To know about the planets is to know about ourselves. The earth is one of them. Whatever their origin, the earth’s is the same. It and they are formed from the same nebula, controlled by the same central body, subject to the same laws, and destined for the same fate in the end. In this, the stars and the planets are not alike. They all shine upon us with the same sweet friendliness, and commonly we make no difference between them in our feeling for them. But the stars are bright and beautiful acquaintances living far away in their own domain. The planets are members of our own family, bone of our bone and flesh of our flesh, living comparatively near to us, within the domain of our common source of life, the sun.

One evening last autumn I was coming up Broadway, New York, with a friend, when we encountered at Union Square a man with a six-inch telescope directed toward the eastern sky. He was soliciting those who passed to stop and look at Mars and Saturn. Both of these planets were then very bright. They were also fairly near together, and so low in the east that one could scarcely help seeing them. But the people passed back and forth with hardly so much as a glance at the man and his telescope, and for the most part never even raised their eyes to the sky with a passing curiosity to see what it might be that he wanted to show them. My friend and I stopped and took each a view first of Mars and then of Saturn. While we were looking at the planets, a few of the passers-by began to loiter about, half smiling at us for so playing in public, slightly curious to see how we were faring at it, but for the most part apparently indifferent to what we were seeing. We had a fine view of Saturn lightly resting in his nest of rings, and an equally good view of the comical “eye” of Mars.

After we had finished, one or two others, evidently prompted by our example, followed us at the telescope. One or two inquired of us what the stars were that had so interested us, and one, pointing to Mars, wanted to know if it was Venus. As the crowd grew larger a few more ventured to take a look, much as they might venture to take their chance at hitting the bull’s-eye in some shooting-gallery. With the telescope pointed at Saturn, the man droningly chanted: “This planet is 887,000,000 miles from the sun. The ring you see is 170,000 miles in diameter,” and so on. These, to be sure, were the facts—and most marvelous facts, too—but without much meaning to one who knows nothing much about the planets; and the manner of their recital certainly did not make them alluring. I could not myself help feeling that the people there were missing a valuable opportunity, and that it would be only fair to them for some one fairly to cry out: “Come here and look at this planet. It is different from anything else you have ever seen or ever will see. It was at one time a part of the same nebulous mass that we were a part of. It is in the same system of worlds with us. It was formed in the same way that this world was formed. It is in itself the most wonderful thing you ever saw, and it is bound, as we are, to the sun by the ever-drawing tie of gravitation. The very position of our own world in space is more or less influenced by it. If anything should happen to it, it might be a serious matter to us.”

For it is true that we are thus closely bound to the planets. The family tie among us is of far more force and significance than in any ordinary case of common origin. Human family ties wear, as we know, often into the merest threads, or even become no ties at all. But that between the earth and the planets remains apparently as close and strong as ever it was. The law of gravity, under which the earth draws toward its center every atom of matter surrounding it, and thus holds together all the atoms composing it, is not solely terrestrial in its application. It is probably universal. It certainly applies to every part of our little family of worlds. Every particle in the solar system attracts toward it every other particle in that system with a force determined by its mass and its distance. The sun, by reason of its immense size, compels the earth and all the other planets forever to circle around it. But the planets themselves have just as much power of attraction as the sun, atom for atom.

Thus, while the sun controls the motions of all of them, each pulls at the other, and, according to its power, determines how much the path of each shall vary from the course around the sun it otherwise would make. In the case of the smaller planets, this gravitational influence is, of course, very slight, and so subtle that we here on earth are not even conscious of it. But it is, nevertheless, real and continuous. It is greatest between the two largest planets, Jupiter and Saturn; but it was enough in the case of Uranus and Neptune to lead, by its mere manifestation on the earth, to the discovery of Neptune, the farthest planet.

Being thus of the same origin with the planets, having the same life history, being bound to them in space by a tie that is perhaps eternal, how can we fail to have the most intimate interest in their nature and all that concerns them?

But in addition to their close relationship to us there is, to make them of peculiar interest, the fact that, after the sun and the moon, they are for our eyes the most splendid objects in all the brilliant panorama of the sky. Such of them as we can see at all with the naked eye are most of the time much brighter than any first-magnitude star. As they wander from constellation to constellation the soft light of their placid faces gives a beauty and variety to the spectacle that endears them to us, and at the same time enhances by contrast their own charm and that of the glittering, unchanging stars.

There is nothing that gives one such a sense of sweet familiarity with the heavens as a really recognizing acquaintance with the planets. They are not, like the stars, associated with particular seasons. They come sometimes with the gay company of stars that dance their way across the cold winter skies, and sometimes with those that shine during the soft summer nights. Often in the spring and autumn we see some one of them before the sun is fairly down, and, before the light of an ordinary star can yet be seen, hanging in lone brilliancy as the evening star; and often an early riser has the reward of seeing one as a morning star glowing almost in the rays of the rising sun. Thus they are, one and another, with us at all times and seasons, and it accords with the fact of the relation being a family one that we have in their coming and going a sense of frequency and informality which we cannot have in the more regular and seasonal coming and going of the stars.