We have a problem. In a 10-billion-year-old galaxy there should have been ample opportunity for at least one species to escape its own mess, and to spread across the stars, filling every niche. That this species doesn’t seem to have come calling leads to Fermi’s Paradox—if life isn’t impossibly rare, then where is everyone? Efforts to scan the skies for signs of intelligent life have come up blank too, adding to the puzzle. Perhaps the vast gulfs of interstellar space and the narrow windows of time for communicative species to exist within shouting distance of each other are to blame. Intelligences might be like small ships passing in the night in a vast ocean. Actual close encounters of any kind could be exceedingly unusual.
Another explanation for the great silence of the galaxy is that any surviving intelligence out there is so different from us, so radically evolved, that we can’t even conceive of its forms or behaviours. As a consequence, actually detecting and recognising it could be next to impossible. That’s a bit of a downer.
But there is also a possibility that lies between such extremes and it might be the most probable of all. When our first encounter or detection finally occurs, it could be a machine intelligence that appears in our sights.