Actually, Demis' logic of no civilization in this galaxy was compelling.<br>If there's some civilization in the galaxy, they are likely millions or billions years ahead of us, which means that our galaxy must be full with the Dyson sphere and massive artifacts. But the universe is surprisingly silent.,(reply>), Since the noise of remote sentients must travel at the speed of light, the lifetimes of our civilizations are sadly not overlapping in the same time and place with the communications signals. Consider the distances between any two galaxies, and the time duration of existence of human kind's radio receivers as one example of the low likelihood of successful communication between two such parties. We definitely have alien neighbors.  But our mere 100 Earth years of technological  capability to hear them, and perhaps similar for them to hear us, is just too brief.