Our Night Skies May Be Undergoing A Change

Images of the night sky above Glacier National Park in the USA and above Berlin. In cities, clouds scatter artificial light back down towards the ground, drastically increasing the sky brightness. In natural areas, clouds make the sky darker. Credit: Left photo: © Ray Stinson, Glacier National Park, USA; right photo: © Christopher Kyba, Berlin, Germany.

When it comes to astronomy-friendly lightning, everyone knows that red is the preferred color for preserving night vision.At least its comfortable and easy on the eyes… and we’re used to it.

Now, scientists of the Freie Universität Berlin and the Leibniz Institute of Freshwater Ecology and Inland Fisheries in Germany predict night sky glow may be about to go through some dramatic changes worldwide… and red will become the new black. The research team predicts that the use of light emitting diodes in street lamps will cause the sky to become more blue. To investigate these changes, the team has created a measurement device used to demonstrate how the sky currently contains more red hues on cloudy nights as compared to clear ones. 

In their report, entitled “Red is the New Black” and published in the journal Monthly Notices of the Royal Astronomical Society, the investigative team has pointed out how new types of lighting technology has affected the color of urban lighting. Christopher Kyba, physicist at the Freie Universität and lead author of the study, explains: “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.” However, it will take a long time – and a great deal of study – to thoroughly examine the broad term affects on the ecology.

Lights (Photo credit: cycloctopus)

The new machine is already hard at work studying how clouds themselves can cause brightness in urban areas. “For almost all of evolutionary history, clouds made the night sky darker, just like they do in daytime”, said Franz Hölker, ecologist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, study author, and leader of the project “Verlust der Nacht” (Loss of the Night).

In regions illuminated by artificial light, the role the clouds play has now been reversed and the impact is judged on size – size determined by color itself. The research team studied the city of Berlin and discovered the blue end of the skyglow is seven times more radiant on cloudy nights than on clear… and eighteen times stronger in the red end.

Just what role does that play with the ecology? When it comes to nocturnal animals, the visual range most used are now thousands of times brighter near cities than throughout history. The researchers are confident this extra light has a dramatic impact on predator/prey relationships where lighting is everything – such as the relationship between owls and mice.

So what of color? We know the sky is blue during the day because a cloud-free atmosphere scatters the incoming short wavelength light. The scientists are trying to impart their concern to the public, because unless special care is considered when designing lighting, it could cause the sky to become much brighter on clear nights.

A switch to more white LED lighting might be economical – but it could be disastrous. A simple suggestion is to change to solid state lighting and be directional. Lights should be designed so they don’t emit upwards and should use “warm white” lights to keep the blue end emissions at a minimum.

Original Story Source: Royal Astronomical Society News Release.

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