Young Folks' Library: Wonders of Earth, Sea and Sky HTML version
SIR ROBERT S. BALL.
The group of bodies which cluster around our sun forms a little island, so to speak, in the
extent of infinite space. We may illustrate this by a map in which we shall endeavor to
show the stars placed at their proper relative distances. We first open the compasses one
inch, and thus draw a little circle to represent the path of the earth. We are not going to
put in all the planets. We take Neptune, the outermost, at once. To draw its path I open
the compasses to thirty inches, and draw a circle with that radius. That will do for our
solar system, though the comets no doubt will roam beyond these limits. To complete our
map we ought of course to put in some stars. There are a hundred million to choose from,
and we shall begin with the brightest. It is often called the Dog Star, but astronomers
know it better as Sirius. Let us see where it is to be placed on our [pg 297] map. Sirius is beyond
Neptune, so it must be outside somewhere. Indeed, it is a good deal further off than
Neptune; so I try at the edge of the drawing-board; I have got a method of making a little
calculation that I do not intend to trouble you with, but I can assure you that the results it
leads me to are quite correct; they show me that this board is not big enough. But could a
board which was big enough fit into this lecture theatre? Here, again, I make my little
calculations, and I find that there would not be room for a board sufficiently great; in fact,
if I put the sun here at one end, with its planets around it? Sirius would be too near on the
same scale if it were at the further corner. The board would have to go out through the
wall of the theatre, out through London. Indeed, big as London is, it would not be large
enough to contain the drawing-board that I should require. It would have to stretch about
twenty miles from where we are now assembled. We may therefore dismiss any hope of
making a practical map of our system on this scale if Sirius is to have its proper place.
Let us, then, take some other star. We shall naturally try with the nearest of all. It is one
that we do not know in this part of the world, but those that live in the southern
hemisphere are well acquainted with it. The name of this star is Alpha Centauri. Even for
this star we should require a drawing three or four miles long if the distance from the
earth to the sun is to be taken as one inch. You see what an isolated position our sun and
his planets occupy. The members of the family are all close together, and the nearest
neighbors are situated at enormous distances. There is a good reason [pg 298] for this separation.
The stars are very pretty and perfectly harmless to us where they are at present situated.
They might be very troublesome neighbors if they were very much closer to our system.
It is therefore well they are so far off; they would be constantly making disturbances in
the sun's family if they were near at hand. Sometimes they would be dragging us into
unpleasantly great heat by bringing us too close to the sun, or producing a coolness by
pulling us away from the sun, which would be quite as disagreeable.
The Stars are Suns.
We are about to discuss one of the grandest truths in the whole of nature. We have had
occasion to see that this sun of ours is a magnificent globe immensely larger than the
greatest of his planets, while the greatest of these planets is immensely larger than this
earth; but now we are to learn that our sun is, indeed, only a star not nearly so bright as
many of those which shine over our heads every night. We are comparatively close to the