Page:Popular Science Monthly Volume 17.djvu/630

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ASTRONOMERS say that this world of ours, which seems to us so large, is in fact so small in comparison with the sun and stars, that its presence or absence is, to the universe, a matter of inconceivably small importance; and that, even in its own system, it would hardly be noticed by an eye capable of taking in at one view the sun and its attendant planets.

Sir John Herschel gives the following illustration of the size and distance of these bodies: "Choose," he says, "any well-leveled field. On it place a globe two feet in diameter; this will represent the sun; Mercury will be represented by a grain of mustard-seed on the circumference of a circle 164 feet in diameter for its orbit; Venus, a pea in a circle of 284 feet in diameter; the earth, also, a pea on a circle of 430 feet; Mars, a rather large pin's head in a circle of 654 feet; Jupiter, a moderate-sized orange in a circle nearly half a mile across; Saturn, a smaller orange on a circle of four fifths of a mile; Uranus, a full-sized cherry upon the circumference of a circle more than a mile and a half; and Neptune, a good-sized plum on a circle two and a half miles in diameter."

If our earth were struck out of existence, it would hardly be missed from such a system. But this is far from the extreme measure of our littleness. The evening sky is studded with stars. Between us and them is empty space. As we look across it, the distance does not seem so very great, and even astronomers were long in learning how great it is, and how utterly isolated the sun with its train of planets is from even the nearest star. Keeping the same scale as before, in which our inconceivable distance from the sun, 9213 millions of miles, was reduced to a dozen rods or so, and then setting out to visit our neighbors, if we are lucky enough to turn our steps to the nearest, we find before us a journey of nearly 9,000 miles. Had we directed our course to any other of the stars, our road would have been many thousand miles longer. There are stars from which light requires 6,000 years to reach our globe!

Had we gone toward one of them, our journey on the same infinitely reduced scale would have taken us nearly 18,000,000 miles before reaching our goal.

Even this scale gives distances too vast. Let it be changed. Let the sun shrink to a point 1100 of an inch in diameter. The distance to the sun, 9213 millions of miles, would be reduced to nearly one inch. The earth would be only 11000 of an inch in diameter, requiring

  1. Read, January 13, 1880, before the Poughkeepsie Society of Natural Science.