Page:Popular Science Monthly Volume 17.djvu/631

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THE SOLAR SYSTEM AND ITS NEIGHBORS.

1,000,000,000,000 times its bulk to make a globe one inch in diameter. On such a scale our world would be equaled in minuteness only by the animalcules which the microscope reveals. Even then, on this inconceivably reduced scale, the line that would reach our nearest neighbor would need to be something more than three miles long.

Yet that sun, which in this estimate we have mentally reduced to a point 1100 of an inch in diameter, is in reality a body so vast that, were it hollow, and our earth placed at its center, the moon would not only revolve freely around our planet, just as it now does, but on every side the sun would extend more than 200,000 miles beyond the lunar orbit. We have heard so often of the distance from here to the sun, 92⅓ millions of miles, that we begin to think we have some idea of its inconceivable greatness. Yet, so large is the sun that only 107 such bodies, laid so as to touch each other, would be needed to form a continuous bridge from the earth to that luminary. In the sky it appears so small that we find it difficult to realize that scarcely more than 100 times its diameter would reach so far.

However many of us may have sought, by these or by other illustrations, to form some conception of the vastness of the universe, but few have attempted to grasp the measure of that power which compels the planets to move in elliptical orbits instead of flying off in tangents, as, if left to themselves, they would inevitably do; and still fewer have thought of the force with which these bodies tend to pull one another out of their courses. Of these influences astronomers have given no illustrations, yet their contemplation will lead to results that will enlarge our views of the universe, and help us to rise at least a little toward a conception of Omnipotence.

We must work out our conclusions ourselves. The data are all at our hand. We need only to know the distances and masses; the rest is a matter of easy computation. But that our results may not be meaningless from their very greatness, it will be wise to follow the method which we pursue when trying to get an idea of great distances. We take first some unit with which we are familiar—for instance, a mile—and think how many miles it is to some place familiar to us. Then we extend that measure, or some multiple of it, to another place more remote, and then to one still more distant; and thus by degrees we become able to grasp distances whose statement in figures had previously conveyed little or no meaning to our minds. So, in measuring a force, we get a better idea of its greatness if we work up to it in a similar manner.

Of all known substances steel is the most tenacious. If the interplanetary forces can be represented by steel bars of known size, it will at least help to bring them within the limits of our comprehension.

Philosophers have found that a steel wire one tenth of an inch in diameter will support nearly half a ton, while a bar one inch square will not be pulled asunder by less than sixty tons. If two inches