Helena Joyce
Light pollution is a growing problem, with light from cities reaching national parks over 200 miles away. This has a detrimental effect on our view of the night sky, with the Milky Way no longer visible in large cities and metropolitan areas. Light pollution is caused by artificial light sources such as street lights, which are essential for daily life but interfere with our ability to see the stars. To combat this, Dark Sky International certifies communities, parks, and protected areas that preserve dark sites through responsible lighting policies and public education. These locations offer a glimpse of what the night sky looks like without light pollution: a blanket of stars, with the Milky Way stretching across the sky. To find these dark sky locations, one can use resources such as the Light Pollution Map app, which directs users towards areas with minimal light pollution for optimal stargazing experiences.
| Characteristics | Values |
|---|---|
| Night sky without light pollution | Clear, starry night sky with the Milky Way galaxy and constellations visible |
| Light pollution | Excess or inappropriate artificial light outdoors |
| Impact of light pollution | Blocks our view of the stars, affects our natural circadian rhythms, and causes early blooming in flora, disrupting the natural food chain |
| Bortle Scale | Numeric scale from 1 (excellent dark sky) to 9 (inner-city sky) to measure the brightness of the night sky and how well stars can be seen |
| Dark sky locations | Remote deserts in Namibia, American Southwest, Kansas, Grand Canyon area, Hoover Dam area, Montana, Utah, and several states in the middle of the country |
| Light pollution sources | Streetlights, greenhouses, satellites, clouds over cities, haze, dust, and air pollutants |
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What You'll Learn
The Milky Way is visible
Light pollution is a growing problem as cities expand and populations increase. The artificial light from street lamps and buildings obscures our view of the night sky. In large cities and metropolitan areas, light pollution makes it impossible to see the Milky Way with the naked eye.
However, in areas without light pollution, the Milky Way is visible. In Playa del Carmen, Mexico, for example, one observer noted that just a 15-minute drive outside of the town was enough to reveal a stunning view of the stars, unobstructed by artificial light. Similarly, in Kansas, one can escape light pollution by travelling just 10 minutes outside of small towns.
The Bortle Scale is a nine-level numeric scale that quantifies the astronomical observability of the stars and any interference caused by light pollution. A level 1 on the scale indicates excellent dark skies, while a level 9 indicates inner-city skies. In locations with less light pollution, rated as a 1-2 on the Bortle Scale, the night sky is transformed, and even galaxies can be seen.
The constant level of artificial light in our cities is not just a problem for stargazers; it also has an impact on our natural circadian rhythms. Researchers have found that artificial light can confuse flora and fauna, causing trees and plants to initiate spring early, which can have knock-on effects on the natural food chain.
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Stars appear in greater numbers
Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It is caused by artificial light sources such as streetlights, which affect our view of the night sky. In highly light-polluted areas, it is impossible to see the Milky Way with the naked eye. Light pollution can cause glare, light trespass, and skyglow. The latter is caused by artificial light scattered in the atmosphere, which can be worsened by clouds and air pollution.
Without light pollution, stars appear in greater numbers. The night sky is filled with a blanket of stars, with the Milky Way stretching across it. In places with little to no light pollution, the stars are absolutely stunning. One observer, upon witnessing a sky free of light pollution in Playa del Carmen, Mexico, regretted not having brought their telescope. Another observer in Amboy, on a new moon, reported being able to see all the stars.
To find places with minimal light pollution, one can use the Bortle scale, which measures the brightness of the night sky and how well the stars can be seen. It runs from 1 (excellent dark sky) to 9 (inner-city sky). Dark grey spots on light pollution maps are Bortle 1 locations, perfect for stargazing. Some of the darkest skies in the US can be found in the desert Southwest/Great Basin region, about an hour's drive from any city. There are also certified Dark Sky preserves that are worth visiting.
Outside of the US, some of the darkest skies in the world can be found in the remote deserts of Namibia. There are also several International Dark Sky Places worldwide, which are communities, parks, and protected areas that preserve and protect dark sites through responsible lighting policies and public education. These locations provide opportunities for people to experience the wonder of a truly dark sky, surrounded by a vast blanket of stars.
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Light pollution affects nature and humans
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It has been described as a nuisance when it becomes inefficient, annoying, and unnecessary. Light pollution affects what we can see in the night sky, blocking our view of the stars. For instance, a photographer's time-lapse video from San Jose (light pollution level 8) to the Eureka Dunes in Death Valley (light pollution level 1) revealed what we miss out on in the night sky due to light pollution.
Light pollution has harmful effects on both humans and nature. For humans, research suggests that artificial light at night can negatively affect human health, increasing the risks of obesity, depression, sleep disorders, diabetes, breast cancer, and more. According to the American Medical Association, brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity. Furthermore, a 2023 paper published in GeroScience highlights the growing number of studies underlining the complexity of the correlation between light pollution and Alzheimer's disease.
In addition, light pollution has disrupted the natural rhythm of day and night, which is encoded in the DNA of all plants and animals. For instance, researchers in the UK have found that artificial light confuses trees and plants, causing them to initiate spring early. This impacts the natural food chain.
Light pollution also harms wildlife and ecosystems. Insects, for example, are drawn to artificial light, creating a fatal attraction that results in declining insect populations. This negatively impacts all species that rely on insects for food or pollination. Some predators exploit this attraction, affecting food webs in unanticipated ways.
To address light pollution, organizations like DarkSky International work with communities and professionals to establish codes and statutes that reduce light pollution. They also educate the public on how excessive artificial light can harm humans, wildlife, and the climate.
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Light pollution is caused by artificial light
Light pollution is a pressing issue that has been exacerbated by the increasing demand for artificial lighting in cities and expanding populations. The night sky, one of nature's most awe-inspiring creations, is now obscured by the glow of artificial light, which has far-reaching consequences for both humans and the environment.
Artificial light sources, such as streetlights, security lights, and illuminated signs, contribute significantly to light pollution. This excessive and inappropriate use of outdoor lighting has a detrimental impact on our ability to observe the stars and other celestial bodies. Light pollution is not limited to urban areas; it stretches into rural regions, affecting the natural cycles of flora and fauna. For example, researchers have found that artificial light confuses trees and plants, causing them to initiate spring prematurely. This disruption to natural rhythms has knock-on effects on the food chain.
The negative consequences of light pollution extend beyond the ecological realm. Medical research suggests that exposure to excessive artificial light at night can have adverse effects on human health. Studies have linked light pollution to various health issues, including sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease. The constant presence of artificial light disrupts our natural circadian rhythms, affecting sleep patterns and physiological processes.
Furthermore, light pollution poses a serious threat to nocturnal wildlife. It can confuse animal navigation, alter competitive interactions, and disrupt breeding and migration patterns. For example, sea turtle hatchlings find the ocean by moving away from the dark silhouette of dunes, a behavior that is interfered with by artificial lights. Similarly, juvenile seabirds become disoriented by lights as they leave their nests, resulting in high mortality rates.
Light pollution is caused by the excessive and inappropriate use of artificial lighting, primarily from outdoor sources. This pollution obscures our view of the night sky and has far-reaching consequences for human health, wildlife behavior, and the environment. To mitigate these impacts, it is essential to reduce light pollution by employing shielded light fixtures, dimming lights, and turning off unnecessary lights.
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Light pollution is measured by the Bortle Scale
Light pollution is a growing problem, affecting our view of the night sky and disrupting our natural circadian rhythms. It is caused by artificial light, such as streetlights, which obscure our view of the stars. Light pollution is not limited to big cities, it also encroaches on rural areas.
The Bortle Scale is a nine-level numeric scale that measures the brightness of the night sky in a particular location. It was created by amateur astronomer John E. Bortle and published in the February 2001 edition of Sky & Telescope magazine. The scale ranges from Class 1, representing the darkest skies on Earth, to Class 9, representing inner-city skies with the highest levels of light pollution.
The Bortle Scale helps skywatchers evaluate and compare the darkness of night-sky observing sites. Each class is described in terms of the visibility of notable celestial objects and light sources in the sky, taking into account the interference caused by light pollution. For example, a Class 1 sky would allow a direct-vision naked-eye observation of the Triangulum Galaxy (M33). In contrast, at Class 8 or 9, most constellations are invisible to the naked eye due to artificial light.
The Bortle Scale is closely related to the Naked-Eye Limiting Magnitude (NELM), which represents the faintest star(s) visible to the naked eye under the conditions being measured. The Bortle Scale also corresponds with Sky Quality Meter (SQM) measurements of sky glow. These tools help astronomers and astrophotographers assess the quality of their observing sites and determine the impact of light pollution on their observations.
By using the Bortle Scale and other resources, such as light pollution maps and apps, individuals can find locations with minimal light pollution and experience the beauty of a clear night sky, free from artificial light interference.
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Frequently asked questions
Without light pollution, the night sky is filled with a blanket of stars, with the Milky Way stretching across the sky.
Light pollution blocks our view of the stars at night. It occurs in three ways: glare, light trespass, and skyglow. Glare is the bright and uncomfortable light that interferes with our vision. Light trespass is the unintended spill of artificial light into other spaces. Skyglow is the brightening of the night sky from human-caused light scattered in the atmosphere.
Light pollution levels are measured using the Bortle scale, which ranges from 1 (excellent dark sky) to 9 (inner-city sky). To find places with minimal light pollution, look for dark grey spots on a light pollution map, which correspond to Bortle level 1. Some places with low light pollution include remote deserts in Namibia, the American Southwest, Montana, Utah, and Kansas.
