Thus be it simple or compound, small or large, a crystal or a mountain-chat,every inorganic aggregate on the Earth undergoes, at some time or other,a reversal of those changes undergone during its evolution. Not that it usuallypasses back from the perceptible into the imperceptible, during any periodin which it is or can be exposed to human observation. It does not becomeaeriform and invisible, as organic aggregates do in great part, though notwholly. But still its disintegration and dispersion carry it some distanceon the way towards the imperceptible; and there are reasons for thinkingthat its arrival there is but delayed. At a period immeasurably remote, everysuch inorganic aggregate, along with all undissipated remnants of organicaggregates, must be reduced to a state of gaseous diffusion, and so completethe cycle of its changes. §181. For the Earth as a whole, when it has gone through the entireseries of its ascending transformations, must remain exposed to the contingenciesof its environment; and in the course of those ceaseless changes going onthroughout a Universe of which all parts are in motion, must, at some periodbeyond the utmost stretch of imagination, be subject to energies sufficientto cause its complete disintegration. Let us glance at the energies competentto disintegrate it.
In his essay on "The Inter-action of Natural Forces," Prof.
Helmholtz states the thermal equivalent of the Earth's movement through space,as calculated on the now received datum of Mr. Joule. "If our Earth,"he says, "were by a sudden shock brought to rest in her orbit -- whichis not to be feared in the existing arrangement of our system -- by sucha shock a quantity of heat would be generated equal to that produced by thecombustion of fourteen such Earths of solid coal. Making the most unfavourableassumption as to its capacity for heat, that is, placing it equal to thatof water, the mass of the Earth would thereby be heated 11,200 degrees; itwould therefore be quite fused, and for the most part reduced to vapour.
If then the Earth, after having been thus brought to rest, should fall intothe Sun, which of course would be the case, the quantity of heat developedby the shock would be 400 times greater." Now though this calculationseems to be nothing to the purpose, since the Earth is not likely to be suddenlyarrested in its orbit and not likely therefore suddenly to fall into theSun; yet, as before pointed out (§171), there is a force at work whichit is held must at last bring the Earth into the Sun. This force is the resistanceof the ethereal medium. From ethereal resistance is inferred a retardationof all moving bodies in the Solar System -- a retardation which some astronomerscontend even now shows its effects in the relative nearness to one anotherof the orbits of the older planets. If, then, retardation is going on, theremust come a time, no matter how remote, when the slowly diminishing orbitof the Earth will end in the Sun; and though the quantity of molar motionto be then transformed into molecular motion, will not be so great as thatwhich the calculation of Helmholtz supposes, it will be great enough to reducethe substance of the Earth to a gaseous state.
This dissolution of the Earth and, at intervals, of every other planet,is not, however, a dissolution of the Solar System. All the changes exhibitedthroughout the Solar System, are incidents accompanying the integration ofthe entire matter composing it: the local integration of which each planetis the scene, completing itself long before the general integration is complete.
But each secondary mass leaving gone through its evolution and reached astate of equilibrium among its parts (supposing that the available time suffices,which in the cases of Jupiter and Saturn it may not), thereafter continuesin its extinct state, until, by the still-progressing general integration,it is brought into the central mass. And though each such union of a secondarymass with the central mass, implying transformation of molar motion intomolecular motion, causes partial diffusion of the total mass formed, andadds to the quantity of motion that has to be dispersed in the shape of lightand heat; yet it does but postpone the period at which the total mass mustbecome completely integrated, and its excess of contained motion radiatedinto space. §182. Here we come to the question raised at the close of the lastchapter -- Does Evolution as a whole, like Evolution in detail, advance towardscomplete quiescience? Is that motionless state called death, which ends Evolutionin organic bodies, typical of the universal death in which Evolution at largemust end? And have we thus to contemplate as the outcome of things, a boundlessspace holding here and there extinct Suns, fated to remain for ever withoutfurther change?
To so speculative an inquiry, none but a speculative answer is to be expected.
