Light pollution:
GreenLight
the good, the bad and the just-too-bright
BY ANNE L. FISCHER
SENIOR EDITOR
Four hundred years ago, Galileo
made his first astronomical observation through a telescope. Today he
wouldn’t recognize the skies because light
pollution prevents us from seeing the stars
clearly from the most populated areas of
the world. Most people in North America
and Eastern Europe are familiar with an
orangey glow in the sky over populated
areas. In fact, according to the Tucson,
Ariz.-based International Dark-Sky Association (IDA), the orangey sky glow over
Los Angeles is visible from an airplane
200 miles away.
Besides sky glow, there are other forms
of light pollution: glare, an overly bright
point of light; light trespass, light shining
on a location where it is not needed or
wanted; and light clutter, the presence of
too many bright light sources in one area.
Why it’s bad
Although light has many advantages,
allowing people to work and study into the
night, enjoy recreation in the evening, be
safe in dark areas and more, studies show
that excessive lighting has several drawbacks. First, according to David L. Crawford, co-founder of IDA, it’s a waste of
energy.
Light pollution also is having deleterious effects on human health. In 1987, Dr.
Richard G. Stevens, a professor at the
University of Connecticut School of Medicine in Farmington, proposed that electric
lighting at night disrupts circadian rhythms,
causing hormonal changes that could contribute to breast cancer.
Just as it creates problems for humans,
excessive light also harms wildlife. Biologists warn that a kind of cascading effect can take place, with light pollution
affecting animals, their habitat and so
on, to result in devastation of entire ecosystems.
The US Air Force’s Defense Meteorological Satellite Program (DMSP) has
taken satellite images of the Earth since
the 1970s; from these, researchers have
determined that about two-thirds of the
world’s population and about 99 percent
of the US population (excluding Alaska
Full-cutoff lighting reduces light trespass, sky glow
and other light nuisances. Photo by Bob Crelin.
Images taken by satellite show the extent of light pollution across the globe. Photo courtesy of NASA. Data courtesy of Marc Imhoff of NASA Goddard Space Flight
Center and Christopher Elvidge of NOAA National Geophysical Data Center. Image by Craig Mayhew and Robert Simmon, NASA Goddard Space Flight Center.
