He is all that way off on one side of the Sun and when he gets round to the other side he is just as far off in the other direction. So the breadth of Neptune’s whole pathway, from side to side, is not much less than _six thousand millions of miles_. All the other worlds or planets are within that enormous circle, nearer to the Sun. But there are comets belonging to the Sun which journey farther off than Neptune and yet come back from time to time, being held captive by the Sun. Whether our Solar System as a whole is six or ten or twenty thousands of millions of miles across, matters very little. In any case, it is enormous. And yet, though so enormous, the whole Solar System is but one little spot in the great Universe of Stars which God has created. The one Star in our System is the Sun himself. All other Stars are far away, outside his kingdom and away from it. Once upon a time, indeed, the worlds may all have been stars; and the larger planets seem to be still only half-way out of their starry state. Still they are all either cooled or partly-cooled worlds; not stars. A Star is a Sun: and a Sun is a Star. A world, whether cold or hot, if it does not shine by its own light cannot be called a star. We see abundance of stars in the sky, but they are so distant that our Sun, compared with them, is very near us indeed. A wide, wide gulf of cold and darkness, of emptiness and desolation, spreads far on every side around our Sun’s kingdom. That is to say, a wide gulf of what would be cold to our earthly bodies, of what would be darkness to our human eyes, of what looks like emptiness and desolation to our little knowledge. But after all, we cannot see much, we do not really know much! The distance of our Sun has been found out, and the distances of a few Stars have been roughly measured. But what may lie between us and them, who can tell? We are here on our little Earth, down at the bottom of a deep Ocean of Air, tied and bound and unable to get away. What man has seen and learned from the bottom of his air-ocean is indeed very wonderful; but more wonderful by far are the things which he does not know. In earlier chapters we have talked about the worlds in smaller sizes, letting one inch stand always for 2,000 miles. Now, keeping to exactly that same plan, let us try to picture the Solar System on a little scale, with not only sizes but distances thus brought down. The actual distances you know by this time, perhaps, pretty well. You know that Mercury is about 35 millions of miles from the Sun, the Earth about 92 millions, and so on. But it is not easy to see what these figures really mean, millions and billions sound so much alike. So now we will fancy the whole big System shrinking and getting smaller till in every part of it each 2,000 miles has become one tiny inch. Our small moon, being 2,000 miles through, is thus a minute ball one inch through.