Dark night skies are a human right. They must be preserved.
We cannot allow our lights
to shine up. Because of the intensity
of modern urban lighting, with our mercury vapor
and high pressure
sodium vapor lights both in this country and abroad, it has become
necessary that some areas be kept free of this increasing light pollution. There
must be some place at least in this country where anyone can go to see what the Universe
looks like through dark, transparent skies.
We encourage all those who have telescopes to get them out for public use. And
telescopes are, of course, a must if the public is to understand the Universe beyond
confines of our solar system. But light pollution in our major
cities is so bad, that only a
few of the brightest stars can be seen
with the unaided eye. The amateur astronomer in the
city can normally
only show the public our moon and the five brightest planets. There are
nights like tonight when none of these are in our night sky. Even armed with large
telescopes and pollution filters it is hard finding, not to mention seeing, some of the other
spectacular sights of our Universe such as open and globular clusters, nebula, and other
galaxies. Measures could be taken to cut down light pollution, save energy, and still
preserve safety and visibility at night.
The part of signboard and street lights shining upward
is wasted on illuminating the
night sky. The lights shining directly
in your eyes cause your pupils to get smaller,
making it harder for
you to see in dimmer light./ Right now, there is an effort to make
Mexico the first National Dark Sky State. Most of New Mexico is already dark. If
all the street lights in New Mexico were low pressure sodium, as they are even now in
Alamogordo, and if, in addition, they were shielded to 45 degrees off the vertical
downwards, then we would only need a small fraction of the lights we now have, because
the lights would light the roadbed rather than shining in the observer's eyes. When
golden Gate Bridge was first opened in 1938, the bridge lights
were shielded in this way,
so that as you drove down the bridge,
you saw one light after another as you drove under
it. The rest of
the lights didn't shine in your eyes. The reason we need so many lights
is because the lights themselves are shining in your eyes, and keep you from seeing
what the lights were designed to illumine.
I'm told that in Cairo, Egypt, you're not allowed to drive in the city with your headlights
on, with the result that from downtown Cairo you can see the Andromeda galaxy with
your bare eyes. The only reason you need your own headlights on in our cities is because
other headlights are shining in your eyes. And when you look down the street, even
streetlights from blocks away are shining in your eyes. If the
street lights shone only
downwards, so that they could not be seen
from a distance, a very much smaller number
would suffice. And under
those conditions, even our headlights might not be needed in
cities. Headlights would of course be required on the freeways, but it's the cities, not
the freeways, that are the major contributors to light pollution.
Some may argue that we need bright lights
for security. But even security lights should
shine on the burglar
and not in the eyes of the police officers.
If the manufacturers of the street-lighting fixtures were convinced of the efficacy
properly shielding their fixtures, they could supply shielded
fixtures to the municipalities.
This would enormously cut down the
lighting bills. I am told that two and a half billion
a year are wasted in lighting the night sky in this country alone.
The preference for low-pressure sodium lights is
related to the problems of the
professional astronomers, whose images
are fogged by the plethora of spectral lines
arising from our cities.
Low pressure sodium lighting has a minimum of spectral lines.
also makes light pollution filters used by amateur observers more effective.
*If we can cut down all extraneous lighting in our
cities, and all lights shining up,
amateurs will be able to show
more of the public their Universe. Amateur Astronomers
are also a
vital part of the constant lookout for previously undiscovered comets and
asteroids that might pose a threat to earth. When these objects are at a safe distance from
us, they are far to dim for amateurs to pick up from the cities of today, and there are
simply not enough professionals to do the job.
If we can cut down all extraneous lighting
in New Mexico, and all lights shining up,
New Mexico as the National
Dark Sky State will become a haven for astronomers. For
research it is not easy in the contiguous United States to find better weather.
And if astronomical research is to continue, it is incumbent upon all of us to make it
We are grateful to all those who have taken the trouble to shield their lights, and to all
towns that have lighting ordinances. And it is our fervent hope that the public at
will become sufficiently aware of light pollution to insist
on its curtailment.
One of the reasons we Americans like to spend our summers in the national parks is
because there we get to see the unlit sky. One of the efforts of the Sidewalk Astronomers
is to get big telescopes into the national parks so that the visitors will have a
understand the Universe in which we live. As Graham Loftus
said in New Zealand,
"What we need is a big telescope in every village and
and some bloke there with the fire in his eye who
can show something
of the glory the world sails in."
Dark night skies are a human right and must be preserved.
Adapted from an article dated June 5, 1995 by John
L. Dobson, founder of the Sidewalk
Astronomers, with additional material
added by Bill Scott, president of the Sidewalk