What Exactly is Light Pollution?

Today's Night Sky

For the fist time in human history people are growing up without a view of the night sky. Over the last 200 years the effects of urbanization have led to the dimming of the starry beauty we used to be so familiar with. The most devastating aspect of urbanization on the night sky was the advent of artificial lighting in the latter part of the 19th century. After Thomas Edison's patent on the incandescent light bulb electricity became widely available throughout America's cities and street lights and homes were illuminated with the artificial yellow glow of modernity. What followed can only be described as an obsession with artificial lighting. Soon bright flashing bulbs lit up street signs for businesses, theaters, and offices. Neon signs soon became the best way to attract visitors at night. Floodlights were installed on people's homes to create an aura of security, bigger, brighter, and more efficient light bulbs were installed as cities expanded and grew.

We have now become accustomed to the lights switching on even before the sun goes down. The bright, low-hanging haze of city lights can be seen for tens and even hundreds of miles away. All this has left the night sky above our cities and suburbs looking anywhere from a dull pink to blue and many people have been left wondering "What happened to all the stars?"

They're all still there, we just can see them anymore. The light that we've become oh-so dependent on has created an artificial shell around our planet that obscures the once dazzling view of the night sky our not too distant relatives used to know so well. Now only the brightest stars remain visible from cities. The total star count in cities like New York and Los Angeles is a paltry dozen or so. The bright planets Venus, Mars, Jupiter, and Saturn still remain but people often mistake them for stars if they even look up at all. If you desire to get a halfway decent view of the night sky you must leave behind the city lights by about 20 miles, and to view the enchanting Milky Way you must travel even further from lights, up to 50-100 miles.

We are in danger of loosing the night sky altogether as cities get bigger and brighter and suburbs continue to expand. For the first time ever over 50% of Americans don't have reasonable access to a dark sky where the Milky Way can be viewed, and about two-thirds of Europeans don't have access to a dark sky. We are close to loosing a natural wonder that is older even that the planet itself. This is all due to the ever-increasing problem astronomers call light pollution.

What Is Light Pollution?

The International Dark Sky Association defines light pollution as excessive and inappropriate artificial light. There are four components of light pollution that include urban sky glow, light trespass, glare, and clutter. Light pollution is caused by all artificial lighting in some form or another, but the different facets of light pollution have different effects. We'll address each component in further detail.
Urban Sky Glow

Skyglow is brightening of the night sky over inhabited areas that causes thousands fewer stars to be visible and is responsible for the dimming and total loss of the Milky Way. Skyglow can be seen as the bright "dome" of light that hangs over urban and even residential areas and can be seen from many miles away. Skyglow is forcing astronomers, amateur and professional alike, to drive further and further away from inhabited areas. All of the poorly-directed and excessive lighting of the residential, commercial, and industrial sectors contributes to skyglow. Lights that are unnecessarily bright or are not directed properly shoot photons (light particles) up into the sky where they aren't needed. Lights without proper shielding accessories often emit light in a 360 degree circle around the source creating a globe of light. All of these lights combined shooting photons up into the air causes the dome that can be seen from a distance.
Light Trespass

If you've ever been lying in bed trying to fall asleep but couldn't because of a neighbor's bright light shining into your room you've experienced light trespass. The IDA defines light trespass as any light falling where it is not intended, wanted, or needed. Lights that aren't directed, or poorly-directed shine light where the owner didn't intend on but still create a nuisance for neighbors and stargazers. The school where I take my telescope has bright high-pressure sodium lights around the parking lot that significantly interfere with my eye's night adaptation. While most residential lighting is done for ambiance and security reasons, much of it is wasted and annoying to neighbors. This problem can be fixed by simply installing motion sensors on security floodlights and pathway lights.
Glare

Glare is the excessive brightness of lights that causes visual discomfort and actually reduces visibility. The problem of glare is most dangerous on roads when drivers deal with bright headlights and street lights. If you've ever been temporarily blinded by an oncoming driver's white headlights you've experienced disability and discomfort glare. Not only did the brightness of the headlights or street light make your eyes uncomfortable, your ability to see things in the dark was drastically reduced for a short period of time. Additionally, continued exposure to glare can increase tiredness and be dangerous to drivers. The ability to see clearly in the dark is crucial for drivers and while street lights seek to illuminate the road, they can actually damage a driver's night vision and make the road and surrounding noticeably darker beyond the light.
Clutter

The bright, confusing, and excessive groupings of light sources in urban areas are referred to as clutter. This light clutter contributes to all three of the previous categories and is especially dangerous to wildlife as we'll discuss later. Clutter is particularly noticeable along roads where poorly-lit street lights and advertising signs create distractions to drivers and can cause accidents by hiding obstacles such as pedestrians or animals that would have otherwise been visible.


Effects of Light Pollution

We've already covered the most obvious effect of light pollution, namely the disappearance of the night sky, but there are some more far-reaching consequences to humans and nature alike that you may not have been aware of. Light pollution affects both human health and the lives of many animals, especially those that are nocturnal.

One animal that seems to take the hit from light pollution more than any other are migratory birds. Many species of migratory birds fly through or over cities during their migrations and the bright lights of skyscrapers causes them to become disoriented and fly into buildings. Thousands of birds are killed every year in major cities from building collisions.

Another well-know environmental effect of light pollution is the behavior and survival rates of sea turtle hatchlings in places like Florida's Gulf coast. Female sea turtles bury their eggs in the sand along the beaches for their incubation period. When the time comes for them to hatch the newly born turtles must make their way to the water as soon as they can or they'll be dehydrated or eaten by predators such as birds or alligators. The turtles rely on the night sky to navigate to the water as the reflection of the stars on the water make it the brightest direction. When there are bright artificial lights around the beaches where the turtles are they can become confused and unable to find their way to the water. Some die of dehydration, others of being eaten by prey, and others find their way towards road where they get hit by vehicles. Studies have shown a direct link between artificial light and sea turtle deaths on beaches. Luckily, for the turtle's sake, Florida has recently implemented strict lighting ordinances around known sea turtle hatching grounds and the results have drastically improved.

All the negative effects of light pollution on the environment are too many to describe in detail but I'll list some of the most impacting ones.

    Disruption of day-night patterns in nocturnal species
    Increase in algae blooms affecting vegetation growth in lakes, rivers, and large bodies of water and reduced water quality
    Pollinating insects are drawn to bright lights causing the decline of night-blooming plants and the overall change in an area's ecology

Effects on Humans

There are several adverse health effects on humans caused by light pollution. The majority of them are related to the disruption of our body's natural light-dark cycle called the circadian rhythm. Our bodies have what you can call an internal clock that functions differently depending on what time of day/night our body believes it is. Our metabolism, immune and nervous systems are connected to this light-dark cycle.

By far the most interesting and deadly effect of disrupting our body's circadian rhythm is the potential link between artificial light and cancer rates. The brain is constantly producing the chemical known as melatonin which is the driver of our circadian rhythm. Melatonin is also clinically proven to reduce cancer death rates. Treatment of cancer with melatonin proved to reduce the number of tumors that become malignant. The brain produces a higher level of melatonin during dark hours and when we're asleep. When artificial light is abundant our brain can become confused into what time of day it is and alters its production of melatonin accordingly. If there is a large amount of artificial light entering our eyes at night melatonin production levels decrease when they would otherwise be at their highest rate. Continued exposure to artificial light during peak melatonin production hours has been linked to increased cancer rates. One study conducted at the University of Connecticut suggests a link between cancer rates and long exposure to artificial light. Specific caners such as breast and prostate cancer were shown to show and increase in formation and malignancy especially among those who do shift work, such as hospitals.

There are also psychological effect of light pollution that we don't fully know the extent of since this is a relatively new problem. To what extent will we loose our sense of our position in the universe because we can't see what's around us in the night sky? What spiritual effects does loosing the night sky have? In my opinion, we've become arrogant as a species over the last couple centuries. This is due to a mix of reasons such as our technological advancements, our subjugating of the world around us and harnessing it to accomplish our purposes, and our lost sense of positioning in the universe. All it takes is one glimpse of a truly dark sky to understand that in the grand scheme of things we are utterly insignificant and small. A loss of this sense has attributed to an unhealthy pride within the human race.
Massive Energy-waster

Of all the negative effects of light pollution, the one that is most likely to get the attention of the public is its huge effect on your wallet! Artificial lighting is responsible for one-quarter of all the electricity consumption worldwide. Within the United States, it is estimated that one-third of all lighting is wasted, meaning that it is not directed properly or it shines into the sky causing skyglow. Here are some shocking statistics about just how much energy we waste by poorly illuminating our homes, businesses, and cities.

    The amount of energy wasted in illumination each year in the U.S. is the equivalent of 8.2 million tons of coal contributing to 14.1 millions tons of Co2 added to the atmosphere each year
    Financial estimates of the amount of wasted illumination range around $2 billion each year
    We waste about the equivalent of 4.5 millions barrels of petroleum each year on poor illumination! Imagine what that would to to the gas prices if we reduced this!
    The city you live in wastes on average, $69,000 in poorly-illuminated street lights alone every year! Source: physics.fau.edu

I'll stop there and have a legitimate argument for getting our lawmakers scrambling. Imagine the difference cutting down on wasteful illumination could have on our economy and your personal finances!

What Can Be Done?

With such broad and negative consequences, light pollution certainly has to be addressed and dealt with. But what is there that can be done to reduce the amount of light we consume, which has become ever more an indispensable part of modern life? Thankfully, the solution for light pollution isn't all that hard to put in place. The problem is communicating the problem to the public and the lawmakers and getting them to act on it. The solution is as simple as being smart about how we choose to illuminate. Installing the proper light fixtures or adding shielding features to existing lights will work wonders on the amount of energy wasted and the effectiveness of the light to light only the area intended, instead of the sky. The International Dark Sky Association has been leading the way in educating the public about night sky-friendly devices for several years. They have an abundance of resources available to educate about proper fixture choice for each type of lighting need. The IDA also has model light pollution ordinances on their website that can be used as examples for lawmakers. The IDA is a non-profit organization funded by donations so they can always use financial support! Donate or join the IDA if you're passionate about fighting light pollution!

If you want to take action in your area you can begin by checking to see if the IDA has a local chapter in your area. Talking to local lawmakers and business people is a great way to start since that's where all the money and impetus usually comes from. Don't be afraid to speak up because without you we'll never see the adverse effect of light pollution reversed! Most people aren't even aware that light pollution exists so education is the first and most important step.

With the help of you and other citizens along with scientists and politicians we can work towards reclaiming the night sky for all of humanity to see!