When it comes to the question of extraterrestrial life, humans optimistically assume the Universe is prolific. After all, there doesn’t appear to be anything particularly special about Earth, and life not only took hold here on our world, but evolved, thrived, became complex and differentiated, and then intelligent and technologically advanced. If the same ingredients are everywhere and the same rules are at play, wouldn’t it be an awful waste of space if we’re alone?
But this is not a question that can be answered by appeals to either logic or emotion, but by data and observation alone. While our investigations have revealed the existence of an enormous number of candidate planets for life, we have yet to find one where intelligent aliens, complex life, or even simple life is known to exist. In all the Universe, humanity may truly be alone.