Light pollution facts for kids

Light pollution happens when too much or poorly aimed artificial light changes the natural patterns of light and dark in nature. This usually occurs at night. It causes problems for the environment and makes it harder to see the stars in the night sky.

Light pollution affects people's health, as well as the plants and animals living in areas with lots of artificial light. It's not just one type of pollution; it adds to many other kinds of pollution around us.

Even though light pollution can exist during the day, its effects are much stronger at night when the sky is dark. Experts believe that most people (about 83%) live under skies affected by light pollution. Also, almost a quarter of the Earth's land has a bright haze called skyglow.

The amount of land affected by artificial light keeps growing. Light pollution is a big side effect of cities growing larger. It's blamed for hurting health, confusing nature, and making beautiful night views disappear. Studies show that city areas are most at risk. Globally, it grew by almost 50% between 1992 and 2017.

Light pollution happens when we use artificial light badly or when we don't need it. Specific types include light trespass, over-illumination, glare, light clutter, and skyglow. Often, one bad light source can cause several of these problems at once.

Solutions often involve simple steps like adjusting light fixtures or using more suitable light bulbs. Educating people can also help push for new laws. However, because people create light pollution, fixing it involves thinking about political, social, and economic factors.

What is Light Pollution?

Light pollution is simply artificial light appearing in places that should be dark.

This term usually refers to outdoor areas, but it can also mean too much artificial light indoors. There are many negative effects, and some might not even be known yet. Light pollution makes it harder for people in cities to see the night sky. Like other types of pollution, it can harm our environment.

Light pollution is a side effect of modern cities and industries. It comes from lights on buildings, advertisements, outdoor areas like car parks, offices, factories, streetlights, and sports venues. It's most severe in busy, populated areas like North America, Europe, and Asia. Even small amounts of light can cause problems.

People started noticing the harmful effects of light pollution in the late 1800s. But efforts to fix it didn't begin until the 1950s. In the 1980s, a worldwide movement to protect dark skies began with the creation of the International Dark-Sky Association (IDA). Today, many groups around the world teach people about this issue and work to solve it.

About 83% of people, including 99% of Europeans and Americans, live under skies that are more than 10% brighter than natural darkness. This means 80% of North Americans cannot see the Milky Way galaxy.

Types of Light Pollution

Light Trespass: Unwanted Light

Light trespass happens when unwanted light from one property shines onto another. A common problem is when a bright light from outside shines into someone's home window. This can make it hard to sleep. Many cities have rules for outdoor lighting to protect people from light trespass.

The Dark-Sky Association works to reduce light shining upwards into the sky. This light makes it harder to see stars. By limiting light that shines above a certain angle (90 degrees), they also help reduce light trespass.

Government agencies in the U.S. also have rules. For example, the Federal Communications Commission (FCC) handles complaints about bright, white flashing lights from communication towers if they are too strong. The U.S. Green Building Council (USGBC) also gives credit for reducing light trespass in their green building standard, LEED.

You can reduce light trespass by choosing light fixtures that direct light downwards. The IESNA has definitions for how much light can escape upwards, like "full cutoff" (0% light above horizontal).

Over-illumination: Too Much Light

Over-illumination means using too much light when it's not needed.

A huge amount of electricity is used for lighting. In 2020, homes in the U.S. used 81 billion kilowatt hours (kWh) of electricity for lighting. Businesses and factories also use hundreds of billions of kWh.

Not all developed countries use light excessively. There are big differences in how much light is used. For example, American cities send three to five times more light into space per person compared to German cities.

Over-illumination happens for several reasons:

• Standards that aren't based on how our eyes truly work.
• The wrong idea that more light always means more safety, even though it can make things worse.
• Poor design, using brighter lights than needed for a task.
• Choosing the wrong light fixtures or bulbs that don't direct light properly.
• Using hardware that wastes energy.
• Lack of training for building managers on efficient lighting.
• Poor maintenance of lighting systems.
• People wanting "daylight lighting" to reduce crime or attract customers.
• Replacing old lamps with brighter LEDs without reducing power.
• Using indirect lighting, like shining light on a wall to bounce it to the ground.
• Some organizations light up buildings just to show off, not for navigation.
• Lighting allows work to continue beyond natural daylight hours, often for economic reasons.

Most of these problems can be fixed with simple, affordable technology. Public awareness needs to improve for countries to see the big benefits of reducing over-illumination.

Sometimes, a lot of light is needed. For example, indirect lighting can create a "softer" look, which is often preferred in places like bars, restaurants, and homes.

Glare: Blinding Light

Glare is light that is too bright and makes it hard to see. There are different types of glare:

• Blinding glare is like staring at the Sun. It can temporarily or permanently hurt your vision.
• Disability glare is like being blinded by oncoming car headlights. It reduces contrast and makes it much harder to see.
• Discomfort glare is annoying and irritating. It doesn't usually cause danger but can make you tired if you experience it for a long time.

According to Mario Motta, a medical expert, glare from bad lighting is a health risk. This is especially true as people get older. Glare reduces contrast and can make driving unsafe, similar to a dirty windshield in low sunlight. Bright or poorly shielded lights near roads can partially blind drivers or walkers, leading to accidents.

This blinding effect happens because too much brightness scatters light in the eye, reducing how well we can see.

Light Clutter: Too Many Lights

Light clutter means having too many lights grouped together. These groups of lights can cause confusion. They can distract from obstacles that the lights are supposed to show. This can potentially lead to accidents. Clutter is very noticeable on roads with poorly designed street lights or many bright advertisements. Sometimes, lights are even designed to distract drivers, which can contribute to accidents.

Skyglow: The City Haze

Skyglow is the bright haze you see above cities at night. It comes from artificial light reflecting off particles in the atmosphere. Skyglow is bad for astronomy and the health of many living things. It makes stars and the Milky Way much harder to see. It also makes nights unnaturally bright.

Light from Satellites

Even artificial satellites contribute to light pollution. With more and more groups of satellites, like OneWeb, Starlink, and Kuiper, astronomers are worried. The IAU fears that light pollution will increase a lot. This is one of many concerns about too many satellites. People are discussing who should control human actions that block starlight.

How We Measure Light Pollution

Measuring how much skyglow affects the world is tricky. The natural night sky isn't completely dark, even without city lights or the Moon. This is because of two main things: airglow and scattered light.

Airglow is a faint light from high in the atmosphere. It happens when sunlight causes gases to glow, even at night. The sky also scatters light from distant stars, the Milky Way, and even sunlight reflected by space dust (called zodiacal light).

The brightness of the natural night sky changes, but the darkest possible sky is still very faint. In busy cities, the sky can be 100 times brighter than natural.

Measuring with Satellites and Ground Tools

To measure sky brightness accurately, scientists use night-time satellite images of Earth. They use these images to count and measure the intensity of light sources. Then, they use computer models to figure out how much light scatters in the air. This helps them create maps showing sky brightness around the world.

Besides satellites, ground-based tools called Sky Quality Meters (SQMs) are important. These small devices measure how bright the night sky is. Both professional observatories and everyday people (citizen scientists) use SQMs worldwide. They provide detailed information that helps track light pollution over time.

Studies using SQM data have shown that light pollution is increasing. For example, a 2023 study found that sky brightness increased by 1.7% to 3.7% each year in different parts of Europe. These studies also show that in very bright urban areas, the natural changes in sky brightness caused by the Moon are almost impossible to see. This can affect animals that rely on moonlight.

Many countries, like Austria, Spain, Italy, and the Netherlands, have national SQM networks. These networks help measure local light pollution and check if new lighting rules are working.

The Bortle Scale

The Bortle scale is a nine-level system that helps measure how much light pollution there is in the sky. A Bortle scale rating of four or less is needed to see the Milky Way. A rating of one means the sky is "pristine," or the darkest possible.

Global Impact of Light Pollution

Europe

Around Madrid, Spain, the effects of light pollution from the city can be felt up to 100 kilometers (about 62 miles) away.

Light pollution affects large areas. Research in the late 1990s showed that southern England, the Netherlands, Belgium, western Germany, and northern France all had skies two to four times brighter than normal. The only places in mainland Europe where the sky can be truly dark are in northern Scandinavia and on islands far from the continent. Light pollution in Europe increased by 11% to 24% in different light spectrums between 2012 and 2020.

North America

North America has a similar problem, with significant light pollution from Canada's Maritime Provinces to the American Southwest. The International Dark-Sky Association works to identify and protect areas with high-quality night skies. These "Dark-sky preserve" areas are supported by communities and groups dedicated to reducing light pollution. The National Park Service also measures night sky quality in U.S. national parks, from very dark (like Capitol Reef National Park) to very bright (like Santa Monica Mountains National Recreation Area).

East Asia

Light pollution in Hong Kong was called the 'worst on the planet' in March 2013.

In June 2016, it was estimated that one-third of the world's population could no longer see the Milky Way. This included 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 major cities have seen a big increase in light pollution, especially along the eastern coast.

Consequences of Light Pollution

Light pollution has "harmful effects on wildlife, human health, and how ecosystems work." The damage to ecosystems alone is estimated to be billions of dollars each year. Ecosystems with the most light pollution provide 40% fewer natural services.

Impact on Human Health

Medical studies suggest that too much light can cause various health problems. Some lighting design books even use human health as a key factor for good indoor lighting. Too much light or the wrong kind of light can lead to headaches, tiredness, stress, and feeling anxious. Studies on animals also show that unavoidable light can negatively affect mood and anxiety. For people who need to be awake at night, light can also affect how alert and happy they feel.

Outdoor artificial light at night, like modern street lighting, has been linked to risks for obesity, mental health issues, and diabetes in early studies.

In 2007, the World Health Organization's International Agency for Research on Cancer said that "shift work that involves circadian disruption" (messing up our body clocks) is a probable cause of some serious health problems. Many studies have found a link between working night shifts and an increased risk of certain health issues. For example, a study in South Korea found that areas with more artificial light at night had more cases of a specific health problem. Seoul, with the most light pollution, had 34.4% more cases than Ganwon-do, which had the least. This suggests a strong link between artificial light at night and this health problem.

A 2009 discussion by Professor Steven Lockley of Harvard Medical School explained that even dim light entering a room at night can disrupt sleep and reduce a hormone called melatonin. Even small, continuous disruptions to our body clocks, sleep, and hormones can lead to long-term health risks. Red light has the least effect on melatonin.

In June 2009, the American Medical Association supported controlling light pollution. They highlighted that glare is a public health risk that can lead to unsafe driving. Glare reduces contrast, making it harder to see at night, especially for older people.

A 2021 study suggested that light pollution might increase the risk of certain health issues for babies born too early.

Impact on Animals and Nature

While light at night can sometimes be helpful, neutral, or harmful to individual species, it always disturbs ecosystems. For example, some spiders avoid lit areas, while others build their webs on lampposts. Since lampposts attract many flying insects, the spiders that tolerate light get more food. This shows how light at night can change which species thrive and how food webs are affected. Baby sea turtles are also heavily affected. When they hatch, they use natural light to find the ocean. Artificial lights can confuse them, making them go the wrong way.

Light pollution is a big threat to nocturnal (night-active) wildlife. It negatively affects how plants and animals function. It can confuse animal navigation, change how species compete, alter how predators and prey interact, and cause physical harm. Life's rhythm is set by the natural cycle of light and dark. When this cycle is disrupted, it impacts how nature works. Many tiny marine creatures, like zooplankton, can detect very low light levels. A global map of artificial light at night in the ocean shows how widespread this problem is.

Studies suggest that light pollution around lakes stops zooplankton, like Daphnia, from eating surface algae. This can cause algal blooms that harm lake plants and water quality. Light pollution can also affect nature in other ways. For example, entomologists (insect scientists) have found that night-time light can stop moths and other nocturnal insects from navigating properly. It can also negatively impact insect growth and reproduction. Night-blooming flowers that rely on moths for pollination may suffer because artificial light affects their pollinators. This can lead to a decline in plant species and change the long-term ecology of an area.

Fireflies are especially interesting to study for light pollution. They use their own light to find mates and reproduce, so they are very sensitive to environmental light levels. Fireflies are well-known and easy for anyone to spot. Because they are so sensitive and react quickly to changes, they are good bioindicators for artificial night lighting. Scientists believe that artificial lights at night are partly responsible for the decline in some insect populations.

A 2009 study also suggested harmful effects on animals and ecosystems from changes in polarized light. This is called polarized light pollution (PLP). Unnatural polarized light can make animals that use polarized light for navigation behave strangely. It can also change how different species interact.

Lights on tall buildings can confuse migrating birds. The United States Fish and Wildlife Service estimates that millions of birds die each year after being attracted to tall towers. The Fatal Light Awareness Program (FLAP) works with building owners in Toronto, Canada, and other cities. They encourage turning off lights during migration seasons to save birds. Another study found that lights from the Post Tower affected 25 bird species. They discovered that reducing excessive lights increased the survival rate of these birds.

In Washington, D.C., the Lights Out DC program helps document bird collisions with buildings. Volunteers transport injured birds and use the data to advocate for bird-friendly lighting.

Similar confusion has been seen in bird species migrating near offshore oil platforms. Experiments in the North Sea led to new lighting technologies on platforms. These new lights reduced the number of birds circling the platform by 50% to 90%.

Island regions like Hawaii are examples of places where seabirds are confused by night-time light pollution. Even lights closer to the ground, like street lamps, disorient young seabirds as they leave their nests and fly to sea. This causes many deaths, including for endangered species. Programs exist to help, such as dark sky initiatives to filter light pollution in important areas. Rescue programs also help rehabilitate affected seabirds.

Birds migrate at night for several reasons. They save water by flying in cooler temperatures, and some birds use stars to navigate. When city lights outshine the night sky, birds (and some mammals) can no longer navigate by stars.

Sea turtle hatchlings are another victim of light pollution. It's a common mistake to think they are attracted to the Moon. Instead, they find the ocean by moving away from the dark shapes of dunes and plants. Artificial lights interfere with this natural behavior. However, the reproduction and breeding patterns of toads are guided by moonlight. Young seabirds also get confused by lights when they leave their nests, leading to many deaths.

Amphibians and reptiles are also affected. Artificial light during normally dark periods can disrupt the production of melatonin. Melatonin is a hormone that controls body clock and behavior. Some frogs and salamanders use a light-dependent "compass" to find their breeding sites. Artificial light can also cause problems with their growth, eyesight, and how their bodies develop. Near large coastal cities, the natural light cycles from the Moon in the ocean are greatly disrupted by light pollution.

In September 2009, a conference in Northern Ireland discussed the environmental effects of light at night. It covered bats, turtles, and other topics. The environmental effects of light at night were mentioned as early as 1897 in a Los Angeles Times article. It warned that electric lights were killing thousands of insects, which were the main food source for English songbirds. The article feared that if England was lit up everywhere, songbirds would disappear due to lack of food.

Impact on Astronomy

Astronomy is very sensitive to light pollution. The night sky seen from a city looks nothing like what you can see from a truly dark place. Skyglow (light scattering in the atmosphere at night) reduces the contrast between stars and galaxies and the sky itself. This makes it much harder to see faint objects. This is why newer telescopes are built in increasingly remote areas.

Even on seemingly clear nights, there can be a lot of extra light that shows up in long exposure time photos of space. Software can reduce this extra light, but sometimes details are lost. Here's an example of the area around the Pinwheel Galaxy from a light-polluted city:

• The Pinwheel Galaxy in light-polluted skies
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  This is how the Pinwheel Galaxy looks in a light-polluted city like Berlin. It's hard to see!

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  After trying to remove all the extra light, the faint Pinwheel Galaxy is no longer visible. This shows how much light pollution hides faint objects.

Some astronomers use special "nebula filters" that only let through specific colors of light from nebulae. Others use "light pollution filters" that reduce the effects of light pollution by blocking certain colors from streetlights. These filters help improve the view of dim objects like galaxies and nebulae. However, these filters are not a perfect solution. They reduce the brightness of the object and change its color. No filter can make the sky as dark as a truly dark location for looking at or photographing space.

Light pollution affects faint, spread-out objects like nebulae and galaxies more than stars. Most such objects become invisible in heavily light-polluted skies above major cities. A simple way to tell how dark a place is, is to look for the Milky Way. From truly dark skies, it appears bright enough to cast a shadow.

Besides skyglow, light trespass can affect observations if artificial light shines directly into a telescope. This causes a glow across the field of view, which reduces contrast. Light trespass also makes it hard for a person to get used to the dark. To reduce this, astronomers might flock (add a dark, fuzzy lining to) the telescope tube or use a light shield. Some even observe under a black cloth to get maximum dark adaptation.

Impact on Air Quality

A study found that light pollution destroys certain chemicals in the air called nitrate radicals. These chemicals normally help reduce atmospheric smog from cars and factories at night. So, light pollution can stop the air from cleaning itself, making smog worse.

Impact on Natural Sky Polarization

At night, the polarization of the moonlit sky is greatly reduced in cities with light pollution. This is because scattered city light is usually not strongly polarized. Animals use the sky's polarization pattern for orientation and navigation, so this reduction can affect them.

Economic Impact

Many businesses, like gas stations and hospitals, operate 24 hours a day. With the rise of online shopping, many factories and shipping companies also work around the clock. These industries need light inside and outside for worker safety. As a result, "40% of the United States and almost 20% of the European Union population has lost the ability to view the night sky."

Researchers are looking at how light pollution affects people who work night shifts. In 2007, the International Agency for Research on Cancer (IARC) warned that shift work might increase the risk of certain health problems. However, it's not possible to stop shift work in essential industries like hospitals.

Studies suggest that light pollution is mainly a problem caused by richer countries with more industries. Countries with paved roads, high resource extraction, and high GDP often have more light pollution.

China is a rapidly growing country. A recent study found that light pollution is increasing in its eastern coastal cities. This is where major industrial factories are located.

The United Nations declared 2009 as The Year of Astronomy. Researchers then urged for a better understanding of artificial light and its role in social, economic, and environmental issues. They warned that uncontrolled use of artificial light could cause big, unpredictable changes globally. It's not enough to just focus on energy-efficient light bulbs. We need to look at the wider effects of light pollution on society, nature, and human health.

Humans need some artificial light at night for work, safety, and driving. But research shows that artificial light disrupts the lives of animals. Recent studies suggest we might find a good balance. A 2021 article looked at how seasonal light changes affect animals. It suggested that future research should find the safest amount of light exposure (how long and how bright) that benefits both humans and animals. This data could help set limits for light levels.

Noctalgia: Missing the Stars

Noctalgia is the feeling of sadness or loss because you can no longer see a starry night sky. It includes the grief of not being able to experience the wonder that people often feel when stargazing.

This term was created by Aprana Venkatesan and astronomer John Barentine in August 2023. They defined it as the loss of cultural identity and practices, like storytelling and stargazing, and ancient knowledge, like celestial navigation. They argued that the night sky is an important part of global heritage and deserves protection.

Solutions for Light Pollution

People who care about Energy conservation say that we need to change our habits. We should use lighting more efficiently, waste less light, and avoid creating unwanted illumination. Several industry groups also agree that light pollution is an important issue. For example, the Institution of Lighting Engineers in the UK provides information on how to reduce its impact. However, research in 2017 suggested that simply using less energy might not be enough to reduce light pollution because of a "rebound effect" (where people use more light because it's cheaper).

We can measure light levels using tools or computer models. The results are often shown on maps. To deal with light pollution, authorities have taken different actions. These range from doing nothing to creating strict laws about how lights can be installed and used.

Reducing Light Pollution

Reducing light pollution means many things, like reducing skyglow, glare, light trespass, and clutter. The best way to reduce it depends on the specific problem. Possible solutions include:

• Using light sources that are only as bright as needed.
• Turning lights off with a timer, occupancy sensor, or manually when not needed. For example, wind turbines have blinking lights for aircraft. A system called Aircraft Detection Lighting Systems (ADLSs) turns these lights on only when an aircraft is detected.
• Improving lighting fixtures to direct light more accurately where it's needed, with fewer side effects.
• Choosing the right type of lights. Mercury, metal halide, and older blue-light LED streetlights cause more pollution than sodium lamps. This is because Earth's atmosphere scatters blue light more easily. You often see "glare" and "fog" around LED lights when the air is humid, but less so with orange sodium lamps.
• Reviewing existing lighting plans and redesigning them if the current light isn't actually needed.

Better Lighting Fixtures

Most groups fighting light pollution recommend using full cutoff lighting fixtures as much as possible. They also suggest spacing lights correctly for best efficiency. The number and power of lights should match the needs of the area.

Full cutoff fixtures became available in 1959.

A full cutoff fixture, when installed correctly, stops light from shining upwards. Light shining above the horizontal often serves no purpose. When it goes into the atmosphere, it adds to skyglow. Some governments and organizations are now using full cutoff fixtures for streetlights and stadium lighting.

Using full cutoff fixtures helps reduce skyglow by preventing light from escaping upwards. They also reduce glare because you can't usually see the lamp directly. Supporters also argue that full cutoff fixtures are more efficient because light that would have gone into the atmosphere is directed to the ground instead. However, some full cutoff fixtures might trap more light inside, making them less efficient. This suggests some fixtures might need redesigning.

Full cutoff fixtures can allow for lower wattage lamps to be used. This can produce the same or even better results because the light is more carefully controlled. Some skyglow also comes from light reflected off the ground. This can be reduced by using only the lowest necessary wattage and spacing lights properly.

A common criticism is that full cutoff fixtures are sometimes not as attractive. This might be because there hasn't been a big market for them, and people often like to see the light source itself. Because they direct light so specifically, full cutoff fixtures sometimes need expert installation to work best.

The effectiveness of full cutoff roadway lights has also been questioned. Some studies suggest that full cutoff lights need to be closer together to meet lighting standards. This could mean more lights are needed, potentially increasing overall light pollution or energy use. However, in the Italian region of Lombardy, where only full cutoff designs are allowed, they had the lowest energy use for public lighting in Italy in 2007. This law also requires street lamps to be spaced far apart.

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  This kind of LED droplight could reduce unnecessary light pollution in building interiors.

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  A flat-lens cobra luminaire, which is a full-cutoff fixture, is very effective in reducing light pollution. It ensures that light is directed only below the horizontal, which means less light is wasted by directing it outwards and upwards.

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  This drop-lens cobra luminaire allows light to escape sideways and upwards, where it may cause problems.

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  Most Italian regions require "zero upward light," meaning new lights should be full cut-off.

Choosing the Right Lights

Different types of light sources exist, each with different features like efficiency and the colors of light they produce. Often, the wrong light sources are chosen, either because people don't know better or because better technology wasn't available. This can lead to unnecessary light pollution and wasted energy. By updating light sources, we can often reduce energy use and pollution while improving visibility.

Here's a look at some light sources and their impact:

Type of light source	Color	Efficiency (lumens per watt)	Skyglow impact (compared to LPS)
LED street light (white)	warm-white to cool-white	120	4–8
Low Pressure Sodium (LPS/SOX)	yellow/amber	110	1.0
High Pressure Sodium (HPS/SON)	pink/amber-white	90	2.4
Metal Halide	warm-white to cool-white	70	4–8
Incandescent	yellow/white	8–25	1.1
PCA-LED	amber		2.4

Many astronomers ask nearby communities to use low-pressure sodium lights or amber Aluminium gallium indium phosphide LED lights. This is because the main color of light they emit is easier to filter out. These yellow light sources also create much less visible skyglow, making stars easier to see for everyone. In 1980, San Jose, California, replaced all street lamps with low-pressure sodium lamps to help Lick Observatory nearby. Similar programs are now in place in Arizona and Hawaii.

A downside of low-pressure sodium lighting is that the fixtures are usually larger. Also, you can't tell colors apart under this light because it's mostly one color. Some people also find the yellow light less appealing.

To reduce light pollution caused by blue light, it's important to use lamps that produce less blue light while still providing enough brightness. This helps protect star visibility and reduces the harmful effects of artificial night skyglow.

Smart Lighting Plans

Sometimes, reviewing existing lighting plans shows that more efficient options are possible. For example, light pollution can be reduced by turning off outdoor lights that aren't needed. Stadiums can be lit only when people are inside. Timers are very useful for this. One of the world's first efforts to reduce this pollution began in Flagstaff, Arizona, in the U.S. For over 30 years, they have developed rules with the support of the community and local observatories.

The city of Calgary recently replaced most residential street lights with energy-efficient models. Their main reasons were to save money and protect the environment. They expect to save enough energy to cover the installation costs within six to seven years.

The Swiss Agency for Energy Efficiency (SAFE) uses a concept called "specific electric power consumption (SEC)." This helps diagnose and design road lighting. Based on lighting levels in Swiss towns, SAFE has set target values for electricity use per meter of road. This helps ensure environmental protection alongside lighting needs.

A newer method for predicting and measuring light pollution was described in 2008. Scientists developed Outdoor Site-Lighting Performance (OSP). This allows users to measure and improve lighting designs to minimize excessive light leaving a property. OSP can help engineers compare different lighting options.

To reduce light pollution, researchers have developed a "Unified System of Photometry." This system helps measure how much and what kind of street lighting is truly needed. It allows for light fixtures that use less energy while still making things visible, safe, and secure. This new system was needed because our eyes process light differently at night than during the day. Studies using this system suggest that replacing traditional, yellowish high-pressure sodium (HPS) lights with "cool" white light sources (like LEDs) can reduce electricity use while improving visibility at night.

Dark Sky Reserves

In 2001, the International Dark Sky Places Program was created. It encourages communities, parks, and protected areas worldwide to save and protect dark sites. They do this through responsible lighting rules and public education. As of January 2022, there are 195 certified International Dark Sky Places in the world. For example, in 2016 China opened its first dark sky reserve in the Tibet Autonomous Region. It covers a huge area of 2,500 square kilometers (about 965 square miles). These areas are very important for observing space.

Community Action

If more people know about the effects of artificial lighting, it could lead to laws that effectively reduce it. However, some communities might hesitate due to cultural beliefs. In some cultures, darkness might be linked to bad things, while light is seen as progress. Also, society's standards have made humans more active during the day. However, recent studies show that more people are aware of the issue and are experiencing the consequences of too much artificial lighting. A 2020 assessment showed that public awareness increased in the late 20th century. This was due to the internet and the ability to connect globally. Better information and voting can help people understand and care more about this problem.

Dark Infrastructure

Dark infrastructure is about creating and protecting areas with natural levels of darkness. This helps reduce the harmful effects of artificial light on nature. It involves finding and preserving existing dark areas and reducing artificial light at night.

Gallery

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  This long exposure photo of New York City at night shows skyglow.

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  A comparison of the view of the night sky from a small rural town (top) and a metropolitan area (bottom). Light pollution dramatically reduces the visibility of stars.

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  The impact of light pollution on a starry night, seen from 4200 m (13,780 ft) high on Mount Damavand in Iran.

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  The impact of LED lighting on skyglow at night, seen at Tiberias, Israel. Before the move to LED lighting in 2017, there was very little skyglow above the city.

IUCN Report on Natural Darkness

In a 2024 report called "The World at Night: Preserving Natural Darkness for Heritage Conservation and Night Sky Appreciation," the International Union for Conservation of Nature looked closely at light pollution. The report explained how light pollution wastes energy, adds to climate change, and harms ecosystems, human sleep, and traditions. For example, it affects the Māori and their connection to the Pleiades star cluster. The report suggests ways to fix this, like teaching people, making new laws, using dark sky-friendly lighting, and promoting programs that encourage better lighting practices and astrotourism (travel to see stars).

See also

In Spanish: Contaminación lumínica para niños

• Roy Henry Garstang

Concepts

• Dark-sky preserve
• Environmental hazard
• Floodlight
• Flicker vertigo
• Lighting
• Photosensitive epilepsy
• Polarized light pollution
• Scotobiology

Events

• Earth Hour
• National Dark-Sky Week

Organisations

• Commission for Dark Skies (CfDS)
• International Dark-Sky Association
• SKYGLOW

Other pollution

• Noise pollution

Geographical locations

• History of street lighting in the United States
• Light pollution in Hong Kong

Literature

• The End of Night (book)
• Tribute in Light