From Elizabeth Howell, at Space.com:
Would it be easy to determine if the source of a mysterious radio signal was aliens? Probably not. A new paper argues that contact with extraterrestrials will likely be discovered through a prolonged, incremental process rather than an instantaneous eureka-like moment. Eureka — what the ancient Greek mathematician Archimedes allegedly said when he cracked a tough science problem about water displacement — tends to be the exception in science rather than the rule.
Cirkovic said in an email that the community involved in the search for extraterrestrial intelligence (SETI) should instead be prepared for a process that would take a very long time. It may take decades as the SETI community looks at all the reasons aliens might not be the source of a mysterious signal. More.
For one thing, a signal may not have been intended for us. If ever decoded, it could just be one side of a nasty let-it-all-hang-out dispute between neighbours.
See also: Astronomer: Why the search for aliens is a good thing
But surely we can’t conjure an entire advanced civilization?
How do we grapple with the idea that ET might not be out there?