If there really is alien life elsewhere in the Universe, then it's reasonable to ask why we haven't seen it. Surely planet Earth would have been visited by aliens? Does that mean that alien life doesn't exist? This book uses some simple maths to take a sober look at the chances of our actually meeting alien life.
If there really is alien life elsewhere in the Universe, then it's reasonable to ask why we haven't seen it. Surely planet Earth would have been visit...