Seeing the Light…from Space
By Ken Walczak
In my “day job” I often use images of the Earth at night taken from space to understand the impacts of light pollution down here where we live. Every once in a while I’ll stumble upon something that tells a story. This is one of those head scratchers that turned into part detective story, part horror story and part inspiration.
It all started when I was working on an experiment where I’m helping to identify the sources of artificial light at night (ALAN) affecting the Palos Preserves from afar. I was looking through satellite data that covered our region when I saw something that really stood out. Huh? What is that? There was a big bright blob clearly visible from space that caught my eye. I thought gas station, car dealership, maybe a community baseball field lit up for a game - things that are usually very bright. When I looked at the map I discovered it was none of those—it was a single home!
The discovery image. One of these homes is not like the others.
Ok, so how bright is this property really? I did a little digging. I pulled land use data to get an answer. With that data I was able to quantify the amount of light emitting from that one property compared to all the homes in the immediate area. Here’s how bright that house really is. In a two by three mile area around this one home there are more than 4,700 single family properties.
This one property on its own was brighter than 3,446 of them - COMBINED!
That means that you could add up the light emitted from 3,446 homes in the same neighborhood and they would not emit as much light as this single over-illuminated address. In fact, this one home emitted 12% of all the light generated by these 4,700 neighboring properties as seen from space. That’s a lot of light.
The next question is, does this address emit this much light EVERY night? Given that the satellite image I was referencing was from a single night in February, maybe they just happened to be doing something “special” that night. One of our DarkSky Chicago members lives in the area so I asked if she could drive by at night and see what was going on. Our ALAN nightmare was confirmed.
Roadside image of the brightest home in town.
From the road, on a summer night around 10:30PM, we can see countless fixtures blazing up into the night sky. It appears that nearly every tree, every growing thing, was wired for light and then some. In some cases, a single tree was lit by multiple lights - effectively sterilizing their property to any nesting bird or nocturnal animal - let alone the impact it must have on the neighbors and the community. Not shown here: a large, landscaped backyard that was illuminated like the front of the house.
Why?!
The glaring question became, “Why!?” I’d never seen anything of this scale before and yet I worry this is not going to remain a rare case. As my DarkSky Chi compatriot said, she noticed another home near this one with similar lighting. Most likely the case of a residential lighting company drumming up sales in the area with no regard to the damage they are doing to our shared world at night.
True, there’s no doubt this property is way out of the ordinary. And although they make an apt public warning poster for the egregious excesses of light at night, there’s a little more to the story. Looking back at the original data broken down by those 4,700+ single family homes, we can see the forest for the trees (unlike the birds). The brightest 152 homes accounted for 50% of all of the single family home light emissions in the area. That’s only 3% of all properties emitting half the light!
4,733 single family homes in a 2x3 mile area color coded by their brightness as seen from space.
Here’s where these data can help inform effective policy and action. Imagine you lived in this area and you cared about protecting your local nighttime environment—be it for the ecology, the quality of life, the view of a starry sky or energy savings. After recruiting some of your neighbors who also feel the same, you approach your local government. If you’re lucky or persistent, they may ask two questions, “What do you want done?” and “How much will this policy impact our residents?” Your answers can be, “We want to cut our residential light pollution in half!” (Gasp!) and “97% of home owners will not have to change a thing.” (Applause!).
Residential lighting is not the only—or even primary—source of light pollution in most communities, but it is one of growing concern. There’s something precious about where we live and sleep and our families spend most of their lives. With the advent of inexpensive LED technology, companies looking for new markets see homeowners as fresh territory for their services. There is a growing trend of selling light like this as a way to “distinguish” one’s property from their less illuminated neighbors. But that distinction comes at a cost—to our environment, our serenity, health and future. I recommend saying, “No thank you!” and you can add, “Here’s why…”
[If you’ve been approached by or received information from a lighting company who is selling services like this, we’d be interested to know. Please email information to info@idachicago.org]
