Bronte Wells
Light pollution has significantly impacted our ability to see the night sky, erasing stars that should be visible to the naked eye. This issue is especially prevalent in cities and heavily populated areas, where artificial lighting drowns out the natural light of the stars. To escape light pollution, one must travel far from major cities and interstate highways to places with little to no artificial lighting, such as central and northern Nevada, southwestern New Mexico, northern Arizona, and eastern Oregon. While it is challenging to quantify the exact distance one needs to travel to escape light pollution, it is safe to say that the farther you are from major sources of artificial lighting, the better your chances of experiencing a truly dark sky.
| Characteristics | Values |
|---|---|
| Distance one can see buildings on a flat Earth | 50 miles |
| Distance to the Moon | Nearly a quarter of a million miles |
| Light pollution sources | Cities, villages, streetlights, moonlight, humidity |
| Light pollution solutions | Flipping a switch, changing a lightbulb, adding a shield or motion sensor, driving to a less polluted location, light pollution filters (for older light designs), dimming streetlights, using clean technologies |
| Air pollution sources | Chlorofluorocarbon (CFC) and hydrochlorofluorocarbons (HCFC) in aerosol sprays, cleaning solvents, and air conditioners, petroleum-based coatings, vehicle emissions, power plants, refineries, chemical plants |
| Air pollution solutions | Low or zero VOC paints, cleaning products, and processes, water and powder-based coatings, vehicle improvements (evaporative controls, catalyst design, fuel control systems, treatment and retrofit technologies), idle-reduction technologies, gas-electric hybrid vehicles, routine use of continuous monitoring technology, multi-pollutant monitors |
| Air pollution reduction (between 1990 and 2020) | 73% for carbon monoxide, 86% for lead, 61% for annual nitrogen dioxide, 25% for ozone, 26% for 24-hour coarse particle concentrations, 41% for annual fine particles, 91% for sulfur dioxide |
| Benefits of pollution reduction | Reduced environmental damage, improved public health, clearer scenic vistas, protection of the ozone layer, reduced atmospheric levels of fine particle pollution, avoidance of premature deaths |
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What You'll Learn
Light pollution hides stars visible to the naked eye
Light pollution is making it increasingly difficult to see the stars with the naked eye. The night sky is getting brighter every year as light pollution becomes more prevalent, with the sky becoming around 10% brighter annually. This has implications for human health and wildlife, with the stars disappearing before our eyes. The Milky Way, for example, is no longer visible to a third of humanity, and it is estimated that most of the major constellations will be indecipherable in 20 years.
The issue of light pollution was first recognised in the 1970s when astronomers noticed the impact of the rapid increase in artificial light on their work. At that time, the sky was becoming brighter by between 3% and 6% every year. Today, light pollution is not only becoming more widespread, but it is also accelerating. In Europe, light pollution is increasing at a rate below the global average, at around 6.5% annually, while in North America, it is rising at 10.5%.
The increase in light pollution is due to the increased use of light-emitting diodes (LEDs) and other forms of lighting. LEDs are more efficient than older forms of lighting, but they are also making it more difficult to monitor light pollution and observe the night sky. The bluish emissions of LEDs are lacking in red and near-infrared light, which is important for human health. Reddish light stimulates mechanisms in the body that break down high levels of sugar in the blood or boost melatonin production, and the lack of this light in artificial lighting may be contributing to the rise in obesity and diabetes cases.
Light pollution also has cultural and scientific implications. Dr Ashley King, a Future Leaders Fellow at the Natural History Museum, notes that "the first humans could look up at the sky and use it in so many parts of their lives. Whether it was for navigation or telling the seasons, the stars are an important part of our culture." Today, many people can no longer see the stars due to light pollution, and this loss of connection to the night sky can have a significant impact on our understanding of the world around us.
To combat light pollution and improve the visibility of the stars, one can move away from major cities and light sources. In the United States, states like Arizona, Nevada, New Mexico, and Wyoming offer relatively close access to destinations with darker skies and better stellar visibility. Additionally, giving your eyes time to adapt to the dark can also improve your ability to see stars in light-polluted areas.
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The Moon reflects light pollution from the Sun
Light pollution has significantly impacted our ability to see the night sky in all its glory. Those living in less populated areas of the western or mid-western United States, such as Arizona, Nevada, and New Mexico, are fortunate to have relatively easier access to locations with pristine night skies. However, light pollution from distant cities can still be an issue, even in these regions.
The Moon is a significant source of light in the night sky, and it plays a crucial role in our perception of the celestial sphere. "Moonlight" is actually reflected sunlight. The Moon does not emit its own light, but rather reflects a small fraction of the sunlight that hits it, with an albedo, or reflectivity, of about 13.6%. This means that only around one-tenth of the sunlight that reaches the Moon is reflected back into space, compared to Earth, which reflects about three-tenths, and Venus, which reflects over half.
The Moon's distance from Earth, at an average of about 239,000 miles, is a critical factor in its brightness in our sky. Despite its low albedo, the Moon's proximity to our planet means that even a small amount of reflected sunlight is sufficient to make it appear brilliant from our perspective. The brightness of the Moon can be deceiving, as it is often perceived as almost white, but this is an illusion caused by the Sun's reflected light. Up close, the Moon exhibits shades of dark gray, similar to volcanic rocks on Earth.
The Moon's appearance changes throughout the month as it rotates and orbits, causing day and night to occur on different parts of its surface. From Earth, we always see the same face of the Moon, the "lunar nearside", which presents a series of familiar shapes, such as the crescent, half-moon, and full moon. The color of moonlight, especially around a full moon, appears bluish to the human eye compared to other brighter light sources due to the Purkinje effect.
The Moon's reflection of sunlight contributes to light pollution in the night sky, making it challenging to observe dimmer celestial objects. Many astronomers avoid observing sessions around a full moon due to the increased brightness and reduced contrast between celestial bodies and the background. However, the Moon's illumination can also enhance the night sky's beauty, casting sharp shadows on the ground and providing enough light to navigate in darkness.
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Light pollution filters are now ineffective
Light pollution has significantly impacted our ability to view the night sky, with many city dwellers having to travel for hours to find a spot with minimal light pollution.
Light pollution filters were developed to block out specific light pollution wavelengths, allowing astrophotographers to capture images of space without the interference of light pollution. These filters were designed to block out the wavelengths of light emitted by sodium vapour lamps, the main cause of light pollution. However, with the shift to LED lighting, which emits light over a broader spectrum, the effectiveness of light pollution filters has diminished.
LED lighting is becoming increasingly common, and while it reduces the yellow or orange glow from cities, it still contributes to light pollution. This white or blue light is more challenging to block with filters, rendering them ineffective in many cases. While some claim that light pollution filters still work, especially in areas with sodium vapour lamps, the shift to LED lighting means that light pollution filters will likely become obsolete.
For those interested in astronomy, this poses a challenge. Filters can dim everything in the sky, reducing the visibility of sky glow, light pollution, planets, stars, galaxies, and clusters. While they can increase the contrast of emission nebulae, they are of limited use in heavily light-polluted areas. In addition, filters can be expensive, and the cheaper options are often not worth purchasing.
As a result, those seeking pristine night skies may need to travel further to find locations with minimal light pollution. In the continental USA, areas in central and northern Nevada, southwestern New Mexico, northern Arizona, and eastern Oregon offer better opportunities to view the night sky.
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The Clean Air Act has improved air quality
Light pollution, caused by distant cities and villages, has obscured the night sky views our ancestors used to see. However, the Clean Air Act (CAA) has substantially reduced air pollution and improved air quality in the United States.
The Clean Air Act is a comprehensive federal law that regulates air emissions from stationary and mobile sources. The Act has been amended several times since the first federal vehicle emissions standards were set in 1968, with the goal of reducing pollution and improving air quality. The 1970 Act is most often referred to as the Clean Air Act, and it has proven effective in reducing pollution and protecting public health and the environment.
One of the key achievements of the Clean Air Act is the reduction of common pollutants such as particles, ozone, lead, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Between 1970 and 2020, emissions of these pollutants dropped by 78%, leading to dramatic improvements in air quality. For example, all 41 areas that had unhealthy levels of carbon monoxide in 1991 now meet the health-based national air quality standard. The Act has also successfully addressed airborne lead pollution, a previously widespread health concern.
The Clean Air Act has also tackled specific issues such as acid rain and ozone layer protection. The Acid Rain Program (ARP), established under the 1990 Clean Air Act Amendments, aimed to reduce sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions, the primary contributors to acid rain. The program was successful, with a 50% reduction in SO2 emissions from power plants by 2000. The 1990 Amendments also created a Commission on Risk Assessment and Management, tasked with making recommendations for a risk assessment framework.
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Light pollution is solvable with simple solutions
Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It has harmful effects on the environment, wildlife habitats, and our quality of life. Light pollution is solvable with simple solutions.
Firstly, it is important to understand that natural darkness should be the default at night, and artificial light should be used only when necessary. This means that if you do not need a light, switch it off. Every single person can positively impact light pollution by being more considerate about how they light their homes. For example, is it essential to have your driveway lit all night? Could you make do without the fairy lights in the garden?
Secondly, when lighting is essential, it should be fully shielded on the top and sides to prevent light from leaking out into the environment. This can be done by using window shades to keep room lights from escaping your house or hotel room. Similarly, when using flashlights or headlights outside, always point them down to the ground.
Thirdly, light pollution can be reduced by minimizing the use of electronic devices in the evening. After dark, the bright lights of our screens are not needed, so switch to a dimmer night setting. This is also good for our eyes.
Finally, citizens can band together to enact local legislation, and light pollution advocacy can make great strides. Dark Sky International, for instance, works with communities and professionals to establish codes and statutes that reduce light pollution. They also inform the public about how excessive artificial light can harm humans, wildlife, and our climate.
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Frequently asked questions
Light pollution is excess artificial light that brightens the night sky, obscuring our view of the stars.
Light pollution can prevent us from seeing stars and celestial bodies that would otherwise be visible to the naked eye. Light pollution can also negatively impact wildlife, for example, by disorienting migratory birds.
Light pollution can be escaped by travelling to less populated areas, such as national parks, which are often far away from sources of light pollution.
Light pollution can be reduced by limiting the use of artificial light at night, using low-emission vehicles and light bulbs, and implementing light shields and motion sensors.
