Lightscape / Night Sky
NOAA/NGDC/DMSP Digital Archive
Two-thirds of Americans cannot see the Milky Way from their backyards and nearly all live in places with measurable light pollution. Dark night skies, for the first time in history, are becoming an extinct phenomenon. Researchers predict that at the current rate of increasing light pollution, by 2025 no dark skies will remain in the continental United States. The two main culprits are light and air pollution.
Light, a natural and harmless part of our world normally, is out of place at night. Light pollution is defined as the illumination of the night sky caused by artificial light, a problem born with the invention of the light bulb only 125 years ago. Most light pollution, or sky glow, is completely unnecessary and is caused by bad lighting fixtures. Many lights installed in homes, businesses, street lights and billboards are too bright and aimed upwards or sideways. The light scatters through the atmosphere above and brightens the night sky, diminishing the view of it.
Air pollution also decreases night sky visibility, just like it does in the daytime. Air pollution particles increase the scattering of light in the atmosphere, increasing sky glow.
Great Basin National Park offers astronomy programs throughout the summer.
National Park Service Night Sky Team
National Parks harbor some of the last remaining dark skies in the country. The National Park Service Night Sky Team was formed in response to the alarming increase of light pollution even in National Parks. The team documented light from distant cities affecting night skies over 200 miles away. The lights of Las Vegas, Nevada, for example, were visible from 8 different national parks.
The Night Sky Team visited Great Basin National Park in October 2004 and 2005 and tested the light levels to determine the darkness of the night skies. The results? Great Basin's night skies are among the darkest in the country, providing visitors a rare opportunity for stargazing!