Enjoy the darkness

¡SkyCaramba! Weekly astronomy blog for the week ending April 11, 2015

An example of a poorly chosen light fixture sending light in various direction including the sky.A lot of people, even a few who like astronomy, do something that’s harmful to it. Our modern lifestyles require outdoor lighting at night. Poorly chosen and poorly placed lights make it hard or impossible to see most of the stars in the sky. Many astronomy organizations have chosen the week of the new moon in April every year to be International Dark Sky Week. They want to promote respect for the darkness and keeping the light only where it’s needed.

No one is arguing against any and all outdoor lighting. Light the path to your door if you need to. We’re just asking anyone and everyone putting lights outside to consider how much light is really needed and where. Then choose the appropriate light fixture for the job.

A bare light bulb sends light in almost all directions. But does it need to? If your light is meant to show people where the sidewalk and steps are, you don’t need light shining toward the sky. If you need to light up the yard so you can see prowlers, several carefully placed dim lights will fill in shadows. But one bright light will create shadows for someone to hide in. It may even make your neighbors see spots instead of burglars when they look out the window to find out what some noise was.

The best light fixtures for outdoor use shield the bulb from the view of most passersby. A reflective surface inside the fixture directs light to the proper place. And when all of the light can be directed to the right place, you don’t need to generate as much light for the task in the first place. In other words, a dim bulb in a shielded fixture can light the area better than a bright bulb out in the open. Not only does a properly chosen fixture save the night sky, it saves energy.

Light wash not only keeps people from enjoying the stars; it also disturbs wildlife. Possums and badgers need the cover of darkness to eat so they aren’t eaten themselves. Some birds eat by day and eat too much when they don’t know it’s nighttime. Sea turtles that need dark beaches to nest on have fewer places where they can mate.

It would be nice if everyone voluntarily decided to leave outdoor lights off or to use only the minimum light needed and direct it carefully downward. But in some places, people interested in preserving dark skies have found it necessary to lobby legislatures and city councils for restrictions. That started with Lowell Observatory in Flagstaff, Arizona where astronomers asked the city council to prohibit searchlights for use in advertising.

Unfortunately, there’s much work to be done. Everyone who cares about this issue needs to pitch in. From April 13 to 18, 2015, we can make it a point to tell our friends and neighbors that we are turning off the unnecessary outdoor lights out. We all deserve to enjoy the darkness.