To be consistent, therefore, we must either cease to call Aether matter, or else admit that Aether, like all other matter, is gravitative. It is absolutely impossible to be strictly logical and admit that Aether is matter, and not to admit that it is subject to the most universal law that governs matter, as the Law of Gravitation distinctly states that "every particle or atom of matter attracts every other particle." This universal law in view of a gravitationless Aether would have to be amended to "Some particles of matter attract some other particles." Thus the universal Law of Gravitation ceases at once to be a universal law, and such a result is opposed to all experience and experiment. Again, let us apply our third Rule of Philosophy to this supposed gravitationless Aether, and see what the result is.
Our third rule states, that any hypothesis put forward must satisfactorily account for the phenomena sought to be explained and accounted for. The Aether was conceived in order to explain the phenomena of light, and one of the properties it was conceived to possess was elasticity, yet that very conception was devoid of the most fundamental property of matter, without which there is no elasticity, that is, that it was not atomic.
I have already shown in Art. 44, that Aether is atomic, and therefore there is given to the Aether a structure which is capable of exhibiting elasticity, inertia, density, and even Gravitation, while at the same time, the conception is fully in harmony with philosophical reasoning and Newton's Rules of Philosophy.
Let us consider the question whether Aether is, or is not gravitative, from another aspect. For several hundred years, the physical cause of Gravitation has been outstanding, while the world has held the conception that Aether is a gravitationless and frictionless medium. The earth has been rolling on in her orbit year in, year out, together with all the other planets in their annual march round the sun, and yet through all that time no one has been able to suggest, or give any satisfactory or adequate physical explanation, as to what moves the earth along.
I am fully aware that Newton suggested and proved, that it was because of the Law of Gravitation. But I look upon that as a mathematical explanation and not as a physical one.
Now I venture to predict this, that on the assumption of a gravitationless medium, the physical explanation so longed for will always be outstanding, as a gravitationless Aether is synonymous with a frictionless medium, and so long as we admit that there is a frictionless medium, so long will the physical cause of Gravitation, and therefore the physical cause of all the movements of the planets and comets, be outstanding and unexplained.
If, however, instead of being illogical in our reasoning, we become logical, and affirm that Aether is matter, and because all matter is gravitative, therefore Aether is gravitative; and if, instead of being unphilosophical, we become philosophical, and affirm that because a gravitationless Aether violates both the first and second Rules of Philosophy, such a conception must be put away, and in its place a more philosophical conception must be forthcoming, which is that Aether is gravitative; then, upon such a logical and philosophical basis, I venture to premise that the great problem which is still outstanding of the cause of Gravitation, will remain outstanding no longer, and the physical cause of all the movements of all celestial bodies will be put upon a physical basis, in addition to a mathematical one.
If such a result can be arrived at by the logical and philosophical conception of a gravitative Aether, then the three Rules of Philosophy are fully satisfied, and the assumption of a gravitative Aether is warranted on a strictly philosophical basis.
So that Thomas Young is strictly correct from a philosophical standpoint in his fourth hypothesis, when he states: "That all material bodies have an attraction for the aetherial medium, by means of which it is accumulated within their substance and for a small distance around them in a state of greater density but not greater elasticity." He is not, however, correct when he states that though there is a greater density near the body, there is not a greater elasticity, as such an assumption is opposed to experiment and observation in relation to perfect gases, as I shall show when dealing with the elasticity of the Aether.
Again, in view of the fact that the Aether is atomic, it can now be easily understood how it may be subject to Gravitation. The very essence of Gravitation is that atoms, or particles, attract each other. If there were no particles, or atoms, it is obvious that there would be no attraction, and therefore no Gravitation. Wherever, therefore, there are to be found atoms of any kind or sort, whether they be atoms of hydrogen, oxygen, silver or aetherial atoms, there the Law of Gravitation holds good, and attraction between these atoms is to be found. In other words, any substance which is atomic, is also gravitative. Now Aether is atomic as has been shown, and therefore from that standpoint it is also gravitative. It may, however, be objected that the assumption of gravitative properties for the Aether is after all but a speculation, and that Young's fourth hypothesis was only a hypothesis, and that the gravitating properties of the aetherial medium have never come within the scope of direct experiment, without which no hypothesis can be fully accepted.
If such an argument be advanced against a gravitating Aether, then I must differ from those scientists who advance such an objection. My contention is that the gravitating properties of the Aether have already been made the subject of some of the most refined and delicate experiments that have been made during the past few years.
I refer to the experiments of Michelson and Morley of America.
For an outline and explanation of such experiments I must refer the reader to the Phil. Mag. of December 1887.
Now what is the result of these experiments?
I believe it is almost unanimously conceded by all scientists, that their experiments prove that the Aether is carried along by the earth. Let us carefully look at this conclusion and see what it implies in relation to the question at issue.
If the Aether is carried along by the earth, it necessarily follows that there is some governing law or principle which holds it to the earth, while the earth moves through space with its velocity of 68,000 miles per hour.
Now what is that governing principle or law, which is capable of holding such an aetherial atmosphere to its central body? If we wish to be strictly philosophical, it is necessary, according to our second Rule of Philosophy, that we should not go outside experience and the analogy of Nature.
Where is there a similar analogy in Nature to that of the Aether being carried along through space by the earth? I know of only one analogy which can be used, and that is the analogy of the atmosphere, which is also carried along by the earth through space, as it rushes on in its orbit round the sun.
That being so, the question arises, what principle or law holds the atmosphere to the earth? for, whatever be the law which governs the atmosphere, to be consistent with the second Rule of Philosophy, we must infer that the same law also holds the Aether in its place. There is only one answer to the latter question, and that is the Law of Gravitation. If it were not for that law, and the fact that the atmosphere is subject to that law, the atmosphere would simply be swept off from its central body, the earth, as the latter rushed through space with its comparatively enormous velocity.
The only legitimate and philosophical conclusion that we can arrive at, therefore, is that the Aether must be carried along with its central body, the earth, through being acted upon by the self-same Law of Gravitation, and for it to be so acted upon it must obviously be gravitative. It would be unphilosophical to suggest that it was held in its place by any other force, as that would be introducing a new force or law into Nature, contrary to our experience in relation to an exactly similar phenomenon of Nature.
We have therefore, it seems to me, direct proof by actual experiment that Young's fourth hypothesis was correct, and that not only in relation to the atomic world, but also in relation to the planetary world, and the stellar world, all bodies exert an attractive influence upon the surrounding Aether, by means of which the Aether is accumulated near the surfaces of all bodies in a state of greater density, and therefore of greater elasticity.
Let us apply this truth to the solar system, and see what we get. If it is true that the earth exerts an attractive influence upon the surrounding Aether by means of which it is held in its place relatively to the earth, then it is equally true that Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune also exert gravitating or attractive influences upon the surrounding Aether, in the same way that they do upon their own atmospheres. So that in their cases also, the surrounding Aether is carried along by them through space. Professor Stokes has suggested that this is so, in order to account for the aberration of light, as we shall see later on.
Not only so, but the sun also would have an attractive power over the Aether by means of which its aetherial atmosphere would be carried through space, as it moved along in its progress at an estimated rate of 17,000 or 18,000 miles per hour.
I would like to point out here, that this explanation of the effect of the planets' attractive power over the surrounding Aether is only a partial one, as there are other effects directly involved in the fact that the Aether is subject to the gravitating influence of all satellites and planets.
This is not the place, however, to go fuller into the matter, the consideration of the subject being taken up in a later chapter.
Thus I have tried to show a gravitating Aether is strictly in accord with the three Rules of Philosophy, for it is simple in conception, is not contrary to experience, and by it I premise that it is possible to explain the physical cause of Gravitation, with all that is involved in that law.
Once more, if Aether is gravitative, then every atom and particle in the universe, as well as every planet, and sun, and star, exert an attractive power over the Aether, so that every atom is enveloped in an atmosphere of Aether, in the same way that every planet, and sun, and star is enveloped by the aetherial atmosphere.
The Aether, however, while it may flow through the spaces that exist between the molecules of bodies, yet is held bound to those molecules in the same way, and by exactly the same force, that holds the atmosphere to a planet or world.
Further, if the atoms possess different masses or weights, as they do, then each atom would possess an aetherial atmosphere proportionate to its mass, with the result that an atom of carbon, with its atomic weight of 12, ought to possess a denser aetherial atmosphere than an atom of hydrogen, and so on right through the atomic scale. I need hardly point out that this conception of the Aether in relation to atoms, and molecules of bodies, will solve certain problems relating to the density of Aether in connection with matter, which problem up to the present cannot be solved by the present conception of a frictionless medium.
That problem may be stated as follows: Does the presence of matter affect the Aether in any way, so as to load or make it denser? Professor Lodge, in Modern Views of Electricity, in relation to the density of the Aether, writes: "The neighbourhood of gross matter seems to render Aether more dense. It is difficult to suppose that it can really condense an incompressible fluid, but it may load it, or otherwise modify it, so as to produce the effect of increased density."
In view of the fact that Aether is gravitative, the reply is to be found in the Law of Gravitation, "Every particle of matter attracts every other particle of matter, etc.," and as Aether is matter, it will be attracted by the other matter irrespective of whether that matter be in the atomic, molecular, or planetary or stellar form. We shall see that this is so when we come to deal with the density of the Aether.
It may be objected in relation to this aspect of Aether, that Young also asserted that the Aether flows as freely through matter, as the air flows through the trees of the forest, and that such a statement therefore contradicts his fourth proposition regarding the gravitating properties of Aether. A little reflection will, however, put a different construction on this objection.
Let us consider the analogy from the standpoint of experience, and see what that analogy teaches us. From experience we learn that the air is gravitative, but we also learn that it is possible to be moved from place to place as winds, and that as such it can move freely between the trees of the forest, causing their boughs and leaves to tremble and bend beneath its energy and power.
I have yet to learn, however, that while it moves between the trees as separate and distinct objects, such a movement militates or destroys its gravitating properties.
Does the air cease to be any less gravitative, or subject to the Law of Gravity, when it is subject to certain movements, which give rise to certain currents as winds? Such an assumption is altogether opposed to philosophical reasoning.
Whether the air is stationary or in motion, it is ever subject to the great Law of Gravitation, and accepting that as an analogy, the apparent contradiction between the oft-quoted simile of Young and his fourth hypothesis is at once removed, and from analogy we learn that it is quite possible for Aether to move between bodies because of certain currents which may be originated by heat, light or electricity, yet at the same time the existence of such currents does not violate its gravitating tendency.
Young's fourth hypothesis is therefore in perfect harmony with his oft-quoted simile, that the Aether flows through the interstices of bodies as the wind flows through a group of trees, but like the air-currents it does not so flow unless the currents are generated by some form of energy, as heat or light, electricity or magnetism.
From these considerations therefore we are compelled to come to the conclusion that Aether, like all other matter, is subject to the same universal Law of Gravitation. If further evidence of the gravitating tendency of the Aether were required, I would refer the reader to Lord Kelvin's utterance on this subject.
Lord Kelvin, Phil. Mag., November 1899, in relation to the Aether writes: "We are accustomed to call Aether imponderable. How do we know that it is imponderable? If we had never dealt with air except by our senses, air would be imponderable to us, but we know by experiment that a vacuum glass tube shows an increased weight when air is allowed to flow into it. We have not the slightest reason to believe that Aether is imponderable. It is just as likely to be attracted by the sun as air is. At all events the onus of proof rests with those who assert it is imponderable. I think we shall have to modify our ideas of what Gravitation is, if we have a mass spreading through space with mutual attraction between its parts, without being attracted by other bodies."
We have already seen in the previous article that Faraday was of opinion that the Law of Gravitation extended throughout the whole of the solar system, and as Aether fills the solar system, then obviously Aether must also be subject to the Law of Gravitation.
ART. 46. Aether possesses Density.—That matter possesses density has already been shown in Art. 38, and on the hypothesis that Aether is matter, Aether must possess density also. This property has already been postulated for the Aether, in order to account for certain phenomena in connection with the reflection and refraction of light. Young assumed different densities for the Aether near bodies owing to its being attracted by those bodies (Art. 45). Reflection and refraction of light are produced by a change of density of the Aether. It is now generally accepted that the optical difference of bodies depends mainly on the different densities of Aether in association with those bodies. Professor Tyndall, in his Lectures on Light, writes on the density of the Aether as follows: "The density of the Aether is greater in liquids and solids than in gases, and greater in gases than in vacuo. A compressing force seems to be exerted on the Aether by the molecules of these bodies."
Apart, however, from the atomicity and gravitative properties of the Aether, it is difficult to understand how there can be density of the medium, and still more difficult to give a satisfactory explanation of different degrees of density for the same medium, which some scientists assume it to have.
If, however, all that is logically included in the statement that Aether is matter, and therefore is atomic and gravitative, is conceded, then, from the analogy of our own atmosphere in relation to the earth, the density of the Aether, and different degrees of density also, is at once put upon a logical and philosophical basis, as it is brought into harmony with all experience and observation, and is simple in its conception.
On the other hand, an Aether which is not atomic or gravitative cannot possess different degrees of density, except by assuming the existence of some unknown law of which we have no knowledge, which conception is altogether opposed to the fundamental principles of simplicity, observation, and experiment as laid down not only by Newton but by every true philosopher.
Therefore, that Aether can possess different degrees of density, is only the logical outcome of the statement that Aether is matter, seeing that such a statement without the shadow of a doubt must at least imply that it is gravitative.
I need hardly point out, that it is much more philosophical to be able to account for the density of the Aether in a reasonable and philosophical manner, than simply to postulate for the Aether certain properties and qualities, because certain phenomena demand the existence of such properties.
The Aether has been such a hypothetical medium, that it has been easy to postulate for it certain properties, if certain phenomena have demanded the existence of those properties.
Thus if the Aether were required to be elastic, then elasticity was postulated for it; if more elastic, then greater elasticity was added. If density were demanded, then density was postulated, and if less or more density, less or more density was given to it.
That method of speculation may be satisfactory up to a certain point, but no one will admit that such a method is wholly philosophical. It will be a far better method to adopt, if, in dealing with the universal Aether, we can make it conform to certain recognized laws and principles, and from the application of those well-known laws, be able to infer the exact constitution of this space-filling Aether medium.
Now the question arises, if Aether is gravitative, what effect has the Gravitation of any body, be it an atom, or a meteor or planet, sun or star, upon the Aether in which it moves, and which surrounds it?
That we may have some light thrown upon the matter, I would like now to take the reader to Newton's Optics, in order that he may give us his opinion as to this property of density of the Aether. In his nineteenth query Newton (Optics) asks this question—
"Is not this medium much rarer within the dense bodies of the sun, stars, planets and comets than in the empty spaces between them, and in passing from them to great distances, doth it not grow denser and denser perpetually, and thereby cause the gravity of those great bodies towards one another, and of their part towards the bodies, every body endeavouring to go from the denser parts of the medium towards the rarer?"
Here then we have given to us an indication of what is the possible state of things in relation to the gravitation of the Aether, and all bodies in solar and stellar space. The only mistake that Newton made, was in inverting the right order of comparatively dense and rarer parts of the aetherial medium, by putting the rarer parts of the medium near to the bodies, and supposing the denser parts to be farther away in space.
As a matter of fact, the correct view is exactly the opposite, that is, if we are to form our conception by following out those philosophical rules that Newton laid down. For either the rules are right, or his supposition is right. They cannot both be right, as his supposition is contrary to the second Rule of Philosophy, as all experience and observation from the analogy of Nature teach us that a medium enveloping any body, as planet, star or sun, is densest nearest to the body, becoming rarer the further that medium gets away from the central body. Let us take for our illustration the best example, that experience and observation afford, that of the atmosphere surrounding the earth. The analogy is so perfect, that one is almost tempted to believe that the atmosphere and the Aether are in some way intimately associated with each other. Some years ago Lord Kelvin was of the opinion that the Aether was but an extension of the atmosphere, though I am not certain whether he holds that view at the present time. Clerk Maxwell, writing in the Phil. Mag. in May 1861, writes: "I have deduced from this result the relation between statical or dynamical electricity, and have shown that the elasticity of the magnetic medium in air is the same as that of the luminiferous medium, if these two coexistent, coextensive, and equally elastic media are not rather one medium."
Now for the comparison. Both the atmosphere and Aether are matter. Both are atomic, both are gravitative, both possess elasticity, and both possess density. The atmosphere also possesses different degrees of density, so does the Aether. In the case of the atmosphere, however, experience and experiment teach us that the atmosphere is denser nearer the earth than farther away.
When we ascend mountains, it is a matter of common knowledge that the higher we ascend, that is the further we get from the earth, the rarer the atmosphere becomes. When we ascend in balloons, we find that the air becomes so rare and so light, that the blood will flow from the nose, on account of the reduced pressure exerted on it, the pressure inside the body being greater than that outside. Now in accordance with our second Rule of Philosophy, if experience is to be any guide at all, then it most conclusively teaches us that the Aether being subject to the same laws as the atmosphere, the same results inevitably follow. Therefore the Aether nearest the earth is denser than any layer immediately above it, and that layer denser than the one above it, and so on for great distances, with the result that the only conclusion we can come to in regard to the density and rarity of Aether in relation to all gravitating bodies is, that the densest part of the Aether is nearest to them, and the rarest, the farthest away from them. So that while Newton's suggestion in his nineteenth query is correct in principle, it is incorrect in application to space.
I would like to point out here, that what is true of the earth in relation to the density of the surrounding Aether, must also be true, according to our second Rule of Philosophy, of every other planet, or sun, or star. So that every planet, satellite, every sun or star has its atmosphere, if I may so term it, of Aether, which obeys and follows the same laws as the earth's atmosphere does.
This is a most important fact, and has a most important bearing upon the physical cause of Gravitation as applied to each planet, and sun and star, as I shall afterwards show.
I wish now to bring the reader into contact with a Theory of Gravitation that was given to the world by Professor Challis of Cambridge, 1872. In the Philosophical Magazine of June of that year he writes: "I assume that all the active forces of Nature are different modes of pressure under different circumstances of a universal elastic Aether, which presses always proportionately to its density."
Now what I wish to point out is, that while Prof. Challis admits the density of the Aether, and also varying degrees of density, as he states that the Aether presses proportionately to the density, he does not show how that varying density is accounted for. If there is this varying density, then there must be some underlying principle which governs the variation in density, and I know of only one principle or law which can regulate that variation in density, and that is that Aether is gravitative, and being gravitative it not only possesses density, but also variations in density.
Thus by admitting that Aether is gravitative, because it is matter, we have at once a satisfactory explanation for the density of the Aether and also for different degrees of density both in the atomic world, and in the planetary and stellar world.
ART. 47. Aether is Elastic.—In Art. 39, matter was shown to be elastic, and on the assumption that Aether is matter, the elasticity of the Aether, which has been postulated for it by various scientists, can be logically and philosophically accounted for.
In view of the transmission of light through space with a definite and finite velocity, we are compelled to regard Aether as possessing elasticity, similar to that of an elastic solid body.
If we take the analogy of sound, we find that sound is transmitted and propagated through matter, by waves of alternate condensation and rarefaction, and that transmission is regulated by the relation of the density of the medium to its elasticity. Light has been proved to be due to the undulatory wave-motions of the Aether, and in order to account for the transmission of the wave-motion, it is essential that the Aether should possess the property of elasticity.
As Young points out in his First Hypothesis, the Aether possesses this property of elasticity, but with the advance of scientific knowledge and research, the elasticity of the Aether may be said to have passed out of the hypothetical stage, into the state of actual fact and experiment. Both McCullagh and Fresnel have assumed this property of elasticity for the aetherial medium in order to account for certain phenomena of light.
Apart, however, from the atomicity of the Aether, it is exceedingly difficult to understand how such a property can belong to it. Atoms are exceedingly small particles, possessing the property of elasticity, or the power to recover their original shape after distortion or change of shape. If the Aether therefore be atomic, as is pointed out in Art. 44, it can at once be readily understood how the Aether as a whole can possess the property of elasticity. The atoms of the Aether must be inconceivably small, as the light-waves travel with the enormous velocity of 186,000 miles per second.
What must therefore be the atomic vibration which such a statement implies? If, on the other hand, the Aether is assumed to be continuous and non-atomic, it must be seen how exceedingly difficult it is to account for the elasticity of the Aether, as it seems absolutely impossible for a medium which is continuous, and non-atomic, to be able to transmit the waves of light with a finite velocity.
Apart, therefore, from atomicity of some kind or other, elasticity of the Aether is an assumption philosophically incorrect, as it is contrary to that simplicity of conception laid down by Newton, and is also contrary to all experience, and thus violates the second Rule of Philosophy.
Aether therefore must be said to be perfectly elastic; so perfectly elastic, that it is susceptible to the least touch of any natural thing, so that even an atom, so small that it cannot be seen with the most powerful microscope, yet so elastic is this Aether medium, that the least motion or vibration of one of these atoms, though the motion did not exceed the 20- or 40-millionth part of an inch, yet even this would create in the aetherial ocean, Aether-waves, just as a body moving in water creates water-waves, which, radiating from the place of their birth, beget and create others, the process continuing until they reach the margin of the water in which they were generated. It is precisely so with these Aether-waves, when once generated and set in motion. They create others, the process being continued and perpetuated; and, unless arrested in their course, may continue until they reach the very limits and confines of material immensity and space.
It is, perhaps, only necessary to say, regarding the perfection of the elasticity of the Aether medium, that though it takes from 40,000 to 69,000 waves to complete the space of one inch in extent, yet it is done with such miraculous rapidity, as to speed the distance of 186,000 miles in the short space of a second of time; or, taking the number of Aether-waves to complete an inch as 50,000, its elasticity is such that it makes 50,000 x 186,000 x 12 x 5280 vibrations in one second of time.
We have already seen in Art. 39, that according to Boyle and Marriotte's Law, the velocity of a wave-motion, as sound in the air, is determined by the relation of the elasticity of the medium to its density. If the temperature of the atmosphere remains the same, then the elasticity varies in the same proportion as its density.
According to Art. 45, Aether is gravitative, and that fact produces different degrees of density in the aetherial atmosphere of an atom or planet or meteor, sun or star; that part of the Aether being densest nearest the central body, and rarer the further we go away from that body.
Now the question at once arises, what is the effect of the increased density of the Aether near the body upon the elasticity of the Aether?
From the analogy of sound in air, we arrive at the conclusion that Boyle and Marriotte's Law equally applies to the Aether, as it does to the atmosphere of any planet. That is, if the temperature of any stratum or layer of the Aether remains the same, then the elasticity of the aetherial medium in that layer is proportionate to its density, so that while the gravitating property of the Aether makes it denser nearest the central body, the fact that the elasticity is proportionate to the density, does not affect the transmission of any wave-motion.
[Footnote 6: Phil. Trans., 1802.]
ART. 48. Aether possesses Inertia.—From Art. 40 we have seen that all matter possesses inertia, inertia being that property of matter by which it cannot of itself change its state of motion or of rest.
If Aether be matter, therefore, then it must also possess inertia. This property of inertia is already postulated for Aether by scientists, and to that extent is conformable to the Rules of Philosophy. Professor Tyndall, with reference to the inertia of the Aether, writes: "The motion of Aether communicated to material substances throws them into motion. It must be therefore itself a substance. Aether is a substance endowed with inertia, and capable, in accordance with the established laws of motion, of imparting its motion to other substances."
Again, Lord Kelvin in his Address to the British Association, 1901, on the "Clustering of Gravitational Matter in any part of the Universe," states: "Aether we relegate to a distinct species of matter which has inertia, etc." Aether, therefore, according to Tyndall, "is a substance or medium endowed with inertia, and capable, in accordance with Newton's Laws of Motion, of imparting its motion to other substances."
If, however, the Aether is frictionless, as has generally been supposed, then it cannot possess inertia, because to the extent that a body possesses inertia, to that extent it is opposed to being frictionless.
Inertia is really the equivalent of mass, or the amount of matter measured by gravity, and if Aether possesses mass in any sense at all, as it must do if it is matter, then, possessing mass or weight, it must offer resistance to any body moving through it, and to that extent cannot be frictionless. To suppose that the Aether is frictionless, and yet possesses inertia, is to suppose something altogether opposed to all the Rules of Philosophy and therefore of experience.
I have already shown that a frictionless medium is opposed to all philosophy and experience, and is an anomaly in the universe.
On the strictly philosophical assumption that Aether is matter, and therefore atomic and gravitative, the whole question of the inertia of the Aether is reduced to one of common experience. It is, at least to my mind, difficult to conceive of mass without weight or without atomicity, and yet that is the unphilosophical position of the present state of science in relation to the Aether. In other words, while the Aether is supposed to possess inertia, which is dependent upon mass, as measured by gravity, yet it is supposed not to be gravitative, that is, that the mass of the Aether has no weight at all, and therefore is not mass, which assumption contradicts itself. From Arts. 44 and 45, however, we have seen, to be strictly philosophical, that Aether must be atomic and also gravitative. It can now be easily understood how it can possess inertia like any other matter, and is therefore capable of receiving motion from other matter, and also of imparting that motion to other matter.
So that, wherever there is motion of any kind in the Aether, either in the form of vibratory motion as heat, or undulatory motion as light, or rotatory motion as electricity, those motions will affect adjoining matter in the same way that the motion of any other moving matter affects any body with which it comes into contact.
From the fact that Aether possesses inertia, and is also gravitative, we have now to alter our conception of this universal space-filling medium, and in place of a frictionless medium, which is incapable of imparting motion to any body, we have now to remember henceforth that the Aether is matter, which possesses inertia, and therefore has the capacity not only of offering resistance to any body moving through it, as a comet or meteor, but also of imparting the motion which it may receive in any manner to any other matter, as a planet, satellite, or sun, that may be floating in it.
With this philosophical view of the Aether, which is entirely in harmony with our first and second Rules of Philosophy, we shall be able to give a physical explanation of the Law of Gravitation, as we have now a physical medium existing in all atomic, solar, and stellar space, which can both accept motion, and transmit that motion to other bodies. In other words, we have a medium which can both push and pull.
[Footnote 7: Lectures on Light.]
ART. 49. Aether is Impressible.—Another characteristic property of this Aether medium is, that it is as perfectly impressible as it is elastic. So perfectly impressible, that it receives, retains, and perpetuates for thousands of years, and for distances to human mind incalculable, every impression given to it of light, form, colour, tint, and shade; and that, too, with a perfect fidelity that nothing mars, even to the least and most infinitesimal detail.
Therefore, irrespective of distance, wherever there is matter to arrest and reflect the impressions received, there those impressions of light (and all that in the luminosity is involved and contained) become visible and revealed, and wherever there is power of vision to receive and concentrate these Aether- or light-waves, there, not only luminosity or light, but all that constitutes and is involved in that luminosity, becomes at once visible and seen.
It is by this means we see the colour, tints, shades, and forms of suns and planets; of stars, constellations, etc., with all the varied forms, configurations, and movements of the celestial phenomena. Each and every one, small or great, glittering or blazing, sun or planet, are ever creating or generating Aether-waves, and impressing them with all the details and particulars of their nature and existence; and these Aether-waves ever bear upon their mystic wings the impressions received, carrying the information given with lightning speed to the very confines and limits of infinite space or the material universe; beyond which exists nothing but the ever-living and active energy of the Divine, the only unlimited, unbounded, and absolute infinitive.
It is by the interception and concentration of these waves by our perceptive powers, aided with the giant powers of the telescope, that we obtain the information given, or become cognizant of the nature and existence of the varied lights, colours, tints, and shades of the celestial bodies.
The vision, assisted by the giant power of the telescope, collects and concentrates these Aether-waves into a perfect image of those things that gave them birth, and by this means reveals to us the knowledge of things afar, their existence, nature, characteristics, properties, and powers.
Thus it is we see the solar orb, with its huge fires all aglow, obtain a knowledge of its character and powers, see its huge spots, its quivering fringe of flame, and high-leaping prominences, or watch its slowly revolving form.
Thus we see the planets that around it sweep and roll; swift-footed Mercury with his wondrous speed, and dazzling Venus with her silver sheen; Mars the god of war with his ruddy glow, and mighty Jupiter with his orange hue, and the yellow Saturn with her mysterious rings, the blue Uranus, and the more distant Neptune, with all the satellites that to it belong.
Then far far away the brilliant Sirius—the Dog Star, Cygnet, Centauri, the Great Bear, and a thousand others.
The Pleiades and the twenty millions of suns that form our own galaxy and the Milky Way, with all their varied colours, tints, and hues of white, golden, orange, ruby, red and blue, green and grey, silver, purple and yellow, buff and fawn, emerald and green, lilac and coppery. Thus we see the distant Orion, so far away that swift-footed Light, with its speed of more than eleven million miles per minute, has to travel for more than thirty thousand years before it spans the gulf that intervenes between it and us, and brings to us the news of its existence there.
Then the spectroscope with its revealing power literally tears asunder wave from wave, and reveals the mystic message which each doth bear, of the distant things from which they come, of each and every sort and kind.
Thus we know, that in the solar fires there ever burn such things as hydrogen, oxygen and nitrogen, and also, in a vaporous state, aluminium, sodium, iron, magnesium, cobalt, calcium, chromium, copper, manganese, zinc, and others.
Thus light-waves are speeding everywhere, and from all material things. They come from our own sun, and rush in, and flood the earth's aerial veil, the atmosphere; and "Each little atom of matter, like a mirror, reflects and re-reflects them as if in sport, buffeting each luminous ray from one to another, increasing and amplifying it by an infinity of repercussions" (Herschel), and then in their entirety and whole, like a huge multi-mirror, so blend and mingle them that they come to earth's surface in that soft radiance we call Light, and bathe it as in a sea of mellowed glory.
ART. 50. Aether: its Motions.—The question of the exact motions of the Aether is a question which has involved the attention of scientific men for many years, and which is at the present time receiving the attention of some of our most advanced scientists, not only in this country but in other countries also.
Whether the Aether in space is at rest, or is moving along with all the bodies that float in it, so to speak, is a question of the greatest importance to scientists and philosophers generally, as the particular character of the motions of the Aether, which are either suggested or ascribed to it from the analogies of Nature, are sure to have a most important bearing not only on the motions of all the planets and satellites, but also upon such questions as the aberration of light, and such difficulties as presented by Lord Kelvin in his paper on "Clouds on the Undulatory Theory of Light" (Phil. Mag., July 1902).
I need hardly point out that the hypothesis that Aether is gravitative, is bound to play a most important part in the consideration and development of this phase of the study of the universal aetherial medium. It is not my intention, however, at this stage of the work to go fully into the development of this aspect of the subject.
The application of this principle will be considered at the right time, and in the right place. It is, however, generally assumed, that the Aether is at rest in space, and that the earth, the planets, and the sun and all stars, move through it with varying velocity, although, as Lord Kelvin points out, such an assumption is covered with a cloud which up to the present is "as dense as ever." Of course, if the Aether be at rest, and the planets and other heavenly bodies move through it with varying velocity, then the only assumption regarding the Aether is, that it is frictionless, but, as I have shown in Art. 45, this is opposed to all philosophical reasoning, and therefore to experience and observation.
We have, therefore, to postulate for the Aether such motions as shall fulfil all the Rules of Philosophy, that is, shall be simple in conception, shall be in harmony with our experience and observation, and which shall satisfactorily account for the phenomena sought to be explained, that is, the universal Law of Gravitation; for it is by the properties, combined with the motions of the Aether, that the physical cause of Gravitation is alone to be explained.
Let us revert to the question of a stationary Aether for a moment or two, and let us ask ourselves, where is the evidence for such an assumption? Has the sun ever ceased to shine, or to send its light-waves with their enormous velocity speeding through the solar system? So far as experience and observation go, I have never read of any record of such a fact, or that light-waves have ceased to proceed from the sun and fill the solar system with Aether-waves.
Not only is this true of the sun, but it is equally true of every planet and satellite, every meteor or comet, every star and sun that exist or dwell in this aetherial medium; for, as has already been shown (Art. 49), every body emits Aether-waves, and these waves spread out in all directions in a spherical form.
The truth is, that the universal Aether is in eternal motion, and that motion forms the physical life of the universe. If it were possible to destroy the motion, then the whole fabric of the universe would fall to pieces, and the beauty, order, and harmony of the celestial mechanism would be replaced by disorder, confusion, and ultimate ruin. Take any analogy of Nature, and see what such an analogy teaches us. Look at any planet, sun, or star. Do we find any one of these stationary or at rest? Why from the smallest meteorite or satellite, to the largest star that shines in the firmament of heaven, there is nothing but motion; each satellite, planet, sun, and star moving on and on, ever and ever through the countless ages of time until its course is run and its existence ended. But rest, never! Such a thing as rest is unknown in the entire universe, whether it be in the atomic systems of matter, or the systems of stars and suns that form the universe of worlds.
Take another illustration—that of the ocean! Is that ever at rest, with its unceasing wave and tidal motion? Has the reader ever stood on the shore and seen the ocean when it has been absolutely still, or when the tide has ceased to flow? Such a possibility is almost absurd to contemplate. The same argument applies to the air with its regular flow of winds. Now in regard to the aetherial and universal medium, there are just as regular motions as the flowing of the tide round the earth, or the revolving of a satellite round a planet, or a planet round the sun.
And what is as important, all the motions can be as satisfactorily explained and accounted for from the physical standpoint, as the flow of the tide, or the revolution of a planet.
Year in and year out, the motions of the Aether remain the same, governed by the same laws and producing the same effects. Age after age, the Aether has been moving, producing by its various motions the continuity of that beauty, order, and harmony that govern the universe as a whole.
I have already indicated in Art. 45 the effect of Gravitation on the Aether surrounding each satellite, or planet, or star, or sun. As each satellite, or planet, or star moves through the universal Aether, it takes with it its surrounding Aether as indicated in Art. 45, in the same way that each planet or sun takes with it its own associated atmosphere, which is held in contact with it by the self-same force of Gravitation.
In addition to this motion of the aetherial atmosphere through space, there are other motions of this same gravitating Aether that have to be taken into consideration, before a complete and adequate conception of all the motions of the Aether can be arrived at.
I do not intend, however, at this stage to go fully into such motions, but rather wish to lead up to them from a consideration of hypotheses put forward by such men as Rankine, Challis, Maxwell, Lord Kelvin, McCullagh, and Helmholtz, and from a consideration of such hypotheses in the realm of heat, light, and electricity to be able to form a scientific conception of the proper motions of the Aether, as well as a philosophical one.
ART. 51. Energy.—In the days of Newton, and for a long time afterwards, all energy went by the name of "Force." Thus Newton in his Laws of Motion refers to the action of forces on stationary or moving bodies, and shows how the motion of any body is effected by the impressed force. (Art 13.)
As science advanced, and scientific research was carried into the fields of heat, light, and electricity, we find that the various forces began to be particularized, with the result that such terms as electrical force, magnetic force, chemical force, etc., became common and familiar terms. As gradually it became known that one particular kind of force was the outcome of another kind, there was given to the world such terms as the Correlation of Forces (Grove), in which he proved that whenever one kind of force appeared as heat or light, it was at the expense of another kind of force, as electricity.
Of later years, however, another term has crept into Philosophy, and instead of the term Force, which is very indistinct and indefinite in character, there appeared the term Energy, although Force and Energy are not exactly synonymous terms. Thus electricity, heat, and light are forms of energy, and are convertible into one another, in the same way that the forces were convertible. Thus we get transformations of energy in the same way that we had transformations of force, and conservation of energy in the same way that we had conservation of force.
Even the term Energy, however, is being replaced in the present times by something more definite and simple, and instead of the term Energy, we shall find, in the development of this phase of natural phenomena, that that term is being replaced by the simple idea of motion, or modes of motion, and that all forms of energy, as light, heat, magnetism, and electricity, and even Gravitation itself, are due to motion of some kind or other. We will, however, lead up to this truth by looking briefly at the term Energy, and see what it implies and embodies.
Energy, therefore, is that property which a body possesses, by which it is capable of doing work. Thus our ideas of work give us our conception of energy. For example, when a weight is lifted, work is done, and a certain amount of energy is expended in the process. Further, the amount of work done is proportionate to the weight lifted, and the height to which the body is raised. Work is done against resistance, so that whenever resistance is overcome, then work is the result. For example, suppose one pound is lifted one foot high, in opposition to the force of gravity, then work is done, and this amount of work is known as a foot-pound.
If a body weighs ten pounds, and is lifted ten feet, the work done is equal to ten pounds multiplied by ten feet (10 x 10 equals 100), so that one hundred times the amount of work has been done in comparison with the lifting of the one pound one foot high.
As all weight is essentially a gravitational measure, depending upon the intensity of gravity at the place, then, whenever a body is raised or lifted, the work so done is done against the gravity of the earth.
Work is also done, as Newton points out in the first and second laws, whenever we apply force to any body, either stationary or already in motion. The results of all observation and experiments prove, that whenever we have two bodies upon which work is being done, the amount of work is determined by the amount of energy transferred from one body to the other, and that the actual amount of energy gained by one is equal to the amount of energy lost by the other.
Energy is always found in association with matter, so that matter has sometimes been termed the Vehicle of Energy. Wherever, therefore, we find energy of any kind or sort, there we find matter also, as the two are inseparably connected together. Thus, wherever we have heat, we have matter in a particular state of motion, generally understood as vibratory motion Wherever we have light, which is also a form of energy, we also have matter in motion, that is the Aether, in a state of periodic wave-motion; and wherever we have electricity, we have again matter possibly in a state of rotatory motion, as we shall see later on. Energy, therefore, is the power which a body possesses to do work.
ART. 52. Conservation of Energy.—The principle of the Conservation of Energy was first enunciated by Mayer in 1842. The principle may be defined as follows: The total amount of all the energy, as light, heat, electricity and magnetism, Gravitation, etc., in Nature is unchangeable; so that, according to this law, the universe possesses a store of energy which is unchangeable in quantity throughout all time. The energy may pass from one form to another, yet the total amount ever remains the same. It is almost unnecessary to say, that this is a principle which, like the conservation of matter, is incapable of absolute proof, but its assumption has greatly helped scientific thought and speculation from time to time. Clerk Maxwell says (Theory of Heat) on this point: "The total energy of any body is a quantity which can neither be increased nor decreased by any mutual action of the bodies, though it may be transformed into those forms of which energy is susceptible."
The conservation of energy is inseparably connected with the conservation of matter (Art. 30). They cannot be divided, because, if energy is only to be found in association with matter, then if the law of the conservation of matter falls to the ground, the principle of the conservation of energy falls with it. Energy, therefore, like matter, cannot be destroyed or created by any process known to man. As there is no process known, either in the chemical or in the physical world, by which new matter may be created by man, so, in relation to energy of any kind or sort, there is no process known by which man can create or even destroy the smallest form of energy that exists. If energy appears in any body or in any particular form, it is solely because of the loss of energy in some other body, or in some other form.
All changes of energy, therefore, are simply changes due to the difference in form in which the energy is manifested. At one time it will be manifested in the form of light, then of heat, then in mechanical motion, and so on. Joule gave us some good illustrations of this principle of the conservation of energy. He showed us how electricity could be changed into heat, and the heat into work. When light, which is a form of energy, is absorbed by any opaque body, it is found that the body which has absorbed it has become hotter. The energy of light has not been destroyed, but as its energy cannot pass through the opaque body, it has been employed in agitating the particles and atoms of that body, which becomes hotter in consequence.
Thus from the principle of the conservation of energy, which is in operation not only in our planetary world, but throughout the whole of the solar and stellar space, and indeed throughout the whole universe, we arrive at the conclusion that the total quantity of energy throughout the universe is unchangeable. In the evolution and development of worlds, and in the destruction of those worlds after long periods of time, throughout all the varied manifestations of heat, light, electricity, and magnetism, associated with the development and destruction of each globe, the sum-total of the energy of the universe remains the same. Meteors may rush into the atmosphere of planets, and be dissolved into Aether through the friction, comets may be dissolved into their component gases as they near the sun, water may be changed into vapour by the heat of the summer sun, vegetation may be produced from apparently dead matter, and then that vegetation may itself decay and return to the dust by which it had been built up, but throughout all these processes of birth and death, of evolution and devolution, the sum-total of active living energy which is associated with all the phenomena, remains unalterable and unchangeable. Such is the teaching of the great principle of the Conservation of Energy as enunciated by Mayer and Helmholtz.
ART. 53. Transformation of Energy.—One of the chief characteristics of energy is, that we can transform it, and it is chiefly of use to us because of its capability to be transformed, but in all its transformations, the total quantity of energy remains the same. The transformation of energy renders it necessary to the existence of all life, and to all physical change in the universe. Mayer showed us that all energy in the solar system primarily derives its existence from the sun, and that all plant life and physical life owe their continued existence to the energy which is poured out from the sun upon the planetary worlds. So that energy is always flowing from the sun into the surrounding space in the form of light, heat, and electricity, the medium of its passage being the universal Aether.
This principle of transformation teaches us, that heat may be converted into electricity; that light may be converted into heat, or electricity may be converted into either heat or light or both. This principle of transformation naturally follows from the principle of the conservation of energy; because, if energy cannot be destroyed in any way, but is made to disappear by any process, it must reappear in some other form, and therefore has been transformed from its original state. So that, whenever one kind of energy disappears, then it is absolutely necessary, according to the principle of conservation of energy, that some other kind shall be produced. There cannot be any real loss or destruction.
That leads us to the next point regarding this principle of transformation, which is that all transformations of energy take place in fixed proportions. When a certain quantity of coal is burned, a certain quantity of heat, or thermal energy as it is sometimes called, is produced, and the quantity of heat so produced is definitely proportionate to the quantity of coal consumed.
If a certain quantity of coal were burned in a perfect steam-engine, that is one in which there would be no loss of heat, then also a definite amount of mechanical work would be done, which would be strictly proportionate to the heat generated by the consumption of the coal. So that when coal is put into an engine, the potential energy of the coal is transformed into kinetic energy of the steam, and that is again transformed into actual mechanical energy of the engine itself, by which work is done in driving or pushing or pulling the train along, and the amount of work done is proportionate to the coal consumed. Illustrations of transformation are common, and may be seen by any person living in a large town. Thus at any electrical station or electric tram terminus, these transformations of various forms of energy are very familiar sights. We have first the transformation of the coal in the furnace into heat. This heat converts water into steam, whose motion is communicated by proper machinery into a dynamo, the product of which is electricity. That electricity is then conveyed along wires, and work is done by it, by moving trams along the connected tram system, or it may be converted into heat in the carbon filament in the car itself, which, if heated enough, will then produce the electric light. So that starting from the coal, we have several transformations therefrom into the forms of heat, light, motion, and finally mechanical energy, which results in Work. The question arises as to what is the law of equivalence in regard to the transformation of energy. That is, if we have a certain amount of energy of a given sort, how much of any other sort can be produced by it? The answer is partly to be found in a statement made by Joule in 1843, which practically embodies what is known as the first law of Thermo-dynamics, and is as follows: "When equal quantities of mechanical effects are produced by any means whatever, from purely thermal sources, or lost in purely thermal effects, then equal quantities of heat are put out of existence or are generated, and for every unit of heat measured by raising a pound of water one degree F. in temperature, you have to expend 772 foot-pounds of work." From this law we learn that heat may be used to do work, but that a certain amount of heat is always used up in the process. It can also be demonstrated that electric currents can do work, but to generate the currents a certain amount of work must be done.
This equivalence and transformation prevail in all forms of energy, whether it be mechanical energy, thermal or heat energy, or electrical energy.
ART. 54. Potential Energy.—Energy has been divided into two classes, which are termed respectively Potential Energy and Kinetic Energy. We will look at the former first.
Potential Energy may be briefly defined as energy of position.
Thus if we lift a body from the ground, the energy which has been imparted to it is energy of position, or potential energy. A glacier high up the mountain possesses potential energy, because of its position. By the mere fact that it is situated high up the mountain, it has a capacity for doing work by its descent, and if that descent be very sudden, the work done will be destructive work, as it may sweep away all houses and villages in its sudden descent. Thus, by the mere fact of its elevation, it possesses a power of doing work, which it has lost when it has descended. Again, work done in winding up the spring of a clock is stored up in the form of potential energy, and gradually runs out in the form of motion or kinetic energy.
Potential energy is really the complementary principle of kinetic energy. That is to say, the amount of potential energy lost by any body, is equal to the amount of kinetic energy gained by the other body, to which the energy has been transferred. In the case of a body falling, as the potential energy diminishes, the kinetic energy increases, but the total amount of the two combined always remains the same. This is well illustrated in the case of a swinging pendulum. When a pendulum is at the highest point of its swing, its velocity or kinetic energy is zero, but at that point its potential energy is greatest. As it descends, the potential energy decreases, but the kinetic energy increases. When the pendulum is at the lowest point its energy is wholly kinetic, the potential energy being zero at that point, while it has sufficient kinetic energy to raise it to the highest level again. Throughout the cycle of these operations, the sum-total of the two energies always remains the same.
Professor Tait points out, in his Recent Advances in Physical Science, that the available sources of all potential energy may be divided into four classes—
1st. Fuel. 2nd. Food of Animals. 3rd. Water-power. 4th. Tidal Water-power.
All these are different forms of potential energy. Under the head of fuel he includes not only wood, coal, but also all forms of matter that may be used or burnt up by heat, or dissolved by chemical agencies. Thus zinc and lead, which are used in batteries, are merely forms of fuel. That potential energy resides in such things as wood and coal is a matter of common experience. All our coal-fields are stores of energy, which received their energy when in plant form, ages ago, from the sun, and this energy is now being used to drive our machinery, to warm our houses, and to give light to our homes and our cities. It has been calculated that a pound of coal would give out 14,000 heat units, which is equal to 11,000,000 foot-pounds of work, which is also equal to the amount of work a horse can do in five hours. Again, all food, whether it be the food of animals, as vegetables and plants, or of man, as bread, meat, etc., are all forms of potential energy, or energy which is stored up in matter. All forms of food have a certain amount of energy in them, which is used up in the body in building up waste tissue and imparting energy to the physical frame.
Again, all forms of water-power, whether it be in the form of the flowing river or the tidal motion of the sea, possess a large amount of potential energy which may be used up to do mechanical work. They also possess kinetic energy, or energy of motion. We find illustrations of the possession of potential energy by rivers and tides, in the fact that by their fall from a higher to a lower level they may be made to do mechanical work, as in the case of the turning of the water-wheel by the fall of the water, which motion is communicated to machinery, and various forms of work are the result. In Switzerland and America advantage is being taken of the energy of falling water to generate electricity, by means of which villages and towns are being supplied with electric light at a very small cost.
ART. 55. Kinetic Energy.—Kinetic energy may be defined as energy of motion, and is the energy which a body possesses in consequence of its motion. A body in motion thus possesses kinetic energy, which it must impart to some other body before it can be brought to a state of rest. The body may be simply an atom, as a vortex atom, but if it be in motion, as all atoms are, then it must possess kinetic energy, which may be transferred to another atom by collision, or by some other method. As has already been pointed out in previous articles, kinetic and potential energy are complementary to one another, the sum-total of the two combined always remaining the same in any cycle of work, according to the principle of the conservation of energy. We get a good example of this oscillation from kinetic to potential, and vice versa, in the planetary system. When the earth is farthest from the sun, its velocity, and consequently its kinetic energy, is at its lowest point; but there the potential energy is at its greatest. As the earth turns round in its orbit, however, and begins to approach the sun again, its potential energy decreases, while its kinetic energy increases with its increased velocity. So that by the time it has reached the nearest part of its orbit to the sun, its velocity, and consequently its kinetic energy, is at a maximum, while the potential energy is at a minimum. Then as the earth passes round its perihelion, the kinetic energy is used up in assisting the earth to overcome the attraction of the sun. Thus there is this oscillation from kinetic to potential, and from potential to kinetic, year in and year out, as the earth performs its cycle round its central body the sun.
Professor Tait, in the work referred to in the previous Article, gives examples of kinetic forms of energy under the following heads—
1st. Winds. 2nd. Currents of Water. 3rd. Hot Springs and Volcanoes.
It can be readily seen that winds are a form of energy, as we have innumerable instances of the power and energy which they exert. Advantage is taken of that kinetic energy by means of windmills, in which the energy of the wind is imparted to the revolving sails, and thence to the machinery, various forms of mechanical work being the result, as, for example, the grinding of corn, or the pumping of water. The pressure or energy of winds has even been calculated, the following figures being examples—
VELOCITY IN MILES PER HOUR. FORCE IN LBS. PER SQ. FOOT
1 mile. .005 lb. per sq. foot. 5 " .123 " " " 10 " .496 " " " 15 " 1.11 " " " 20 " 1.98 " " " 30 " 4.5 " " " 40 " 7.9 " " " 50 " 12.5 " " "
In the case of currents of water, whether they are in the form of river currents or ocean currents, as has already been pointed out in the previous article, the question of potential energy, or energy of position, is associated with their kinetic energy. Water is taken at a certain elevation, and then allowed to fall to a lower level, and in its fall from the high level to the lower level, its kinetic energy is used to drive mill-wheels, and thus work is done, the kinetic energy of the water being transformed into the motion of the machinery. This machinery may be used to work a dynamo, and thus electric light may be generated, or it may drive an electric motor which may perform all sorts of mechanical work. The great underlying principle of either kinetic or potential energy rests in the fact, that wherever we have energy of any kind or sort, whether it be associated with water, wind, or Aether, there we have the capacity to do work, the amount of work depending upon the amount of energy that exists in the matter which is the vehicle of energy.
In Art. 50 it has been indicated that the Aether possesses several kinds of motions. From the sphere of light and heat, we learn that the Aether possesses certain motions which are always exerted in a direction from the central body, which gives rise to the light- and heat-waves. That being so, it conclusively follows that the Aether possesses kinetic energy, and therefore, possessing this energy, it also possesses the power to do work. It must be remembered we are no longer dealing with a frictionless medium, but with a gravitating medium, possessing mass and inertia, and, that being so, wherever we have the Aether in motion, there we have kinetic energy or the power to do work; and that work will correspond to the particular kind of motion which is exerted on any body by the aetherial motions, and will be equally subject to Newton's Laws of Motion.
ART. 56. Energy and Motion.—An advance, however, as to the meaning of the term Energy has been made within recent years, which brings it more into harmony with that simplicity of conception, and accordance with experience which are the very foundation of all philosophy. Instead of the term Energy, there is now being used another term to denote the forces which form the life of the universe, and that term is the word "Motion."
Professor Poynting says: "All energy is energy of motion" (British Association Report, 1899).
Thus motion is the fundamental principle of all phenomena. If we analyze all forms of energy with which we are familiar, we shall soon find that they are only changes of one form of motion into another. Thus we shall see that heat is a mode of motion, as has been proved by Tyndall, that light is another mode of motion, and that electricity is also a mode of motion. I need hardly point out that this advance in our conception of energy is strictly in accord with the Rules of Philosophy. First, it is simple in conception. When we say that a body possesses energy, whether that energy be potential energy or kinetic energy, it does not convey to the mind some definite concrete fact, as does the statement that a body possesses motion. Every one, whether familiar with scientific teaching or not, understands and is familiar with the word Motion, as it is a common phenomenon of everyday life and experience. As Energy was simpler in conception than Newton's term Force, so Motion is simpler in conception than the rather vague and indefinite term Energy; therefore when we say that all energy is energy of motion of some kind or sort, we state that which is philosophically correct.
It is also in accord with the second Rule of Philosophy, in that it is strictly in harmony with experience and observation. Look where we will, or at what we will, there we find motion of some kind or other, whether it be among the innumerable stars, or in our own solar system, or any phenomena on the earth, or even among the world of atoms in their minute and atomic systems. Such a thing as absolute rest, or stagnation, is unknown in the universe. Wherever there is matter, there we find motion of some kind or other. It may be vibratory motion as heat, or wave motion as light, or rotatory motion as electricity, but motion of some sort is inseparably connected with all matter. So that when we say that all energy of the universe is the energy of motion, and motion only, we state that which according to the second Rule of Philosophy is absolutely correct.
Further, I wish to premise that by the use of the term modes of motion, in lieu of energy, the third Rule of Philosophy will be fulfilled. For if all phenomena of the universe, whether it be heat, light, electricity, be due to different modes of motion, then Gravitation should be explained from the physical standpoint by some kind of aetherial motion also. This I can safely premise will be done, and in the later chapters of this work, Gravitation will be shown to be due to the motions of the aetherial medium which floods all space. By so doing, all the Rules of Philosophy will be fully satisfied, and Gravitation will then be brought into line with all the other forms of motion, as heat, light, electricity, and magnetism, which are in themselves modes of motion, as will be shown in subsequent articles.
ART. 57. Conservation of Motion.—If it be true that all energy is the energy of motion, then the principle of the conservation of energy ought also to apply to all the modes of motion, and in its place we should then have the principle of the conservation of the various forms of motion. This defined would be, that the total amount of all motion in the universe, as heat and light, electricity, magnetism, and Gravitation also, if that be due to the motion of the Aether, is unalterable and unchangeable.
There may be changes from one form of motion to another, from heat to light, and light back to heat; heat into electricity, and electricity into light or heat; from Gravitation into heat or into light, or even into electricity; but the sum-total of the whole remains the same.
Again, as the principle of the conservation of energy is inseparably connected with the conservation of matter, so the principle of the conservation of all the modes of motion is also inseparably connected with the conservation of matter. They cannot be divided, so that wherever we get matter of any kind or sort, there we get motion of some kind, either in the form of heat, light, or electricity, or those aetherial motions which produce those phenomena associated with Gravitation.
As matter cannot be destroyed by any known process to man, so motion cannot be destroyed either. On the vortex atom theory of matter, this principle of the conservation of any mode of motion is perfectly intelligible, especially if added to that theory we have Dr. Larmor's electron theory as the basis of the vortex atom. An atom in its ultimate state is nothing more or less than Aether in rotation, and as Aether is matter, we see that on the assumption of this atomic basis, we have even in the atomic world an illustration of this conservation of matter and motion, as in such an atom we have nothing but matter (i. e. Aether) and motion. Carrying the idea upwards in the atomic scale, if atoms of hydrogen or oxygen are multiples of these vortex atoms, then again we have nothing in all the elements, or combination of the elements, but matter and motion. Again, as all planets and satellites, suns and stars, are but agglomerations of elements, we have still the same two classes of things, matter and motion, and so from the most infinitesimal atom in existence, up to the most ponderous star that exists in the universe, we have running through them all the principle of the conservation of motion, which is to matter the source of all its activities, energies, and powers. Motion, therefore, might almost be said to be eternal. We have heard from time to time of the term perpetual motion. Philosophers have from time to time endeavoured to discover some application of this perpetual motion, but all efforts in this direction up to the present have proved futile. In one sense there is no such thing as perpetual motion. In another sense, that is from the standpoint of the conservation of all modes of motion, as motion cannot be destroyed, it must therefore be perpetual.
It is an absolute impossibility to obtain motion except from some antecedent energy, which is itself a form of motion. It would require the distinctive fiat of an Almighty Creator to produce motion from nothing, and I question whether such a result is obtainable, as I hold that if the Creator, at any time in the history of the universe, set any substance in motion, the source from which that motion was derived, was His own Divine Energy, and in that sense the physical motion was not produced from nothing. Such an assumption is altogether opposed to all philosophical reasoning and experience. I hope to deal with the question either in the last chapter of this book, or in another work.
ART. 58. Transformation of Motion.—Again, if energy be the energy of motion, and the principle of the transformations of energy holds good, then it is equally true that all modes of motion are also transformable. Thus heat is a mode of motion, being due to the vibration of the atoms which go to make up any body. Light is also a mode of motion, being due, as far as solar light is concerned, to the periodic wave motion of the Aether. While electricity, as we shall see later on, is also due to some form of rotatory motion. It has already been shown (Art. 54) that light can be converted into heat, so that the periodic wave motion of light can be transformed into the vibratory motion of heat.
Heat can also be converted into electricity, and if electricity be rotatory motion, then the vibratory motion of heat can be transformed into the rotatory motion of electricity. Again, as electricity can be converted into light, the rotatory motion of electricity can thus be transformed into the periodic wave motion of light. Thus through all the forms of motion with which we are familiar, we find this principle of transformation holds good, so that each form of motion may be directly or indirectly transformed into any one of the other kinds. Whenever, therefore, one kind of motion disappears, it is absolutely necessary, according to the principle of the conservation of motion, that some other kind shall be produced. There cannot be any real loss or destruction of the motion. It may be transformed, but not lost. By the use of proper apparatus, therefore, any form of motion with which we are familiar may be converted into another form, and in the process not the least quantity of any form of motion is lost. Heat may be changed into light, and light into heat; electricity into light, and light into electricity; heat into electricity, and electricity into heat. Indeed, starting from any one form, any of the other modes of motion may be produced, either directly or indirectly, and mechanical effects or work may be produced by each and all. Then, again, the order can be reversed, as by doing work which is simply applied motion, any of the other modes of motion can be produced. Thus heat can be produced by friction, and if the friction which is the outcome of muscular energy be continued long enough, a light will be the result, in the form of fire. When certain forms of work are done, as the turning of the handle of an electrical machine, frictional electricity will be produced. So that not only are all the modes of motion convertible into work, but work itself can be transformed into the modes of motion known as heat, light, electricity, and magnetism.
Now, if Gravitation be due to motion of the Aether, and if it is true that all modes of motion are convertible, then the application of this principle should also hold good in relation to Gravitation. It has been demonstrated by Joule and others that Gravitation can be converted into heat, light, and electricity. It can be converted first into heat. Joule made a number of experiments to ascertain what quantity of heat is produced by falling bodies, that is bodies under the influence of Gravitation. From experiments he has calculated that if one lb. of water falls through a space of 772 feet, it would raise the temperature of the water one degree Fahrenheit—that is, the water after its fall will be one degree hotter than when it started to fall. Here, then, we have the exact equivalence of a certain amount of gravitational motion expressed in terms of heat. So that, whenever motion of a falling body produced by gravity is arrested, heat is generated, and as heat is a mode of motion, it follows that the motion of Gravitation has been converted into the motion of heat. Again, the motion of gravity may be converted into that of light. This may be demonstrated as follows: Lord Kelvin has suggested that the light and heat of the sun are maintained by the falling into the sun of meteorites. Now the cause of the falling of these meteorites into the sun is the Attraction of Gravitation, and therefore if the falling of these meteorites produces light and heat, it necessarily follows that the motion of Gravitation, whatever that may be due to, is converted into the motion known as light and heat. Thus it can be seen that Gravitation, looked at from the standpoint of a mode of motion, is itself conformable to the principle of the transformation of motion, and this is an indirect argument in favour of the fact that Gravitation is itself due to certain motions of the universal Aether.
ART. 59. Motion and Work.—In Art. 52 we have seen that energy is the power which a body possesses to do work, the amount of work which a body can perform being regulated by the amount of energy which such a body possesses. In Art. 57 we have further seen that all energy is the energy of motion, and that wherever we have energy of any kind or sort, whether it be in the form of light, heat, or electricity, there we have motion of some kind or other. That being so, we arrive at the conclusion, that wherever in the universe we have motion of any kind or sort, whether it be the motion of Aether, or wind, or water, there we have the power of doing work, and the work so done will be proportionate to the motion which the medium possesses. The amount of work that air in motion can do has been measured, as we have already seen (Art. 55) that air which moves at the rate of 30 miles per hour exerts a force of 4-1/2 lb. per square foot.
The amount of work that water in motion can do has also been measured. The carrying and erosive powers of a river depend on the rapidity of its currents. It has been calculated that a velocity of three inches per second will transport fine clay; eight inches per second coarse sand; while three feet per second will transport stones as large as eggs.
If, therefore, air moving at the rate of 30 miles an hour can exert a force of 4-1/2 lb. per square foot, what must be the force or pressure of aetherial motion, as light-waves for example, which move with a velocity of 186,000 miles per second? The amount of work which such an aetherial motion can perform has actually been measured by Professor Lebedew of Moscow, and will be dealt with in the chapter on "Light, a Mode of Motion," when the application of the work done on a body, as a planet for example, will also be considered. Work, therefore, can always be done by motion against resistance. This is a fundamental principle in the sphere of dynamics, which is incontrovertible, as all experience, observation, and experiment teach us, that wherever we get motion of any kind or sort, there we have the capacity or power to do work. The work done may be either in the form of pushing a body along, or pulling a body towards a centre. All experience and observation teach us that no body moves (whether it be an atom, or moon, or planet, or sun, or star), unless some other body or medium, which is in direct contact with the moving body, exercises some pressure or pull upon the moving body. The action is purely and simply a mechanical one. So that if this be true, then the earth and the planets, the sun and stars, comets and meteors, are moved through space solely because they are being pushed by some medium, or pulled to the centre by the motions of the same medium. If this can be proved to be true, then, as can be readily seen, our philosophy will then be made to agree with our experience, and the second Rule of Philosophy fully satisfied. As has already been pointed out, there is no such thing as action at a distance, therefore the Law of Gravitation demands a medium for its operation, production, and continuity. Newton distinctly points this out in his Letters to Bentley, where he says: "That one body should act upon another through empty space without the mediation of anything else, by and through which their action and pressure may be conveyed from one to another, is to me so great an absurdity that I believe no man who has in philosophical matters a faculty for thinking can ever fall into it." It has already been pointed out (Art. 42), that the only medium which is universal is the Aether medium, and we have therefore to look to the motions and properties of that medium for the solution of the problem as to the physical cause of Gravitation. That such a medium has motions which are as regular as the tides of the sea, or the trade winds of the atmosphere, will be proved later on, when it will be found that Gravitation, with all that that law implies, is due, as Newton and Challis suggested, to the pressure, properties, and motions of the aetherial medium, which is as universal as Gravitation itself. This being so, it is essential that we should set ourselves to find out from the analogies of Nature, what are those properties and motions of the Aether which give rise to the universal Law of Gravitation. This I propose doing by a consideration of three different modes of motion—viz. Heat, a mode of motion; Light, a mode of motion; and Electricity, a mode of motion. I venture to premise, from a careful consideration of these three truths, that we shall be able logically and philosophically to arrive at the simple, yet grand truth which reveals the physical source of all motion of the universe.
HEAT IS MOTION
ART. 60. Heat is Motion.—On the phenomena of Heat, Newton in his eighteenth query in Optics asks the questions: "Is not the heat of a warm room conveyed through the vacuum by the vibrations of a much subtler medium than air, and is not the medium the same as that medium by which light is reflected and refracted, or by whose vibrations light communicates heat to bodies? And do not the vibrations of this medium in hot bodies, contribute to the intenseness and duration of their heat? And do not hot bodies communicate their heat to contiguous cold ones by the vibrations of this medium propagated from them into the cold ones? And is not this medium exceedingly more rare and subtle than air, and exceedingly more elastic and active?" Thus it can be seen that Newton was of the opinion that heat consists in a minute vibratory motion of the particles of bodies, and that such motion was communicated through what he calls a vacuum by the vibrations of an elastic medium, the Aether, which was also concerned in the phenomena of light.
One of the first experimental investigations into the real nature of Heat was made in 1798 by Count Rumford.
While he was engaged in boring brass cannon in the arsenal at Munich, he was struck with the degree of heat which the brass gun acquired, and with the still more intense heat which the metallic chips, which were thrown off, possessed. Of the phenomena he says: "The more I meditated on these phenomena, the more they appeared to me to be curious and interesting. A thorough investigation seemed even to bid fair to give us a farther insight into the hidden nature of Heat." Rumford therefore set himself to find out by actual experiments what the nature of Heat was. For this purpose he constructed a cylinder, and mounted it so that it could be made to rotate by horse-power. At the beginning of the experiment the thermometer stood at 60 deg. Fahrenheit, and after half-an-hour, when the cylinder had made 900 revolutions, the temperature was found to be 130 deg. Fahrenheit, so that there had been an increase in the temperature of the cylinder of 70 deg. Fahrenheit. The experiment was again repeated in another form with similar results. Rumford in dealing with the results of his experiments said: "It appears to me to be extremely difficult, if not quite impossible, to form any distinct idea of anything capable of being excited and communicated, in the manner the Heat was excited and communicated, in these experiments, except it be Motion."
Only a year later, Davy gave to the world some results of experiments which he had performed, by which he had arrived at a similar conclusion to that of Rumford, viz. that "Heat is motion of some kind." His experiment consisted of rubbing two pieces of ice together, and by so doing showed the ice could be melted. He then caused two pieces of metal to be rubbed together, keeping them surrounded by ice, and still he found that the two pieces of metal when rubbed together, produced heat, and melted the ice. He therefore rightly concluded that heat was produced by friction, and of the experiment adds: "A motion or vibration of the corpuscles of bodies must necessarily be generated by friction. Therefore we may reasonably conclude that this motion or vibration is Heat. Heat then may be defined as a peculiar motion, probably a vibration of the corpuscles of bodies tending to separate them. It may with propriety be called a repulsive motion. Now bodies exist in different states, and those states depend upon the action of the attractive and of the repulsive powers on their corpuscles, or in other words, on their different quantities of repulsion and attraction." It was not, however, till 1812 that Davy confidently stated that "The immediate cause of the phenomena of Heat is motion, and the laws of its communication are precisely the same as the laws of the communication of motion."
The question therefore confronts us, if heat be motion, what is the particular character of that motion? Is it a vibratory motion as Davy suggested, or is it similar to the undulatory wave motion of light? I need hardly point out, that we have evidence in favour of the hypothesis that light is due to some form of periodic wave motion in the Aether, the hypothesis being that known as the undulatory theory. We have also similar evidence in favour of the hypothesis, that heat is also due to some form of motion of the same aetherial medium. Indeed, it can be shown that heat possesses all the properties of light, and is subject to the same laws, with the exception that it cannot affect the sense of sight.
Heat, then, is due to some motion in the universal aetherial medium, that not only fills all space, but also forms an atmosphere around every atom or particle of matter that exists in the universe, and that motion is generally known as a vibratory or backward and forward motion.
Heat, then, may be said to be due to the vibrations of the Aether that surrounds all atoms and molecules, and of which those very atoms are composed, that is if we accept the aetherial constitution of all matter. So that, whenever a body, whether it be an atom or a molecule, or a planet or sun or star, is heated in any way whatever, such bodies excite waves in the surrounding Aether, and these waves travel through the Aether towards us from the heated body with the velocity of light. When these waves fall upon any other body, they become more or less absorbed by the body on which they fall, and cause corresponding vibratory motions in the same, which give rise to the phenomenon of heat in that particular body.
It has to be remembered that nothing definite is actually known as to the character of this vibratory motion. It is called a vibratory motion because it possesses a periodic vibratory movement, but as to its exact character, that has not yet been discovered. I hope, however, to indicate what the motion is that produces heat before the completion of this work.
ART. 61. Heat and Matter.—If it be true that heat is due to the vibrations of the aetherial medium, the question now arises, as to how a body may become heated, and by so doing be transformed into the three stages in which matter is found. We have already seen (Art. 36), that matter may be found in three forms, viz. solid, liquid, and gaseous, and that all these different forms of matter are composed of minute parts called atoms. In the case of the solid, the atoms are held closely together by some strong attractive power, termed cohesion; in the case of the liquid, the atoms have a greater freedom; while in the gaseous form they have a greater freedom of movement than when in either the liquid or the solid state. According to Young's Fourth Hypothesis (Art. 45), we find that all matter, and therefore all atoms have an attraction for the Aether, by means of which it is accumulated within their substance, and for a small distance around them in a state of greater density, and therefore of greater elasticity. In other words, as Aether is gravitative, every atom possesses an atmosphere of Aether in the same way that the earth has its atmosphere of air; and further, the aetherial atmosphere of each atom is densest nearest to the atom, gradually getting rarer and rarer the further the atmosphere recedes from the nucleus or centre, the elasticity or pressure being always proportionate to the density. Professor Challis, in his Dynamical Theory of Light and Heat, states that all the forces in Nature are different modes of pressure under different circumstances of the universal Aether, and as heat is a Force, and therefore a mode of motion, that also must be due to some form of pressure due to the vibrations of the Aether.
Professor Challis on this point says: "According to this theory, the atoms of any substance are kept in position of equilibrium by attractions and repulsions resulting from the dynamical action of the vibrations of the Aether which have their origin at the atoms. Each atom is the centre of vibration propagated equally from it in all directions, and that part of the velocity of the vibration which is accompanied by change of density (of the Aether) gives rise to a repulsive action on the surrounding atoms. This action is the repulsion of heat, which keeps the individual atoms asunder."