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A DOE Solid-State Lighting video about sky glow, featuring commentary by Bruce Kinzey of Pacific Northwest National Laboratory.
Video courtesy of the Department of Energy

The use of lighting for both indoor and outdoor applications is growing around the world, driven by factors like increasing population and economic development that lead to increased electrification. Unfortunately, along with its benefits, the use of lighting potentially brings adverse effects as well, one example being sky glow. Sky glow is an increase in the apparent brightness of the night sky that can serve to reduce visibility for astronomical observation.

Increasing sky glow has been a matter of concern to the astronomical community for, literally, decades. There are natural sources of sky glow, such as a full moon, but we're concerned here with anthropogenic sources. Sky glow would be familiar to most people as that light dome that appears over populated areas that becomes visible, especially when you go outside of that populated area and look back towards it. That dome that you see is an amalgamation of all the light sources that have been exposed to the exterior environment. So this would include not only things like street lights and parking lot lights, but also building security lighting, interior building lighting from the commercial sector or from high rise buildings that's escaping via exterior windows, landscape lighting, sports lighting, vehicular lighting, and virtually anything else that's exposed to the exterior environment.

Uplight is that light that's traveling above a horizontal plane relative to the Earth. This is usually used to describe light that's emitted directly from a fixture, but it also applies to light that's being reflected from the ground or from buildings or from other sources that winds up traveling in an upward direction. Light traveling into the sky scatters via collisions with air molecules, dust particulate, and pollution, as well as water droplets, etc. And that scattering that occurs is what is responsible for the brightening of the night sky or sky glow.