Dark matters
Every year I take a trip away from my light-polluted, urban skies to a star party at a dark-sky site. Every year I meet the same people, and every year we stand in the same part of the field, cold hands in pockets, musing over the same topics in the dead of night. There is something cosy about the familiarity of it all.
And one question that always comes up as we gaze skywards is, “Do you think it’s as dark here as it used to be?”
The answer to this question is usually anything but comforting, as the glow in the sky from surrounding villages and towns appears to creep higher and brighter than the year before. In fact, as we made the journey to the star party this year, the amount of building work taking place around each settlement on the map was staggering; new houses seemed to be popping up everywhere. Houses that were once on the very edge of town are now surrounded by new developments.
Of course, there is a need for new housing in the UK, nobody would dispute that. The worry, from an amateur astronomer’s point of view, is the effect all these new properties will have on overall light pollution, as there’ll be more streetlights and other new sources of light in previously dark areas.
While controlled LED lighting and street-light switch-offs help to reduce overall skyglow, the inescapable conclusion is that where new houses replace undeveloped fields, the skies are not as dark. So when we look at statistics released by the Department for Communities and Local Government and see that the number of dwellings in the UK increased by 800,000 homes in the 2012-2017 period, with an even greater number planned by 2020, perhaps it’s no surprise that our skies are deteriorating.
Satellite surveys published by the American Association for the Advancement of Science back this up: radiance (artificial light shining or directed upwards) from light pollution in the UK alone rose around 2 per cent annually between 2012 and 2016, and a whopping 9.1 per cent globally.
There is a great irony in all this. The 21st century has seen remarkable advances in the astronomy equipment available to amateurs. From cooled CCD cameras, to cheap Go-To mounts and even affordable large refractors and Ritchey-Chrétien optics, today we really do have some brilliant kit within our reach. What a desperate shame that as the equipment we can use gets better, the skies we use it on get worse. I often imagine a scenario where the father of observational astronomy, Galileo, is somehow alive and in my observatory. I can just imagine his face as he marvels at Saturn’s rings, Jupiter’s storms and the polar caps of Mars. Then we use a camera to observe whirling galaxies, intricate supernovae remnants and blooming hydrogen clouds. Almost hugging the telescopes he declares “This equipment is amazing, fantastic, I love it, but tell me, what on Earth happened to the beautiful sky? It used to be so dark.”
I’m still working on an answer to his question that doesn’t give him the impression that humankind has gone completely mad.