I distinctly remember reading the German equivalent of the National Geographic Magazine in my late teens and being in total awe about an image of the earth at night. I can’t quite remember what exactly fascinated me so much about the image. But I remember purchasing it in poster format and having it pinned to the wall in my room.
The image is back!
Well, a newer version of it. NASA just published night lights images that are a product of collaged satellite imagery taken between April and October, 2012.
I am hooked again and began to study the images in more detail. Because Chicago is home, I found the North American section of the images the most intriguing.
What is the source of this fascination? The amount of wasted light energy.
Think of it! Most, if not all, of the light that reached the satellite missed its intended target. It is poor lighting design. Rather than directing the light to the ground, we waste more than necessary into the skies. And there is a name for it: Light pollution.
I wish I still had access to that image from about 25 years ago, so that one could compare now to then. Would there be a visible difference? By how much did light pollution increase? Who knows, NASA is probably already working on some “now vs. then” comparison images.
Taking a closer look at Chicago; the only landscape feature that we can make out is Lake Michigan. Everything else is overwritten by the glare. It has been rumored that Chicago is among the most overlit cities in the U.S. And one way or another, we all have to pay for it.
The National Geographic Magazine issue of November 2008 was titled “The End of Night”, with an enticing cover page. The feature article (Our Vanishing Night) had another image of Chicago that told the story of mis-appropriated light energy.
The article and images caused quite a stir as they were published right at the time when our former Mayor Richard Daley pushed to have the height of the street light poles and their spacing reduced. The net sum of that directive would be even greater light pollution at increased energy cost, due to an increase in the actual number of light fixtures.
I am not sure if those street lighting guidelines are still in place, or if common sense prevailed and led to the abandonment of the guidelines.
When turning to the sparsely populated southwestern U.S. (norther Nevada), a different picture emerges. Here, actual landscape features are visible, illuminated by the moonlight.
Maybe the lesson of these images is not just about the wasted energy due to light pollution, but also that one sometimes can see more in the dark. How about this as a concept for lighting design?
Not sure what I mean? The Department of Physics, Florida Atlantic University, has a web page that goes into the details of why overlighting impairs our ability to see beyond the light domes and safety issues associated with light pollution.
If you are not into reading that much right now, take a look at these two pictures from the International Dark Sky Association.
One would have thought that more lighting would let us see more. As counterintuitive as it seems, the opposite is often the case. It’s less about the amount of light but more about the smart and targeted output.
Similar demonstrations to the one above can be found on the web page of the Illinois Coalition for Responsible Outdoor Lighting. The web page also devotes one section to the style of light fixtures used in Chicago and includes some metrics to the probable amount of energy wasted.
Too anecdotal? No problem. Out of all places, Chicago was subject to a scientific study that looked into the correlation of alley light levels and crime rates: The Chicago Alley Lighting Project. What did the report find? An increase in crime activity with an increase in light levels.
May be less really is sometimes more.
Even though our small project is only one tiny speck in this big picture, I feel better than ever about our choice of dark sky fixtures for the front door.
I have to think about what we could tackle next to help us stay “on the dark side.”