Dark Sky
From Slackerpedia Galactica
The mythical Holy Grail of astronomers. Basically, a location that has little to no light pollution to interfere with observing. Studies suggest patches of dark sky may eventually die out on Earth.
Generally, major downtown urban areas have "mag 2" skies, which means one can see stars that are magnitude 2 and brighter. Suburbs of major urban areas can get down to 4th magnitude (or 4.5). A typical "dark sky" has seeing that is limited by the human eye, usually magnitude 6-6.5. The Milky Way will appear as a bright path through the sky. Sometimes it can be difficult to make out constellations due to all the stars.
Anywhere away from lights will have good skies. Deserts, mountains and cruise ships typically have dark skies. Sometimes, dark skies can be seen from airplane windows. If one is flying during a meteor shower, be sure to ask the pilot to make an announcement to the passengers. They will sometimes dim the cabin lights also.
Olber's Paradox
In 1826, the astronomer Heinrich Olbers asked, "Why is the sky dark at night?" Basically, if the Universe is infinite and full of stars, then the combined light of all the stars should make the sky glow. But it doesn't - at least, not because of other stars. It has a complicated answer, but basically it's because the Universe is too young for some of the light to have reached us yet and also because very old light has been red shifted out of the visual spectrum.
External Links
- Dark Sky Locator
- International Dark Sky Association
- Dark Sky Switzerland
- Dark Sky Society
- Olber's Paradox Tutorial
- Dark Sky Friendly Outdoor Lighting from Starry Night Lights (commercial link)
