Tom Jonard's Light Pollution Page

When you say the word pollution your listener is apt to think of dirty water and litter by the side of the road.  But there is pollution of another kind that does not involve dirt or trash and even seems benign.  There is a pollution of the dark night sky -- stray light -- that is pollution because like all pollution it is an artifact of human activity and it sullies the natural order.  Aside from clouds (and here in Ohio we have our share of those) what most gets in the way of seeing the stars these days are the lights -- street lights, security lights, night-time activity lighting, and advertising lighting.

Unless a neighbor's security light is shinning in their bedroom window (a type of light pollution called "light trespass") the average person is likely to say, "So what?  We have to have lights at night to see where we are going and what we are doing."  And they are right.  My point is not to turn out the lights but to call attention to something else.  Come back to the hilltop above with me.  What  do you see?  You see thousands of street lights beaming their light into your eye on a hill miles away -- not the streets on which they were meant to shine!  You can see them because some of their light is inadvertently used to dimly illuminate your hilltop lookout.

For the standard cobra-head light fixture about 22% of the light produced is wasted in this way.  It not only illuminates distant hills, it shines off suspended dust and water in the air and makes the sky glow.  And that faint glow is the light pollution that out-shines the fainter stars.  From a distance a city looks like a dome of light on the horizon.  And we pay for this display.  We could have 22% more light where we want it without paying more in taxes or we could have a 22% reduction in the cost of lighting our streets if we replaced poorly designed fixtures with full cut-off fixtures (which direct more light down).

So what can you do about it?  Well if you've gotten this far you've taken the first step:  You've become aware.  A simple second step we could all do which would have a direct impact would be to ask your local lighting authority to replace the street lights in front of your house.  You might think they will ignore you but you might be surprised and you'll never know until you try.  I actually live in Westerville, OH which is a suburb of Columbus and the City of Westerville replaced three lights around my house upon request.  The result is that observing from my backyard is much more practical and enjoyable because it is darker.

You should also be aware that all street lights must and will be replaced over time.  Mercury vapor lights deteriorate from the moment they are turned on, producing less and less light year after year.  While they are being replaced anyway they should be replaced with something more efficient like a full-cutoff fixture.  So another thing you can do is write to the local lighting authority and let them know that you are concerned and that you would like to see old lighting replaced with full cut-off fixtures and the same used in new construction.  Again my home town of Westerville has been using these in all new road construction and the difference is remarkable (due to the reduced glare, which I won't go into here but which is another concern for effective lighting).

Sometimes I think that some amateur astronomers bury their heads in the sand over this topic.  They do this by giving up on city and town viewing and going to their "dark sky" site where they brag that the "light dome" from this or that town is only 5 degrees on the horizon.  Well I've got news for you all.  Twenty-five years ago that light dome was not there!  And 25 years from now it will be worse, everywhere!  If we had a time machine to transport an amateur from 25 years ago to observe with us today they would probably laugh at us for what we call a "dark sky" site.  We are losing the sky and now's as good a time as any to do something about it.  It is the only time anything we do will have an effect on our lives.

There is a lot more to this issue than seeing the stars at night the way God intended and using tax money efficiently.  There are also issues of light trespass, how glare reduces the ability to see at night (especially for older people like me), whether lighting helps or hinders criminal activity and the impact of artificial light on the natural day/night cycles of animals.  For more information go to the web site of the International Dark-Sky Association.

Here's a picture of Los Angeles showing typical urban night-time lighting
sprawl:

Here's a picture of the United States at night from space:

.Return to Tom Jonard's Astronomy page