People who live in cities are rarely aware of the natural cycles in the sky; even the moon, powerful enough to read by, is barely noticed. The Civil Twilight Design Collective won the Metropolis Next Generation Design Competition with this wonderful idea: "
Lunar resonant streetlights sense and respond to ambient moonlight, dimming and brightening each month as the moon cycles through its phases. Utilizing available moonlight, rather than overwhelming it, saves energy and mitigates light pollution, while facilitating the urban experience of one of the most fundamental and beautiful cycles of nature."
They note that streetlights account for 38% of all electricity used for lighting in the US, and that 2/3 of Americans can no longer see the stars. A combination of LEDs and lunar resonance could save 90% of this electricity, and kids could see stars again. ::Lunar Resonant Streetlights via ::PSFK