Light Pollution

Your sky, your observations, your data

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People have looked up to the sky at night for millennia. Some have searched the stars for the answer to the question “where are we going?” sometimes figuratively (astrology), and literally (for navigation). In the 20th century, the stars started to disappear from the night sky, as glow from electric lights in cities outshone them. These days, some citizen scientists are looking to the night sky to find out whether the widespread adoption of LED lighting is making the problem of skyglow worse or better.

In many citizen science projects, the main or only role of participants is to collect data. We wanted to change that for our project, and put the data and tools to analyze it back into the hands of the public. Our new web application, my sky at night, does just that.

The image below shows skyglow data collected in Europe from four different sources: visual observations from our Loss of the Night app (LON), visual observations from the Globe at Night project (GAN), observations with the Dark Sky Meter app for iOS (DSM), and observations taken by citizen scientists with a Sky Quality Meter (SQM). You can filter by year and project to decide which data to show in your browser (selecting all data will take a while to download, clicking on “load only displayed area” will help speed this up).

"Groups of skyglow observations in Europe. Credits: Christopher Kyba & interactive scape".

“Groups of skyglow observations in Europe. Credits: Christopher Kyba & interactive scape”.

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Measuring the environmental impact of light pollution from orbit

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Inside the scientific community there are many people, with a few sceptics, who claim that the blue light is the most harmful in various parameters. The glare on roads, disruption of circadian cycles, correlation of epidemiological studies on the incidence of breast and prostate cancer, sterilization of crops, problems to observe the stars are just some of the effects of blue light. But, as in any negative impact, must always distinguish between the loss and profit. LEDs generally have many benefits: the possibility of dimming at will (temporarily or in the presence function), greater directionality and greater range of colour temperatures, even with the possibility for some devices to change this dynamically.

However, for evaluating a dilemma like this, a rigorous monitoring and impact evaluation becomes very necessary. Enter the “Cities at Night” Project.

This image of Milan was acquired after the transition to LED technology in the centre. The illumination levels appear to be similar or even brighter in the centre than the suburbs, and the amount of blue light is now much higher, which suggests a greater impact on the ability to see the stars, human health and the environment. Credit: Samantha Cristoforetti.

This image of Milan was acquired after the transition to LED technology in the centre. The illumination levels appear to be similar or even brighter in the centre than the suburbs, and the amount of blue light is now much higher, which suggests a greater impact on the ability to see the stars, human health and the environment. Credit: Samantha Cristoforetti.

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We are losing the night

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Hipparchus was the first to develop a star catalog of the night sky using his naked eye. This catalog contained about 850 stars that he discriminated by their brightness into six categories or magnitudes (1).

Nowadays that would have been an impossible task to repeat from a human settlement. The artificial lights that illuminate our cities are being poorly addressed and they emit light into the sky waning the darkness of night.

Overview Central American Astronomical Observatory of Suyapa.

Figure 1: Overview Central American Astronomical Observatory of Suyapa. Credit: The Central American Astronomical Observatory of Suyapa.

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Skyglow: measuring light pollution in the UK

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Skyglow is the halo-like artificial illumination of the night sky above towns and cities. It’s also the name of a major new study into light pollution in the UK by Hillarys. Using satellite images taken between 1992 and 2014, Skyglow shows how the UK’s night-time skies have changed. The research charts a 28% decrease in light pollution*, with falls in every region – and projects this data into the future. You can see the interactive satellite imagery and full study on the Skyglow project page. Or keep reading to find out the story behind the story.

Credit: Skyglow Project

Credit: Skyglow Project

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Light stories on film

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As a science journalist, one of the crucial questions I regularly ask myself is: “why should my audience care about this story?” Of course there are many factors that determine whether or not something is news-worthy. But one of the fundamental requirements is that stories must connect with people on some form of emotional level. That may be intrigue, excitement, awe, shock, anger, or any other of the remarkable array of human responses. The one thing you must avoid is indifference. With science being abstract at times, it is the job of the science journalist to show their audience how and why the thing you are communicating matters to people.

Fortunately, the International Year of Light and Light=based Technologies (IYL 2015) is a veritable treasure trove of great stories. At its core, this year is about people doing fascinating things with light that can have profound effects on other people’s lives.  To me, this became clear at the opening ceremony of IYL 2015 at the UNESCO headquarters in Paris. I met a diverse cast of characters doing all manner of intriguing and important things with light and light-based technologies. That included Nobel laureates, aid workers, artists, engineers, and many more. I even learned a new word when I met a “speleologist” (aka cave scientist) presenting a photo collection of caves in Haiti. The images demonstrated how light and shadow can reveal the geological richness of these environments in stunning detail.

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