More efficient public lighting could save energy, cut carbon emissions - and help astronomers, writes Dick Ahlstrom.
What pollutes our skies, wastes natural resources, threatens bird and animal life and robs us of access to a beautiful amenity? Not coal smoke, not vehicle exhaust or discharges from chimneys. The culprit is light.
The growth in urban living has brought with it the annoyance of light pollution. It shines into our homes from neighbouring security lights. It creates a dull orange glow over our cities and towns. And it is the bane of astronomers around the world.
Amateur and professional astronomers are fighting back however, improving our view of the night sky and saving energy in the process.
"Light pollution is outside lighting spilling out where it is not needed," explains Prof Mark Bailey, director of the Armagh Observatory. "This is totally wasted energy, and that light energy goes up to reflect off dust and other particles to produce the glow we see over cities." The result is an obscured night sky, not just for astronomers but for everyone. Our over-lit cities and suburbs have made it impossible to see more than a handful of stars in a clear night sky, and the Milky Way has effectively disappeared.
"It has destroyed a natural amenity, a clear view of the night sky," suggests Terry Moseley of the Irish Astronomical Association. "People aren't aware of the beauty of the night sky above their heads."
There is a simple physiological reason for this, he explains. The bright artificial lighting causes your pupils to constrict, even though you might be standing some distance from the nearest light. "Your eye doesn't adjust properly, your pupils never open up enough to see the night sky," says Moseley.
This means few nowadays can watch a meteor shower or the aurora borealis, and only a few constellations come into view. "Even what used to be considered the best observatories in the world have been affected because of light pollution," Prof Bailey states.
And while Armagh can still conduct meaningful observations that make a contribution to astronomy, things are getting more difficult.
"There is a lot of astronomy that can still be done, provided that the illumination of nearby cities is controlled. I think it is very important that we should be able to do good research from our home base without having to travel," says Bailey.
This isn't just about inconvenience, it is a question of wasted resources. Our local authorities spend about €300 million a year on lighting and a third of this could be saved through better designed light fittings, according to estimates from Astronomy Ireland.
"Full cut-off fixtures" can project light towards the ground only, suggests Moseley. "If you have a properly designed fitting you can reduce the wattage needed by up to 50 per cent." This would deliver a huge saving to the tax payer and also reduce the carbon footprint associated with this wasted electricity.
The energy used by two 500-watt home security lights produces as much carbon in a year as driving 16,000km, adds Prof Bailey, half the distance from Ireland to Australia. "Even if you switch to energy-saving bulbs, this is just missing the point. You are still using electricity that probably isn't needed."
It is also impacting on wildlife, he argues, disturbing nocturnal hunters, drawing insects towards light away from ground-based predators and changing the natural rhythms of bird life.
There are signs of change, says Moseley. "Some local authorities and road engineers have started to address the issue." He argues for the creation of "light reserves" where there would be very little lighting, but much improved views of the night sky. Countries including Belgium and the US have held "lights out" nights when everyone is encouraged to switch off and view the night sky.
The International Dark-Sky Association holds an annual conference which in 2009 comes to Armagh, during the UN's International Year of Astronomy. The all-Ireland conference will highlight the problems and what can be done about them.
See the Irish Light Pollution Awareness Campaign website, http://www.ilpac.eu, and the Armagh Observatory's website, http://star.arm.ac.uk/darksky/armagh.html. See also the Dark'Sky Association's website, www.darksky.org