by Grant Allen
CHAPTER III.
THE SOLAR SYSTEM.
Among the minor aggregating masses into which the cosmical nebula may be supposed to have split up, in the course of its general aggregative cycle, was a group of matter out of which our own solar system has been developed. In its earliest separate phase we may suppose this group to have consisted of various minor portions, in varying stages of aggregation, revolving in a single direction around their common centre. (Details about the direction of Neptune and Uranus may be safely neglected.) We may further suppose that the nebulous or quasi-nebulous mass thus composed again divided itself, along its weakest cohesive lines, into other portions, which have aggregated into the existing planetary groups; while these latter again subdivided themselves into the central masses and their satellites. It is immaterial for our purpose whether, with the earlier evolutionists, we regard these changes as taking place in a relatively homogeneous substance, a diffused nebula, or whether, with their later followers, we set them down to aggregative action in comparatively solid and discrete masses (meteors), like those which we know to exist in large tracts within the sphere of the solar system. But the important point to notice in either case is this, that these groupings and sub-groupings took place under the influence of Forces, and that the Potential Energy of separation between the masses or molecules became Kinetic as they clashed together, and assumed the form of Heat. The various masses thus became each of them a little sun, aggregating around their several centres, and radiating their Energy into the surrounding ether. As in other cases, some small portion of this Energy would fall upon neighbouring masses, belonging either to the same system or to other systems, and would there do a little towards retarding the aggregation of their matter and the dissipation of their Energy; but the greater portion would doubtless be lost in the vast interstellar spaces; so that the general result would be a loss of Energy to matter, and a gain of Energy to the ethereal medium.
The various planets and satellites thus formed would still possess Potential Energy in virtue of their continued separation from one another. They would also possess Molar Kinetic Energy in virtue of their orbital movement, which acts as a preventive to their immediate aggregation with their common centre, the sun. And, finally, they would possess Molecular Kinetic Energy through the vibratory movement of their molecules, derived from the previous Kinetic Energy of their aggregative motion. But as their particles vibrated, they would part from moment to moment with portions of their Energy to the surrounding ether. This loss of Energy would only largely affect the periphery of each mass, and would at first be inconspicuous at the centre. It would also affect the smaller masses much more rapidly than the greater, for two reasons; both because the amount of aggregating matter being less, the amount of heat generated would also be less; and because losses of heat from the periphery could not so easily be made up by conduction from the centre. The smaller masses would accordingly cool at their surfaces at comparatively early periods; while the larger ones, in proportion to the amount of unaggregated matter within the sphere of their attraction, would continue for long periods to receive fresh accessions to their molecular Energy, and to radiate Light and Heat into the surrounding ether. Especially would the largest mass of all, the central sun, continue for an immense era to aggregate the surrounding masses and to radiate the liberated Energy into the space around.
Further, we may conclude that as the surface of each mass parted with its Energy, its superficial molecules would be drawn together by the Forces of cohesion and chemical affinity. We should thus get a solid cohering framework on the exterior of each mass, as soon as it had parted with a considerable portion of its molecular Energy to the surrounding ether. Through this cohering crust, the central Energy would slowly escape by conduction: until, sooner or later, we might expect each such mass to consist of a cold and inert collection of molecules, the whole Energy of whose previous separation had been yielded up to the ether. But a special incident of this transference might occasionally occur to break the monotony of its simple course. As the central Energy escaped through the cohering crust, there might be a tendency for the interior molecules to be drawn together under the influence of cohesion and gravitation. A second crust would thus tend to form itself beneath the outer one. Thereupon, the Force of gravitation might outweigh the cohesion of the outer crust, which would yield under the strain and fall in upon the subjacent mass, breaking along its line of least cohesion. Each such fall would be itself a change of Potential into aggregative molar Kinetic Energy, as the masses fell together; and when they clashed, the Energy would assume the molecular form and be given off as heat. But, however the aggregation takes place, as the matter of each group aggregated more and more closely round its centre, the Energy of its previous separation would be given off as heat, and would finally be imparted, as in every other case, to the ethereal medium.
While each mass was thus parting (by radiation) with the Molecular Kinetic Energy resulting from its previous separation and aggregative motion, it would also be parting, though more slowly (by ethereal friction) with the Molar Kinetic Energy of its orbital motion. Each satellite would thus be drawing progressively nearer to its primary, and each planet to the sun. As every unit of Energy was lost, gravitation would draw the body one unit nearer to its relative centre. It might thus be expected that each satellite would aggregate with its primary before the primary planet aggregated with the sun. At each such aggregation, though the greater part of the orbital Energy would doubtless be already dissipated, yet it is probable that as the two bodies glided together (for they would not fall, as is often erroneously said) there would be a considerable residue of Energy still remaining, which, on the shock of collision, would be converted into molecular motion (or heat), and would be sufficient to reduce the bodies to a molten state. But this incident, instead of interfering with the final aggregative process, would really hasten it: because the new united body would at once begin radiating off its heat into space, and once more cool down to a mass of cold and inert molecules. In other words, all the remaining Energy of separation belonging to the satellite in virtue of its discrete condition, and all the remaining Kinetic Energy of its orbital motion, would thereupon be dissipated into the surrounding ether: and the united mass would continue to gravitate slowly towards the central sun. What is thus probable of the satellites in relation to their primaries is equally probable of the planets in relation to the sun. As their Energy of orbital motion is dissipated by ethereal friction, we conclude that they are drawing nearer and nearer, step by step, to the centre of our system. And there is no reason to doubt that they will continue to do so until they each slowly aggregate with the central mass, converting their remaining Energy as they clash together, into heat, which will itself go for a time to swell the volume of solar Energy, and will be radiated off like the rest into surrounding space. Finally, when the sun has aggregated with himself all the matter of the solar system, we may conclude that he will ultimately radiate off all the molecular Energy derived from their aggregation, and become himself a cold and inert mass, like some of those burnt-out stars revealed to us by astronomy. And then we may imagine that this single sphere, which contains all the matter of our system, will itself proceed to aggregate with some other mass, in that general cosmical group of which it forms an unimportant member. Of course, it is impossible to conjecture which of these aggregations will take place first; and it is quite conceivable that the whole solar system might clash with some other group of worlds before its various members had time to aggregate in this regular order with one another; but if our suggested theory of a general subordination of systems and cycles to a common cosmical centre be correct, then just as each satellite would aggregate with its primary before that primary had time to aggregate with the sun, so each planet would have aggregated with the sun before the sun had time to aggregate with its superior mass. However this may be, it will be sufficient if we regard the probable course of events in the solar system as a specimen of th
e probable incidents everywhere accompanying the course of aggregation round the common cosmical centre, and briefly hinted in the preceding chapter.
At the present moment of time, we occupy a middle point in the systemic epoch thus sketched out. The sun, our central mass, is still in a state of rapid molecular motion, which he imparts as Radiant Energy to the ether. He has yet much outlying matter to aggregate, and it seems probable that small aggregations are from day to day taking place. Of the planets, the smaller have cooled down sufficiently to possess a firm and coherent outer crust, while the larger are still in a very volcanic state. The satellites have probably radiated away all their proper heat, and are already cold and inert to their centres. The surface of the most easily observed, our own moon, shows the vast corrugations which result from the continual collapses of the crust upon the once heated nucleus, and the reactions of the molten interior upon the coherent outer shell: — corrugations relatively (if not absolutely?) much greater than any at present found upon the surface of our own earth. Some small fraction of the Energy radiated from the sun falls upon the cooled exteriors both of planets and satellites. Of this, the greater portion is reflected back by dispersion, as we see from the case of the moon, in every direction (only a small fraction of this fraction again falling upon other masses). But a certain lesser portion is used up in heating the outer crusts, in setting up evaporation, currents, and winds, and in producing the phenomena of organic life. These secondary separative reactions of radiated Energy upon the surface of a planet form the great mass of those phenomena which are generally observed by human beings.
CHAPTER IV.
THE EARTH.
As we pass from the solar system to our own planet, we leave the region of hypothesis, and arrive at that of known facts.
The earth is a collection of material particles, the vast majority of which, so far as revealed to our observation, are in a state of stable aggregation with one another, molar, molecular, chemical, and electrical. Its centre may be — and probably is — still occupied by a molten (though rigid) mass, whose heat has not yet been fully conducted away: but the outer crust, except at its exposed surface, consists of matter aggregated in those molecularly cohering and chemically passive masses known as rocks. Its exterior is not absolutely regular, but is in places corrugated into certain elevations and depressions which we call mountains, table-lands, valleys, and ocean-beds. The portions elevated above the general level possess Potential Energy in virtue of their elevation: but the Force of gravitation being interfered with by that of cohesion, this Energy cannot assume the Kinetic Mode without the intervention of an external Liberating Energy. In short, while the centre of the earth may still possess some molecular Energy of its own, which is only slowly escaping through the outer crust, its hard exterior is for the most part thoroughly aggregated and almost devoid of relative Kinetic Energy, except so far as it obtains small daily increments from the solar radiation.
If for a moment we leave out of consideration the solar Energy thus absorbed, we can form some conception of the appearance which the earth would possess, supposing it left to its own resources. The whole ocean and all the other water on the earth would be frozen into a solid mass. There would be no plants or animals on the surface, nor any winds, storms, rain, snow, or lightning. What might be the condition of the atmosphere we cannot say; but we may guess that it would be greatly diminished in size, if not absolutely reduced to a solid form. Motion upon the surface would be all but unknown: the only movements which could ever occur being those which would occasionally result from those internal causes that give rise to earthquakes and volcanic eruptions. These would still take place, as the gradual loss of Energy from the central mass would make the Force of gravitation outweigh that of cohesion; and the Potential Energy which thereupon would be mobilised might act as a liberative agent to certain masses on the slopes, besides causing perhaps a temporary melting of some small portion of the solidified water through volcanic heat. But these incidents would themselves only accelerate the loss of the remaining proper Energy of our planet, which would soon be imparted to the ethereal medium, and leave our earth at last a perfectly inert mass of aggregated particles.
In the world as we know it, however, very different phenomena are observable; and all these are due to the separative action of Energies radiated from the sun, which fall upon our earth, acting partly as separative agents for the superficial molecules, and partly as liberative agents for the various Potential Energies whose mobilisation is prevented by interfering Forces. Falling upon the atmosphere, the Kinetic Energy of ethereal undulation prevents its aggregation and keeps it permanently in the gaseous form. If it be objected that the non-absorption of radiant heat by the gases of the atmosphere is opposed to this view, it may be answered that actual absorption is not necessarily implied: it will be sufficient for our purpose if the original molecular mobility of the gases is not diminished by communication with the ether. We cannot experiment upon the conduct of oxygen or nitrogen at the absolute zero of temperature, but we have no reason to doubt that at some extremely low point they would follow the example of all other bodies, part with their molecular Energy to the surrounding ether, and pass through the liquid into the solid form. We know already that carbonic anhydride can assume the frozen condition, and it is hardly probable that the simple atmospheric gases would not do the same, under similar circumstances, could we only command sufficient Power for their liquefaction. Falling upon the water, the ethereal Energy acts in opposition to its cohesive Force, and keeps it habitually in the liquid state, at least in tropical and temperate climates. Nor is it only by compelling them to assume the gaseous and liquid forms that the ethereal Energy displays its separative nature on air and water: it also acts in opposition to gravitation. It heats many water-molecules till they evaporate, and then raises them to considerable heights in the air. It expands the atmosphere of the tropics (by conduction and convection), and causes the phenomena of monsoons, winds, and storms. In a similar way it produces the ocean currents. And it thus becomes the cause of all motions on the face of the earth, except those of organic beings, to be treated hereafter. It must be noticed throughout, however, that these disintegrative effects are only directly produced upon the liquid and gaseous substances in which the force of cohesion is very slight. Those more solid and coherent masses, the rocks, are little acted upon, and that only indirectly, by Liberating Energies in the liquids and gases, as will more fully appear hereafter.
But the Energy which thus falls upon the surface of the earth from day to day, and sets up these separative actions in its less coherent superficial molecules, does not long remain upon the face of our planet. Each portion of the earth’s surface is turned (on an average) for one half of each twenty-four hours towards the sun, and for one half away from the sun. The heat which struck it during the day and was partly absorbed by its superficial molecules is more or less radiated away to the ether during the succeeding night. In such a case as that of Sahara, where there is no organic life on whose production the Energy is permanently expended, and little vapour of water to retain the heat — almost all the Energy received during the daytime is radiated away at night, so that the thermometer often sinks below the freezing point. Here we have the naked facts uncomplicated by the problems of life and the interference of rain and wind. On the ocean, the solar Energy absorbed by the water raises large masses of watery vapour to a considerable height. There, the vapour parts sooner or later with some of its Energy to the ether, and aggregating in the form of rain, converts the remainder from the Potential to the Kinetic Mode, finally yielding it up again as heat when it once more reaches the ocean. So in this case too, though less conspicuously than in the former, the absorbed Energy, after causing temporary separations, is before long dissipated, while the particles which it affected once more aggregate in obedience to their inherent Forces. On the ordinary fertile land-patches the solar Energy is partly returned at once by radiation, as in Sahara; partly used up in e
vaporation, as on the ocean; and partly employed in the production of living organisms. In the first case, the retransference of the Energy to the ether is obvious; in the second case, though less immediate, it yet takes place, as explained above, when the vapour falls again as rain; but in the third case, the transfers are more involved, and will have to be treated in separate chapters. It will be enough for the present to point out that every organism sooner or later dies, and that then the Energy which was embodied in its production is once more given up to the ether on the chemical aggregation of oxygen and other decomposing agents with its component atoms.
Let us now look in detail at a few of the ways in which the separation, yielded up to the ether by particles of solar matter as they aggregated, is reconverted into separation between slightly-coherent mundane particles, and is finally transferred again to ether.
A lake in the northernmost part of the temperate zone is frozen over during the winter. The comparatively small amount of solar Energy which affects it does not suffice to separate its particles from their cohesive union. But when the earth shifts its position by oscillating slightly on a particular axis, the conditions of aerial refraction are altered, and the amount of radiant Energy which is concentrated on this particular spot is largely increased. The first effect of this Energy is to loosen the aggregated molecules from their solid state and to make them assume the liquid form. The Energy thus absorbed remains in the water as ‘latent heat,’ in other words either as Potential Energy of separation or as Kinetic Energy of motion: and when the water again freezes, it is yielded up to the surrounding atmosphere, often in the visible form of warm mist. After the separative Power has produced this first effect in melting the ice, fresh quantities are from day to day poured upon the surface of the now liquid lake. Here, the heat produces further separation between the superficial molecules, so that even the slight cohesive power of liquids is overcome, and the particles assume the vaporous state. Thereupon they are raised into the air, and drifted about by the winds, which themselves result from the separative action of heat. After a time, the particles lose by radiation and convection much of their Kinetic Energy, and begin once more to aggregate into rain-drops. These fall upon the surrounding heights, and finally find their way again into the lake. But the Energy which raised them has by this time been dissipated, and fresh Energy will be required to make them once more assume the form of vapour. Nor is this all. As the drops fall upon the mountain side, they employ part of their Energy in overcoming the cohesion of its molecules. In this way they slowly wear away the elevations on the earth’s surface, and carry down their particles to the valleys or the sea. In so doing, they act as liberating agents for the Potential Energy of these masses, and so assist in working out the general plan of aggregation. It is true that new mountains are from time to time slowly upheaved in place of the old ones, but these are themselves mere apparent exceptions, as they really represent a general lapse of the surrounding crust: and their heights are in turn worn down by watercourses, glaciers, and percolation. In short, the solar Energy expended in evaporation is ultimately employed as a liberating agency for the Potential Energy of separation possessed by such masses as are raised above the general gravitative sea level of our planet. These masses, though their cohesion is for a while destroyed, aggregate in the end as new sedimentary deposits; and so the whole process becomes merely one more step in the gradual aggregation of matter and dissipation of Energy to the ether.
