Science & Technology

Something in the Air

In this age of greenhouse gasses and smog advisories, air pollution has gotten a pretty bad name, and rightly so. But it still looks pretty trippy.

Air pollution is divided into four categories: criteria air contaminates (which create smog and acid rain), persistent organic pollutants (which travel well and bioaccumulate in body tissues), heavy metals (which enter the food and water supply) and toxins (which will, in one way or another, kill you). These substances are produced by a variety of sources. Transportation, fossil fuels, industrial processes, agriculture and transboundary air movements (which, rather than determining the trajectories of extremely agile kangaroos, deal with pollutants that are widely carried from one area to another) are among an ever-growing list of culprits. Air pollution is also partially derived from natural sources-phenomena such as volcanoes, dust storms, forest fires and sea spray all contribute to particles in the air.

The upshot of all this is that we get spectacular sunsets.

Chemicals change the refraction of light, particularly at sunset, and so all those pollutants result in brilliantly coloured skies. As the sun sets, light scatters. According to George Dissanaike in the 1991 New Scientist article entitled “Painting the Sky Red,” “Larger particles scatter more of the light, and the effect depends on wavelength. The scattering is stronger in the green-yellow parts of the spectrum as well as in the blue.” In urban areas where pollution consists of larger particles in the air, pollutants filter these shades, such that the sunlight that did manage to reach through the pollution appears a deeper shade of red.

And after the sun sets? Look at the sky above nearly any major city and you’ll see an uncanny glow above-the reflections of millions of lights, often referred to as skyglow, a condition that obscures stars in the night sky.

In North America, skyglow is so severe that steps have been taken towards creating what are known as ‘dark sky reserves,’ where energy-efficient, low-sodium lighting is used to both reduce skyglow and facilitate astronomical observations. In Mont-Mégantic National Park, which contains one of Canada’s foremost astronomical observatories, night-sky visibility was so threatened that it has become a dark sky reserve-one of four in Canada, and the only one to exist in a suburban area. This is partially due to the efforts of ASTROLab, a group dedicated to preserving the area and fighting light pollution. Last May, Natural Resources Canada donated $250,000 to help in their efforts. “The goals of the ASTROLab campaign dovetail perfectly with… our intention to develop national standards for lighting efficiency,” says Parliamentary Secretary Jacques Gourde. However, measures will need to be much more wide-spread to prevent fading any view of the stars for good.

Steps may never be taken toward clearer skies and visible stars, but at least toxic chemicals and light refraction will serve all your surrealist needs.

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