“Surely they are not moving now?”

“Oh, yes, and with velocities proportionate to those of the real bodies; but you know that whilst the actual movements of the sun and planets are so rapid, the dimensions of the system are so vast that if you could survey the whole from a standpoint in space, as we are supposed to do, it would appear at rest.  Let us look at them a little closer.”

I followed Gazen along the gangway which encircled the orrery, and allowed us to survey each of the planets closer at hand.

“This kind of place would make a good theatre for a class in astronomy,” said I, “or for the meetings of the Interplanetary Congress of Astronomers, in the year 2000.  You can turn on the stars and planets when you please.  I wish you would give me a lecture on the subject now.  My knowledge is a little the worse for wear, and a man ought to know something of the worlds around him—­especially if he intends to visit them.”

“I should only bore you with an old story.”

“Not at all.  You cannot be too simple and elementary.  Regard me as a small boy in the stage of

    “’Twinkle, twinkle, little star,
      How I wonder what you are!’”

“Very well, my little man, have you any idea how many stars you can see on a clear night?”

“Billions.”

“No, Tommy.  You are wrong, my dear boy.  Go to the foot of your class.  With the naked eye we can only distinguish three or four thousand, but with the telescope we are able to count at least fifty millions.  They are thickest in the Milky Way, which, as you can see, runs all round the heavens, over your head, and under your feet, like an irregular tract of hazy light, a girdle of stars in short.  Of course we cannot tell how many more there are beyond the range of vision, or what other galaxies may be scattered in the depths of space.  The stars are suns, larger or smaller than our own, and of various colours—­white, blue, yellow, green, and red.  Some are single, but others are held together in pairs or groups by the force of gravitation.  From their immense distance they appear fixed to us, but in reality they are flying in all directions at enormous velocities.  Alpha, of the constellation Cygnus, for example, is coming towards us at a speed of 500 million leagues per annum, and some move a great deal faster.  Most of them probably have planets circling round them in different stages of growth, but these are invisible to us.  Here and there amongst them we find luminous patches or ‘nebulae,’ which prove to be either clusters of stars or stupendous clouds of glowing gases.  Our sun is a solitary blue star on the verge of the Milky Way, 20 billion miles from Alpha Centauri his next-door neighbour.  He is travelling in a straight line towards the constellation Hercules at the rate of 20,000 miles an hour, much quicker than a rifle bullet; and, nevertheless, he will take more than a million years to cover the distance.