Helena Joyce
Light pollution, the excessive or inappropriate use of outdoor artificial light, is a global issue that affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects. Skyglow, a type of light pollution, is the scattering of light in the atmosphere at night, which reduces the contrast between stars and galaxies and the sky itself, making it much harder to see faint objects. Skyglow is caused by the cumulative effects of dozens, hundreds, or thousands of light sources, such as streetlights, cars, and buildings, Light pollution, the excessive or inappropriate use of outdoor artificial light, is a global issue that affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects. One of the most pervasive forms of light pollution is skyglow, which refers to the scattering of light in the atmosphere at night, reducing the contrast between the sky, stars, and galaxies, and making it harder to see faint objects. Skyglow is caused by the cumulative effect of numerous artificial light sources, such as streetlights, cars, and buildings, illuminating the sky above urban areas. It interferes with natural body rhythms, migration patterns of birds and sea turtles, and the ability of trees to detect seasonal changes. The adverse effects of skyglow have led to a global movement advocating for the reduction of light pollution, with organisations like Dark-Sky International and DarkSky Texas working to combat skyglow through education, awareness, and the implementation of lighting ordinances.
| Characteristics | Values |
|---|---|
| Definition | Skyglow is the brightening of the night sky, mostly over urban areas, due to the electric lights of cars, streetlamps, offices, factories, outdoor advertising, and buildings. |
| Synonyms | Light pollution, skyglow light pollution |
| Affected areas | More than 80% of the world’s population, and 99% of Americans and Europeans, live under sky glow. Skyglow affects 23% of the world’s land area. |
| Impact on astronomy | Skyglow reduces the contrast between stars and galaxies and the sky itself, making it much harder to see faint objects. |
| Impact on wildlife | Skyglow interferes with the migration patterns of birds and sea turtles. Insects and small animals are attracted to areas with more light. |
| Impact on vegetation | Skyglow may interfere with trees’ ability to detect seasonal changes and increase their chance of being killed by an early frost. |
| Impact on humans | Artificial light can wreak havoc on natural body rhythms in humans. Studies show that blue light may disrupt sleep patterns, with some suggesting links to mental illness, cancer, cardiovascular disease and other medical disorders. |
| Solutions | The Dark-Sky Association was started to reduce the light going up into the sky. DarkSky Texas directs much of its efforts toward educational and awareness events. |
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What You'll Learn
- Skyglow is caused by the cumulative effect of multiple light sources
- It reduces the visibility of stars and other celestial bodies
- Skyglow affects human health and wildlife behaviour
- It can be reduced by lowering the amount of up-facing or unshielded outdoor lighting
- Some places have developed standards for outdoor lighting to protect citizens against light trespass
Skyglow is caused by the cumulative effect of multiple light sources
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a global issue, with 83% of the world's population living under light-polluted skies. One of the most pervasive forms of light pollution is skyglow, which refers to the scattering of light in the atmosphere at night, brightening the night sky and reducing the contrast between stars, galaxies, and the sky itself.
The impact of skyglow is far-reaching. It affects both humans and wildlife, disrupting natural body rhythms and sleep patterns, with potential links to mental illness, cancer, and other health issues. For astronomers, skyglow reduces the visibility of celestial objects, forcing them to move their observation stations further away from cities. It also impacts the migration patterns of birds and sea turtles, which instinctively follow the moon's glow, causing them to get lost. Insects and small animals are attracted to the brighter areas with more light, leading them towards cities and highways.
To combat skyglow, organizations like DarkSky International and DarkSky Texas are working to raise awareness and educate people about the effects of light pollution. Local zoning laws and construction codes also need to address skyglow to reduce sky brightness. Additionally, updating light sources to more appropriate and energy-efficient options can help reduce light pollution while improving visibility and efficiency.
The cumulative nature of skyglow means that diminishing its effects requires coordinated, cumulative efforts. Lowering the amount of up-facing or unshielded outdoor lighting is crucial for reducing overall sky brightness. By working together and making conscious choices about lighting, we can help mitigate the impact of skyglow and reclaim the beauty of a dark, starry night sky.
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It reduces the visibility of stars and other celestial bodies
Light pollution is a global issue, affecting human health, wildlife behaviour, and our ability to observe stars and other celestial bodies. It is caused by the excessive or inappropriate use of outdoor artificial light. One notable type of light pollution is skyglow, which refers to the scattering of light in the atmosphere at night, brightening the night sky, mostly over urban areas.
Skyglow reduces the visibility of stars and other celestial bodies in several ways. Firstly, it causes a glow across the field of view, reducing the contrast between stars, galaxies, and the sky itself. This makes it much harder to observe faint celestial objects, such as diffuse sky objects like nebulae and galaxies, which have low surface brightness. Even on clear nights, there can be a lot of stray light that becomes visible during long exposure times in astrophotography.
The impact of skyglow on visibility is particularly noticeable in urban areas, where light pollution is more acute. People living in cities with high levels of skyglow often struggle to see more than a handful of stars at night. For instance, 80% of North Americans cannot see the Milky Way galaxy due to light pollution.
The effects of skyglow extend beyond reducing the visibility of stars and galaxies. It also affects the behaviour of wildlife, such as birds and sea turtles, which instinctively follow the moon's glow for migration. Skyglow makes this halo less noticeable, causing them to get lost. Additionally, insects and small animals are attracted to areas with more light, leading them towards cities and highways.
The reduction in visibility of celestial bodies caused by skyglow has significant implications for astronomy and science. Astronomers have been forced to move their observation stations further away from cities in search of darker skies. This separation from nature and the night sky can also have cultural and philosophical impacts, as noted by Henry Beston: "Today’s civilization is full of people who have not the slightest notion of the character or the poetry of night, who have never even seen night."
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Skyglow affects human health and wildlife behaviour
Skyglow is the brightening of the night sky, mostly over urban areas, due to the electric lights of cars, streetlamps, offices, factories, outdoor advertising, and buildings. It is a major side effect of urbanisation and is one of the most pervasive forms of light pollution.
The human body clock, or the circadian rhythm, is affected by skyglow. Nocturnal light interferes with the production of melatonin, a hormone that is released when it is dark and inhibited when there is light present. An increased amount of light at night lowers melatonin production, which results in sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems. Recent studies have also shown a link between reduced melatonin levels and cancer.
Artificial light can also disrupt the natural body rhythms of animals, as seen in a study of blackbirds in Germany, where birds in the city were found to be active earlier than birds in natural areas. They woke and sang as much as five hours sooner than their country cousins.
Biologists at the University of Antwerp in Belgium have also demonstrated how skyglow alters the biological clock of wild animals. They observed that nightjars in Belgium flew around instead of resting during moonless nights. In contrast, nightjars in Mongolia were inactive during a full moon night due to overcast weather obscuring the moonlight.
Skyglow can also impact the migration patterns of birds and sea turtles, which instinctively follow the moon's glow to guide their migration. Insects and small animals are also attracted to areas with more light.
Overall, skyglow has significant effects on human health and wildlife behaviour, disrupting natural body rhythms and altering migration patterns.
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It can be reduced by lowering the amount of up-facing or unshielded outdoor lighting
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a global issue, with 83% of the world's population living under light-polluted skies. One major form of light pollution is skyglow, which is the scattering of light in the atmosphere at night, brightening the night sky, particularly over urban areas. This reduces the contrast between the sky, stars, and galaxies, making it much harder to see fainter objects.
Skyglow is caused by the electric lights of cars, streetlamps, offices, factories, outdoor advertising, and buildings, turning night into day for people who work and play long after sunset. It is estimated that 80% of North Americans cannot see the Milky Way galaxy due to skyglow.
One easy way to reduce skyglow light pollution is by lowering the amount of up-facing or unshielded outdoor lighting. Unshielded lighting allows light to spill over into unwanted areas, such as a neighbour's property, and causes glare issues. This can impact safety and security at night, as glare from unshielded lights can create harsh shadows where criminals may hide.
To reduce the amount of up-facing or unshielded outdoor lighting, it is recommended to use shielded lighting fixtures that minimize glare and light trespass. LED lights are more directional than other types of lights and can be shielded in densely populated areas. When a light source is shielded, the light is focused downward or inward, reducing spillover into unwanted areas. For outdoor lighting, it is also recommended to use warmer colour temperatures, such as yellow, red, and amber, as these colours do not affect nighttime vision and produce less glare.
In addition to using shielded and warmer-coloured lighting, it is important to reduce the overall amount of lighting used. This can be achieved by using fewer lights, creating smaller targeted illumination areas, and reducing the duration of their use. Dimmers, motion sensors, and timers can also help to reduce average illumination levels and save energy.
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Some places have developed standards for outdoor lighting to protect citizens against light trespass
Light pollution, caused by the excessive or inappropriate use of outdoor artificial light, is a global issue that affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects. One of the most pervasive forms of light pollution is skyglow, which refers to the scattering of light in the atmosphere at night, brightening the night sky, particularly over urban areas.
Skyglow reduces the contrast between the sky, stars, and galaxies, making it harder to observe faint objects in the night sky. This is a major concern for astronomers, who have noticed the effects of skyglow since the earliest days of electric street lighting.
Light trespass is a specific type of light pollution that occurs when unwanted light enters one's property, such as through a window or over a neighbour's fence. This can cause issues such as sleep deprivation and fatigue, as artificial light can disrupt the natural body rhythms and circadian rhythms of both humans and animals.
Recognising the adverse impacts of light trespass, several places have developed standards for outdoor lighting to protect citizens' rights and well-being. For example, in December 2021, the Board of Supervisors adopted a Light Trespass Ordinance, updating definitions and regulations to prevent light trespass onto neighbouring properties and protect dark night skies in certain regions. This ordinance includes standards such as maximum light levels measured at property lines and stricter standards for mountain and desert regions.
Additionally, the International Dark-Sky Association has developed model lighting ordinances to assist cities in reducing light pollution. Flagstaff, Arizona, was the first municipality to enact a light pollution control ordinance in 1958, and it was designated the World's First International Dark-Sky Community in 2001. Since then, over a dozen other cities have followed suit, including Sedona, Arizona, and Borrego Springs, California.
To prevent light trespass, outdoor lighting designers can employ strategies such as using dark sky light fixtures, full cut-off fixtures, practical brightness levels, and proper placement and aiming of lights. By adopting these measures, communities can strike a balance between illumination and the preservation of dark night skies, mitigating the negative impacts of light trespass on human health and the environment.
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Frequently asked questions
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects.
Skyglow is a type of light pollution that is caused by the scattering of light in the atmosphere at night. It is created from the cumulative effects of dozens, hundreds, or thousands of light sources.
Skyglow reduces the contrast between stars and galaxies and the sky itself, making it harder to see faint objects in the night sky. It can also interfere with the internal, twenty-four-hour clock that guides day and night activities and affects physiological processes in nearly all living organisms.
