With the first direct detection of gravitational radiation by LIGO, we've entered a new era in science. Gravitational wave astronomy promises to be the most exciting field in the physical sciences for the next decade. So should we start looking for signals from ET in this data?
Until now, all of our attempts to detect signals from extraterrestrials have relied on electromagnetic radiation, mostly radio. But what if we're completely missing the boat? Maybe other civilizations are so advanced that they've been using gravitational radiation all along -- after all, it penetrates almost perfectly through the universe.
While I have no doubt that people will comb through the gravitational wave data to search for signals, it's almost inconceivable that a civilization would use this means of communication. The same thing that prevents gravitational radiation from being absorbed as it pulsates through the universe is what makes it impractical as a means of communication. Gravity is an incredibly weak force, and the energies needed to produce a detectable signal are enormous. To produce a signal like the one LIGO detected, you would need to get your hands on a couple of black holes much larger than the sun, and move them around at will. OK, so maybe you can't find any black holes. A couple of neutron stars would work. Any civilization powerful enough to manipulate neutron stars or black holes could just as easily rearrange the stars in their galaxy to spell out messages: "Eat at Joe's!" A similar idea is the basis of the Fredric Brown short story, "Pi in the Sky" (easily available online if you want to read it). So don't hold your breath -- I don't think SETI will move over to the LIGO project anytime soon.