stronomers have been looking for evidence of alien civilisations for over 60 years now. Known collectively as the Search for Extraterrestrial Intelligence (SETI), much of the work to date has involved some fairly restrictive assumptions. In particular, it tended to focus on the detection of radio signals, assuming the aliens are blasting these out at high power either as a deliberate attempt to announce their presence, or for other reasons of their own. A second assumption behind traditional SETI is that the alien signals are continuous
