When you're looking for signs of an extraterrestrial civilization, you can take two basic approaches. Think back to Frank Drake's initial SETI experiment at Green Bank in 1960, when because of limited resources and time he chose specific targets: Epsilon Eridani and Tau Ceti. The choice made sense at the time because both were nearby stars and SETI, fresh off the classic paper "Searching for Interstellar Communications" by Philip Morrison and Giuseppe Cocconi, was just beginning to define a methodology. Drake studied his targets near the 1.420 GHz frequency -- the 21 centimeter hydrogen line -- that the authors had suggested. Of course, sky surveys are also possible, of which SETI@home may be the most widely known. Here the idea is to make no assumptions whatever about the location of a SETI signal and observe the entire sky. SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is an attempt, for example, to analyze radio telescope data...