1. Where are the aliens?
One night about 60 years ago, physicist Enrico Fermi looked up into the sky and asked, “Where is everybody?” He was talking about aliens. Today, scientists know that there are millions, perhaps billions of planets in the universe that could sustain life. So, in the long history of everything, why hasn’t any of this life made it far enough into space to shake hands (or claws … or tentacles) with humans? It could be that the universe is just too big to traverse.It could be that the aliens are deliberately ignoring us. It could even be that every growing civilization is irrevocably doomed to destroy itself (something to look forward to, fellow Earthlings). Or, it could be something much, much weirder. Like what, you ask? Here are nine strange answers that scientists have proposed for Fermi’s paradox.