As Skipper Wilson charts his course for France, he is going to notice a change in the night sky. He’s already said farewell to the constellations of the Southern Hemisphere, and soon he’ll have to say goodbye to many of the stars he can see in the night sky in the Northern Hemisphere, as well.
That’s because light pollution, or excess light in the earth’s atmosphere, hides stars from our view. As Skipper Wilson gets closer to areas where lots of people live (such as the European coast), he will start to see fewer and fewer stars each night.
It’s not just at sea that light pollution becomes obvious. You might have noticed it yourself. Near a city at night, the whole horizon glows. It doesn’t really look all that dark, and, although you can see some stars, it’s not really that many. On the other hand, if you go to a spot way out in the country, you’ll be surprised at how dark it gets — and how many stars suddenly come out of hiding.
Roughly 6,000 stars are visible from around the world without the help of a telescope. In the darkest spot on the clearest, moonless night, you can see about half that number. We know there are lots more stars in the sky. Why can’t we see more? In part it’s because some are so far away that their light isn’t bright enough for us to see without some extra help. And in part it’s because to see the faint light that stars give off, you have to be in a place that is less bright than the light you’re trying to see. (That’s also why you can’t see stars during the day.)
Light pollution doesn’t just hide the stars. It also affects animals and ecosystems. Newly hatched sea turtles immediately leave the beaches where they are born and head to the sea. Scientists have found that too much light confuses them and makes it hard for them to reach the ocean safely. Other scientists, who study the tiny animals that live in lakes believe that these zooplankton are confused by a more light sky and don’t come up to feast on the algae growing on the surface of the water at night. Also, birds and moths and insects have trouble flying at night when there is too much light.
What causes all this light pollution? Too many lights that are set to give off too bright a light. Also, light that instead being aimed down at the ground, where we are using it to see, escapes into the night sky.
To fight the problem of light pollution, cities and counties and countries have started to put laws into place that limit the sorts of lights that can be used outside at night, where they can be placed, and how bright they can be. Scientists hope that more people will become interested in the dangers of light pollution and will talk to their local governments. This video is one way that people from around the world are starting conversations with each other about light pollution.
Too Bright at Night (6-8)
Night Lights (6-12)
Dark Skies Initiative Aims to Boost Stargazing (3-12)
Earth Hour 2009 (3-12)
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