Press release No. 180). Multiple studies have documented a correlation between night shift work and the increased incidence of breast and prostate cancer. One study which examined the link between exposure to artificial light at night (ALAN) and levels of breast cancer in South Korea found that regions which had

#585414