Light Pollution

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Both of the elementary school students at my house are studying astronomy this month, which means, weather permitting, we’ll be outside three nights a week identifying constellations and tracking the progress of the moon and the planets. If you live in town and you’ve tried this yourself, you know we’ll be prevented from seeing much of what’s out there by the glow of artificial light in the sky.

Sky glow, which obscures our view of the heavens at night, is the most commonly recognized effect of bad lighting, or light pollution.

But bad lighting also causes a number of other problems. It creates glare, which is light that shines in our eyes rather than on things we need to see, and light trespass, unwanted light that strays into our yards and windows. Bad lighting is also the source of what some call light clutter, the unappealing and visually confusing nighttime environment so common in modern cities.

Beyond its undesirable visual effects, bad lighting also wastes energy—a lot of it! One reasonable calculation puts the cost of wasted light in the U.S. at one billion dollars a year. The energy used to produce that wasted light would equal at least six million tons of coal, or twenty-three million barrels of oil.

Why is such waste so widely accepted? Because we’ve come to equate more light with better safety and security. But that is simply not the case. In fact, overly bright, misdirected light can actually do more harm than good. Light that shines in our eyes prevents us from seeing hazards as we walk or drive at night. Widely scattered, bright light also creates hard shadows, which can conceal criminals while making victims visible. Worst of all, excessive, poorly designed lighting can make us feel safe when we should actually be on guard.

The principles of good lighting are really pretty simple. Good lighting shines down, only where it is needed, rather than sideways, where it causes glare, or up, where it causes sky glow. Good lighting is bright enough to light only what needs to be illuminated, and does not
create harsh transition zones between light and dark areas. Good lighting is also energy efficient and on only when it is needed.

It’s actually pretty easy to spot well-designed light fixtures once you know what to look for. They have the light source high, with a top and sides that direct light downward. It’s worth noting that you can illuminate even large areas such as parking lots and ball fields with such fixtures.

In poorly designed fixtures the light source is not fully shielded, either on the sides or at the top. The worst offenders are drop-lens cobra fixtures—the ones that loom over our arterial streets in town and the lighted portions of many interstates. Most locales have a policy of replacing these as they wear out with far superior flat lens fixtures that shine light only where it’s supposed to go. Other poorly designed fixtures include the super bright barn light fixtures found on power company poles, and decorative globes that shine light in all directions

You can do your part to reduce light pollution by replacing poorly designed fixtures on your property with well-designed ones. And remember as you do this that you’ll likely recover the cost of new fixtures with the money you save on electricity to operate them. If you want to go beyond that, check in with the Champaign-Urbana Astronomical Society or the U of I Astronomical Society concerning local efforts to promote dark skies.

With good lighting we’ve got nothing to lose, and an entire universe to gain.