This is not a romance, a dream of pure contemplation, an outside view of ourselves: it is our own history, fatal and inevitable. Since an hour ago, every one of us, reader or writer, rich or poor, wise or ignorant, infant or greybeard, whether we are active or asleep--since an hour ago every one of us has described in the sky an invisible track of more than 60,000 miles, for our planet traces out 580 million miles per annum merely by its revolution round the Sun, and a centenarian lives to mark out a distance of 58,000 million miles. Now, it is found that these speeds are the very condition of the stability of the universe: the heavenly bodies, the Earth, planets, satellites, suns, stellar systems, star clusters, galaxies, and remote universes, are mutually sustained by the equilibrium of their attractions. They are all suspended in the void and maintain themselves in their ideal orbits simply because they turn quickly enough to create a centrifugal force equal and opposite to the attraction exerted upon them, so that they remain in an unstable but perpetual equilibrium. Our Sun carries us along towards the constellation of Hercules: this has been known for a hundred years; but we know now that the constellation of Hercules forms part of our sidereal universe and that that universe is travelling in a certain direction. We therefore only perceive relative movements. Whither are we going? Vain question. We are going--into infinite space. Formerly people were troubled, not without reason, concerning the solidity of the foundations of the world, for before the isolation of our planet in space and its movement round the Sun had been demonstrated it seemed indispensable to give to the Earth an unshakable foundation and an unlimited route. But since the heavenly bodies rise and set and pass under our feet this foundation had to be given up, apart from the fact that it did not satisfy the most far-seeing minds. It is quite impossible for us to conceive a material pile, however solid or thick, even as thick as the Earth’s diameter and rooted in infinite space, just as one cannot imagine the real existence of a stick which has only one end. However far the mind can descend towards the base of that material pillar, the end must come at last, since only empty space can be without end, and then that terrestrial pillar serves no purpose at all since it is itself without a support. Besides, travellers succeeded one day in voyaging all round the globe, and nowhere was this imaginary pillar discovered. The modern conception of force in contrast with the ancient idea of matter has a philosophical import without precedent in the whole history of the science. It teaches, proves to us, and convinces us that the visible, palpable, material universe rests on the invisible and the immaterial, on imponderable force.