CHAPTER VI
A PLANET’S HISTORY
Self-sustained Stage
UP to this point in our retrospective survey the long course of evolution has taken one line, that of dynamical separation of the system’s parts with subsequent reunitement of them according to the laws of celestial mechanics. Of this action I have submitted the reader my brief: departing in it from common-law practice, in which the cause of action is short and the brief long. And I have, I trust, guarded against his appealing on exceptions.
From this point on we have two kinds of development to follow: the one intrinsic, the chemical; the other incidental, the physical. Not that, in a way, the one is divorcible from the other. For the physical makes possible the chemical by furnishing it the conditions to act. But in another sense, and that which is most thrust upon our notice, the two are independent. Thus oceans and land, hills and valleys, clouds and blue sky, as we know them,—everything, pretty much, which we associate with a world,—are not universal, inevitable, results of planetary evolution, but resultant, individual, characteristics of our particular abode. They are as much our own as the peculiar arithmetic of waiters is theirs, or as used to be the sobriety of the country doctor’s horse—his and no other’s. Our whole geologic career is essentially earthly. Not that its fundamental laws are not of universal application, but the kaleidoscopic patterns they produce depend on the little idiosyncrasies of the constituents and the mode in which these fall together. Our everyday experiences we should find quite changed, could we alight on Venus or on Mars.
On the other hand, the chemical changes which follow a body’s acquisition of heat, setting in the moment that heat has reached its acme and starts to decline, are as universal as the universe itself. They are conditioned, it is true, by the body’s size and by the position that body occupied in the primal nebula, but they depend directly upon the degree of heat the body had attained. The larger the planet, the higher the temperature it reached and the fuller its possibilities. Even the planets are born to their estate. Thus the little meteorites live their whole waking life during the few seconds they spend rushing through our air. For then only does change affect their otherwise eternally inert careers. That the time is too short for any important experience is evident on their faces.
Heat is most intimately associated with the very constitution of matter. It is, in fact, merely the motion of its ultimate particles, and plays an essential part in their chemical relations. Just as a certain discreet fervor and sufficient exposure for attraction to take, make for matrimony, so with the little molecules, a suitable degree of warmth and a propitious opportunity similarly conduce to conjunction; too fiery a temperament resulting in a vagabondage preventative of settled partnership and too cold a one in permanent celibacy. You may think the simile a touch too anthropomorphic, but it is a most sober statement of fact. Indeed, it is more than probable that in some dull sense they feel the impulse, though not the need of expressing it in verse. That metals can remember their past states seems to have been demonstrated by Bose, and is certainly in keeping with general principles as we know them to-day. For memory is the partial retention of past changes, rendering those changes more facile of repetition.
A high degree of heat, then, makes chemical union impossible, because the great speeds at which the molecules are rushing past each other prevents any of them being caught. Lack of speed is equally deterrent. Nor is it wholly or even principally, perhaps, a movement of the whole which is here concerned, but a partitive throbbing of the molecule itself. Certain it is that great cold is as prohibitive of chemic combination as great heat. Phosphorus, which evinces such avidity for oxygen at ordinary temperatures as to have got its name from the way it publishes the fact, at very low ones shows a coolness for its affinity amounting to absolute unconcern. Thus only within a certain range of temperature does chemical combination occur. To remain above or below this is to stay forever immortally dead. To get hot enough in the first place, and then subsequently to cool, are therefore essential processes to a body which is to know evolutionary advance.
To pen the history of the solar system and leave out of it all mention of its most transcendentally wonderful result, the chemical evolution attendant upon cooling, would be to play “Hamlet” with Hamlet left out. For the thing which makes the second half of the great cosmic drama so inconceivably grand is the building up of the infinitely little into something far finer than the infinitely great. The mechanical action that first tore a sun apart, and then whirled the fragments into the beautifully symmetric system we behold to-day, is of a grandeur which is at least conceivable; the molecular one that, beginning where the other left off, built up first the diamond and then humanity is one that passes our power to imagine. That out of the aggregation of meteorites should come man, a being able to look back over his own genesis, to be cognizant of it, as it were, from its first beginnings, is almost to prove him immanent in it from the start. Fortunate it is that his powers should seem more limited than his perceptions, and the more so as he goes farther, else he had been but the embodiment of conceit.
We must sketch, therefore, the steps in this marvellous synthesis; hastily, for I have already spoken of it elsewhere in print and repetitions dull appreciation,—in the appreciative,—though we have the best of precedents for believing that, even in science, to be dull and iterative insures success; the dulness passing for wisdom and the iteration tiring opposition out.
In the Sun all substances are in their elemental state. Though its materials are the same as the Earth’s, we should certainly not feel at home there, even if we waived the question of comfort, for we should recognize nothing we know. We talk glibly of elements as if we had personal acquaintance with them, man’s innate snobbery cropping out. For to the chemist alone are they observable entities. No one but he has ever beheld calcium or silicon, or magnesium, or manganese, and most of us would certainly not know these everyday elements if we met them on the street. Of all the substances composing the Earth’s crust, or the air above, or the water beneath, practically the only elements with which we are personally familiar are iron, copper, and carbon, and these only in minute quantities and in that order of acquisition; which accounts for the stone, iron, and bronze ages of man, ending we may add with the graphite or lead-pencil age of early education.