These are difficult figures for the imagination. If a bullet fired from a Maxim gun at the sun kept its muzzle velocity unimpaired, it would take seven years to reach the sun. And yet we say the sun is near, measured by the scale of the stars. If the earth were a small ball, one inch in diameter, the sun would be a globe of nine feet diameter; it would fill a small bedroom. It is spinning round on its axis, but since it is an incandescent fluid, its polar regions do not travel with the same velocity as its equator, the surface of which rotates in about twenty-five days. The surface visible to us consists of clouds of incandescent metallic vapour. At what lies below we can only guess. So hot is the sun's atmosphere that iron, nickel, copper, and tin are present in it in a gaseous state. About it at great distances circle not only our earth, but certain kindred bodies called the planets. These shine in the sky because they reflect the light of the sun; they are near enough for us to note their movements quite easily. Night by night their positions change with regard to the fixed stars.
It is well to understand how empty space is. If, as we have said, the sun were a ball nine feet across, our earth would, in proportion, be the size of a one-inch ball, and at a distance of 323 yards from the sun. The moon would be a speck the size of a small pea, thirty inches from the earth. Nearer to the sun than the earth would be two other very similar specks, the planets Mercury and Venus, at a distance of 125 and 250 yards respectively. Beyond the earth would come the planets Mars, Jupiter, Saturn, Uranus, and Neptune, at distances of 500, 1806, 3000, 6000, and 9500 yards respectively. There would also be a certain number of very much smaller specks, flying about amongst these planets, more particularly a number called the asteroids circling between Mars and Jupiter, and occasionally a little puff of more or less luminous vapour and dust would drift into the system from the almost limitless emptiness beyond. Such a puff is what we call a comet. All the rest of the space about us and around us and for unfathomable distances beyond is cold, lifeless, and void. The nearest fixed star to us, on this minute scale, be it remembered,—the earth as a one-inch ball, and the moon a little pea—would be over 40,000 miles away.
The science that tells of these things and how men have come
