Light Pollution: Hiding The Stars

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is a big problem that is getting bigger. Light pollution competes with starlight, drowning out the light from faint objects like galaxies and nebulae and increasing the brightness of the sky background. It washes out starlight in the night sky, making it harder to see stars and constellations. In a light-polluted city, you can see about 200 stars, while in a dark sky area, you can see up to 3000 stars without any visual aid on a moonless night. Light pollution also interferes with astronomical research, disrupts ecosystems, has adverse health effects, and wastes energy.

Light pollution washes out starlight

Light pollution is caused by excessive, misdirected, or obtrusive artificial light, often from outdoor sources such as streetlights, billboards, and car headlights. This artificial light competes with the light from stars, making it harder to see them. The problem has been exacerbated by the recent rise in LED lighting, which is more energy-efficient but also broadens the emissions that flood the sky with light.

The impact of light pollution on stargazing is significant. It drowns out the light from faint celestial objects like galaxies and nebulae, and increases the brightness of the sky background, making it harder to see stars. This is particularly true for diffuse objects, which are easily suppressed by even moderate light pollution. The Milky Way, for example, is no longer visible to one-third of humanity due to light pollution, including 60% of Europeans and 80% of Americans.

Light pollution also has other negative consequences, including disrupting ecosystems, affecting human health, and wasting energy. However, it can be mitigated by using light only when and where it is needed, directing light downward, and using energy-efficient bulbs.

It affects human health

Light pollution has a significant impact on human health, affecting our biological welfare and natural day-night cycles. The intrusion of artificial light at night can cause sleep disorders and disrupt the production of melatonin, a potent antioxidant and anti-carcinogen. This disruption has been linked to various health issues, including insomnia, depression, hypertension, attention deficit disorder, obesity, diabetes, heart disease, and certain types of cancer.

The human eye is sensitive to light photons, which can affect our biology and physiology. Even in a lit urban environment, our retinas are exposed to these photons, potentially disrupting our circadian rhythm. This disruption can have far-reaching consequences, affecting our hormone production, cell regulation, and other biological activities regulated by our circadian clock.

Research has found a correlation between light pollution and an increased risk of breast cancer. A study in Israel, for example, showed a 73% higher risk of developing breast cancer among women residing in areas with high levels of outdoor artificial lighting at night. The suppression of melatonin, a hormone produced at night, is thought to be a key factor in this increased risk.

Light pollution can also have indirect health impacts. For instance, it can disorient wildlife such as sea turtles, causing them to wander onto roadways and risk being struck by vehicles. This not only harms the turtles but can also create hazardous situations for motorists.

The widespread use of LED lights, while energy efficient, has drawn concern from health officials due to their potential impact on human health. Overall, light pollution is a pressing issue that requires attention and action to mitigate its adverse effects on both human and wildlife health.

It disrupts ecosystems

Light pollution has a detrimental impact on wildlife and ecosystems. For billions of years, life on Earth has relied on the natural rhythm of day and night, which is encoded in the DNA of all plants and animals. Humans have disrupted this cycle by lighting up the night.

Plants and animals depend on Earth's daily cycle of light and dark to govern essential behaviours such as reproduction, nourishment, sleep, and protection from predators. Artificial light at night has been shown to have negative and even deadly effects on many creatures, including amphibians, birds, mammals, insects, and plants.

Light pollution radically alters the nighttime environment for nocturnal animals, turning night into day. Predators that hunt using light and prey species that depend on darkness for cover are both affected. Research scientist Christopher Kyba notes that "near cities, cloudy skies are now hundreds or even thousands of times brighter than they were 200 years ago. We are only beginning to learn what a drastic effect this has had on nocturnal ecology."

Wetland habitats that are home to amphibians such as frogs and toads are impacted by the glare from artificial lights. Their nighttime croaking, which is part of the breeding ritual, is disrupted, interfering with reproduction and reducing populations. Additionally, artificial lights can disorientate adult and baby sea turtles, causing them to move away from the ocean and towards danger.

Bird species that migrate or hunt at night rely on moonlight and starlight for navigation. Artificial light can cause them to wander off course and collide with illuminated buildings and towers. It can also disrupt their migration timing, causing them to migrate too early or too late and miss ideal conditions for nesting and foraging.

Light pollution also affects insects, with declining insect populations impacting all species that rely on them for food or pollination. Some predators exploit this attraction to artificial light, further affecting food webs.

It impacts astronomy

Light pollution has a significant impact on astronomy. It washes out starlight in the night sky, making it harder for astronomers to observe celestial objects and interfering with their research.

From a light-polluted city, one may only be able to see about 200 stars, whereas a dark sky site can offer a view of up to 3000 stars on a moonless night. Light pollution drowns out the light from faint objects like galaxies and nebulae, and increases the brightness of the sky background, making it difficult to observe faint stars.

The use of LED lighting in cities has exacerbated the problem. While energy-efficient and cost-effective, LEDs produce broad emissions that flood the sky with more light than traditional low-pressure sodium lamps. This makes it challenging for astronomers to carry out their observations, even in suburban areas.

The Bortle scale, a nine-level numeric scale, is often used to classify the level of light pollution in a particular location. It measures the night sky's brightness, quantifies the observability of celestial objects under light pollution conditions, and compares the darkness of observing sites. Class 1 on the scale represents excellent dark sky viewing with no interfering light, while Class 9 represents inner-city sky viewing where light significantly reduces the number of visible objects.

Light pollution has also led to a loss of connection with our cultural heritage. In the past, artists, writers, and composers drew inspiration from the night sky, and people could easily observe the Milky Way even in cities. Today, due to light pollution, this experience is becoming rarer, and future generations may miss out on this source of wonder and inspiration.

It can be reduced with proper shielding

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by light fixtures that scatter light above the horizontal plane, such as streetlights, greenhouses, and satellites. This form of pollution has harmful effects on wildlife, ecosystems, energy consumption, and human health.

Light pollution competes with the light from the stars, making it harder to see them. It makes the atmosphere much brighter than the natural night sky, drowning out the light from faint objects like galaxies and nebulae.

Light pollution can be reduced with proper shielding. Light shields are accessories that can be attached to the top and/or sides of light fixtures. They are also known as light shrouds or glare shields, and they focus light downward or inward so that it does not spread in unwanted directions. This prevents light from spilling into unwanted areas, such as neighbouring properties, and reduces glare.

The use of light shields can also improve night vision and enhance safety in public spaces and neighbourhoods. They can be particularly useful in sports fields, where they can stop light pollution upward and limit sideways glare for players and spectators.

Light shields are especially important for LED lights, which have a broader emission range than traditional low-pressure sodium lamps and can further brighten the sky. LED lights are also more directional than other types of lights, so they can still benefit from the use of shields in densely populated areas.

In addition to light shields, there are other strategies to reduce light pollution, such as using shades or covers, minimizing light use, reducing decorative lighting, and using lighting controls like dimmers, motion sensors, and timers.

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