“As children, we fear the dark. Anything might be out. here. The unknown troubles us. Ironically, it is our fate to live in the dark. This unexpected finding of science is only about three centuries old. Head out from the Earth in any direction you choose, and—after an initial flash of blue and a longer wait while the Sun fades—you are surrounded by blackness, punctuated only here and there by the faint and distant stars. Even after we are grown, the darkness retains its power to frighten us. And so there are those who say we should not inquire too closely into who else might be living in that darkness. Better not to know, they say. There are 400 billion stars in the Milky Way Galaxy. Of this immense multitude, could it be that our humdrum Sun is the only one with an inhabited planet? Maybe. Maybe the origin of life or intelligence is exceedingly improbable. Or maybe civilizations arise all the time, but wipe themselves out as soon as they are able. Or, here and there, peppered across space, orbiting other suns, maybe there are worlds something like our own, on which other beings gaze up and wonder as we do about who else lives in the dark…Life is a comparative rarity. You can survey dozens of worlds and find that on only one of them does life arise and evolve and persist… If we humans ever go to these worlds, then, it will be because a nation or a consortium of them believes it to be to its advantage—or to the advantage of the human species… In our time we’ve crossed the Solar System and sent four ships to the stars… But we continue to search for inhabitants. We can’t help it. Life looks for life.” ~Carl Sagan