All the planets, like our earth, move round the sun, and are kept in their places by means of a wonderful power which we cannot see, but which is one of those "laws of nature," as the rules which God has made for His great universe are sometimes called, about which I told you that they never alter. It is a law, or rule, that, in the world around us, "the same causes always produce the same effects." If you think a little about this, it will become plain to you that it is so, and if you observe carefully you will see that this rule is the same in connection with the smallest as well as the greatest things; if it ever seems that it is not so, be sure that this is only because you do not yet know all about what you have been observing. And now learn a little about the beautiful rule by which the planets are kept in their places.
Two hundred years ago, Sir Isaac Newton discovered that everything in the universe attracts or draws every other thing to itself, and this power or attraction he called "the force of gravitation." I cannot do much more than tell you the name of this "law," but you will learn more about it one day I hope, and see how simple and yet how wonderful it is. An astronomer of our own day says, in his Story of the Heavens, that there are "grounds for believing that the law of gravitation is obeyed throughout the length, the breadth, the depth, and the height of the entire universe," and a little observation and thought will enable you to see something of its working in the world around us.
Do you remember my telling you how fond I was of swimming boats long ago? When my brother and I used to launch our paper boats—not on the river, but in that big tub in the yard—our great difficulty was to keep them from running each other down, and becoming dismal wrecks before they had completed their first voyage. We did not know why, but it seemed as if the vessels of our tiny fleet would drift towards each other, in spite of all our efforts to keep them apart. Have you not found it so with your boats? It certainly was with ours, but we should have been surprised if anyone had told us that as they ran against each other, our paper boats were but obeying the "law of gravitation," each little vessel drawing the other to itself by a power which it had of attracting it. Knowing this rule makes many things plain. If you throw your ball high into the air, it is sure to come down again. Why? Because the earth, which is a much larger ball, attracts it to itself by the law of gravitation; by the same law, the drops of rain in a shower fall to the ground; by the same law, we and all the people upon the globe are able to stand firm on it; by the same law, the great earth itself, the moon, and all the planets are kept in their places. But what is the mighty magnet which has power to draw the earth to itself? It is that wonderful globe the sun, which is more than a million times as large as the earth; and though it is so far, far away—at a distance greater than we can have any idea of—yet by its mighty power of drawing them to itself, makes our earth, as well as the other planets, move round it in the most beautiful order, and keeps them all in their places.
Although Newton felt sure that this unseen but resistless power, of which he afterwards spoke reverently as "the finger of God," kept the moon going round the earth and the earth round the sun, yet he was at first silent about his great discovery; he worked and waited for long years, until he had proved that it was not merely a happy guess, but that he had really discovered the rule which governs the motion of sun, moon and stars. Then he explained the reason why the moon is always moving round the earth, and the earth and other planets round the sun, instead of all moving on in a straight line; it is because everyone of the heavenly bodies attracts all the rest, and thus the smaller move round the larger, all in perfect order and harmony.
[Illustration: SAILING THE BOAT]
You must not think that this force set them all moving; it only governs their movements, the earth pulling the moon to itself, and the sun in like manner pulling all the planets with gentle but resistless power, and keeping them all moving round himself—their glorious centre.
You will learn by-and-by what has been found out about the other planets. All I shall tell you of them now is, that they are, like the earth, quite dark in themselves. The light they give is reflected light from the sun; just like the light which comes to us from another planet, which belongs, not to the sun, but to our earth, and indeed is so near home that I am sure you can find out its name for yourself. Of the seven other planets which belong to the sun, the nearest in size to our earth is one which shines with a lovely soft light, and is sometimes the evening, sometimes the morning star. Ask someone to show you Venus; and I think you will soon learn to look for her in the evening, and to love her pure, calm radiance. This star is peculiarly beautiful in the early morning, when she seems to shine alone in the sky, and reminds us how, in the last book of the Bible, the Lord Jesus speaks of Himself, and says, "I am the … Bright and Morning Star." What a beautiful name for us to know the Lord Jesus by! There are some children who know Him by that name, and they are watching for that bright star to appear.
I will tell you of one. Her name is Sharley; but she is not May's sister Sharley, and I do not think she is quite so old. This little girl had been obliged to go away from her home, to stay for some time in the Children's Hospital. This is a bright, pretty place, with pictures and flowers and toys. But it was not at all like home to poor little Sharley; and as she thought of her mother and her sisters she sobbed and cried in her little bed, and buried her head under the pink quilt, and refused to be comforted. A lady came to see her, and brought her a picture-book; but still she hid her face, and cried, "Oh, do let me go home!" The lady tried to please her by showing her a stuffed squirrel, and telling stories about how she had seen the merry little creatures, with their bright eyes and red bushy tails, running about in the beech-woods, eating nuts. But no, nothing that she could do or say would win a smile or a bright look. At last she noticed a little Testament lying upon the tray across her bed, beside the toys which had been given her to play with, and she said, "Is that your own Testament, Sharley? Will you find the place and read me your favourite verse?"
In a moment the little girl stopped crying, and turned over the leaves of her Testament till she came to the very end; and she put her finger on the verse, "Surely I come quickly. Amen. Even so, come, Lord Jesus." As she pointed to the words the lady read them, and then asked, "Do you want Him to come?"
Sharley did not speak, but nodded her head.