Page:Popular Science Monthly Volume 9.djvu/684

656 of heat and cold at different periods of the year would be fatal to life. If the orbit of Jupiter were as eccentric as that of Mercury, the attraction of the larger planet would cause the smaller to change their approximately circular orbits into very long ellipses; such would be the disturbance that they would fall into the sun or fly off into remote space. The moon would approach nearer and nearer to the earth with every revolution; the year would change its character; violent heat would succeed to violent cold; the planets would come nearer and nearer; we should see them portentous in size and aspect, glaring and disappearing at uncertain intervals; tides, like deluges, would sweep over whole continents; and, finally, the fall of the moon or one of the planets to the earth would result in the absolute annihilation of both of them.

Another reason for supposing that the solar system is the result of one separate act of creation is, that all parts of it are subject to one uniform law—that of gravitation. By that law every particle of matter attracts every other particle with a force directly proportionate to its mass. This force varies as the inverse square of the distance: that is, if the attractive force of a given mass at one mile were called 1, at two miles it would be 2 $$\times$$ 2 $$=$$ 4, or ¼ of 1, and so on. This law of the inverse square, as it is called, is but the mathematical expression of a property which has been imposed upon matter by the Creator. It is no inherent quality, so far as we know. It is quite conceivable that the central law might have been different from what it is. There is no reason why the mathematical fact should be what it is except the will of the Being who imposed the law. Any other proportion could equally well be expressed mathematically, and its results calculated. As an instance of what would occur if any other proportion than the inverse square were substituted as the attractive force of gravity, suppose, at distances 1, 2, 3, the attractive force had varied as 1, 2, 3, instead of the squares of those numbers. Under such a law any number of planets might revolve in the most regular and orderly manner. But under this law the weight of bodies at the earth's surface would cease to exist; nothing would fall or weigh downward. The greater action of the distant sun and planets would exactly neutralize the attractive force of the earth. A ball thrown from the hand, however gently, would immediately become a satellite of the earth, and would for the future accompany its course, revolving about it in the space of one year. All terrestrial things would float about with no principle of coherence or stability—they would obey the general law of the system, but would acknowledge no particular relation to the earth. It is obvious that such a change would be subversive of the entire structure and economy of the world. From these and similar considerations, it follows that, although other laws are conceivable under which a solar system might exist, the solar system, such as we know it, could only exist under the actual