ENVIRONMENT

Taking in the view from Gerlach, Nevada. (FiveThirtyEight)

What is light pollution?

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit, including today’s MapMaker Interactive map.

Discussion Ideas

• The FiveThirtyEight essay details a visit to the least light-polluted community in the United States—the tiny town of Gerlach, Nevada. What is light pollution?
  • Light pollution describes the artificial illumination of the night sky. Light pollution can limit visibility of faint stars and other celestial objects.
  • At least one study describes light pollution as the alteration of natural lighting levels by anthropogenic sources of light. Natural lighting levels are governed by natural celestial sources (mainly the Moon) natural atmospheric emission (airglow), the stars and the Milky Way, and zodiacal light. Natural phenomena may influence light, including atmospheric conditions (such as the presence of storm clouds) and snow cover.

 

• Why is artificial light considered “pollution”?
  • The National Park Service identifies the night sky as a cultural resource, a natural resource, and an economic resource.
    • Cultural Resource: Through light pollution, “we have lost the connection with our roots, of literature, of philosophy, of science, of religion—all are connected with the contemplation of the night sky. “Every culture known to us throughout our history has created constellations and has read the sky as a way to deal with the mystical,” says one dark-sky enthusiast in Nevada.
    • Natural Resource:
      • Professional and amateur astronomers depend on dark skies for accurate Earth-based optical observations.
      • “Nearly half the species on Earth are nocturnal—active at night instead of during the day. The absence of light, natural or otherwise, is a key element of their habitat. Many species rely on natural patterns of light and dark to navigate, nest, mate, hide from predators, and cue behaviors … For example, migrating passerine birds reference stars to fly at night and can be disoriented by city lights and towers. Sea turtle hatchlings orient toward the brightest light on the beach, but instead of being drawn to the safety of sparkling waves on the ocean, they are often drawn toward roads and parking lots, where they quickly perish. And amphibians, with vision far more sensitive than that of humans, are prone to be disoriented by light.”
      • In humans as well as animals, “[c]ircadian disruption can alter not only sleep cycles but also core body temperature, hormone levels and gene expression … [one scientist] has explored the links between electric light and some of the so-called diseases of modern life: obesity, diabetes, depression and cancer.”
    • Economic resource:
      • Over-illumination (such as lights that shine upward into the sky, or that illuminate empty areas or buildings) wastes energy and money.
      • “Astrotourism” is a small but growing industry that includes stargazing programs, night walks, full moon hikes, and other such activities.

 

• When was light pollution identified as an issue?
  • Almost as soon as the switch was flipped on the first electrical light. FiveThirtyEight notes that in an “1887 letter to the editor of Science, one G. Thompson observed that ‘some disadvantage or evil appears to be attendant upon every invention, and the electric light is not an exception in this respect.’ His hometown, Washington, D.C., had recently installed outdoor electric lighting—and spiders followed. Their prey was plentiful in the new light, Thompson reasoned, but their webs blocked views and dirtied surroundings. And, he noticed, the spiders seemed to ‘take possession of the portion of the ceiling of any room which receives the illumination.’”
  • The first dark-sky ordinance in the U.S. was passed in the city of Flagstaff, Arizona, in 1958. It banned searchlights in order to protect the dark skies for research at nearby Lowell Observatory.
  • The first national light-pollution law wasn’t enacted until 2002, in the Czech Republic.

 

• Take a look at the second bookmark in today’s MapMaker Interactive map, which uses our “Lights at Night” layer. Why do you think so many places not illuminated by artificial lights are not official “Dark Sky Communities”?
  • Paperwork, basically. Communities have to apply to be designated a Dark Sky Community. Part of the application process includes having a local organization that “has shown exceptional dedication to the preservation of the night sky through the implementation and enforcement of a quality outdoor lighting ordinance, dark sky education and citizen support of dark skies.” Many genuinely dark-sky communities in rural Africa, South America, Australia, and Northern Asia simply have not invested in these local nonprofit organizations.

 

• Take a look at the third bookmark in today’s MapMaker Interactive map, which uses our population density and “human footprint” layers. What are some relationships between a community’s light pollution, population density, and land use?
  • Urban areas, which have high population density, are much more vulnerable to light pollution.
  • Regions whose land-use includes a stable and widespread electrical grid are more prone to light pollution. Homes, businesses, schools, and hospitals are often well-lit and even over-illuminated in the developed world.

 

• How can we combat light pollution?
  • Use timers to reduce or eliminate lighting when it’s not needed.
  • Direct light to areas that need it, and not upward (when lighting outdoor areas), or toward walls, windows, or ceilings (when lighting indoor areas).
  • Encourage businesses to eliminate “daytime lighting” outdoors.
  • Participate in Globe at Night, an international citizen-science campaign to raise public awareness of the impact of light pollution. Citizen scientists measure and submit their night-sky brightness observations. It’s easy to get involved—all you need is computer or smartphone, and these 5 Simple Steps!

 

TEACHERS TOOLKIT

FiveThirtyEight: The Darkest Town In America

Nat Geo: Nearly 80% of U.S. Populations Can’t See the Milky Way

Nat Geo: Where are the world’s dark-sky communities? map

International Dark-Sky Association: International Dark Sky Communities

National Park Service: Night Skies

Globe at Night