When a 1994 earthquake knocked out the power in Los Angeles, many residents called local emergency centers to report seeing a strange "giant, silvery cloud" in the dark sky. They were scared because many of them had never seen the Milky Way over the expansive city. But for most of the residents in Los Angeles, that became the story of how they first saw the wonder of our galaxy. Of course, this is neither Edison nor his breakthrough invention's fault; however, since the electric lighting began to shine across the world, the night sky has began awash in electric light. Streets, yards, parking lots, billboards, skyscrapers, hospitals, schools and many other buildings and structures glow throughout the night, polluting the environment with something that many are not even aware exists: Light pollution.
Light pollution is the introduction of artificial light, either directly or indirectly, into the natural environment. This phenomenon is pronounced in urban centers where city lights diminish the view of stars, planets and other celestial objects. A satellite view at night shows light pollution as glowing regions around urban areas. In addition to brightened skies around cities, light pollution also refers to any outdoor light that creates glare and interferes with the natural night environment.
This does not mean that electric lights are bad. Artificial lights obviously benefit society in various ways, including one of the most important: Extending the length and productivity of a day. Lights also offer increased safety at night as well as more time for work and different type of activities that require light. However, the moment we begin consuming more than what we need, light becomes annoying and unnecessary.
Since light pollution is one of the fastest growing and most pervasive forms of environmental pollution, most of the research suggests that light pollution can have lasting and adverse effects on the health of both humans and wildlife.
Sky glow, light trespass, glare and over illumination are all forms of light pollution. Sky glow is the bright halo that appears over urban areas at night, a product of light being scattered by water droplets or particles in the air. Light trespass occurs when unwanted artificial light from, for instance, a floodlight or streetlight spills onto an adjacent property, lighting an area that would otherwise be dark. Glare is created by light that shines horizontally. Over illumination refers to the use of artificial light well beyond what is required for a specific activity, such as keeping the lights on all night in an empty office building.
What might happen?
If you are working as part of a group that observes the stars, planets and other parts of the cosmos, then it might not be possible for you to make your observations properly due to the inhibition of the light released from the earth. This type of pollution also influences wildlife and plants. Night lighting disorients hatching sea turtles, migrating birds and nocturnal animals. Lights attract insects, which, in turn, may interfere with the pollination of nocturnal flowers. In humans, light pollution can interfere with natural circadian rhythms by preventing the production of melatonin, the chemical that regulates sleep patterns, and low melatonin levels have been linked to increased cancer risks.
If the light pollution is very bad in your city or country, do not worry too much. But do continue to care about it and take the following steps in order to begin making a small but significant difference. First, start with your own neighborhood. Make sure outdoor lights reflect downward in what are called fully-shielded fixtures. Also consider exchanging high-watt bulbs for dimmer ones and selecting warm-white lights with low emission blue lights. A great way to save energy and reduce trespassing light is to turn off outdoor lights unless needed.
Regardless of the amount of light pollution, look at the sky and try to catch the stars while you can.