We do not always feel this, because the very much greater attraction of the earth hides--or smothers, as we may say--the lesser attraction of each small thing for another. But though you and I might stand side by side upon earth, and feel no mutual attraction, yet if we could mount up a few thousands of miles, far away from earth, and float in distant space, there we should find ourselves drawn together, and unable to remain apart. Now precisely as an apple falling from a tree and a stone dropping from a cliff are dragged downward to the earth, just so our earth and all the planets are dragged downwards towards the sun and towards each other. The law of the earth’s attraction of all objects on its surface to itself was indistinctly suspected a very long time ago; but it was the great Newton who first discovered that this same law was to be found working among the members of the whole Solar System. The sun attracts the earth, and the earth attracts the sun. But the enormous size of the sun compared with our earth--like a great nine-foot globe beside a tiny one-inch ball--makes our power of attraction to be quite lost sight of in his, which is so much greater. The principle of gravitation is of far wider scope than we have yet indicated. We have spoken merely of the attraction of the earth, and we have stated that its attraction extends throughout space. But the law of gravitation is not so limited. Not only does the earth attract every other body, and every other body attract the earth, but each of these bodies attracts each other; so that, in its more complete shape, the law of gravitation announces that “every body in the universe attracts every other body with a force which varies inversely as the square of the distance.” It is impossible for us to overestimate the importance of this law. It supplies the clue by which we can unravel the complicated movements of the planets. It has led to marvelous discoveries, in which the law of gravitation has enabled us to anticipate the telescope, and, indeed, actually to feel the existence of bodies before those bodies have even been seen. We come now to another question. If the sun is pulling with such power at the earth and all her sister planets, why do they not fall down upon him? What is to prevent their rolling some day into one of those deep rents in his fiery envelope? Did you ever tie a ball to a string, and swing it rapidly round and round your head? If you did, you must have noticed the steady outward pull of the ball. The heavier the ball, and the more rapid its whirl, the stronger the pull will be. Let the string slip, and the rush of the ball through the air to the side of the room will make this yet more plain. Did you ever carry a glass of water quickly along, and then, on suddenly turning a corner, find that the water has not turned with you? It has gone on in its former direction, leaving the glass, and spilling itself on the floor.