Some of the greatest mysteries of the universe are questions that remain unanswered. Where did life on Earth come from? Since Earth exists in space, can life exist elsewhere in our galaxy? And if life does exist throughout the universe, where are all the aliens? Welcome to Fermi's paradox, defined as the clear lack of evidence for alien life in our universe despite the seemingly endless opportunities for it to emerge and flourish. It is a mystery that continues to spark the imaginations of people worldwide. Nowadays we are alone in the midst of the Great Silence that surrounds us. But what are the conditions for alien life forms to evolve on a planet and subsequently contact us? And how can we justify our loneliness, based on the idea that there are other living beings? This book discusses and examines the possible solutions to this paradox and also how they reflect on us, our past and our future.