Where Are They? Why I Hope the Search for Extraterrestrial Life Finds Nothing

About this book

The Great Filter can be thought of as a probability barrier. It consists of the existance of one or more highly improbable evolutionary transitions or steps whose occurrence is required in order for an Earth‐like planet to produce an intelligent civilization of a type that would be visible to us with our current observation technology. You start with billions and billions of potential germination points for life, and you end up with a sum total of zero extraterrestrial civilizations that we can observe. The Great Filter must therefore be powerful enough — which is to say, the critical steps must be improbable enough— that even with many billions rolls of the dice, one ends up with nothing: no aliens, no spacecraft, no signals, at least none that we can detect in our neck of the woods.