Light pollution and the fight for darker skies

Photo:1.6-meter telescope at Mont-Mégantic National Park. Photo by Guillaume Poullin (

When was the last time you saw a starry sky? Last night? A week ago? If you live in a big city, odds are it wasn’t recently. A few hundred years ago, before the industrial revolution and the plague of light pollution, things were different. Anyone could look up at the sky at night and see the milky way. That is, unless you live in a particularly overcast or rainy location. In a dark place away from light pollution, over nine thousand stars are visible to the human eye. In a city, that number is reduced to less than fifty. Today there are fewer places that are untouched by man made light.

Photo: Comparison of a rural area (lower) and a dark area (higher). (Wikipedia).


But what is this ‘light pollution’? When the the world pollution is mentioned, most people think of air pollution, or chemicals polluting our waters and oceans. The problem with these types of pollution is that they are hard to get rid of. Light pollution is rather different. It may be disruptive, but we only need to switch off the lights to make it disappear. Unfortunately, the majority of our planet is bathed in man made light twenty four hours a day. Therefore, switching off the lights is obviously easier said than done.

Photo: World atlas of artificial sky brightness (


Photo: The milky way as seen from Findochty, in rural Scotland. Notice the orange glow in the corner, which is caused by light pollution from the village (photo by Alexander Dutoy).


Light pollution, second to bad weather, is the bane of many an astronomers’ career. Aside from ruining the view of the night sky, light pollution interferes with astronomical research. Unfortunately, many older observatories, including the one here at St Andrews, are affected by nearby light pollution. This makes it difficult to see dim objects such as far away stars, or very dim stars that are washed out by the sky glow. Another way light pollution interferes with research is rather sneaky. Often, astronomers measure the spectrum of a star or galaxy in order to find out it’s chemical composition. However, the skyglow caused by streetlights can actually interfere with these spectra and cause unwanted lines. The spectrum below is of a galaxy in the constellation of Hercules, where the white horizontal line is the galaxy. The vertical lines, however, were caused by nearby mercury streetlamps! [1]

Photo: The spectrum of a galaxy ruined by nearby street lamps (photo: [1]).

Light pollution does much more than hide the stars and planets at night. The bright lights disrupt many natural cycles, and sadly millions of birds die every year because of this. These birds get confused by unnatural light and have accidentally flown into buildings. If you’ve seen Planet Earth 2, you may remember the baby sea turtles who hatch on the beach. These turtles use the moon’s reflection in the water to make their way to the sea. Many didn’t make it to the ocean. Instead, they wandered onto busy roads, attracted and confused by the streetlights. There, they met their death, only moments after arriving into this world. [2] Light pollution disrupts many natural ecosystems and creature rituals including migration, hunting and breeding. The long term impacts of man made light could lead to extinction of many species unless we do something about it.

Photo: Footage from Planet earth 2 of hatched baby turtles who met an unfortunate ending on a city road (photo: BBC). Fortunately the Barbados Sea Turtle Project has volunteers working around the clock to look after these little guys and make sure they make their way safely to the sea without being squished by cars or eaten by predators.

It gets worse. Light pollution is a tremendous waste of energy and money, which is alarming considering the current state of the environment. Light pollution actually contributes towards other types of pollution, namely air pollution from the burning of fossil fuels. Approximately 15 millions tonnes of carbon dioxide are emitted every year in order to power homes in the US. 35% of this light is wasted due to poor lighting design. This ultimately costs the US government $3 billion per year, wasted on light pollution. If you wanted to undo these carbon dioxide emissions you’d have to plant 600 million trees. [3] And that’s only America – light pollution is abundant in Europe, Japan, India, and many other places. Think about how many trees you’d have to plant to undo all of the air pollution caused by man made lighting!

Fortunately, there are people who are campaigning for the preservation of dark skies. The main authority on combatting light pollution world wide is the International Dark Sky association (IDA), founded in 1988. IDA works in a number of diffierent areas including educating the public and government about night sky conservation and providing the public with resources to “help bring back the night”. IDA runs the Parks and Protected Areas program, which helps nature reserves and national parks acquire outdoor lighting products that are dark sky friendly and won’t disrupt eco systems. Currently there are 42 IDA approved dark sky parks around the world, with 4 here in the UK. IDA also awards the title of ‘dark sky reserve’ to any smaller area with dark skies; so far there are 13 of these reserves worldwide with 5 of them here in the UK. [4]

Photo: The Scottish Dark Sky Observatory, which lies in the Galloway Dark Sky Park (

Although light pollution is a massive problem worldwide, there are ways we can all help to make our skies a little darker. The first thing you can do is inspect the outdoor lighting around your home, and replace it with efficient and energy saving LEDs. Another thing you can do is talk to your local community. IDA has a number of different resources free to take include brochures, videos and online information. Finally, you can spread the word online. You can follow IDA on instagram, twitter, tumblr and facebook – so follow them and show your support for dark skies!

And of course, if you didn’t get my hint about planting trees earlier on, you can plant a tree! There are many charities that can help you do this including the woodland trust and trees for life. I’ll leave off with one of my favourite, and very relevant quotes: “The best time to plant a tree was fifty years ago. The second best time is now”.

Photo: To become an IDA member follow this link! (photo: [4]).









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