Toddlers, I know from experience, believe themselves to be very, very special — the center, in fact, of the entire universe. With maturity, however, most of us learn that we are not quite as special as we thought. Other people are important, too.
It’s similar with Earthlings in general. As humans have learned about the size of the cosmos (and our not-so-central place in it), we have grappled with weighing our specialness against the possible existence of alien beings on other worlds. Given the amazing diversity of life on Earth, it makes sense that life here is just one example from a cosmic multitude. If so, the next question becomes whether we can find the others.
That quest is at the heart of this special issue, which explores our