Just as, before the birth of the Earth, other worlds had flourished in space, so also after the death of our planet will the universe continue to exist, as it existed during the human era. And in the world of which we speak, a new and flourishing humanity shone in the joy of another sun. What had happened was in direct opposition to what terrestrial theologians had taught us concerning the end of the world. For them the end of the world was to have meant the end of the living universe and the establishment of a celestial and infernal world. For every one of the mortals inhabiting the future globe of which we speak, life passed with the fugitive and inexorable speed of the river which flows from its source to the sea, day by day, month by month, year by year, so swiftly that at the end of its course all the moments of that life seem to touch. The inhabitants of the world of Andromeda lived on their immense globe and occupied themselves with their personal affairs as if our Earth had never existed and without suspecting that long before them, in the past, our human race had played the game of destiny, cradled in the illusion that they existed alone in the world. Nobody thought, amid the common people, that worlds succeeded each other in time as well as in space. Only the thinkers standing on the heights from which the whole of things and events can be surveyed, realised that important truth, that the doctrine of the plurality of worlds applies to eternity as well as to infinity. * * * * * In our attempts to arrive at an idea of the constitution of the universe, two questions constantly and inevitably present themselves to our minds: the questions of Space and Time. They are correlative, but their interpretations are far from being identical, as is often supposed. Space does not exist by itself, nor does time. It is impossible to imagine the suppression of space. It is asserted in vain that space is the interval which separates two objects, and that if the objects are suppressed, space vanishes also. That is a pure scholastic sophism. The definition is not exact. One can safely say that it is impossible to suppress by a thought the place where objects could be. The place, the locality, that void, if you like, by whatever noun it is designated, is there quite ready to receive any object which our imagination can suppose to be there. Even though the universe did not exist, if nothing, absolutely nothing, existed, that nothing would still be space, empty space ready to receive an object. We are then forced to conclude that space exists by itself, even if it cannot be measured in any way. It is not the same with time. Time is created by the movements of the heavenly bodies. If the earth did not turn, nor the stars, if there were no succession of periods, time would not exist. It is astronomy which has created time. If you suppress the universe, space continues to exist, but time ceases, vanishes, disappears.