This simple cosmogony, which merely translates what our eyes show us, has been that believed by every people in their infancy. Among the savage tribes of the two worlds, in America and in Africa, as in the ancient East, among the Romans as among the Egyptians and the ancient Greeks, this coarse simplicity and absolute ignorance of the constitution of the world prevailed. On this profoundly false basis all the ancient religions were founded. The social customs of modern peoples are based upon the same errors. Language has consecrated them; the earth is everywhere called the _world_, as the ancients called it (_mundus_, κόσμος); every one says the sun _travels_, or _goes_, from east to west, and that the stars _rise_ and _set_. Poetry has set its eternal seal on this vicious system, and has, so to speak, consecrated it, by clothing it with all the _prestige_ of genius and imagination. Modern astronomy has caused the false skies of antiquity to vanish away; it has dispersed the pretensions of the celestial vault, sown with brilliant spots, and substituted a simple mass of coloured air. It has revealed the true office of each of those stars which we see by day or by night. It has fixed, in an indisputable manner, the real place of the earth in the universe, and, to say the truth, that place is singularly small. We know now, that the earth, far from being herself the world, is only an imperceptible point of the world. If we only compare it with the sun, we know that our globe is one million three hundred thousand times smaller than the sun. This takes us far away from the idea of the ancient Greeks, who thought they ventured much in asserting that the sun was as big as the Peloponnesus. In addition, the earth has been dispossessed of all privileges. It was believed formerly to be unique and unrivalled, we now know that there are an infinity of other globes similar to the earth, so that she is no more than one individual in a group of other individuals who resemble her. We know that the earth figures among the planets, that she is only a planet of our system. What, then, is a planet? the reader will ask. An attentive gaze directed to the stars of night will make him understand it. Let him examine, on any fine evening, the star which is pointed out to him as Mars or Jupiter, and to which a certain position is assigned at a given hour. Then, a few hours later, let him come and look once more for Mars or Jupiter, and he will perceive that the position of Mars or Jupiter, with respect to the other stars, is changed. Or he may do better still. Let him look at Mars or Jupiter through the telescope of an observatory, or the glass of one of those open-air astronomers who are to be found in the public ways in Paris and other great cities. Thus he may see Mars or Jupiter change his place under his own eyes. While the other stars remain motionless, Jupiter or Mars will pass away from the field of the glass.