The point of view of this book is human interest in the other worlds around us. It presents the latest discoveries among the planets of the solar system, and shows their bearing upon the question of life in those planets. It points out the resemblances and the differences between the earth and the other worlds that share with it in the light of the sun. It shows what we should see and experience if we could visit those worlds.While basing itself upon facts, it does not exclude the discussion of interesting probabilities and theories that have commanded wide popular attention. It points out, for instance, what is to be thought of the idea of interplanetary communication.