Читать книгу Star-land: Being Talks With Young People About the Wonders of the Heavens онлайн

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Let us try to illustrate in another way the exceeding remoteness of the sun. So please imagine that you were on the sun, and that you took a view of our earth from that distance. To find out what we must expect to see, let us think of a balloon voyage. If you were to go up in a balloon, you would at first see only the houses, or objects immediately about you, but as you rose the view would become wider and wider. You would see that London was surrounded by the country, and then, as you still soared up and up, the sea would become visible, and you would be able to trace out the coasts, east and west and south. If, in some way, you could soar higher than any balloon could carry you, the whole of the British Islands would presently lie spread like a map beneath. Still on and on, and then the continent of Europe would be gradually opened out, until the great oceans, and even other continents, would at last be caught sight of, and then you would perceive that our whole earth was indeed a globe. The higher you went, the less distinctly would you be able to see the details on the surface. At last the outlines of the continents and oceans would fade, and you would begin to lose any perception of the shape of the earth itself. Long ere you had reached the distance of the sun, the earth would look merely as the planet Venus now does to us. It is instructive to consider how small our earth would seem if it were possible to view it from the sun. Think of that very familiar little globe, a lawn-tennis ball, which is two and three-quarter inches in diameter. But suppose a tennis ball were at the opposite side of the street, or still further away; suppose, for example, that it were half a mile away, what could you expect to see of it? And yet the earth, as seen from the sun, would appear to be no larger than a tennis ball would look when viewed from a distance of half a mile.