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
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
Here's a picture of Los Angeles showing
typical urban night-time lighting
Here's a picture of the United States at
night from space:
Where would you go on this map to see the
stars as they were made to be seen?
It is better to blow out one
candle than to curse the light.
to Tom Jonard's Astronomy page