Universal gravitation

“ I will endeavour to give an outline—but it can only be an outline—of this startling hypothesis, which makes universal gravitation an effect of the motions of ether, and dispels the idea hitherto entertained that it is an attractive force inherent in particles of matter, by which they are enabled to exert a pull upon other particles at a distance from them in space. ”

“ You see a stone or other substances fall to the ground, and you ask, What makes them fall, and what controls them? Why will they not rise? Has any person ever found out the cause of this? No; even Sir Isaac Newton's principles of gravitation have failed to show it; as learned a man as he was, he has only given us an index or key to the effects, but not the cause of those effects. He has taken great pains to show us that when anything falls to the ground, it is the effect of the law of universal gravitation ”

“ We have, then, the same reason for supposing that air and water, in other parts of the system, are governed by universal gravitation, and exercise themselves the attractive force of gravitation, which we have for making the like suppositions with regard to the most solid bodies. ”

“ Turning from the heavens to the earth, and ignoring such primitive observations as that of the distinction between land and water, we may note that there was one great scientific law which must have forced itself upon the attention of primitive man. This is the law of universal terrestrial gravitation. The word gravitation suggests the name of Newton, and it may excite surprise to hear a knowledge of gravitation ascribed to men who preceded that philosopher by, say, twenty-five or fifty thousand years. ”

“ Epicureans had possessed as just ideas on cosmography as those of several of their contemporaries, which they neglected, and but a portion of the knowledge of geometry which had then been attained, they would in all probability have easily discovered the laws of universal gravitation and its mechanical cause. Laws, whose discovery and demonstration are the greatest glory of the mightiest genius that has ever lived; and cause, whose comprehension has long been the object of ambition of the greatest physicists and is now the stumbling block of their successors. ”

“ I am well convinced that since the law governing the intensity of universal gravitation is similar to that for light, the thought will have occurred to many physicists that an ethereal substance moving in rectilinear paths may be the cause of gravitation, and that they may have applied to it whatever of skill in the mathematics they have possessed. ”

“ Propounds the theory of universal gravitation.To the force producing this tendency of bodies to approach each other the designation of attraction of gravitation, or gravity, is given. All heavy bodies fall to the earth in such a way that the direction of their movement is toward its centre. Newton proved that this is the direction in which they must necessarily move under the influence of an attraction of every one of the particles of which the earth is composed, the attraction of a sphere taking effect as if all its particles were concentrated in its centre. ”

“ On the contrary, the size and weight of every sun and star that floats in the broad expanse of ether would under the law of gravity tend to bring about just such a universal catastrophe.
If the boasted law of gravitation prevailed to-day, or ever did prevail, such would be the disastrous results. The law of gravitation tends to aggregate all bodies into one. If the universe was under the dominion of gravity there would be but one vast globe in all the universe, and if there was a man on it there would be but one enormous giant. Newton's law of gravitation is "large bodies attract small ones." ”

“ Summary.—Thus, then, on a review of the whole, we find all things are endowed with attractive power, and that there is no particle which is not directly or indirectly related, in manifold ways, to the other particles of the universe. There is, first, the universal attraction of gravitation, under which every particle is, by a fixed law, drawn to every other within the sphere of existence. There is, secondly, the attraction of cohesion or aggregation, which acts at short distances, and unites the otherwise loose atoms of bodies into coherent masses. ”

“ Nor can we suppose the structure of the globe alone to be exempt from the universal fiat, though ages may pass before the changes it has undergone, or that are now in progress, can be referred to existing causes with the same certainty with which the motions of the planets and all their secular variations are referable to the law of gravitation. ”

“ Sequel to the Epoch of Newton.—Reception of the Newtonian Theory. Sect. 1.—General Remarks. THE doctrine of universal gravitation, like other great steps in science, required a certain time to make its way into men’s minds; and had to be confirmed, illustrated, and completed, by the labors of succeeding philosophers. ”

“ There, though the weight of a given mass of matter is different from what it is with us, it is nevertheless determined by the law that determines here—the law of gravitation. There energy is indestructible, and is measured as it is measured among us, by work. Then is there any boundary that we can assign to natural law—is it not omnipresent, universal? ”

“ Our knowledge would have to be enormously increased before we could assert that gravitation was in operation throughout this very limited region; and even when we have proved this, we should only have made an infinitesimal advance to a proof that gravitation is absolutely universal. ”

“ All results harmonizing, Newton was justified in reaching the conclusion that gravitation is a universal property of matter. It remained, as we shall see, for nineteenth-century scientists to prove that the same force actually operates upon the stars, though it should be added that this demonstration merely fortified a belief that had already found full acceptance. ”

“ On the other hand, gravitation itself—more universal than anything else in the universe—may be interpreted in terms of strains on world-lines, or, what amounts to the same thing, strains of space-time combinations. ”

“ This universal force of gravity is at work in the fall of an apple and the tidal wave no less than in the course of the planets round the sun and the movements of all the heavenly bodies. Newton had the immortal merit of establishing the law of gravitation and embodying it in an indisputable mathematical formula. ”

“ Elasticity is the real origin or indispensable intermediary of all the more important physical phenomena of the universe. . . . In a word, the function of elasticity in nature is at least as important as that of universal gravitation. Indeed gravitation and elasticity should be considered as effects of the same cause, which correlate or connect all the material parts of the [242] universe ”

“ The gravitational theory, which emerges out of the general theory of relativity, is, in contradistinction to the Newtonian theory, built up, not upon an elementary law of the gravitational forces, but upon an elementary law of the motion of a body in the gravitational field. ”

“ Now the whole structure of science would be hopelessly undermined had not scientific men come to have the fullest confidence in the invariability of certain of these sequences of events. Let us, for example, take the familiar and fundamental observation that any unsupported object, having what we term weight, invariably falls directly towards the centre of the earth. We express this fact in terms of a so-called law of gravitation, and every one, consciously or unconsciously, gives full deference to this law. ”

“ Beyond the facts of constant and of signal failure, these restless, resolute probings by the human mind in all directions, serve as the cumulative bases of a new induction ; and by the very sharpness of the contrasts brought to view at every point between the tentative conjecture and the determinate experience, they enforce the assurance, that whatever else the principle of gravitation may be, it is not in its essence any form of motion. ”

“ In the vast area of its action, which opens before the eye of the mind, we see a power spanning all space, and linking together every one of those myriads of worlds which spangle the robe of the Infinite, and we are compelled to pause. Is this principle of gravitation a property of matter, or is it a power higher than the more tangible forces, is the question which presses on the mind. If we regard it as a subtile principle pervading all space, we compel ourselves to look beyond it for another power yet more refined ”

“ Thus, it would be impossible to escape a duality in our conception of gravitation, if by gravitation we imply the cumulative action of both effects, yielding the one observable attraction of matter for matter. ”

“ When we pass from the elements of matter to the laws which govern it, we also find the clearest proofs of identity. That the fundamental law of gravitation [ 188] extends to the whole physical universe is rendered almost certain by the fact that double stars move round their common centre of gravity in elliptical orbits which correspond well with both observation and calculation. ”

“ We have made comparative estimates of the weight of the earth and planets, and have reason to believe that the force expression of gravitation attains a maximum at about one-sixth the distance toward the center of the earth, then decreases, until at the very center of our planet, matter has no weight. This, together with the rule I repeated a few moments ago, is about all we know, or think we know, of gravitation. Gravitation is the beginning and gravitation is the end; all earthly bodies kneel to gravitation. ”

“ The special theory of relativity can, therefore, be regarded only as a stepping-stone to a more general principle, which orders gravitational phenomena satisfactorily into the principles of mechanics. ”

“ This is the verdict of science, as the systematic form of human experience. In the form of gravitation we understand that each body depends upon every other body, and the annihilation of a particle of matter in a body would cause a change in that body which would affect every other body in the physical universe. Even gravitation, therefore, is a manifestation of the whole universe in each part of it, although it is not a manifestation which exists for that part, because the part does not know it. ”

“ But these apparent deviations are merely appendages to the great general law, in order that creation may be perfect in all its parts. For instance, there is a general law of what is termed gravitation which causes bodies to fall to the earth from a given height, with the same velocity according to their specific gravity. ”

“ Conceive the synthesis of both, and you have matter as a fluxional antecedent, which, in the very act of formation, passes into body by its gravity, and yet in all bodies it still remains as their mass, which, being exclusively calculable under the law of gravitation, gives rise, as we before observed, to the science of statics, most improperly called celestial mechanics. ”

“ The great doctrine of gravitation and attraction, the substratum of the Newtonian philosophy, is amply verified by numerous observations and experiments. Whether that which constitutes the principle of gravity be, in itself, an incorporeal or spiritual substance, or a materia subtilis, some very subtile kind of ethereal fluid, is a question which does not at all affect the actual existence of such a power. ”

“ If an atom were isolated in space it would have no weight. If influenced by other matter, there must be some physical medium to convey the influence, or gravity is not in accordance with the laws of force and motion. Which horn of the dilemma shall we take? Let us first admit that there is a principle of gravitation, affecting all planetary or atomic matter, and that there exists a highly elastic medium, pervading all space, conveying to us the light of the most distant stars, and that this medium is not affected by gravity. ”

“ So now in the present day, in spite of the continual demolition of spiritualistic views (i. e. views of action without the intervention of matter) by advancing science, the modus operandi of gravitation remains the one outstanding subject for doubt ; and it appears to be assumed by many (much in analogy with the former question of "specific inductive capacity ") that experiments with the view to decide whether any minute specific differences might exist in the effects of gravity, dependent on structure, form, &c. ”

“ You will not mind my using this word, for when I say that this penny-piece gravitates, I mean nothing more nor less than that it falls toward the earth, and, if not intercepted, it would go on falling, falling, until it arrived at what we call the centre of gravity of the earth, which I will explain to you by-and-by.
I want you to understand that this property of gravitation is never lost; that every substance possesses it; that there is never any change in the quantity of it; and, first of all, I will take as illustration a piece of marble. ”