The taint of city lights

City Lights

Look up at the sky tonight. What will you see? If you live in a rural area, you’ll probably see a the glittering of stars as faint as pinpricks. Maybe even the arch of the Milky Way. If you live in a city, however, the night sky will look very different. You’ll probably see the moon. Some stars. Maybe. The reason for this major difference in the night sky is because of something called light pollution.

Light pollution is problematic for anyone interested in the night sky. Apart from the brightest objects in the heavens, nothing is a match for the sheer illuminative power of a city at night.

I saw the unpolluted night sky for the first time on a camping trip when I was a teenager. It was with an organization called the Governor General’s Youth AwardThose trips were the most physically challenging things I had ever done, but I loved it. I got to travel to another island and see so much cool stuff. Among those things were the stars. I saw the faint creamy curve of the Milky Way. I saw the flash and fall of a meteor. I saw more stars than I could have imagined existed.

UNESCO has declared 2015 the International Year of Light and Light-Based Technologies  and one of the mandates of this celebration of light is to address light pollution. Light pollution is essentially wasted light. All of those building lights, street lights, headlights, the lights in our homes all contribute to light pollution. According to the their site:

“Light Pollution” is a form of environmental degradation in which excessive artificial outdoor lightings, such as street lamps, neon signs, and illuminated sign boards, affect the natural environment and the ecosystem. The wasteful light emitted directly upwards or reflected upwards from poorly-designed artificial light sources can be scattered by clouds, fog, and pollutants like suspended particulates in the atmosphere.
Dark Skies Awareness, 2015 IYL

Scientists have been studying light pollution for some time

For the most part people are aware of the way that light pollution makes it harder and harder to see celestial bodies. However, there are other important ways that light pollution impacts both us and our environment. Light pollution has been known to disorient fledgling birds when they first leave their nests, disrupt reproductive cycles of lemurs, deter seed-dispersing tropical bats and inhibit rainforest regeneration, influence the composition of insect and marine invertebrate communitiesand affect plant growth and subsequently food webs. On a more human level, “white light” as apposed to “orange” light inhibits the production of melanin, a compound necessary for regulating our biological clock.  

Scientists know that light pollution is bad but the problem with studying the it is that scientists have a hard time quantifying the actual amount of light pollution.

A project that has just released some scientific data is the Cities at Night ProjectThis citizen science project has a number of apps available and its long-term aim is to create a high resolution image of the Earth at night. It collaborates with astronauts at the International Space Station to photograph cities at night. A thesis published in August 2015 by Alejandro Sánchez de Miguel was the first time that ISS images were used for scientific studies on light pollution.

One of the outcomes of the study was verifying that the diffuse glow seen from space is actually scattered lights from streetlights and buildings and is responsible for the brightening of the night sky in and around cities.

Cities at Night is a collaboration between the Universidad Complutense de Madrid in Spain and the Cégep de Sherbrook in Canada. The project is cataloguing over 130000 images from the ISS’s high-resoltuion archive and geo-referencing them to a place on a map. By combining space and ground measurements it allows researchers to map light pollution over extended areas. What’s great is that because it’s a citizen science project, you can help too.

How you can help with this project

Dark Skies ISS  is one way to help the project. There are over 1,200,000 images taken by the ISS but few of them are actually catalogued and even fewer are geo-referenced. The biggest problem is that computers can’t distinguish between city lights, stars, the moon or other celestial lights (e.g. northern lights).

DarkSkies ISS

It’s pretty straightforward and kind of a cool way to contribute to science. You go to the site, you can register if you want to but you don’t have to and you classify pictures. An image can either be: black, a city, stars, an aurora, an astronaut, none of the above or you simply can’t tell.

There are a lot of people contributing to this project so if you’re interested head over the website and sort through pictures.


Dr Ash Signature

Author’s notes:

My Writing 101 prompt for today is to take an image and use it as a spring board. I wanted to talk about light pollution from cities.

Image- City at Night via unsplash


First use of ISS astronaut pictures for light pollution studies- Discovering the nature of diffuse light seen from orbit by INTERNATIONAL ASTRONOMICAL UNION, August 2015 via Eurekalert



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