Bronte Wells
Light pollution is a growing issue that has received relatively little attention. Artificial brightening of the night sky is altering a fundamental human experience: the opportunity to view and ponder the sky at night. The Milky Way is obscured by light pollution in many parts of the world, with nearly 80% of people living in North America unable to see it from their location. To see the Milky Way, one must be in an area with minimal light pollution, such as rural British Columbia, or travel far from city centers to reach truly dark skies. The Bortle Scale and the Dark Sky Scale are two classifications that rate the level of light pollution in an area, with the darkest sites being the best for viewing the Milky Way.
| Characteristics | Values |
|---|---|
| Light pollution level where the Milky Way is visible | Class 4 or 6 |
| Countries with the least light pollution | Chad, the Central African Republic, and Madagascar |
| Percentage of people in North America unable to see the Milky Way | 80% |
| Percentage of people globally unable to see the Milky Way | 33% |
| Countries with high light pollution | Germany, Singapore, the United States |
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What You'll Learn
The Bortle Scale
There are nine levels to the Bortle Scale, with Class 9 being the most extreme amount of light pollution. A Class 1 Bortle sky, on the other hand, means that one can observe M33 (Triangulum Galaxy) as a direct-vision naked-eye object. According to one source, a Class 4 or 5 sky is "fairly good by many people's standards", and the Milky Way is visible but not dramatically so. Another source mentions that the brightest pollution level where the Milky Way is still visible is Class 6, described as a "bright suburban sky".
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Light pollution by country
Light pollution is a pressing global issue that negatively impacts human health, wildlife behaviour, and our ability to observe celestial objects. The problem is particularly acute in densely populated urban areas, with the worst light pollution occurring in major cities worldwide.
The impact of light pollution varies across different countries, with some regions experiencing more severe effects than others. Here is a look at the situation in several countries:
United States
The United States is known for its extensive light pollution, particularly in highly urbanised areas such as New York City and Los Angeles. Oil and gas fields in the country have been found to contribute significantly to light pollution, outshining even its major cities. This has detrimental effects on bird migration patterns and behaviours.
United Kingdom
In the UK, light pollution levels vary across the country. While some areas, such as the village mentioned on the UK map in the reference, fall between classes 2 and 4 on the Bortle Scale, allowing for a decent view of the Milky Way on clear nights, other areas experience much higher light pollution.
Germany
Light pollution in German cities has been found to impact the behaviour of blackbirds (Turdus merula). The artificial night lighting and traffic noise in urban areas cause these birds to become active earlier than their counterparts in less illuminated regions, disrupting their natural habits and migration patterns.
Vietnam
Vietnamese cities were excluded from a light pollution study due to persistent cloud cover, which hindered the availability of satellite data. This highlights the challenge of accurately assessing light pollution levels in certain regions with unique geographical characteristics.
Global Initiatives
It is worth noting that there is a global movement to reduce light pollution, and many cities have adopted a "Lights Out" program to minimise the impact on bird migration. Additionally, organisations like the American Medical Association are supporting efforts to control light pollution due to its adverse health effects on humans.
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Light pollution by US state
Light pollution is a significant issue in the United States, impacting the visibility of celestial bodies such as the Milky Way. The Bortle Scale, which ranges from Class 1 to 9, is often used to classify light pollution levels, with higher classes indicating greater light pollution.
According to various sources, a Class 4 or lower on the Bortle Scale is typically required to observe the Milky Way with the naked eye. In the United States, light pollution levels vary across different states, with some states experiencing more intense light pollution than others. Here is an overview of light pollution levels in different regions of the US:
Northeastern States
The northeastern region of the United States, including states like New York, Pennsylvania, and Massachusetts, tends to have high light pollution levels due to urbanization. This region is home to several major cities, such as New York City, Boston, and Philadelphia, which contribute significantly to light pollution. As a result, observing the Milky Way from heavily populated areas in the Northeast can be challenging.
Western States
The western United States, particularly along the West Coast, also experiences significant light pollution. States like California, Washington, and Oregon have large metropolitan areas, such as Los Angeles and Seattle, which produce substantial light pollution. However, due to the varied terrain and presence of national parks in the western states, there are also remote areas with minimal light pollution, offering better opportunities for Milky Way observation.
Southern States
The southern region of the United States, including states like Texas, Florida, and the Carolinas, presents a mixed picture when it comes to light pollution. While there are major cities like Houston and Miami that contribute to light pollution, the southern states also have vast rural areas with lower population densities. These rural areas often provide darker skies and better conditions for observing the Milky Way.
Midwestern States
The Midwest, encompassing states like Illinois, Michigan, and Wisconsin, has a combination of urban and rural areas. The presence of large cities, such as Chicago and Detroit, contributes to light pollution in the region. However, the Midwest also boasts expansive agricultural lands and less populated areas where light pollution levels can be lower, making it possible to view the Milky Way under favourable conditions.
It is worth noting that light pollution levels can vary within a state, depending on factors such as population density, industrial activity, and the presence of metropolitan centres. Additionally, natural factors like cloud cover and atmospheric conditions can also influence the perception of light pollution and the visibility of the Milky Way.
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Light pollution in urban areas
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is one of the most prevalent issues facing the developed and developing worlds today, and it has a detrimental impact on the health of people, wildlife, and the environment. Light pollution can come in several forms: light trespass, when unwanted light escapes from one property into adjacent properties; over-illumination, or using excessive light where it isn't needed; light clutter, the redundant clusters of lighting found in many urban centers; and sky glow, the collective light pollution found over big cities.
Urban areas are particularly susceptible to light pollution due to the high concentration of artificial lighting used in buildings, streets, and advertising. This excess of artificial light can have negative consequences for both human health and the environment. For example, a study cited in the journal Environmental Health Perspectives found that women living in areas with high levels of light pollution had a 73% higher chance of developing breast cancer than those in less brightly lit areas.
Light pollution also disrupts the natural behaviors of animals, such as migration patterns, wake-sleep habits, and habitat formation. For instance, sea turtles and birds that rely on moonlight for migration can become disoriented and lose their way due to the presence of artificial lighting. Additionally, large numbers of insects are drawn to artificial lights, which can impact the food sources for birds and other animals.
To address light pollution in urban areas, several measures can be implemented. These include shielding lights to reduce glare, dimming lights to provide only the necessary amount of illumination, and turning off lights when they are not needed. Organizations such as the International Dark Sky Association (IDA) work to educate the public about the impact of light pollution and promote the use of lighting practices and technologies that reduce light pollution.
In terms of viewing the Milky Way, light pollution can significantly impact the visibility of the night sky. According to the Bortle Scale, which measures the darkness of the night sky, a Class 5 or higher rating indicates that the Milky Way is not visible to the naked eye. To observe the Milky Way, a location with minimal light pollution, such as a Class 4 or lower on the Bortle Scale, is recommended.
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Light pollution and astronomy
Light pollution is a growing concern for astronomers and stargazers alike. The artificial brightening of the night sky is altering the opportunity for people to view and ponder the sky above in the evening hours. Even small increases in night sky brightness can degrade this experience. According to a 2016 study, nearly 80% of people in North America are unable to see the Milky Way from their location due to light pollution.
The Bortle Scale and the Dark Sky Scale are two systems used to classify the darkness of the night sky. The Bortle Scale ranges from Class 1, representing the darkest skies, to Class 9, representing the brightest skies. Similarly, the Dark Sky Scale rates the darkness of the sky from Class 1, the darkest, to Class 9, the brightest.
To see the Milky Way with the naked eye, a dark sky location is essential. The amount of light pollution that obscures the view of the Milky Way depends on various factors, including geographical location, weather conditions, and the level of artificial light present. In highly populated urban areas, light pollution from streetlights, security lights, and lit-up buildings can create a dome of purple-grey haze that washes out all but the brightest stars.
To observe the Milky Way, it is recommended to find a location with minimal light pollution. This may involve travelling away from city centres and populated areas. The darker the sky, the better the viewing conditions for the Milky Way. A Class 4 rating on the Bortle Scale is considered good enough to view parts of the Milky Way, although a Class 1 or 2 rating will provide a more impressive and detailed experience.
Some regions are recognized for their exceptionally dark skies and are designated as Dark Sky Reserves. These areas, such as central Idaho in the United States, possess clear skies that are virtually untouched by light pollution. Efforts to reduce light pollution in cities are also being advocated, with the aim of creating welcoming urban spaces that allow people to experience both the city lights and the brilliance of the stars above.
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Frequently asked questions
Any amount of light pollution can dramatically affect the visibility of the Milky Way. Even in areas with low light pollution, the Milky Way may only be weakly visible on clear nights.
Chad, the Central African Republic, and Madagascar are the countries least affected by light pollution. Over three-quarters of their populations experience pristine, ink-black night skies.
99% of the United States and Europe live under light-polluted skies. In some places with high levels of light pollution, such as Singapore, people never experience true night due to artificial twilight.
A Dark Sky Reserve is a designation by the International Dark-Sky Association that recognises regions with pristine night skies virtually untouched by light pollution. The United States' first Dark Sky Reserve is pending approval under the pristine nighttime skies of central Idaho.
The Bortle Scale is a 9-point scale that measures the darkness of the night sky. The darkest skies are Class 1, and the brightest are Class 9. The brightest pollution level where the Milky Way is visible is described as Class 6, or a bright suburban sky.
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