On the second of the 12 days of CultureLab, Debora MacKenzie tells of how light pollution in the sky is making it harder to see the wonders of the Milky Way. Why not help record the damage?

For each of the 12 days of Christmas, here’s something to beguile, distract – and leave you with questions for the year ahead

Call me Scrooge, but I expect to spend my holidays trying not to think about how the Paris climate deal is probably too little, too late. I’m going to think happy thoughts instead, or at least to think about a problem we might solve.

Luckily, I know just the thing.


Earlier this year I took my family camping in a national park in my native Canada. With us was a young man raised in England’s urban north, on his first trip to North America. His reaction to the geographic distances, serving sizes and traditional scare-the-foreigner bear stories had been gratifyingly predictable.

What I didn’t expect was his reaction when he walked out onto the shore by our campsite after dark. Kejimkujik National Park is a Dark Sky Preserve – there is so little light pollution you can see the entire night sky.

My kids grew up in Brussels where heavily lit highways leave almost no stars visible. But at least on previous trips they had seen our galaxy stretching to the glow-free horizon. The boy from Bolton hadn’t, and he was gobsmacked.

Invisible Milky Way

He’s not alone. Researchers calculate that more than 70 per cent of North Americans and 50 per cent of Europeans live under enough skyglow to make the Milky Way invisible.

That could change, as a revolution is underway in the technology of street lights, which cause most light pollution. LEDs need far less energy than old street lights, so they are cheaper to run, encouraging cities worldwide to switch.

As LEDs focus light better, the story goes, this means less wasted, scattered light to cause skyglow. Except it doesn’t.

LEDs produce more blue light than the old street lights – precisely the wavelength a human’s dark-adapted night-time eye is most sensitive to. This more than makes up for the reduced scatter. Last year, researchers calculated that LEDs make skyglow two to three times worse, making more people unable to see the Milky Way unless their street lighting is reduced to at least half its current level.

Right now we don’t even know how bad the problem is. You can help find out, through a citizen science project called Loss of the Night, a phone app that allows ordinary people to track what stars they can see, and thus how bright their sky is.

Because of the sheer number of observations, the data can track changes in brightness despite the occasional inaccuracy of amateur observers. So far it suggests that between 2006 and 2012, reported brightness didn’t increase, even though urbanisation, and with it lighting, certainly did. In an update to the project this December, users can now view and manipulate the data themselves.

Natural rhythms

The International Dark Sky Association says there are solutions, including well-designed lights and LEDs that emit less blue, like the “warm white” bulbs sold for home lighting. It wants cities to get this once-in-a-lifetime shift in infrastructure right. Given our sorry record on climate-friendly tech, I wonder if they will.

They should: skyglow has far worse effects than making the Milky Way invisible in Bolton, including screwing up the natural rhythms of many wild species. Still, our friend’s reaction made me realise that seeing the galaxy on a regular basis is important too.

It is also a reminder that we are a tiny planet in a big universe – and if our pollution warms Earth past what our society can cope with, we have only ourselves to blame.

As it is, any intelligent life out there might see our night lights blink off someday – because no one intelligent allows their waste products to block their view of the cosmos. Or topple their civilisation, come to that. We could at least try to get that first one right.

Image credit: Mike Kemp/In Pictures/Corbis artist: Robert Indiana