Eastern Seaboard and Midwest glow
in this satellite image.
All this light is wasted,
say astronomers, who argue that reducing
light pollution would
also save money.
International Dark Sky Association
Mount Wilson Observatory,
high above the
Los Angeles basin
in the San Gabriel Mountains of
does it take to sell
a car --when the store
POSTED 20 APRIL 2000
In most cities, there's little point in gazing at the sky -- unless you're
fascinated by the sight of a few stars and some airplanes against a glowing
background. If you have not seen a truly dark sky, you may not know that the urban glow conceals a network
of uncountable stars in intriguing constellations.
Whether or not you've
given the subject a second thought, astronomers are certainly having nightmares
about the rapid brightening of the night sky. Already, light pollution
has ruined major observatories like California's Mount Wilson for deep-space
astronomy. An equally pressing but invisible problem emanates from radio-wave
pollution. As the world lunges toward a wireless future, the
transmitters and satellites at the backbone of the global network are
drowning faint signals from distant galaxies.
and radio pollution pose a growing problem to astronomers who use ever-more
sensitive instruments to view the strange conditions of the early universe.
After all, astronomers can only "see" objects that are brighter than the
background. When the background brightens, faint objects get lost.
It's ironic and
a bit sad, says Johannes Andersen, general secretary of the International
Astronomical Union. Photons -- particles of light -- that have traveled
for literally billions of years may get swamped by pollution in the last
thousandth of a second before they reach a telescope. Simply putting telescopes
in space is not a surefire solution, he adds, due to staggering costs
and the increasing hazard of space
just astronomers who suffer, says Andersen. Lots of people find the ever-brightening
night annoying, and animals that are programmed to prefer the dark may
avoid brightened habitat. Sea turtles can get lost searching for a beach
to lay eggs, and their hatchlings may confuse over-lit beachfront resorts
for the ocean horizon, wasting precious energy needed to find the sea
and escape predators.
solution to light pollution is pretty simple, according to these outdoor
Avoid making excess light, and use reflectors and shields to direct light
toward the ground. Tucson, Ariz., for example, is credited with a forward-looking
plan to reduce light pollution at the nearby observatory at Kitt Peak.
Wasted light, Andersen
emphasizes, produces glare that "prevents you from seeing rather than
helps you." Since that wastes money, Andersen hopes that economics may
someday overpower the urge to turn night into day.
As astronomers try to stem visible light pollution, they face a second,
more insidious form of pollution: radio waves. This form of electromagnetic
radiation gives a picture of cool objects in the universe, and may carry
signals from remote civilizations.
To grasp the delicacy
of radio astronomy, Andersen urges you to consider this fact: "The total
radiation collected by all the world's radio telescopes during the last
half century would suffice to light an ordinary flashlight bulb for a
of a second!
Unlike light pollution,
which tends to be local, communications satellites cover essentially the
entire Earth, threatening every potential site for a radio telescope.
If we could see radio waves, Andersen stresses, "We'd not have a dark
sky at all."
have some protection from regulations that have placed certain frequencies
-- such as the radiation emitted by hydrogen -- off limits to broadcasters.
However, some satellites, like those in the Soviet global positioning
system, are notorious for emitting noise at frequencies outside their
assigned slots, Andersen says. And as radio astronomers peer further out,
they detect ancient radio signals from objects that are rapidly moving
away from us. Due to the Doppler effect, these signals appear in unprotected
bands. More pollution is on the horizon: Andersen notes that a recent
United Nations conference heard about plans to launch 1,700 communications
satellites in the next decade. And astronomers are also losing sleep over
proposals to launch giant satellites carrying advertising to be "enjoyed"
from the ground.
It doesn't take a genius to realize that astronomers are in the unfortunate
position of standing in the way of progress, defined as advertising, universal
communications and urban growth. Their current strategy is to prevent
disasters rather than trying to clean them up. "We want to negotiate agreements,"
Andersen says. "We don't imagine we can prevent satellites from being
sent up ... but we're trying to be proactive, to take action with authorities,
trying to get rules in place before things get set up, rather than find
out about them when it is too late."
-- David Tenenbaum