Mr Barlow.—Supposing, then, the sun were to be removed to a much greater distance than it is now, what would happen? Would it appear the same to your eyes?
Tommy considered some time, and then said, "If the ship grows less and less, till at last it appears a mere speck, by going farther and farther, I should think the sun would do the same."
Mr Barlow.—There you are perfectly right; therefore, if the sun were to depart farther and farther from us, at last it would appear no bigger than one of those twinkling stars that you see at so great a distance above your head.
Tommy.—That I perfectly comprehend.
Mr Barlow.—But if, on the contrary, one of those twinkling stars were to approach nearer and nearer to where you stand, what do think would happen? Would it still appear of the same size?
Tommy.—No, sir. The ship, as it came nearer to us, appeared every moment larger, and therefore I think the star must do the same.
Mr Barlow.—Might it not then appear as big as the sun now does, just as the sun would dwindle away to the size of a star, were it to be removed to a still greater distance?
Tommy.—Indeed I think it might.
Mr Barlow.—What, then, do you imagine must happen, could the sun approach a great deal nearer to us? Would its size remain the same?
Tommy.—No; I plainly see that it must appear bigger and bigger the nearer it comes.