Have you ever questioned: What do astronomers mean by light pollution? How often do you hear about light pollution? Surely, not a lot of times.
Light pollution is a real issue that makes the night sky significantly less beautiful and affects amateur and professional astronomers and it is not talked about enough as it continues to grow. In this article, we will explore everything about light pollution and the major question: What do Astronomers mean by Light Pollution?
1. What Is Light Pollution?
Light pollution refers to the excessive artificial light that unnaturally brightens the night sky. It reduces the visibility of celestial objects in the night sky, disrupts ecosystems, causes wastage of energy and also affects human health at a certain level. It is primarily a result of poorly designed or overly bright outdoor lighting fixtures that emit light that scatters and diffuses in the atmosphere. This type of pollution diminishes our ability to observe stars and other celestial phenomena, disrupts the natural behaviours of nocturnal wildlife, interferes with human sleep patterns, and contributes to unnecessary energy consumption which has further environmental impacts.
2. Types Of Light Pollution
Light pollution is of several types. The types of light pollution are categorised based on their distinct characteristics and effects. Some categories may also overlap each other.
The major defined types of light pollution will be discussed ahead.
Skyglow is the omnipresent layer of bright light that covers the night sky. This phenomenon is often seen in populated areas and cities. The scattering of artificial light by the particles and molecules in the atmosphere causes skyglow. You might have seen a hazy, orange or yellow glow that overpowers the natural darkness of the night sky from the rooftop of your house. Skyglow makes it difficult to see stars, galaxies, and other celestial objects.
According to a study about artificial light at night and light pollution, 83 per cent of the people experience skies polluted by light pollution and 23 per cent of the world’s land area is affected by skyglow. Another study about global trends in nocturnal power emissions showed that light pollution has only accelerated, it is estimated that light pollution has increased by at least 49% from 1992 to 2017.
A glare is usually a light that shines very intensely and hits directly. An example of glare can be when you look at the sun and experience intense and direct light. Such exposure to light can be dangerous if it is prolonged and the intensity of brightness is high. In lesser extreme conditions, it may cause general discomfort and strain to the eyes. Generally, glare may be divided into three ways: blinding glare, disability glare and veiling glare.
2.2.1. Blinding Glare
A blinding glare is caused due to direct exposure to intense light, like staring at the sun for too long. Such light may leave one with temporary or even permanent vision issues.
2.2.2. Disability Glare
A disability glare can be dangerous, it occurs when lights are bright and intense enough to cause a disability. It may cause a decrease in visibility due to the eyes’ inability to adapt to both the bright and dim areas in the field of view. This particularly affects drivers who experience difficulty seeing the road when cars and vehicles with overly bright headlights are coming from the front or when light scatters through the fog.
A veiling glare is a particular instance of disability glare in which the scattering of light takes place in the eye. This glare is usually common in urban areas which have bright streetlights as the streetlights make the light scatter in all directions. It occurs due to reduced contrast courtesy of excessive brightness, or to the reflection of light from dark areas in the field of vision when the luminance is way too similar to the background light.
2.2.3. Discomfort Glare
A discomfort glare is not intense enough to cause any serious vision restrictions or reduction in visibility but they may cause discomfort or strain for a while. On longer exposure, they may cause fatigue to the eyes but no potential long-term harm.
Clutter refers to a lot of bright lights together. It may also be a visual stimulus, this usually happens when a large number of light sources are grouped. That may lead to confusion and difficulty in distinguishing individual objects from each other. Such clusters are often seen in urban environments in the form of billboards, and huge illuminated complexes such as sports stadiums, office buildings, shopping malls, and showrooms. Places like these require a lot of electricity or need to compete for attention so light clusters are used as attractions. But they are quite distracting and overwhelming.
Over-illumination happens when an unnecessary amount of artificial light for particular task results in a waste of energy and resources. This type of light pollution not only contributes to the aesthetic view of the night sky but also has concerning environmental and economic repercussions.
Over-illumination raises two major concerns; the expenses and energy wasted on electric lights and the health concerns surrounding exposure to excessive artificial lights.
According to a report from 2016, lightning accounts for approximately 19% of the global electric energy consumption which is approximately 3000 TWh. The International Energy Agency estimated that if the current consumption remains the same the global electricity use for lighting will grow to about 4250 kWh by 2030 which would be an alarming increase of more than 40%.
Major factors that lead to over-illumination include not turning off lights when not in use, relying overly on electrical lights instead of natural light during the day time, the intensity of brightness being more than necessary, and having too few electrical controls.
Health effects of over-illumination appear in the form of fatigue, headaches, hypertension, medically defined stress, and anxiety. These effects may further induce more dangerous health concerns.
2.5. Light Trespass
Light trespassing is when unwanted or intrusive artificial light from sources beyond one’s property enters one’s personal space or areas where the light is not intended to be. Light trespass reportedly causes sleep deprivation, problems with sleeping patterns and a disruption in the natural nocturnal environment.
Several municipalities in the U.S. have established standards for outdoor lighting against light trespass. The International Dark-Sky Association has developed a set of model ordinances and regulations around lighting to prevent light trespass.
To reduce light from going up into the sky, The Dark-Sky Association has prescribed the angles of light sources to be such that they must be at a lesser angle than 90° above the nadir. This also helps to reduce light trespass as it majorly happens at this range as well. Zoning codes in many areas also include provisions related to outdoor lighting.
3. Causes Of Light Pollution
Several factors contribute to light pollution, in this section, we will go through the major factors that are responsible for light pollution.
3.1. Poor Planning While Installation
The way lighting is engineered to be placed, consideration of the required amount of intensity, and the angle of lighting fixtures play a crucial role in determining light pollution. The placement of outdoor lighting fixtures, including signage and streetlights, and the ones in open areas require a significant amount of consideration. Poorly designed fixtures can create issues such as glare as well as light trespass. An excessive grouping of bright lights due to improper planning can lead to light clutter as well.
3.2. Irresponsible Use Of Artificial Lightning
Leaving lights on because of unintentional negligence or ignorance for a long duration of time causes not just light pollution but also overconsumption of energy. The timers of the streetlamps are often not adjusted according to the change in seasons which contribute to an excessive light emission.
3.3. Overpopulation and Urbanization
Overpopulation and urbanization have increased the concentrations of businesses and residences, particularly in cities and suburbs. When these entities are clustered together without heeding proper planning and zoning regulations, it results in several forms of light pollution. The proximity of commercial and residential spaces is responsible for skyglow and glare, mostly in cities.
3.4. Smog and Clouds
Natural atmospheric phenomena such as fog, smog and clouds can also exacerbate light pollution. The artificial light emitted by city lights scatters further due to fog, smog and clouds and makes the surrounding environment look much brighter than it naturally would. As a result, light pollution levels can increase, even in areas with relatively low light sources.
The intense, bright lights from vehicles; the headlights and taillights, especially during the night time add to the nighttime light pollution. In places where there is high traffic density, the vehicle lights remain on for a lot of time. This kind of pollution can extend beyond roadways, and impact nearby homes and neighbourhoods as well.
3.6. Nighttime Lighting
All the forms of nighttime lightings, such as illuminated signs, billboards, and advertising displays, outdoor lighting, vehicle headlights contribute majorly to light pollution. These bright and flashy displays increase skyglow and overpower the natural night environment.
3.7. Downtown Illumination
Downtown areas with high-rise buildings, skyscrapers, offices, malls and commercial spaces are often heavily illuminated at night. The continuous use of lighting for traffic, buildings and commercial purposes combines to create a bright urban glow that affects the night sky’s visibility and overall quality.
4. Effects Of Light Pollution
4.1. Health Concerns
The excessive presence of artificial light at night has profound implications for human health. Medical research indicates that light pollution and over-exposure to artificial light can lead to a range of adverse health effects. Improper lighting design, especially with high-intensity and improperly tuned lights, can increase the incidences of headaches, worker fatigue, stress, anxiety, and even decreased sexual functionality in humans. Exposure to light at night also disrupts circadian rhythms, affecting alertness, mood, and sleep patterns. The use of outdoor artificial light, particularly contemporary street lighting, has been linked to various health risks such as obesity, mental disorders, and diabetes in a lot of studies.
According to the World Health Organization, shift work that disrupts natural circadian rhythms may be a probable carcinogen. Several studies show a link between night shift work and an increase in the rates and probability of breast and prostate cancer. A study conducted in South Korea shows a correlation between areas with high levels of artificial light at night and higher rates of breast cancer in the area.
A newer 2021 study published in Southern Economic Journal found that light pollution has an impact on preterm births before 23 weeks of gestation.
4.2. Ecosystems and Wildlife
Light pollution poses a huge threat to ecosystems and wildlife. The effect of light at night impacts different species variably but it invariably disrupts nocturnal behaviours and the interactions of species with the ecosystems.
For instance, light pollution can interfere with animal navigation, alter predator-prey relationships, and cause physiological harm. Animals and plants depend heavily on natural light for their routine patterns and habits. The disruption caused by artificial light can affect the ecological dynamics of several species.
Some examples of how animals’ and plants’ ecosystems and routines are affected by light pollution are:
- Zooplankton, such as Daphnia, do not eat surface algae due to exposure to light which causes algal blooms and ultimately the ecosystem of the lake.
- Nocturnal insects, such as moths, are affected by nighttime lightning as it hinders their navigation. This may further impact their reproduction and development as the night-blooming flowers depend on nocturnal insects for pollination. In the long term, it may lead to a larger change in the ecosystem.
- Fireflies are good indicators of light pollution’s impact as they rely on their light for reproduction and are sensitive and responsive to changes in their environment.
- Light on tall structures causes disruptions for migratory birds. A study shows that the light produced by Post Town has affected over twenty-five bird species. The Fatal Light Awareness Program (FLAP) has encouraged building owners in Toronto, Ontario, Canada and other cities to turn off the lights during migratory seasons after birds were killed at a large magnitude.
4.3. Economic Impact
Light pollution has gotten worse with urbanization, and industrialization. Industries, factories and offices now operate for longer hours and almost around the clock. Sectors like healthcare, manufacturing, and e-commerce require artificial lighting for safety and operational purposes. This demand for continuous lighting contributes to light pollution. Research indicates that light pollution is more prevalent in developed and industrialized countries with high GDPs.
Astronomy is heavily affected by light pollution because artificial light reduces the visibility of celestial objects in the night sky. Skyglow reduces the contrast between stars, galaxies, astronomical objects and the night sky. The objects look faint and are not seen, especially in cities. You may see this contrast when you find that in relatively rural areas, astronomical objects are visible sharply. Light trespass can also impact telescopic observations because of reduced contrast and the light glare that hinders observations.
We will delve into this deeper in the next section.
5. What Do Astronomers Mean By Light Pollution?
Astronomy is a branch of science that deals with celestial objects, space and the universe. Astronomers study and observe the celestial bodies in the sky. Light pollution largely impacts their work and observation as it creates an obstruction.
Astronomy experts are certainly affected but amateur astronomers too find it difficult to enjoy the night landscape. Urban areas and cities are no longer suitable places if you wish to study astronomy but there are remote such as the Atacama Desert in northern Chile where you can find pitch-black skies for the best visual and photographic astronomy experiences
5.1. Reduction Of Visibility
Excessive artificial lighting results in a bright skyglow that obscures stars, galaxies, and other celestial objects. Faint objects become hard and nearly impossible to observe, and the depth and clarity of astronomical objects through astronomical instruments as well as images decrease significantly. Diffused sky objects like nebulae and galaxies are more affected by light pollution than stars due to their low surface brightness.
The scattering of light casts skyglow in the atmosphere, which in turn reduces the contrast between celestial objects and the sky itself. This leads to reduced visibility. New telescopes are designed to adapt to these issues.
One of the simple indicators of light pollution is the visibility of the Milky Way. In dark skies, Milky Way appears bright but unfortunately, it is now not visible to around one-third of the world.
5.2. Challenges Faced In Astrophotography
Even in apparent clear skies, exposure to any stray light makes the details less visible in astrophotography. Certain software is used to reduce stray light and improve the object details and image quality.
5.3. Filters Used To Combat Light Pollution
Astronomers use narrow-band “nebula filters” and broad-band “light pollution filters” to mitigate and soften the effects of light pollution. Nebula filters allow only specific wavelengths from nebulae, while light pollution filters reduce effects from sodium and mercury-vapour lamps.
However, light pollution reduction (LPR) filters have limitations, they can only reduce the brightness of the object being observed block light of certain wavelengths which alters the colour of objects, and they are less effective for galaxies and stars.
5.4. Light Trespass and Glare
Light trespass may occur while viewing a celestial body through a telescope. When artificial light directly enters the telescope tube, it reduces contrast and creates a glare across the field of view. Astronomers combat this glare generated by flocking the telescope tube to reduce reflection or using light shields or dew shields to block lights from the majority of angles.
5.6. Atmospheric Pollution
Light pollution contributes to unnatural atmospheric conditions as well and researchers found that light pollution destroys nitrate radicals that aid in reducing atmospheric smog at night.
Research presented by Harald Stark from the National Oceanic and Atmospheric Administration indicated that light pollution hinders the normal reduction of smog produced by emissions.
6. What Can You Do To Reduce Light Pollution?
As responsible citizens and conscious humans, we must take individual steps to protect night landscapes, conserve ecosystems and mitigate the harmful effects of pollution. There are a few ways you can contribute to reducing light pollution and you may also encourage others to follow suit.
6.1. Turn The Lights Off!
The easiest and the first step towards mitigation of light pollution is to prevent over-illumination which makes up for a large part of it. Turning off artificial lights when natural daylight is present, turning off lights when they are not in use, turning off vehicle’s headlights in traffic and not leaving lights on for prolonged periods. This would also help you conserve energy, and reduce overconsumption but will also keep your electricity bills minimum.
6.2. Use White Light Low-Energy LED Lights
Using white light, energy-efficient LED lights are advised because they do not contribute largely to light pollution.
If up are getting new lights, especially for outdoor lighting, do look for the International Dark Sky Association (IDA) certification. IDA approves light fixtures that meet strict guidelines to minimize glare, light trespass, and skyglow. You can also use features like timers, motion sensors, and dimmers to save energy. Make sure your lights are shielded, so they shine down instead of up.
6.3. Timers and Motion Sensors
Timers may be set according to the length of days and seasons for streetlights and outdoor lighting especially to ensure lights are switched off during the daytime when there is enough exposure to natural light.
Another interesting way is motion sensors. Barcelona has already made motion sensors for lightning a reality. Motion sensors detect movement and accordingly switch on the lights for the time being a person is in motion around them or approaching them. Such technology can be effective in energy conservation as well as save us from over-illumination and skyglow.
7. Conclusion: What Do Astronomers Mean By Light Pollution?
Light pollution is a grave issue, it not only makes it difficult for astronomers to study space, celestial bodies, constellations and stars from Earth but also disrupts ecosystems and life patterns of nocturnal animals. In addition, light pollution is detrimental to human health and contributes to mental distress as well. It is important to create public awareness about its impact and encourage everyone to contribute less and less to light pollution by just making more conscious choices.