Their family relationship to one another and to the sun is so evident that it colors our judgment about them as individuals; and when we happen to find, upon closer approach, that one of them, the earth, is covered with vegetation and water and filled with thousands of species of animated creatures, we are disposed to believe, without further examination, that they are all alike in this respect, just as they are all alike in receiving light and heat from the sun.
This preliminary judgment, arising from the evident unity of the planetary system, can only be varied by an examination of its members in detail.
One striking fact that commands our attention as soon as we have entered the narrow precincts of the solar system is the isolation of the sun and its attendants in space.

The solar system occupies a disk-shaped, or flat circular, expanse, about 5,580,000,000 miles across and relatively very thin, the sun being in the center.

From the sun to the nearest star, or other sun, the distance is approximately five thousand times the entire diameter of the solar system.

But the vast majority of the stars are probably a hundred times yet more remote.

In other words, if the Solar system be represented by a circular flower-bed ten feet across, the nearest star must be placed at a distance of nine and a half miles, and the great multitude of the stars at a distance of nine hundred miles! Or, to put it in another way, let us suppose the sun and his planets to be represented by a fleet of ships at sea, all included within a space about half a mile across; then, in order that there might be no shore relatively nearer than the nearest fixed star is to the sun, we should have to place our fleet in the middle of the Pacific Ocean, while the distance of the main shore of the starry universe would be so immense that the whole surface of the earth would be far too small to hold the expanse of ocean needed to represent it! From these general considerations we next proceed to recall some of the details of the system of worlds amid which we dwell.