Artificial lighting in space could indicate alien life

MSNBC : Researchers have proposed a novel way of detecting extraterrestrial life: looking for artificial illumination. They hypothesize that if humans light up their cities at night, perhaps other beings do as well. In a paper submitted to the journal Astrobiology, Abraham Loeb of Harvard University and Edwin Turner of Princeton University suggest looking at the change in light from an exoplanet as it moves around its star; if the orbit is elliptical, the amount of reflected light will change with the distance from its star, but the amount of artificial light should remain constant. Unfortunately, at present, Earth’s day side is some 600 000 times brighter than its night side. For the method to work, any artificial brightness of the night side would have to be comparable to the natural brightness of the day side. Nevertheless, as radio-based searches have yet to turn up any sign of intelligent life on other worlds, and as new and better telescopes are being deployed, searching for brightly lit alien cities may one day prove viable.