Posted by Ellery McNaughton @EJ_McNaughton

Dear Batman,

I have a bone to pick with you. Maybe you’ve been too busy fighting crime and/or Superman to notice that sky glow from artificial light sources is a global issue. Light emitted upwards from artificial sources is scattered by molecules in the atmosphere, creating a glow that is brighter than the natural night sky. Aside from making it harder to sneak around in your Bat-Plane, sky glow also reduces star visibility (and therefore sights like these), and has a myriad of potential impacts on the environment. It is for this reason that I find your use of the Bat-Signal downright irresponsible.

You see Batman, when it comes to outdoor lighting there are three main ways to reduce sky glow. The first is to reduce light trespass into the night sky by shielding or directing the light source downwards. The second is to reduce the amount of light emitting into the night sky by dimming or switching off the light source. The third way is to reduce the scattering of light in the night sky by avoiding light sources that emit strongly in the blue part of the spectrum (as short wavelengths scatter more). Ideally these three methods should be used together. Props to you for somewhat shielding your light with a bat symbol, but I can’t help but feel that this is due to aesthetics, rather than good lighting practice.

In short, your Bat-Signal is polluting the night sky with its bright, upward emitting white light. Don’t take my word for it, go ahead and measure Gotham’s sky glow for yourself. I use a Sky Quality Meter (Unihedron) for my research, but there are also various apps you can easily access and use with your Bat-phone (e.g. Dark Sky Meter or Loss of the Night). You can test for yourself the variations in sky glow around your city, and help out with citizen science while you’re at it!

Honestly Batman, you’re known as the Dark Knight. Please at least try to live up to that.

Ellery McNaughton is a PhD student in the Centre of Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. Her project will investigate the effects of a city-wide changeover in streetlight technology on urban bird behaviour and ecosystem function. She is supervised by Margaret Stanley, Jacqueline Beggs, Kevin Gaston (University of Exeter, UK) and Daryl Jones (Griffith University, Australia).

Posted by Ellery McNaughton @EJ_McNaughton

Like Santa, ALAN probably sees you when you are sleeping. ALAN will be trying to get in through your window tonight. Perhaps you haven’t noticed ALAN. But ALAN is always there. ALAN may be having serious impacts on your health. ALAN kills innocent birds and baby turtles for fun.

And yet, who doesn’t love ALAN? Who hasn’t invited ALAN into their homes and cities?

Artificial Light At Night (ALAN) is a global issue. If you live in an urban area you cannot escape it. Streets, buildings, sports fields, parks, monuments – all are lit up come night time, and it’s easy to see why. Light enables us to see better, feel safer and do more at night. Plus it looks pretty. Bonus!

Light pollution doesn’t get the same attention that water or air pollution does. Perhaps this is because it doesn’t add a physical pollutant to the environment. Perhaps it is because it is seen as transient – once the lights are switched off in the morning, problem solved. Or perhaps it is because we have forgotten what the night sky should look like, so we fail to realise just how polluted our skies are. Whatever the reason, traditionally light pollution has only been an issue of concern among astronomers.

Recently however, there is light on the horizon in addition to light in our skies. There has been a surge of research into the myriad effects of ALAN on the environment (e.g. this special issue in Proc. R. Soc. B). Citizen science is being used to better understand variations in the levels of light pollution. The United Nations proclaimed 2015 to be the International Year of Light and Light-based Technologies, while the Nobel Prize in Physics for 2014 was awarded to the inventors of the blue light-emitting diode. This recent focus on light, light technologies and ALAN in particular opens up opportunities for discussion and thought on these issues. And really, this needs to happen. Because ALAN is most definitely on the naughty list, and we need to talk about it.

Ellery McNaughton is a PhD student in the Centre of Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. Her project will investigate the effects of a city-wide changeover in streetlight technology on urban bird behaviour and ecosystem function. She is supervised by Margaret Stanley, Jacqueline Beggs, Kevin Gaston (University of Exeter, UK) and Daryl Jones (Griffith University, Australia).