Works of Grant Allen, page 785
Electrical Liberating Energies are those which release Electrical Units from the interference of a Force antagonistic to Electrical Affinity. The usual vagueness of electrical science prevents any definite treatment of these phenomena; but we may consider the Energy which closes the circuit of a battery, or brings the discharging tongs to a Leyden jar, as essentially analogous to the cases noted above. Their fundamental similarity will be seen if we recollect that any Energy spent in overcoming the cohesion of the glass partition in the Leyden jar, and so causing it to break, would produce exactly the same effect.
Under the head of Liberating Energies it will be convenient to include those other Energies which act so as to permit the escape of suppressed Kinetic Energies. Such will be the Energy which turns the valve of a steam-engine or the stopcock of a vessel containing compressed gases. A more familiar instance is found in the Energy which draws the cork of a champagne bottle. And if we were correct in supposing an analogy between known suppressed Energies and explosive nitrogenous compounds such as gunpowder and nitro-glycerine, then the match or blow which explodes them acts as an analogous liberating agent. Liberating Energies of this description may be conveniently described as Liberators of Suppressed Energies.
CHAPTER XIV.
MISCELLANEOUS ILLUSTRATIONS.
After so long and so abstract an exposition, it may be well to give a few selected concrete illustrations, showing the interaction of the principles already laid down, before we proceed to those still more abstract and difficult problems which yet lie before us. We have hereafter to frame some clearer notion of the Relation between Ether and Matter, the Nature of Energy, and the Nature of Movement; which questions will require a power of abstract thought and concentration which is not possessed by every reader. But it may aid our comprehension of these highest abstractions if we more firmly grasp the concrete phenomena in which they are dimly manifested.
A lump of ice lies loosely on a mountain top. Its molecules are rigidly bound together by the Force of cohesion. The Force of gravitation tends to attract it, but the cohesion of intervening molecules interferes, and it cannot further aggregate, cannot get any lower, of its own accord. It possesses Potential Energy in virtue of its separation from the dead level of ocean: but that Energy cannot assume the Kinetic Mode so long as the interfering Force of cohesion prevents it. There are, however, various conceivable ways in which a Kinetic Energy may intervene to liberate it. The wind may blow it over; a man may hit it with his stick; or a peal of thunder may shake it down. In any of these cases, it will go down as a mass, all its molecules still locked together by cohesive Force. Again, the Kinetic Energy of ether (which we commonly know as Radiant Heat) may fall upon the mass, while still perched on its pinnacle. In that case, the motions of the ether particles will be communicated to the ice molecules, just as the motion of one billiard ball is communicated to another — or still more exactly, as one pendulum might set another in synchronous motion by striking it time after time. Under the influence of this separative Power, the molecules will slowly be unlocked from their cohesive union, and the ice will be melted. But the Energy which thus acts as separative to the molecules in their relation to cohesion, acts also as liberative in their relation to gravitation. The Potential Energy of each molecule (visible Energy of position) now becomes Kinetic, and they roll down the mountain side in the form of water. Let us suppose that they unite on their course and make a cataract. When they reach the level below (which for argument’s sake we will suppose to be that of the sea) all their Potential Energy has been transformed into Kinetic. Omitting the small amount lost by friction on the way, this Kinetic Energy is immediately transformed once more, as the water reaches the surface, from the Molar to the Molecular species. It becomes heat, and is radiated off into the surrounding space. Our ice has thus entirely parted with its Potential Energy to neighbouring bodies, and to the ethereal medium, though the water which represents it still holds all the Kinetic Energy which originally melted it. It cannot again be raised to the mountain top without the integration of fresh Energy. Whence is this to come? In the majority of cases it is supplied by the Radiant Heat of the sun. This Energy, working upon the surface of the sea, causes separation amongst its superficial molecules, which thereupon rise into the air. Thus we see that the same Energy which overcomes the faint cohesion of the water also overcomes in part the force of gravitation. The heated molecules, being less attracted than the colder, are pushed upward by their pressure, and rise to a considerable height. The agent in raising them is Energy. So that the very same motion which keeps the planets from aggregating with the sun, keeps the water molecules from aggregating with the earth. So long as they retain this Energy they continue to float at a great height. But they cannot retain it long. The surrounding objects at that height are very cold — in other words, are not in a state of high molecular vibration. Accordingly, when the molecules encounter a cold mountain top, towards which they are attracted by molar Forces, they part with their heat and aggregate under the influence of cohesion into ice. Their Kinetic Energy is now all gone, and nothing remains to them but the Potential Energy of their separation from the level of the sea. And then the whole cycle of changes begins over again.
Let us look next at a totally different instance, that of a cross-bow. This is a common illustration with physicists, and it has already been once hinted at, but no detailed explanation was given, because it will be presently seen that the case is much more complicated than at first sight appears. The Kinetic Energy of human muscles is employed in pulling the string back to the notch. The bow is then bent. Now this bending implies two forms in which the energy becomes dormant, which answer to the common expressions, tension and pressure. The molecules in the convex portion of the bow are pulled slightly apart from one another, but not beyond the sphere of their mutual attractions. We have consequently here a state of Potential Energy due to the separation of particles strongly influenced by cohesive Force. The molecules in the concave part of the bow, on the other hand, are pressed closely together upon one another by the Energy employed, which here acts in opposition to the Kinetic Energy of the molecules, whose natural vibrations are thus in part suppressed. Accordingly we have here a state of suppressed Energy. Both of these of course tend to become Kinetic, but are prevented by the interfering cohesion of the string and the trigger. The separative nature of the Energy employed is clear from the fact that if the string is pulled too far back, the strain upon the cohering particles becomes too great, and the sphere of their mutual attraction being transcended, they break apart with a snap. In the present case, however, having merely bent and bolted our bow, we have all our Energy bottled up in a dormant state. Next, let us release the string. The Energy which we employ in doing so, acts as a Liberating Energy with reference to the Potential Energy of the convex part, and as a Liberator of Suppressed Energy with reference to the concave part. It removes that cohesive obstacle, the trigger, which interfered with the mobilisation of the dormant Energies. The Molecular Force of cohesion now draws together the separated molecules of the convex part, and their Potential Energy becomes Kinetic. Through the medium of the string it is communicated to the arrow. The arrow flies rapidly through the air, parts with a small portion of its Energy by friction, but retains most of it till it pierces the target. Here, part of its Energy is used up in producing separation between the particles; while the remainder is given off in the form of heat. And so all our Energy is once more yielded up from its original possessor, the bow.
Again, let us take a case where chemical activity is concerned. A lump of coal possesses Potential Energy in the separation of its atoms from those oxygen atoms towards which it is attracted by Chemical Affinity. So long as they are merely in mechanical conjunction with one another, the interference of some other Force (probably cohesion) prevents them from aggregating. But when a Liberating Energy is applied in the shape of a match, the atoms rush together in a mutual embrace. Their Potential Energy becomes Kinetic, and they aggregate. But the Energy of their separation is not destroyed. It is communicated to the ether as Radiant Heat. In this state it may either pass away from our earth altogether, or it may be communicated to other bodies, in which case it is said to be absorbed. Let us suppose it is absorbed by a boiler of water. The water molecules are then thrown into a state of vibration, which rapidly severs them from one another until they assume the form of steam. If this steam is allowed to issue from the boiler, it will rapidly give off its Energy to neighbouring bodies, the ether included, and the Energy which first passed from the coal and oxygen to the water, will now pass from the water to the ether. But we may use the boiler to turn an engine. In this case part of the Molecular Kinetic Energy is transformed to the Molar species in the piston. It is then used up in initiating movements in the wheels and cranks, all of which are finally retransformed into the Molecular Species by friction. If the engine is stationary, the friction will be between its parts; if locomotive, between its parts and the rails. Ultimately, in every case, all the Energy is yielded up to the ether in the Kinetic Mode and radiated off into space.
Now what is the conclusion which all these cases force upon us? That whenever Forces succeed in aggregating masses, molecules, atoms, or electrical units, the Energy of their separation, passing into the Kinetic Mode, is transferred to surrounding bodies, and after many or few vicissitudes is finally handed over to the ethereal medium. This is the point which must next engage our attention.
CHAPTER XV.
THE DISSIPATION OF ENERGY.
In the definition of Force given in our second chapter, a Force was stated to be a Power which initiated aggregative motion and resisted separative motion in two or more particles of ponderable matter, and possibly also of the ethereal medium. In the definition of Energy, given in our third chapter, an Energy was stated to be a Power which initiated separative motion and resisted aggregative motion in two or more particles of ponderable matter or of the ethereal medium. This addition in the latter case, and its qualified omission in the former, was intentional and significant. Though we cannot dogmatically say that the ether does not possess Forces, we do not know it to possess any; and if it does, the resistance which they offer to separation appears to be almost infinitesimal. It may well be that ether is merely a more tenuous kind of matter, animated by the same Power as the ponderable bodies: but even if it is, we know that it can be conspicuously affected by Energy, while we do not know that it can be conspicuously affected by Force. From this difference flows a very important corollary which may be formulated as follows.
The Energy liberated from the Potential Mode when bodies or particles aggregate under the influence of Force tends ever to assume the Kinetic Mode, and to be transferred from ponderable matter to the ethereal medium.
As Liberating Energies are perpetually setting free Potential Energy, and permitting aggregative motions to be set up under the influence of Force, and as the Kinetic Energy thus liberated is transferred to adjacent bodies, a part of it at least must be transferred to the ether. Furthermore, as that part of it which is transferred to the ether is radiated off in every direction into space, it must happen that the greater part of it is lost for ever to ponderable matter, and imparted to the ethereal medium. For, although some portion of the Energy may meet in its course with ponderable matter, and be absorbed thereby, yet inasmuch as the interstellar spaces are vastly larger than the interspersed ponderable heavenly bodies (so that in most directions motion may be continued in a straight line for ever without meeting one) it necessarily happens that the greater portion will never meet with any ponderable matter, but will go on, presumably ad infinitum, traversing the ethereal medium. This principle, which will be fully expounded in its concrete aspect in Part II. of this work, must at present be accepted in this its abstract aspect, on the ground here laid down.
Again, though much radiant Energy may fall upon any one mass from another (as on the earth from the sun), yet inasmuch as this Energy is the correlative of an aggregation which has taken place in the radiating mass, whereby some of its Potential Energy has become Kinetic and been imparted to the ether, and inasmuch as the portion absorbed by that particular mass bears an infinitesimal ratio to the portion radiated ad infinitum, it must follow that on the whole every aggregation involves a loss of Energy to ponderable matter and a gain of Energy to the ethereal medium.
Once more, even that portion of Energy which is absorbed by any other mass will in part be used up in Liberating Energies (as when solar heat melts a piece of ice on a mountain top), and will accordingly itself be a cause for future transfers of Energy from ponderable matter to the ethereal medium. And finally, this absorbed Energy itself will in part at least be radiated off from the absorbing mass and imparted once more to the ethereal medium.
We thus see in every case that all Energy tends to be lost by ponderable matter and transferred to the ethereal medium.
CHAPTER XVI.
THE NATURE OF ENERGY.
We now come to the most abstract and fundamental question of all. What is the true nature of Energy? In the beginning of this book we took it for granted that Force was equivalent to Aggregative Power and Energy to Separative Power. That first assumption, however, is in reality the point which our treatise is meant to prove, and we have tried to prove it by running through the chief manifestations of Power and showing how simply and truthfully they can all be formulated on this principle. We have endeavoured, in other words, to point out the perfect congruity of our assumption with fact. Having done so first in the abstract, we shall proceed to show how the phenomena which form the subject-matter of the various sciences, and how the concrete course of events in the universe, can be expressed in terms of our formulæ. But before we go on to these departments of our subject, we must try to gain a clearer conception of the real nature of Energy.
Energy is Separative Power. Every Energy in the Universe was primordially a mere statical separation of masses, molecules, atoms, or electrical units. If there were no such power as Force, every one of these bodies would have remained for ever apart and immovable. But as forces draw together these mutually attractive material objects, their Energy assumes for a moment the Kinetic Mode. The falling water, the moving glacier, the oxygen rushing to unite with the coal, each pass for a shorter or longer period through the Kinetic stage. As they aggregate, their Energy is given off in some other form of motion, involving separation. But as they move about, they part with this motion in separating other masses or molecules, and the attractive Force soon brings them together again.
And what is the meaning of the Law of Conservation? Simply this: that the total of statical separation, plus the total of motion, in all particles whatsoever, material or ethereal, is always a constant quantity. In other words, separation can never yield to aggregation without generating an equivalent amount of motion, which itself may pass into separation of some other sort: while, conversely, motion can never cease without generating either an equivalent separation or an equivalent other motion. Thus a body at a height cannot fall without generating an amount of motion proportionate in a known ratio to its mass and height, which motion itself is transferred on the body’s fall to its several molecules, causing a separative action among them; and this motion is again transferred to the ether: while, similarly, a piece of coal cannot combine with oxygen without yielding up its separation in the form of molecular motion, which motion may raise vapour of water to a considerable separation from the earth’s central mass, and be itself finally yielded up to the ether. In short, the alternative Modes of Energy are Actual Separation, and Motion which eventuates in Separation.
Furthermore, no body can be prevented from saturating its aggregative tendencies except by an Energy. There is no known way in which the total of bodies can be kept apart from their closest conjunction with one another except by continuous motion, like that of a planet, a top, or a vibrating molecule. Even the case of Interference of Forces, which at first sight seems an exception, is not really so (though for convenience’ sake we have treated it as such), because to suppose that the suspended ball will break its string or the weight push through the table is to suppose that a weaker aggregative tendency will overpower a stronger one. In all the larger bodies of the Universe we see the discrete state maintained by orbital Energy: and in all the molecules of liquids and gases on this earth we see the discrete state maintained by heat, or continuous vibration.
CHAPTER XVII.
THE NATURE OF MOTION.
Last of all comes the question, — What is Motion? Divesting our minds of all concrete associations and looking at the phenomenon in itself, we arrive at the following unfamiliar conclusion.
Motion is the Mode by which Energy (or Separation) is transferred from one portion of matter to another, and ultimately from matter to the ethereal medium.
When the Motion is simply separative we see this in a moment. A ball fired upward, a weight carried to a height, or an atom disengaged from a compound, show us motion as equivalent to separation, in its naked form. When we look at Motion along a line at equal distances from the attractive centres — as in the case of a locomotive running along a level — we do not at first see how the Energy can be considered as separative. But as soon as we reflect that the Energy required for the purpose is entirely relative to the resistances which must be overcome — as soon as we recollect that if there were no friction, the initial Energy would carry on the moving body for ever, and that where there is little friction the moving body continues to proceed for a long period in the same direction without conspicuous loss of speed — we see that each new increment of energy from the burning coal is used up — not in intensifying the rate of motion, but in overcoming friction, in wearing down the projecting particles of the machinery and the rails, in producing heat, and so, ultimately, in setting up separative actions. This case leads us on to that of a planet having orbital Energy, or a molecule having Vibratory Motion. In both these instances the substance to which the Energy is imparted is far subtler and more tenuous, being in fact the ethereal medium. Yet in both we see that as their Energy is lost, they aggregate with attractive bodies, and we thus perceive the separative nature of their motion. At the same time we see it as a mere incident in the transference of separation from matter to ether. Lastly, in the case of aggregative movements, we see that the Motion replaces for a time the separation of masses, molecules, atoms, or electrical units, as they rush together; but we also see the same separation afterwards transmitted to some other form of matter or to the ether, as heat, light, electrical separation, or some other form of separative Energy.
