Page:Popular Astronomy - Airy - 1881.djvu/82

68 producing what is called occultation. But they are not only further off than the moon, but they are a good deal further off than the moon; and the reason for knowing it is this; suppose one object is close behind another, then the more distant object will either be hidden by the nearer, in whatever part of the earth we may observe it, or will not be hidden at all. But suppose the more distant object to be a long way off, then, when it was hidden from one part of the earth, it would be visible to another part of the earth. Now, that is the case with regard to the eclipses of the sun and occupations of the stars. If we examine into the appearances of an occultation, as seen at different parts of the earth, in some parts a star is hidden by the moon, in others it is not hidden at all. If we examine into the circumstances of a solar eclipse, as seen at different parts of the earth, in some parts the moon is seen on the north side of the sun: in other places the moon covers the sun; and in other places the moon is seen on the south side of the sun. It follows that the sun is, a good deal further off than the moon. Thus it appears that the system of heavenly bodies which surrounds the earth is of considerable size. The moon is far off; the sun and stars are much further off than the moon. The moon, therefore, is not a small body, and the sun (which in spite of its great distance appears so large) must be a very large body. The stars are either connected in one system, or are so very far off that their relative movements are insensible.

Now, is it more likely that this large frame of things is turning one way, or that this small earth is turning the other way? Anybody must see at once, from the magnitude of things, that it is most probable