It never gets dark at night in many cities throughout the world. This is because of light pollution coming from streetlights, building lights, floodlights, and neon lights for stores and other businesses. You can see the glow of many cities in the sky as you approach on the highway at night. This is called sky glow. Some cities give off so much sky glow that they could be seen from the space shuttles orbiting the Earth!
Too much light can make the stars disappear. Astronomers have to go to places with less light to see the night sky. Observatories need to be in low light areas and have laws passed to keep them that way.
The California Institute of Technology built an Observatory on Palomar Mountain in the 1930s for their 200-inch telescope. It was very dark and perfect for looking at the heavens. They could see very faint, distant galaxies! Then southern California boomed. Millions of people moved there building homes and businesses and driving cars all night long. The resulting sky glow ruined the Palomar Observatory's view of the sky. Local governments have tried to keep the light down so they can continue their important astronomy work, but it's a tough thing to do.
Too much light can make it hard for people to rest. A fence around your yard does not keep the light from your neighbor's house out of yours. Glaring lights can blind drivers and cause accidents. Bright lights at work all day can give you a headache. It can raise your blood pressure and make you nervous.
Over millions of years animals and plants have adapted to the night-day cycle of Earth. Light pollution makes even the night bright in some places. This can seriously disturb the life patterns of wildlife. Have you noticed what happens when you leave the porch light on at night in the summer? It is swarmed by insects that are confused by this artificial light. Bright lights confuse animals. It can distract them from their normal patterns.
An example of how humans can change their habits to help deal with light pollution occurred with sea turtles. Baby sea turtles hatch out at night. They are guided to the ocean by its lightness compared to the surrounding darkness of the beach. Hotels built on the beaches changed that with outdoor lighting that lit up the beach. Baby turtles, attracted to the lights of the hotels, headed inland instead of to the ocean. They were eaten by predators, run over by cars or just dried up and died. Laws were passed that make hotels turn out their outside lights during the weeks that baby turtles are hatching out every year.
You can help reduce light pollution while saving energy. Turn off lights when you aren't using them. Use the lowest watt light bulbs you can. Keep your lamps pointed down onto what you are looking at and not out your windows.
(Included in PDF)
Light Pollution - Read and React
1. What causes the skyglow that ruined the Palomar Observatory’s view of the night sky?
2. Name three ways light pollution can badly affect people?
3. Name a way light pollution has affected wildlife at your house (think summer nights on your front porch):
4. How have hotels protected hatching seasturtles from light pollution?
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Amsel, Sheri. "Pollution (Light)" Exploring Nature Educational Resource ©2005-2019. October 15, 2019
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