WHAT I KNOW ABOUT ALIENS
Yet across the gulf of space, minds that are to our
minds as ours are to those of the beasts that perish,
intellects vast and cool and unsympathetic, regarded
this earth with envious eyes, and slowly and surely
drew their plans against us.
—H. G. Wells, from The War of the Worlds
From its title, you might expect this to be a very short chapter. I’ve never met an alien, I don’t know that I’d recognize an alien if I saw one, and I’m not even sure that aliens exist. So what do I know about aliens? Nothing, absolutely nothing.
But you didn’t really expect me to end the chapter quite so quickly, did you? I may not be able to say anything about aliens with 100 percent certitude, but as we discussed in chapter 2, science rarely can prove anything to be true beyond all doubt. Instead, science gives us a way to examine evidence and then to choose among possibilities. Sometimes the evidence for a particular possibility will become so overwhelming that we will regard it as truth. For example, that is the case for the idea of Earth going around the Sun rather than vice versa, an idea for which the evidence is so strong that it’s difficult to imagine anyone seriously arguing with its reality.
We can also use science to consider various possibilities about aliens. If you knew nothing at all about life or the universe, you might guess that beings like us could live just about anywhere, including in space and on the Sun. Indeed, many ancient myths incorporated ideas much like this, since they often imagined mortals joining the gods among the stars. Today, based on what we know about the needs of life, we can be pretty confident that the best place to find life is on a planet or a large moon—an idea that we’ll discuss in more detail in coming chapters. We can be similarly confident that we won’t find beings traveling through space unless they first grew up