Light pollution

from Wikipedia, the free encyclopedia

The earth at night (1994/95; composite photo from satellite images)
Visible starry sky in the country and in the big city
Taurus constellation in the big city and in the countryside

The concept of light pollution ( English light pollution ), including light pollution , rare light pollution called the permanent absence referred to total darkness in the affected areas of the world and evaluated at the same time this fact negative. The processes that lead to this state are called light immission . The night sky is brightened by mostly artificial light sources , especially if the light is also emitted upwards. The light is scattered in the air layers of the earth's atmosphere , with which the superimposition of natural darkness is connected. Cities are also referred to as their dome lights .

The lack of darkness has numerous disturbing influences:

  • on the flora and in particular on the fauna as insect deaths. In the last 10 years many nocturnal insect species have become extinct in Europe and over 90% of the animals
  • on the biological day-night cycles of many animals
  • and increasing insomnia in humans
  • severe impairment of astronomical observations of the night sky. For example, the Milky Way in cities and their suburbs are no longer visible.

The processes assessed as light pollution are a special form of environmental pollution - but atypical insofar as the fictitious switching off of all artificial light sources would result in almost complete darkness.

In the highest category of darkness, about 6500 stars can be seen with the naked eye with average good eyesight, which are considered to be free-sighted in the astronomical sense ( “counted in the sky” ). They have an apparent magnitude (magnitude) up to 6.8 mag. In cities that are heavily polluted by light, only a few dozen stars or no stars at all are usually visible.


Technical causes

Hong Kong : light-polluted night sky
The light bell of the "City of Light" Jena from 7 km away
Light bell over Karlsruhe from 7 km from the city center. The roof of the house is much darker than the sky

The main cause of light pollution is the large amount of light that is radiated or reflected upwards , which is then reflected again and widely scattered by layers of the atmosphere, atmospheric dusts or water droplets: Air is brightened when it is penetrated by light. This is mainly caused by the Tyndall effect , through the scattering of light (more precisely through Mie scattering ) on suspended particles in the air such as fog droplets , airborne dust or other aerosols, as well as through reflection and refraction .

This results in the well-known bells of light over the cities - for example, a city with a population of 30,000 brightens the sky within a radius of around 25 kilometers, some brightly lit ski areas even over 50 km. This disturbance is “light smog ” in the real sense, as a diffuse mist of light.

The biggest sources of light pollution are large cities and industrial plants , which illuminate the night with street lights , neon signs , video walls , floodlights and industrial lighting. Lighting systems are primarily responsible for this upwardly directed light, since they emit their light largely unused to the sides and upwards (light losses). Such radiation can, however, also be a desired effect in the building and system lighting or lighting.

Strong directional emitters have another major potential for interference. This includes, for example, the high beam of motor vehicles, which, in order to illuminate at least 200-300 meters sufficiently, can still be very dazzling from a distance of many kilometers. For a few years now, discotheque operators have been using projection spotlights like searchlights , the skybeamers , which project dancing beams of light onto the night sky. In individual cases, legal measures have been successfully implemented against this type of advertising . The contribution of light art or laser shows to general light pollution is also increasingly viewed critically. The most recent cause is strong laser pointers .

In addition to the general risk of glare, such sudden flashes of light from moving directional spotlights are also very annoying in astronomy, because they can render long-term exposures unusable in an instant or produce artifacts that make it difficult to track down real astronomical events.

Economic and demographic causes

Light pollution is a side effect of industrialization , the growing standard of living as a result of strong economic growth , especially in emerging countries , but also of global population growth . It occurs in high intensity especially in densely populated regions of the early industrialized nations . However, the disappearance of completely dark areas at night is also a side effect of the conversion of areas that were previously near-natural or used by agriculture or forestry for residential, transport and commercial purposes.

Hoped for positive effects of the use of artificial light in the open air

(White) “light to see” in connection with (blue or red) “light to see” on the station bridge in Vechta
Highlighting the sights of Heidelberg with "light to look at"

In 2007 the city planner J. Alexander Schmidt dealt with the question of the sense of using artificial light in the open air. He made a distinction between three functions of light: "light to see", "light to look at" and "light to look at".

More safety

The light for seeing (and being seen) is, according to Schmidt, indispensable for safety reasons. “Statistically speaking, traffic accidents at night are generally disproportionately more frequent and severe than during the day. A large number of studies have demonstrably shown that the lighting of publicly accessible rooms compensates for the disadvantages of darkness (poor contrast vision , decline in the state of adaptation ) by making danger spots, obstacles and other road users (people, vehicles) more clearly recognizable public space must be bright enough, but only illuminate the areas that are safety-relevant.

Visualization of "beautiful" objects in the dark even during the day

The light to look at represents a kind of "optical makeup" for objects that should be better accentuated at night. It is an “accent light that is used to illuminate architecture, trees, walls, sculptures or fountains. It should give the impression that these elements shine out of themselves. ”The aesthetic need of the observer for a“ beautiful sight ”is satisfied with successfully used accent lighting.

Many objects are not specifically illuminated, but also their surroundings. Most of the “astronomical” light pollution is caused by radiation directed upwards, for example when church towers are illuminated too widely .

Illuminated advertising and light art

For light to view include neon signs , decorative objects lighting elements, as well as all forms of light art . In 2002, an association of cities called "LUCI (Lighting Urban Community International)" was founded. The Italian word "luci" (German: "lights") is alluded to. One of the goals of the network is to create an “urban identity” by promoting light art, especially in the form of illuminations. “Festivals of Light”, which take place regularly, are an important instrument for reaching this goal.

Positive evaluation of brightness

During the GDR era, the following joke was circulating in East Germany about the Berlin TV tower : “Which four seas can you see from the TV tower? Above the sea of ​​clouds, below the sea of ​​houses, in the west the sea of ​​lights and in the east nothing more. ”In this joke, the abundance of lights in capitalist West Berlin stands for all the positive things that GDR citizens longed for at the time, the darkness of the real socialist East Berlin and the surrounding area of Brandenburg, on the other hand, for backwardness, a lack of urbanity and lack of freedom. Even today, not only in the vicinity of Berlin, some consider a “lack of light” in “dark areas” as a “lack of urbanity” and thus of attractiveness. Today, this threatens above all to deter potential customers with good purchasing power. The organizers of the “ Berlin Leuchtet ” festival in September 2018 welcomed the fact that the fallow land of a former freight yard near Berlin's main train station had been cleared and the “Europa City” quarter had been built on.

Events and festivals that put the viewer in a positive mood with the help of artificial light are mostly rated positively. Although z. For example, if the city of Fulda attaches great importance to the success of the Rhön Star Park, it rates the continued operation of the city's own Christmas market as legitimate maintenance of tradition . The city prescribes operators of huts (in Section 8 (2) of the Christmas Market Statute) at the Christmas market to use light sources up to the gable of the huts so that a beautiful, impressive overall picture is created (Section 2 of the Christmas Market Statute). The contribution to the containment of light pollution is that light sources at the Fulda Christmas market must emit a warm light and must not exceed a certain brightness.

In his sermon for the 2012 Easter Vigil , Pope Benedict XVI. : “Light enables life. It enables encounters. It enables communication. It enables knowledge, access to reality, to truth. And by enabling knowledge, it enables freedom and progress. Evil is hiding. Light is therefore also an expression of the good that is and creates brightness. It is the day when we can work. That God created light means: God created the world as a space of knowledge and truth, as a space of encounter and freedom, as a space of good and love. [...] With the resurrection of Jesus the light itself is newly created. He draws us all into the new life of the resurrection and conquers all darkness. It is the new day of God, which applies to all of us. ”The problem is not the physical darkness, but rather, according to the Pope, the“ God's darkness ”and the“ value darkness ”. The fact that people “can light up our cities so brightly today that the stars of the sky are no longer visible” is a misinterpretation of the divine commandment: “Let there be light!”.

Sabine Frank, avowed Catholic, full-time employee in the Star Park Rhön and in her own words "only official night protection officer in Germany", interprets the words of Benedict XVI. to the effect that man himself shoots the stars out of the sky by making them invisible and does not need to be surprised “when the sky is so far from us in the figurative sense.” God wants “to live in the dark”.

Use of stray light

Urban scattered light allows safe walking on paths that are not directly illuminated and not shaded by trees, even at midnight at the new moon , and in special cases, such as a very straight flood dam, even safe cycling, at least as long as encounters and intersections occur only very sporadically and no brightly lit motor vehicle -Traffic occurs. In the vicinity of heavy industry plants that are externally illuminated to be on the safe side, but also of car storage areas and motorway stations, the illuminance can reach several times that of a high full moon , which, however, casts sharp shadows on objects. If the eye is sufficiently adapted to the darkness, the path and the landscape appear equally bright up to the horizon, thus allowing a great view. In contrast, the luminosity of a wheel light or a headlamp extends typically only 10–50 m, even with good, i.e. narrow bundling, because the more distant ( illuminance decreases with the square of the distance from a point light source) appears less bright than what is closer.

The sky behind the contours of objects is brightened by scattered light and allows good orientation when moving in hilly terrain, along a valley, on paths, in settlements or in sparse forests. Scattered light also makes it possible to read an unlit pointer wristwatch or to recognize luggage and items of clothing, for example to put on a jacket. If you have a good knowledge of the location, light from one direction on the horizon can be assigned to a known city and thus serve as directional orientation. A high lighting contrast between the city and the rest of the surroundings around the observer up to the same distance, which can be 30 km and more, is useful. On the way between 2 cities, you can also estimate your own relative position on the connecting route by comparing the brightness of the sky.


Overall, light pollution affects more than 80% of the world's population , and over 99% in Europe and the United States . For example, much of the urban population has never seen the Milky Way . Between 2012 and 2016 the illuminated area of ​​the planet increased again by 9.1 percent. Given the world's growing population, that's not surprising. However, the brightness of the already illuminated areas has increased by 2.2 percent - probably even more because the measuring devices could not fully measure blue light - although darker LED lamps are now being used in many areas .

In Europe , more than half of the population is affected by light pollution. Worldwide, their annual growth averages 6%. In Germany it is around 6%, in Italy 10% and in other countries such as B. Japan up to 12%. Peak values ​​of growth were and are measured in fast-growing metropolitan areas, especially in the USA, so the light emission in southern Ontario increased by about 7-10% per year, in Tucson before 1972 by up to 15% every year. In fact, some estimates put it up by 30 percent annually in some US cities. In the last 150 years the brightness of clear nights in Berlin has increased tenfold, that of cloudy nights by up to a thousand times.


Effect on living organisms

Seabirds like this yellow-billed shearwater on Tenerife are often particularly affected by light pollution on island archipelagos. Young birds in particular are attracted by light sources on their first night flights and, once on the ground, cannot take off again because they need an elevated position to do so.
Accumulation of dead insects in a street lamp

Light pollution affects existing ecosystems. Just as polluted seas, soils or air spaces are no longer habitable for many species, the shrinking of areas that are only illuminated by celestial bodies during the terrestrial night also has diverse consequences. The field of research into the effects of darkness on living beings is the relatively young discipline of Scotobiology ('darkness biology ').

Plants are influenced in their growth cycle by an artificially brightened environment : What is absolutely desirable for cultivated plants in nurseries can become a problem for sensitive natural plants. It has already been observed many times that deciduous trees in the immediate vicinity of street lamps lose their leaves late, which in turn can lead to frost damage.

The widespread white light sources with a high proportion of blue in the spectrum represent a considerable problem for the navigation or orientation of nocturnal insects and also for migratory birds .

In particular, the effects of nocturnal artificial lighting on insects are well documented. Studies from 2000 show that in Germany an average of 150 insects perish on a single street lamp every summer night. If you extrapolate that to the approximately 6.8 million street lamps on German streets, this equates to over a billion insects every night . Numerous other light sources such as the lighting of commercial and industrial areas, advertising spaces or private households are not yet taken into account. The greater the wavelength of the light, the lower the attractiveness of moths.

In addition to insects, numerous other animal species are damaged by light pollution. For example, nocturnal artificial light affects the orientation of migratory birds and, among other things, causes birds to fly into brightly lit buildings and get injured or die in the process (the so-called "tower kill phenomenon").

On island archipelagos especially young sea birds are as shearwaters and petrels vulnerable to light pollution. During their “maiden flights” from the nesting caves on the cliffs to the open sea, they are attracted by strong artificial light sources, go to the ground in a disoriented manner and can no longer take off because they need an elevated position to take off. Often they starve or die of thirst, are run over or killed by predators . In the Balearic Islands, however, the share of young birds that perished in the annual breeding success was only between 0.13 and 0.56%. The deaths are therefore not endangering the survival, but construction measures should be taken to prevent impairment in the vicinity of larger colonies.

The negative influence of night lighting on various species of sea ​​turtles , whose offspring on a beach that is too brightly lit, cannot find their way into the water and thus become easy prey for predators, is also well documented. Effects on numerous other nocturnal species such as bats or frogs have been observed, but in most cases of suspected influence there is still a need for further research.

The effects on the chronobiology of the human organism (as well as on other animals ) have also not yet been conclusively researched. However, increasing sleep disorders among city dwellers as well as disturbances in the hormonal balance of humans (day-night cycle, menstrual cycle of women) have already been proven or are the subject of current research. Further physiological disorders cannot be ruled out - for example, an Israeli research group published data in 2008 that suggest a connection between the intensity of artificial lighting at night, against which those affected are not adequately protected by technical blackout devices, and the risk of breast cancer . A contribution of the extended brightness to the acceleration , for example the early onset of puberty , is also postulated .

Social and cultural consequences of “unnatural” brightness

In the course of the invention of artificial lighting, the day-night rhythm has shifted for many people: people used to be almost exclusively active during the day and rested at night. That has changed due to the permanent availability of lighting . For example, timetables do not take into account whether the time of arrival or departure falls on a terrestrial day or a terrestrial night; What is decisive for them is the time in the respective time zone. It is controversial what effects the expected flexibility in terms of time, especially being (having to) be active with artificial lighting, has on people ( see also: Subjective and social day ).

The perception of natural phenomena, which can only be seen when it is largely dark , although their visibility at night was still a matter of course for earlier generations, is severely restricted , especially in large cities and metropolitan areas, due to the artificial illumination of the night. These include, for example, a shining starry sky , the Milky Way , the direct experience of the planets , shooting stars , or even fireflies . The fact that such natural spectacles can no longer be generally experienced by the aesthetic observer is considered a loss of natural beauty . A more modern view is therefore that that nocturnal darkness - in the sense of the English Heritage -Begriffes - a natural as well - cultural is (natural / cultural heritage) , the more important than basic humanity historical experience and cultural techniques , at least in some regions to get. These cultural traditions include, in particular, navigation and time and calendar calculations , but also a rich mythological treasure. A more concrete application of this is, for example, that archaeo-astronomical monuments (historical observatories and stone setting) require not only monument protection but also a light protection area in order to remain legible as evidence of the times : the nocturnal darkness becomes part of the concept of monument .

Restriction of astronomical observation and research

Orion constellation , taken under dark (left) and light-polluted skies (right)

The absence of a really dark night sky particularly affects astronomical observation and research. Even when the night sky is apparently clear, there is a large amount of scattered light , which is clearly visible in astrophotography with longer exposure times. By removing the false light with the help of image processing, details of the starry sky are increasingly lost in the images. The following picture in the area of ​​the galaxy Messier 101 with the apparent brightness of 7.5 m with all fixed stars up to the 10th magnitude was taken on a clear night in a big city with a bright lens ( f-number 1.2) with an exposure time of five seconds and taken at an exposure index of ISO 12800 near the zenith :

As a rule, only a few very bright stars can be seen with the naked eye over a brightly lit city . Extensive, weaker objects such as the Milky Way, the Large and Small Magellanic Clouds , the Andromeda Galaxy or the famous Great Orion Nebula are known to many people only from stories. Details such as the star color are also barely noticeable. The number of stars visible with the naked eye is mostly only 200 to 500, in city centers even only a few dozen, while in the past it was generally around 6500 - today only in very dark areas.

Observatories that were still in operation in some large cities in the last century have meanwhile had to cease scientific operations or be relocated to remote locations (well-known example: the Vatican observatory ). Large high-performance telescopes have to be erected with enormous effort in the most remote areas of the world (such as in the Atacama Desert in Chile) - which, in addition to light pollution, also minimizes the influence of natural restrictions (air humidity, wind).

In addition to optical impairment of the problem is here electrosmog ( English radio-wave pollution ) for radio astronomy also becoming an increasing problem.

For the Starlink project, 12,000 celestial bodies are to be brought into orbit by 2027 to ensure nationwide internet coverage on earth via satellites . As early as April 2020, astronomers criticized the strong light reflections of the large solar cells of the many bodies. SpaceX announces that it is working on reducing reflexes.

Unnecessary energy consumption

There are currently no studies on how much energy is consumed by light sources and building lighting. For the United States , it is estimated that just under $ 1 billion a year was spent on nighttime lighting as early as the 1990s.

How high a proportion of the corresponding expenditure is “unnecessary”, however, cannot be quantified, since the question of which forms and intensities of lighting are “necessary” is disputed.

Problem awareness and remedial options

Measures against light pollution require that initiatives that follow the motto: "More light in public spaces!" Are replaced by initiatives that assume that before each installation of new light sources in the open air, in the sense of a technology assessment, their ecological effects, not only with regard to light pollution, must be examined and weighed against the hoped-for advantages. For example, since the 2000s, many cities in Europe have developed so-called lighting master plans in which u. a. the valorization of sights in the city at night, especially through their illumination , is rated positively. Neon signs are also appearing in new places in cities.

Without a comprehensive paradigm shift in the sense of the opening sentence to this section, the success of the measures mentioned below appears questionable. In 2012, for example, a dispute arose in the city council of Hanover about the legitimacy of urban measures to curb light pollution. On the grounds that the city is no longer getting dark and there are too many sources of light, Social Democrats and Greens asked the city's environmental committee for the administration to develop a “concept for reducing light pollution”. A CDU councilor was indignant: “This is the stupidest proposal I've ever read. It shows the ideological regulation rage of red-green. "A representative of the FDP in the city council said:" They are now completely freaking out. The security of the citizens is jeopardized. "The managing director of the City-Gemeinschaft, an association of the retail trade :" The political proposal has the potential to be the farce of the year. To demand a blackout is unworldly. Light attracts people and increases sales. ”The existential fears of retailers, not only in large cities and not only in city centers, have increased across Germany since 2012 due to the strong increase in Internet trade .

Politicians who feel responsible for light emissions in public spaces are increasingly open to initiatives to prevent light pollution. However, they also reveal conflicting goals: "Overall, in the area of ​​public lighting facilities, there has already been a rethinking towards energy-saving and environmentally friendly lighting concepts in recent years," stated the Bavarian Ministry of the Environment in 2018 . However, artificial light sources are a necessary part of the infrastructure, from road traffic to lighting for safety reasons. The installation and operation of lighting systems would still have to be in accordance with legal requirements, especially in the areas of immission control, construction, traffic and nature conservation.

Those responsible for the Rhön Star Park concluded in 2018: “Light pollution has decreased in public spaces. The municipalities are increasingly retrofitting their street and building lighting to be environmentally friendly. ”However, it is still difficult to get a grip on glaring lighting on commercial and private areas that is getting out of hand. Probably only the worst of the stupid "light sinners" can be punished by the state executive.

Concrete technical measures

Different light radii for street lighting : The variant on the right describes targeted lighting without having to accept any significant restrictions.

UNESCO , IAU (International Astronomical Union) and CIE (International Commission on Illumination) created a comprehensive program of measures to prevent light pollution as early as 2007, which is based on the intelligent lighting paradigm . The catalog covers both public and private lighting and includes:

  • Limited and adapted lighting times for the outdoor lighting, as well as advertising or decorative lighting ( Starlight Saving Time , at night only during high to medium traffic volumes, i.e. primarily the beginning of the night)
  • Reduction of unnecessary lighting (both too intense and too less targeted)
  • more directional lighting (from above instead of below or towards the horizon)
  • Shielding from light sources to prevent radiation upwards and to the sides
  • Complete renunciation of lighting fixtures that only radiate upwards (such as skybeamers , laser floodlight effects, floor lights )
Lighting situation on La Palma after changing to orange street lamps shining downwards

Here the concept of the Upward Light Ratio (ULR, upward light component) was introduced. Where specific light protection measures are taken, this should be 0 on the device side, and measured during operation (including reflections) over the horizontal plane of less than 0.5 cd / klm ( luminous intensity per source luminous flux ). Recommended directional markings for lamps are full cut-off  (FCO) or CIE G6. With recommendations such as Guide to the lighting of urban areas (CIE-136-2000) or Guide on the limitation of the effects of obtrusive light from outdoor lighting installations (CIE 150-2003), modern, technically oriented guidelines on light protection are now available. Older regulations are also being revised accordingly.

Furthermore, it is beneficial to use light sources that emit reddish light at the longest possible light wavelengths, since the light particles deflected by Rayleigh scattering on the air molecules in the earth's atmosphere are backscattered more strongly the shorter and therefore the bluer the light wavelength.

Street lighting is being changed, for example, by using dimmers and replacing the high-pressure mercury vapor lamps with sodium vapor lamps or by using light-emitting diode technology. Such changes made it possible, for example, to reduce power consumption by 20 percent in downtown Augsburg. However, the light spectrum of light-emitting diodes that are used for lighting purposes has a very high blue component, which is particularly strongly distributed in the atmosphere due to Rayleigh scattering. It is therefore necessary to use special light-emitting diodes with a high proportion of orange to protect against light.

If necessary , the switching on of the street lighting is tested via motion detectors . As a result, only those road sections are illuminated in which there is a need for brightness depending on the situation.

Since a reduction in lighting without accompanying measures leads to less traffic safety, there would have to be special regulations for the terrestrial night in order to protect pedestrians if there is no or insufficient nighttime lighting. Light protection zones can be set up by authorities in which the use of high beam by drivers is prohibited, especially since high beam can generate great brightness over many kilometers. At the same time, the permitted speed in light protection zones is limited to 50 km / h.

In the inner cities of Villingen and Schwenningen, Christmas lights may no longer be attached to living trees since 2018 , so that stressed trees can survive more easily.

International programs and light protection legislation

Hemispheric evening spring night sky with the Milky Way (in the right half of the image) in the International Star Park Westhavelland with a cloudless, but slightly hazy sky during astronomical twilight without moonlight. All around on the horizon you can see the light pollution of the surrounding villages caused by scattered light in the troposphere , in the east (left) the bell of light from Berlin, 50 to 90 kilometers away .

Light protection zones have always been set up around the sites of large observatories in the sense of a contractual nature conservation , so that observing astronomy can be carried out undisturbed (the first regulations of this kind were for the protection of the urban observatory in Flagstaff / Arizona in 1958).

There have been designated light protection areas ( English dark sky places ) in Canada and soon afterwards also in the USA , in 2009 the first were designated in Europe. In 2007 UNESCO , UNWTO , IAU and other international organizations published the Declaration in Defense of the Night Sky and the Right to Starlight at a conference in La Palma 2007 ( La Palma Declaration ; Initiative Starlight 2007 ). The concept of a UNESCO Starlight Reserve was also developed there. In the course of the International Year of Astronomy 2009 (IYA2009), the Dark Skies Awareness initiative was started as a network and public relations platform with regard to the problem. Also since 2009 the IUCN Dark Skies Advisory Group (DSAG), a working group of the International Union for Conservation of Nature and Natural Resources  (IUCN), has been dealing with the designation and classification of light protection areas and the criteria for them. Over 50 areas are currently registered with the DSAG. This means that light protection can also be included in the ordinances and management plans for protected areas.

In some states, explicit laws have now been introduced to get light pollution under control:

  • the first law in the world was the Spanish Ley del Cielo in 1988
  • In 1999, Chile passed laws ( Norma de la Contaminación Lumínica ) to limit light pollution in the northern zones and thus to keep the country as a location for the observatories ( ESO , CTIO-NOAO , etc.). Responsible is the Oficina de Protección de la Calidad del Cielo del Norte de Chile  (OPCC)
  • The Lombardy region drafted a light protection law in 2000 (LR della Lombardia 17/00), but most of Italy's provinces now have relatively strict regulations
  • The Czech Republic was a pioneer in national legislation on light pollution, but has only partially implemented the strict templates created in 2002 (a first protected area was only established in 2009 across borders with Poland).
  • Slovenia has had an anti-light pollution law since August 30, 2007 ( Ordinance on Limit Values ​​for Light Pollution, Ul RS 81/2007).
  • In Bavaria there has been a ban on sky radiators since August 1, 2019 (Bavarian Nature Conservation Act). In addition, the lighting of the facades of public buildings between 11 p.m. and dawn was banned (Bavarian Immission Control Act).

In 2007 a public petition on light pollution, supported by 7,828 signatories, was introduced to the German Bundestag . A majority, consisting of politicians from the CDU / CSU, the SPD and the Left, voted against adapting the legal framework to avoid light pollution.

In order to draw attention to the wasteful use of artificial light at night and the associated negative consequences for the environment, people and nature due to light pollution, Earth Night was launched in July 2020 as a global action. The aim is to achieve at least one almost naturally dark night per year by having people reduce or switch off light from 10 p.m. (local time) until dawn. The initiative is initiated by the nationwide volunteer association Godfather of the Night.

Regional and local programs

Efforts to curb light pollution are currently underway, especially at some regional levels:

On the Canary Island of La Palma , a UNESCO biosphere reserve , street lamps have been changed due to the light protection law and the lighting times have been regulated by law. At the heights of the Roque de los Muchachos there, the use of the high beam is prohibited - also because of the observatory located there (European Northern Observatory ) .

In 2008, a network of environmental agencies in Central Switzerland demanded that every lighting device must be examined with regard to the criteria of necessity, shielding (radiation only in desired directions), direction from top to bottom, illuminance and type of light as well as time limits that only facilities with all the required properties may be approved.

In Austria there has been the project Die Helle Not since the early 2000s , which is supported by the state ( Tyrol ), the federal government ( Ministry of Life ) and the European Union and won the CIPRA competition Future in the Alps in 2005.

An initiative against commercial light pollution and an action for more recognition of environmental pollution by light were founded in Düsseldorf. operates through nightly patrols with subsequent education of employees and owners.

Augsburg is known throughout Germany as a “model city for environmentally friendly lighting”. In Germany there are also some initiatives on light protection areas. So that was 2014 Rhön Biosphere Reserve by the International Dark-Sky Association as the second area after Star Park Westhavelland as SternPark excellent, which only areas given is offering a natural night scenery.

As part of the IUCN protected area classification, there is also the category Dark Sky Community ('light protection community'), there are only a few communities registered, but a closer connection with the local Agenda 21 , the sustainability program of the UN, or European programs such as Energy-efficient municipality / Energiestadt / European Energy Award .

In Germany, the nationwide initiative has been in existence since September 2019 for large-scale education on the subject of light pollution, including proposed solutions. With the help of volunteer team members, sponsorships for the night are symbolically awarded to traders, municipalities, associations, etc., provided that they improve their outdoor / advertising lighting according to the recommendations of the sponsors of the night or are already using their outdoor / advertising lighting well or even in an exemplary manner.

Measurement and classification

In contrast to seeing scales , the degree of light pollution is mainly determined without optical aids. In addition to some simple methods of classification, such as counting stars in a certain region of the sky, there are also recognized scales. The most common is the Bortle scale published in February 2001 by John E. Bortle .

The concept of the UNESCO Starlight Reserves recommends the full moon criterion (<0.27  lux ) for the core zone of protected areas , that is, the artificial nocturnal lighting remains at least below the maximum natural.

See also: Light Sanctuary: Categorization



  • P. Cinzano, F. Falchi, C. Elvidge: The first world atlas of the artificial night sky brightness . In: Monthly Notices of the Royal Astronomical Society , Volume 328, 2001, pp. 689-707. bibcode : 2001MNRAS.328..689C . doi: 10.1046 / j.1365-8711.2001.04882.x .
  • Franz Hölker et al .: The Dark Side of Light: A Transdisciplinary Research Agenda for Light Pollution Policy . In: Ecology and Society . Volume 15, No. 4, 2010, full text (PDF)
  • Madeleine Klein: Light Pollution - A New Environmental Problem . (PDF) Ludwigsburg 2004
  • Josiane Meier, Ute Hasenöhrl, Katharina Krause and Merle Pottharst (eds.): Urban Lighting, Light Pollution and Society. Routledge, 2014. ISBN 978-1-138-81397-7
  • B. Mizon: Light Pollution - Responses and Remedies . Springer-Verlag, 2001, ISBN 1-85233-497-5
  • David Owen: Our Far-flung Correspondents. The dark side. Making war on light pollution . In: The New Yorker . August 20, 2007 ( online ).
  • Thomas Posch, Anja Freyhoff, Thomas Uhlmann (eds.): The end of the night - global light pollution and its consequences . 1st edition. Wiley-VCH, Weinheim 2010, ISBN 978-3-527-40946-4 ( limited preview in Google book search).
  • HE Schwarz: Light Pollution: The Global View . Kluwer Academic Publishers, 2003, ISBN 1-4020-1174-1
  • The death of the night . In: Der Spiegel . No. 7 , 2009 ( online ).



Guidelines and Recommendations


  • Dennis Köhler, Stefan Hochstadt, Manfred Walz (Hrsg.): Light Region - Positions and Perspectives in the Ruhr Area . Klartext, Essen 2010, ISBN 978-3-8375-0404-0

Web links

Commons : light pollution  - collection of pictures, videos and audio files
Wiktionary: light pollution  - explanations of meanings, word origins, synonyms, translations


Collections of facts

Media reports

Recommendations for action and legal requirements

Individual evidence

  1. a b The term light smog (from the English light smog ) is usually seen more extensively, it includes not only the brightening of the night sky, but also the brightening of bedrooms and the "flickering" of artificial light sources and screens due to the refresh rate .
    See Ill through artificial light ( Memento from March 9, 2013 in the Internet Archive ) In: ; Florian König: Natural alternating fields, electrosmog and light smog and their effect on people. In: NET-Journal , Volume No. 15, Issue No. 7/8, July / August 2010.
  2. Simon Mitton: The exploration of the galaxies , Springer-Verlag, Berlin / Heidelberg 1978, p. 19 ( online ).
  3. Light immissions, measurement, assessment and reduction: Joint circular of the Ministry for Climate Protection, Environment, Agriculture, Nature and Consumer Protection - V-5 8800.4.11 - and the Ministry for Building, Housing, Urban Development and Transport - VI.1 - 850 of December 11, 2014 ( MBl. NRW. 2015 p. 1 ).
  4. International Dark-Sky Reserves ( memento of April 9, 2014 in the Internet Archive ),, accessed online on October 24, 2013 (link no longer available).
  5. Andreas Hänel: Protected areas for the starry sky . In: National Park 4/2007, pp. 12–16.
  6. In 2003, for example, the Higher Administrative Court in Koblenz prohibited the operation of a Skybeamers in Kandel with reference to the population's "need for rest and relaxation" (file number: 8 A 11286 / 02.OVG).
  7. These have become popular even at astronomical field events, as they can now be used to show in the true starry sky as well as in planetariums. Nevertheless, caution and caution apply here as well, as well as consideration for the light protection of others. Green Laser Pointer Usage , The Royal Astronomical Society of Canada (English).
  8. ^ J. Alexander Schmidt: Light in the city. Guiding principles and strategies for innovative lighting concepts . 2007. p. 14f. (27 f.) (PDF; 880 kB), accessed on December 27, 2018.
  9. Network homepage LUCI ( Memento of 4 May 2011 at the Internet Archive )
  10. Berlin lights up: Europa City . 17th September 2018.
  11. ^ City of Fulda: Statute on the Christmas market in the city of Fulda . October 27, 2017.
  12. ^ Sermon by Pope Benedict XVI. at the Easter Vigil 2012 . April 7, 2012.
  13. "God wants to live in the dark" . January 10, 2018.
  14. Note. This effect was still significant in 1990, when wheel headlights were based at best on a 2.4 W halogen lamp and power generation by means of a side-running dynamo, which was only of limited reliability, required around 10 W of physical effort. At that time, their high weight and high price made poorly developed lights with or for batteries less attractive.
  15. Fabio Falchi et al .: The new world atlas of artificial night sky brightness . In: Science Advances . tape 2 , no. 6 , 2016, doi : 10.1126 / sciadv.1600377 .
  16. Christopher CM Kyba et al .: Artificially lit surface of Earth at night increasing in radiance and extent . In: Science Advances . tape 3 , e1701528, 2017, doi : 10.1126 / sciadv.1701528 ( ).
  17. F. Hölker, et al .: The dark side of light: a transdisciplinary research agenda for light pollution policy. In: Ecol. Soc. , 2010, 15 (4), 13.
  18. Recommendations for avoiding light emissions. In: Federal Office for the Environment , accessed on July 3, 2016 .
  19. Light pollution at night: the sky over cities turns red. In: Spiegel Online , accessed on August 11, 2012.
  20. Petition against light pollution. (No longer available online.) NABU , November 21, 2007, archived from the original on March 7, 2008 ; Retrieved July 3, 2016 .
  21. Recommendations for avoiding light emissions, Federal Office for the Environment, Forests and Landscape (BUWAL), Bern, 2005.
  22. When night turns into day. In:
  23. Cleve 1964.
  24. Travis Long Core, Catherine Rich: Ecological Light Pollution . In: Frontiers in Ecology and the Environment , 2 (4), 2004, pp. 191–198 (PDF).
  25. Airam Rodríguez, David García, Beneharo Rodríguez, Esteban Cardona, Lluís Parpal, Pere Pons: Artificial lights and seabirds: is light pollution a threat for the threatened Balearic petrels? In: Journal of Ornithology , 156 (4), 2015, pp. 893-902.
  26. On the influence of artificial lighting on animals. In: Website of the University of Vienna .
  27. science-online .
  28. Kloog, I., Haim, A; Stevens, RG; Barchana, M. & Portnov, BA: Light at night co-distributes with incident breast but not lung cancer in the female population of Israel. In: Chronobiology International 2008 Feb; 25 (1): 65-81.
  29. a b Dirk Eidemüller: Where have the stars gone? . . October 12, 2018.
  30. cf. Night Sky Heritage. International Dark Sky Association (, accessed February 10, 2019).
  31. Tell me where are the stars, where have they gone? In: .
  32. Gloomy prospects for stargazers ( memento of March 13, 2007 in the Internet Archive ) . West German radio.
  33. ^ David Tenenbaum: Blinded by the light. Feeling light-headed. In: , April 20, 2000
    Literature on Space-borne Radio Interference . ( Memento of 2 November 2013, Internet Archive ) In: . Committee on Radio Astronomy Frequencies (CRAF), European Science Foundation (ESF).
    see. the National Radio Quiet Zone in the US.
  34. Too bright: SpaceX “dims” its satellites, April 23, 2020, accessed April 23, 2020.
  35. ^ D. Crawford: Light Pollution: The Problems, the Solutions, Preserving The Astronomical Windows . In: Proceedings of Joint ASP Conference , Vol 139, 1998, bibcode : 1998paw..conf ... 13C
  36. die urbanauten: lighting plans in Germany . April 24, 2006. Page 9 (PDF; 1.1 MB).
  37. Daniel Blum: Too bright, too bright, too unhealthy. Politics discovers light pollution . April 10, 2013.
  38. ↑ Star Park Rhön is committed to combating light pollution . August 24, 2018.
  39. Guided tours in the Rhön Star Park are popular . (Frankfurter Neue Presse). August 25, 2018.
  40. a b c UNESCO-WHC, UNESCO - IAU, CIE, OTPC-IAC (ed.): Starlight Reserve. Concept - Dimensions - Categories - Criteria . Recommendations. March 2009, sections Zonation Criteria and General recommendations on outdoor lighting , p. 19th ff. resp. 24 ff . ( (PDF)).
  41. in analogy to English daylight saving time for summer time .
  42. Recommendations for promoting energy-saving and environmentally friendly outdoor lighting , in: Information folder on the Star Park in the Rhön Biosphere Reserve , Star Park in the Rhön Biosphere Reserve, accessed on September 7, 2017.
  43. Gloomy prospects for stargazers - Augsburg takes light pollution seriously ( Memento from March 13, 2007 in the Internet Archive ) Westdeutscher Rundfunk. (Annual cost savings of 250,000 euros, that's 1 € per inhabitant and year).
  44. Rainer Kayser: World Atlas of Light Pollution. In: Welt der Physik , June 10, 2016, accessed June 11, 2016.
  45. Light pollution hampers vision - fewer people can see stars. In: n-tv , June 10, 2016, accessed June 11, 2016.
  46. Intelligent control systems. ( Memento of October 29, 2013 in the Internet Archive ) In: .
  47. with further links .
  48. Fabian Riesterer: Environmental protection instead of tree lighting. In: . November 24, 2018. Retrieved November 27, 2018 .
  49. a b Standards & Regulations . ( Memento of March 4, 2016 in the Internet Archive ) In: , regulations and guidelines in other countries, accessed October 28, 2013.
  50. ^ Declaration in Defense of the Night Sky and the Right to Starlight (La Palma Declaration) . ( Memento from December 11, 2013 in the Internet Archive ) (PDF; 1.3 MB) International Conference in Defense of the Quality of the Night Sky and the Right to Observe the Stars. La Palma, Canary Islands, Spain 2007. Starlight Initiative, La Palma Biosphere Reserve, Government of the Canary Island, La Palma, 2007 - with the original text of the declaration; Weblink: Declaration in Defense of the Night Sky and the Right to Starlight. ( Memento from August 20, 2014 in the Internet Archive ) In: .
  51. Programs to Involve the Public in Dark Skies Awareness during the International Year of Astronomy. Dark Skies Awareness: seeing in the dark (
  52. Ley 31/1988 de 31 de octubre, sobre Protección de la Calidad Astronómica de los Observatorios del Instituto de Astrofísica de Canarias. ( Ley del Cielo , ).
  53. La Oficina de Protección de la Calidad del Cielo del Norte de Chile - OPCC.
  54. Misure urgenti in Tema di Risparmio energetico ad Uso di Illuminazione esterna di Lotta e all'Inquinamento luminoso Legge n.17 del 03/27/00 della Lombardia Regione (material in a Tread on
    Status 2013: Lombardia 17/00, Emilia-Romagna 113/03, Marche 10/02, Lazio 23/00, Campania 13/02, Veneto 22/97, Toscana 37/00, Piemonte 31/00, Valle d'Aosta 17 / 98, Basilicata 41/00, Abruzzo 12/05, Umbria 20/05, Puglia 15/05, Friuli – Venezia Giulia 15/07, Liguria 22/07; Leggi contro l'inquinamento luminoso , Pierantonio Cinzano: Inquinamento luminoso in Italia - Light Pollution in Italy (, with overview map).
  55. Struggle for the beauty of the night. In: .
  56. 4165. Uredba o spremembah in dopolnitvah Uredbe o emisiji snovi v zrak iz malih in srednjih kurilnih naprav, Stran 11093. Uradni list RS, št. 81/2007 (i. D. G. Online, ).
    Slovenian Light Pollution Act, (content translated into German);
    Light Pollution Law of Republic of Slovenia, 2007. In: .
  57. Light pollution: What has been banned since August. In: BR24. Bayerischer Rundfunk, October 7, 2019, accessed on January 1, 2020 .
  58. Petition 546: Immission control - light pollution. In: German Bundestag , accessed on July 3, 2016 .
  61. Environmental departments of the cantons Uri, Schwyz, Obwalden, Nidwalden, Zug and Lucerne: Leaflet light pollution: 5-point checklist. (PDF) Retrieved January 1, 2019 .
  62. About us. Project makes history. In: Die Helle Not. Retrieved October 26, 2013 .
  64. Model City Augsburg . ( Memento from May 9, 2008 in the Internet Archive ) Bavarian State Office for the Environment.
  65. Jörn Perske: The fight against the light. Editorial, Südthüringer Zeitung , August 27, 2018.
  66. The Alps: Source of Renewable Energy . (PDF; 5.8 MB) CIPRA, Canton St.Gallen; Publication for the conference "Ways to the Energy City" from 3./4. May 2012 in St. Gallen.
  68. Fabio Falchi, Pierantonio Cinzano, Dan Duriscoe, Christopher CM Kyba, Christopher D. Elvidge, Kimberly Baugh, Boris A. Portnov, Nataliya A. Rybnikova, Riccardo Furgoni, June 10, 2016: The new world atlas of artificial night sky brightness. In: doi: 10.1126 / sciadv.1600377 (June 12, 2016)