Jan 20 2023

Dark Skies – A Vanishing Resource

Published by under Astronomy
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When I was a child I loved looking up at the night sky and seeing thousands of stars. I especially loved seeing the disc of the Milky Way spreading across the sky. I can’t remember when this first dawned on me, but as an adult I can no longer do this. When I look up into the sky, even on a clear night, I can still see lots of stars, although not as many, and I can’t make out the Milky Way. It’s simply not visible.

The problem of light pollution was also brought home to me when I visited Australia. Seeing the southern sky was always an item on my bucket list – to see the Southern Cross, the Magellanic clouds, and Alpha Centauri. I have been in the southern hemisphere three times. The first two times I never got a look at the night sky. So on the third trip I made it a point to go somewhere where I would get a good view of the night sky. I had to drive over an hour from Christchurch to get that view. It was magical, and definitely worth the effort, but it really demonstrated for me the extent of light pollution.

A recent study published in Science found that:

Trends in the data showed that the average night sky got brighter by 9.6% per year from 2011 to 2022, which is equivalent to doubling the sky brightness every 8 years.

There are many reasons for this. One is the increasing switch to LED lighting. Because they use much less electricity, people and simply using more lighting (a general trend over human history – the more available lighting is, the more we use). But also LED lights are whiter than older street lighting, and emit more in the blue frequencies that tend to scatter more in the atmosphere and interfere more with human vision. The result of all this lighting creates “skyglow” which reduces the ability to see the night sky with the naked eye.

This is one of those problems that’s easy to ignore. Many people might not even notice – it’s hard to notice what’s not there. And as new generations grow up with increasing light pollution they don’t even know what they are missing. I can look back on my childhood and remember the difference. This is definitely becoming and “old man” thing – “When I was a kid you could see thousands of stars. Why you could see the edge of the galaxy itself. You kids today don’t even know what you’re missing.”

I know there are a lot of things to worry about in the world, and this might not rank high on many people’s lists, but I think it is important enough to care about. This is just one more way that people are becoming isolated from nature. Increasingly studies are showing that psychological wellbeing is tied to access to nature. Research is just beginning to look specifically at the effects of access to dark skies, but preliminary evidence suggests the effect extends there as well. But even if the effect is only subjective, it’s fair to observe that many people simply like nature and desire access to it, including the ability to see the night sky.

One of my hobbies has been, since grade school, naked-eye astronomy. I have tried to share this love with my daughters, but it has been difficult. There are few good opportunities, and typically only the brightest stars are visible. Gazing at the night sky was part of what made me interested in astronomy and science in general. We are now planning a family trip, probably this summer, to a dark sky location. That’s what it comes to.  I have to travel hours away to a designated dark sky location just to get a view I could have in my backyard as a child.

There are things that can be done to mitigate the continued increase in skyglow. This does not involve sacrifice, just doing things smarter. Street lamps, for example, can aim downward, limit their brightness, and use frequencies of light that are fine for safety and illumination but reduce scatter and skyglow. They can also be limited in number – there’s a streetlamp outside my house, in a cul-de-sac, in a rural neighborhood. It is entirely unnecessary. Horizontal lighting also interferes significantly with skygazing. This can be fixed as a simple matter of zoning regulations.

I don’t expect cities to become dark sky zones, but we can stabilize and decrease the amount of light they generate. This would decrease the distance one would have to travel from a city to get a good view of the sky. Suburbs and towns could significantly reduce their contribution to skyglow without hampering safety. This could also reduce electricity demand for unnecessary lighting.

This ties once again into the fact that there are simply a lot of people on Earth. Anything we do collectively is big, and has a huge impact on the environment. This means we have to do things smartly, and thoughtfully. Otherwise there are bound to be unintended consequences from the cumulative effects of collective action. There are some clear win-wins here – we just need to take them.


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