the same direction, and their paths all lie very nearly in one plane.
Some of them have one or more moons, or satellites, circling about them
in imitation of their own revolution about the sun. 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