You might remember that we’ve railed against light pollution before, and since we’ve been talking a lot about lighting this week, we figured now would be a good time to bring up the subject matter again. Today we’ve brought in guest writer / night sky activist Anthony Arrigo to talk about the overly-bright light continuing to plague our night skys..

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Light pollution affects the vast majority of the inhabitants of this planet. Right here in the US, 19 out of 20 people live under skies that are clouded by light pollution. In fact, more than 2/3 of Americans live in places where they can no longer see the Milky Way at night. This sad state of affairs that speaks volumes about the wasteful nature of our society. In a nutshell, Light Pollution is misdirected or misused light… generally resulting from an inappropriate application of exterior lighting. Light pollution is not simply a by-product of outdoor lighting. It is a by product of improperly directed lighting. With just a bit of thought and ingenuity, light pollution could be virtually eradicated.

Light Pollution, Return of the night, sky glow, starry nights (Images: International Dark-Sky Assocation. When the eastern power grid failed, from Ontario to New York City, in August 2003, it revealed something many city dwellers had never seen: from horizon to horizon, a sky full of stars. Then the power came back on.)

Light Pollution comes in several flavors… each with its own negative effects. These are:

Sky Glow Sky glow is light escaping into the night sky and causing a glow over urban/suburban areas. Sky glow is probably the most recognizable aspect of light pollution, and its the glow we see above cities and towns when viewed from a distance.

To put the problem in perspective, estimates place the cost to the US in the neighborhood of $5,000,000,000-10,000,000,000 annually. That’s $5-10 Billion dollars with a capital “B”. This is not the sum total of all outdoor lighting, this is just that portion of outdoor lighting that is so misdirected as to light up the night sky. This is an incredible sum of money to simply waste, and yet that’s exactly what we do year after year. In fact, the problem is actually increasing in magnitude and cost.

Light pollution and the return of the night

Glare Glare is light shining dangerously out into peoples eyes as they walk or drive by. Improving nighttime visibility is the number one reason for installing lights, and yet often times the lights we install to help us to see at night actually hinder our ability to do so. Sadly, improperly chosen exterior light fixtures are almost the norm.

Often times, an outdoor light fixture is chosen because it is “pretty” to look at in the daytime, with little consideration given for how it will perform at night. These glass fixtures that are so common nowadays often shine more light horizontally than down. This means that the majority of the light emitted by these fixtures put out is aimed right into your eyes. That doesn’t do anyone any favors when it comes to visibility…

Glare is the result of an excessive contrast between bright and dark areas. Glare is a particularly important road safety issue, as poorly shielded lights along roadways may partially blind drivers or pedestrians and contribute to accidents.


Light Trespass Light trespass is unwanted light shining onto a neighbors property or into their home. Light trespass is probably the most offensive form of light pollution as, often times, it affects people inside their own homes. Forget about sky glow robbing us of star-filled skies, light trespass intrudes into our most private lives. See if you have any light trepass in your own home… After dark tonight, open up all the curtains in your home and then turn off the lights. Wait a few moments for your eyes to adapt. Then, pay a visit to the to each room in your home. Odds are quite high that at least a few will show signs of light trespass. Take note of any light shining onto the ceilings or walls. This is light trespass. Look out the window and you can identify the trespasser. It is very likely one of your closest neighbors.

How can we stop this insidious spread of artificial light into our nighttime skies?

One of the easiest solutions is to:

Utilize “full cutoff” street lamps Full Cutoff fixtures are fixtures which directs all emitted light down towards the ground. These type of fixtures come in all shapes and sizes. The common, defining characteristic is that the light source is usually contained within a solid housing. By controlling where light goes, we can more efficiently use the light that is generated. Higher wattages are not needed, since we’re no longer wasting vast quantities of light.. As a result, these fixtures generally consume far less energy for a given lighting task, placing them high on the list for efficiency minded lighting engineers. Full cutoff fixtures provide better visibility with lower operating costs for a win-win situation.

full cutoff streetlamp

Light pollution is a common, pervasive problem in our technologically advanced society, yet it is not a natural outgrowth of progess, but instead a byproduct of our incredibly abundant and wasteful society. Light pollution only exists because we allow it to exist. The technology to prevent light pollution has existed for years, but it is the societal lack of concern that has allowed it to grow into a multi-billion dollar problem.

Outdoor lighting is a fact of life in our 7x24x365 society. We need outdoor lighting to enable us to get around and conduct our affairs safely. Proper outdoor lighting is not about doing without light – but instead is about using light only where, when and in the quantities needed. Using the minimum amount of light & energy for a given task should be the goal of every lighting engineer, and the standard against which all their work is judged.

Guest writer Anthony Arrigo is an avid astronomer and night sky activist. His company, Starry Night Lights, specializes in night sky friendly outdoor lighting products.