Page:Popular Astronomy - Airy - 1881.djvu/83

Rh the earth is turning round. And, as regards the stars, the mere circumstance of their seeming to move all in a piece is a strong proof that they do not move sensibly, but that the earth moves. If you apply the same reasoning to any ordinary sublunary considerations, you will be struck at once with the conclusion. If I am sailing in a ship on the open sea and see vessels moving about me in all directions, and if any person in the ship asserts that our own ship is at rest and that all the others are moving, there is nothing particularly unreasonable in it. But if I am entering into the Ipswich river, and I see not only ships moving, but every church and warehouse, and the solid banks which connect them, moving past me, and if a friend at my elbow should say, "you are not moving, but all these solid things, churches and houses, and fixed objects and banks, are in motion," I should consider him to be a madman. The argument is precisely the same as applied to the heavens. If we had nothing but the sun and moon turning about in various ways, even then, and remarking their great size and their great distance, and the great speed with which they must be supposed to turn, (for the moon must be supposed to move at the rate of 60,000 miles an hour, and the sun very much quicker,) their daily revolution round the earth would be very unlikely. But when we have things of such an immovable character as the system of the stars, (like that of the banks of a river, or the solid erections which are there visible, as compared with our small sailing ships,) then the reason of man tells him at once that these things must be things of a fixed character—and that if these things be things of a fixed character, it is we who are turning and the earth which goes round. This is reasoning which ought to be received, and I cannot see why