The mainstream search for extraterrestrial intelligence (SETI), now running for more than 50 years, relies on the hope that aliens will either leak or broadcast radio signals out into space.

In recent years, however, humanity’s own radio voice has softened with the shift to cable and Earthward-pointed satellite broadcasts, while our cities have grown brighter. If we are any guide, alien hunters should look to city lights instead, argue Loeb and Edwin Turner of Princeton University.

Lisa Grossman, “Alien bright lights, big city could reveal ET," New Scientist, 3 November 2011

Fascinating to me in how it reveals humanity’s limitations: the only way we know how to look for life is to look for ourselves. Right down to very specific, and potentially unique, forms and uses of technology. I mean, lots of scifi’s most utopian imaginations of aliens are those in which vast civilizations are sustained without significant disruption of natural patterns. But if such civilizations exist, they are the ones we’re least likely to find.