Detectability of Extraterrestrial Technological Activities

Radio Waves

       In the last  thirty  years,  most  of  the  SETI  projects have been
       developed in the radio region of  the  electromagnetic  spectrum.  A
       complete description of the techniques that all the present and
       near-future SETI programs are using for detecting extraterrestrial
       intelligence radio beacons  can be found elsewhere  (e.g.,  Horowitz
       and Sagan, 1993).  The general hypothesis for this kind of search is
       that there are   several   civilizations  in  the  galaxy  that  are
       transmitting omnidirectional radio  signals  (civilization Type II),
       or that these civilizations are beaming these kind  of  messages  to
       Earth.  In this  section  we  will discuss only the detectability of
       extraterrestrial technological manifestations in the radio spectrum.