Night Time Sky Could Become Bluer Thanks To LED Lighting

Lee Rannals for redOrbit.com – Your Universe Online

Light pollution has been a growing problem recently, and as skylines continue to grow, the night sky becomes dimmer and dimmer. A new shift is taking place in lighting though, and researchers estimate that the color of the night sky may be changing as well.

Scientists writing in the journal Monthly Notices of the Royal Astronomical Society said they have used a new instrument to study how clouds affect sky brightness in urban areas, and how the future of LED lighting might change what we see when we look up.

“The current worldwide trend of replacing gas discharge lamps with solid state lighting, such as LEDs, will affect the radiance and spectrum of urban skyglow.” Christopher Kyba, physicist at the Freie Universität and lead author of the study, said in a press release.

Franz Hölker, ecologist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries and study author, said for nearly all of evolutionary history, clouds have made the night sky darker, just like what we witness during the day time.

In areas with artificial light, the effect of clouds is now reversed, and the size of the effect depends on the color. The team found that in Berlin, the blue portion of skyglow is 7 times more radiant on cloudy nights than on clear nights, and 18 times more for the red part.

The authors say that cloudy skies are now thousands of times more radiant near cities than they ever have been before. They believe the addition of this extra light affects predatory-prey relationships where the predator hunts using vision.

The sky is blue in daytime because the cloud free atmosphere is good at scattering short wavelengths of light. The scientists believe that unless special care is taken in design and implementation, a switch to whiter LED lights could make the sky brighter on clear nights.

The team believes that cities that have changed to solid state lighting should purchase lamps that emit no upward light, and use “warm white” lights with as little blue light as possible.

Last year, Professor Robert Stencel of Denver University invited me up to the Meyer-Womble Observatory on top of Mount Evans, a 14,148-foot mountain.

On top of the mountain, it is about a 35 mile sight line to Denver, giving you a beautiful view of the city. However, one thing I have never noticed before that Dr. Bob pointed out was how the color of the city affects the night sky. He showed a city across the way that used covers for their lighting, and how you couldn’t even see the clouds that hovered over them.

As a plane flew over the mountain, its lights lit up the clouds it was flying underneath, making the effect that lighting has on clouds all the more clear.

The “Red is the New Black” research paper makes an argument that is backed up by the astronomy community. In order to have a prettier sky, as well as keep our night-dwelling animal friends happy, we need to ensure we take proper action when lighting up our streets at night.

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