On Light Pollution

by Patrick O'Malley

Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/NGDC, DMSP Digital Archive

I recently showed this picture to friends of mine to elicit their honest reactions, and did not get the myriad responses I expected. What I did get were responses like: 'Oooh, how beautiful!' and 'Wow, look how far we've come!', basically all positive responses. Whether they were mystified or awe-inspired they certainly weren't disgusted as I am when I see pictures like this one.

I agree that this is a significant and very interesting picture, but beauty is in the eye of the beholder - and to my eye this picture doesn't convey much beauty. I find almost any pictures of the Earth from space to be quite beautiful and awe inspiring, reminding us all how generally insignificant our short lives are - in the cosmic scheme of things. However, I prefer pictures from space of the daytime side of Earth. In those the presence of humans is almost entirely undetectable, this is the way it should be.

Pictures of the Earth at night taken from space only serve to remind us of our nearly omnipresent wasteful and short-sighted nature. All the light that you are seeing is wasted, costing millions of dollars every year that serves no purpose other than to block out the otherwise amazing view of the heavens we see from Earth. There is a reason that when people get back from a trip to 'the country', or sparsely populated regions, they rave about having never seen so many stars. There's no mystery, the reason is light pollution. Were it not for our wasteful solutions to the necessary evil of artificial light, that unfettered view of the Milky Way you saw from the country would be visible in all but the most densely populated, and therefore heavily lighted areas.

This picture is actually a composite of multiple exposures taken on moonless, cloudless nights by one of NASA's many Earth-aimed satellites, and it has much to tell. When looking at this picture it becomes clear at once why Africa is often referred to as 'the dark continent' (even though Antarctica, with no year-round human residents, is technically the darkest). The same goes for largely dark Australia, although the lack of copious amounts of light pollution there has more to do with its densely concentrated coastal populations rather than the continent's widespread poverty and lack of modernity, as is the case with Africa. Then there is North America. In terms of light pollution, the good old US of A has everyone beat. Western Europe is coming up, as are India and the far East, but so far America is easily the most light polluted country, making North America the most light polluted continent. Notice the almost complete saturation of the United States with wasted light, and it's nearly unbroken concentration east of the Mississippi. Makes one wonder where astronomers, amateur and professional, are spending their nights (the answer is very rural areas and at high elevations).

It is almost laughable that all this light pollution could be avoided by simple additions or modifications to existing outdoor lights that waste light upwards. There are hoods that can be added to streetlights, city lights, highway lights, outdoor home lighting, and whatever other fixtures need them that are designed to allow the lights to do what they are meant to, which is of course to provide light on the ground. Outdoor lights are so poorly designed that they either waste a higher percentage of light upwards than down, or they do more harm than good by creating blinding amounts of glare. In most cases, one properly designed and directed light can do the work of two or three typical street lights. The glare caused by unnecessarily powerful and uncovered bulbs in street lights ends up counter-acting the very light that it is providing, cutting it's efficiency by fifty percent or more. That doesn't even take into account the percentage of light from the bulb that isn't even aimed down, but escapes upwards. Many people rationalize facts about outdoor lighting inefficiency and its effects with claims that more lights equal less crime. There are innumerable contradictory studies about the effect of outdoor lighting, poorly designed or otherwise, on the levels of crime in a given area. From what I have read the strongest arguments conclude that the levels of crime in a given area have less to do with the amount of outdoor lighting than with the various demographics and socio-economic strata of the people and businesses in that area. So if all that light doesn't have a measurable effect on crime, and the fixtures providing that light are poorly designed and waste money, then what good are they?

Clearly I've gone off on a rant, but I wanted to give you some of the thousands of words that this picture is worth. What I've presented here is just a cursory summary of this situation, but as a resident of one of the most light-polluted cities in America, Chicago, I am uniquely privy to the frustrations one who is aware of the problem faces. Human progress and colonization are indeed amazing facets of our species, and this picture is a remarkable visual demonstration of our power. However it serves as a reminder to me at least of our fundamental weaknesses and what we are missing. Is there anyone who wouldn't like to walk outside on a cloudless night and see a horizon-to-horizon river of light in the form of our galaxy, the Milky Way, beckoning us to look up and understand or at least enjoy it? The reason people all over the world don't marvel over the night sky that much anymore isn't because we've outgrown it or understand it fully - far from it - it's because we can't see it! Take back the night sky.

For more information visit the International Dark Sky Association's website at:
http://www.darksky.org/index.html