Red Dawn

One-fifth of us cannot see the Milky Way        NASA photo

By now, everyone in or near an urban area is used to the reddish glow of the night sky. But what is that doing to us and the flora and fauna?: http://blogs.discovermagazine.com/crux/2012/08/23/why-is-the-night-sky-turning-red/
As we turn to more energy-efficient lighting, our nights may turn bluer again, but LEDs might have their own downsides: http://news.nationalgeographic.com/news/2012/08/120814-lighting-energy-leds-bluer-night-skies-technology/