Natural motion

“ Modern philosophers maintain that the laws of motion are the same for celestial and terrestrial bodies;—that all motions are natural according to the above description;—but that in terrestrial motions, friction comes in and alters their character,—destroys them so speedily that they appear to have existed only during an effort. ”

“ It would be easy to show that the fundamental laws of motion, in whatever form we state them, possess a very preeminent simplicity, compared with almost all others, which we might imagine as existing. ”

“ To conceive the manner in which a motion may be conveyed from one part of a substance to another, whether solid or fluid, we may attend to what takes place when a wave is made to run along a stretched string, or the surface of still water. Every part of the string, or water, is in succession moved from its place, and agitated with a motion similar to that of the original impulse, leaving its place and returning to it, and when one part ceases to move the next receives as it were the impression, and forwards it onward. ”

“ The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed. ”

“ This proposition determines the modality of motion in respect of Dynamics; for a motion, which cannot take place without the influence of a continuously active external moving force, proves indirectly or directly original moving forces of matter, either of attraction or repulsion. ”

“ For by compounding the proper motion of the body with that motion, which the impulse alone would rate, you'll have the motion with which the body will go off from a given place of impulse, in the direction of a right line given in position. ”

“ There is natural harmony in rapid motion over a long smooth line, and slow motion over a short jagged one. A simple case like this may help us to answer the question, When is the relation between velocity and direction harmonious? ”

“ All matter universally seeks to maintain itself in its natural state; hence, water in motion seeks to maintain its course according to the force by which it is propelled, and if it meets with opposition it finishes the length of the course it began in a circular and reflex motion. ”

“ If a body impinge upon another, and by its force change the motion of the other, that body also (because of the equality of the mutual pressure) will undergo an equal change, in its own motion, towards the contrary part. ”

“ I shall now add some things relating to the forces of progressive bodies, and to the density and resistance of those mediums in which the motions hitherto treated of, and those akin to them, are performed. ”

“ Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon. ”

“ Those several truths demonstrated above concerning the motion of bodies about the focus of the conic sections will take place when an attracting sphere is placed in the focus, and the bodies move without the sphere. ”

“ 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. ”

“ For those authors who treat of the motion of heavy bodies used to consider the ascent and descent of such bodies, not only in a perpendicular direction, but at all degrees of obliquity upon any given planes ”

“ The ancients held that motions were to be distinguished into natural motions and violent,—the former go on without diminution—the latter are soon extinguished;—the motions of the stars are of the former kind;—those of a stone thrown, and in short all terrestrial motions, of the latter. ”

“ The understanding leads all other predicates pertaining to the nature of matter back to this, and thus natural science is throughout either a pure or an applied doctrine of motion. ”

“ Resistance is usually ascribed to bodies at rest, and impulse to those in motion; but motion and rest, as commonly conceived, are only relatively distinguished; nor are those bodies always truly at rest, which commonly are taken to be so. ”

“ In the physical world we are congnizant of but four elementary or primordial ideas, beside the inevitable Time and Space. They are Matter, Force, Position, and Motion. Of these, motion is simply change of position; and force is recognized as the agent in every change of motion. ”

“ Many of the most eminent thinkers of the present time are disposed to regard all the active principles of nature as “modes of motion,”—to look upon light, heat, electricity, and even vital force, as phenomena resulting from “change of place” among the particles of matter; this change, disturbance, or motion, being dependent upon some undefined mover. ”

“ Do not the vegetation which covers our globe, the phenomena of life which we experience within us, and in the animals around us, require a continual motion of matter, an ebb and flow, so to speak, of action and reaction of bodies on each other, in reality or in appearance? Do not the phenomena of electricity, of magnetism, of galvanism, appear to be principles of great activity, the origin of motion wherever they exist, rather than objects indifferent to motion or rest? ”

“ Free motion, arrested motion, the effort, the speed, and the direction of motion, such are the sensorial elements, which, in all probability, constitute the foundation of our ideas on space and its properties. ”

“ We must here remember that motion as speed is inherent and constant in the particle and that motion as path is always determined from without, but the particles within the body are all external to one another, and therefore the direction of motion which is internal to the body is in obedience to the laws of heredity, and the direction of motion which comes from without the body is heat, gravity and strain. ”

“ So now it was further shown that the myriad properties or qualities of matter are simply the expression of myriads of activities which are all in a final analysis motions; that no motion is ever lost but only transformed, and that every kind of motion at any moment perceptible—whether in the form of movement through space, or of light, or heat, or electricity, or the actinism that builds up the green stuff in the leaves of plants—owes its existence to the metamorphosis of some previous kind of motion. ”

“ Hitherto I have laid down the definitions of such words as are less known, and explained the sense in which I would have them to be understood in the following discourse. I do not define time, space, place and motion, as being well known to all. Only I must observe, that the vulgar conceive those quantities under no other notions but from the relation they bear to sensible objects. And thence arise certain prejudices, for the removing of which, it will be convenient to distinguish them into absolute and relative, true and apparent, mathematical and common.
I. ”

“ What are the causes of motion?—Gravity is one. The influence of heat, which is itself caused by the motion of atoms, the effects of electricity, etc., and finally, the power of force in men or animals—any of these causes will produce motion. But a body at rest cannot put itself in motion, nor can a body in motion stop itself, or change its condition of motion. ”

“ Motion depends upon certain external disturbing and directing forces acting upon all matter; and, consequently, as every mode of action is determined by some excitement external to the body moved, motion cannot, philosophically, be regarded otherwise than as a peculiar affection of matter under determinable conditions. “We find,” says Sir Isaac Newton, “but little motion in the world, except what plainly flows from either the active principles of nature, or from the command of the willer.” ”

“ For that Motion which can continue long in one and the same part of a Body, can be propagated a long way from one part to another, supposing the Body homogeneal, so that the Motion may not be reflected, refracted, interrupted or disorder'd by any unevenness of the Body. ”

“ The question, ‘What becomes of light?’ merges in the more general one, ‘What becomes of motion?’ And the answer, on dynamical principles, is, that it continues for ever. No motion is, strictly speaking, annihilated ”

“ Are the Physical Forces modes of Motion?—Motion defined—Philosophical Views of Motion, and the Principles to which it has been referred—Motions of the Earth and of the Solar System—Visible Proofs of the Earth’s Motion on its Axis—Influence of the proper Motions of the Earth on the Conditions of Matter—Theory of the Conversion of Motion into Heat, &c.—The Physical Forces regarded as principles independent of Motion, although the Cause and often apparently the Effects of it. ”

“ The causes, as they exist at any moment, having produced a certain motion, that motion, becoming itself a cause, reacts upon the causes, and produces a change in them. By altering the distance and direction of the central body relatively to the planet, and the direction and quantity of the force in the direction of the tangent, it alters the elements which determine the motion at the next succeeding instant. ”

“ 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. ”

“ It is the sensations of sight, of touch, and even of the muscular sense. Motion is a fact seen by the eye, felt by the hand; it enters into us by the perception we have of the solid masses visible to the naked eye which exist in our field of observation, of their movements and their equilibrium and the displacement we ourselves effect with our bodies. Here is the sensory origin, very humble and very gross, of all the mechanics of the atoms. Here is the stuff of which our lofty conception is formed. ”

“ The general law that the change of motion is proportional to the moving force and takes place in its direction, provided we take care always to regard the reaction of curves, surfaces, obstacles, &c., as so many real moving forces of (for a time) unknown magnitude, will always help us out of any dynamical scrape we may get into. ”

“ For instance, if we consider the particular case of the earth and sun, we would conclude, according to whether we referred motion to the earth or sun, either that the sun was rotating round the earth every twenty-four hours, or else that the earth was rotating on its axis. ”

“ In conservation of matter, energy, what you will, in plenitude, in motion as only relative and so as always under a principle of uniformity and constancy or even immobility, in motion too as inclining to vibration, which suggests poise or tension, or to rotation, in which we see rest as well as motion, and finally, not to extend what might be a long list, in the infinity of space and time or of quantity, the physical sciences have hidden entrances for the silent, usually unnoticed admission of what is psychical. ”

“ Although the doctrine of motion in connexion with force, which is the subject of mechanics, is by far the most important form in which the consideration of motion enters into the formation of our sciences, the Pure Doctrine of Motion, which treats of space, time, and velocity, might be followed out so as to give rise to a very considerable and curious body of science. ”

“ Which motion we may be allowed to call circular, in the same way as Aristotle says that the air and the rain emulate the circular motion of the superior bodies; for the moist earth, warmed by the sun, evaporates ”

“ By influences external to this earth the balance of these forces is continually disturbed; and in the effort to restore the equilibrium, we have the production of all the varied forms of matter, and the manifestation of each particular physical principle or power. As motion and attraction, balanced against each other, maintain the earth in her elliptical orbit, so the opposition of forces determines the existence of the amorphous rock, the light-refracting crystal, the fixed and flowering plant, and the locomotive animal.
An eternal round of chemical action is displayed in nature. ”

“ And upon this Principle, it is very easie to make several sorts of contrivances that should thus wreath and unwreath themselves, either by heat and cold, or by driness and moisture, or by any greater or less force, from whatever cause it proceed, whether from gravity or weight, or from wind which is motion of the Air, or from some springing body, or the like.
This, had I time, I should enlarge much more upon; for it seems to me to be the very first footstep of Sensation, and Animate motion, the most plain, simple, and obvious contrivance that Nature has made use of to produce a motion ”

“ But motion—even the finest material motion, that of ether, (which, in consequence of the very important discovery of the conservation of force and of the mechanical equivalent of heat, made by Robert von Mayer, at present is taken to be heat) —is so decidedly a material process, the sensation of motion is so decidedly a reflex of the material in something immaterial, that the assertion of a transformation of motion into sensation seems to us only to change the point of view, and not to explain the difference, but to efface it. ”

“ Everything maintains itself by motion. And if it were possible to describe a diameter of air on the sphere of the earth, like to a well, which would extend from one superficies to the other, {151} and if a weighty body were dropped into this well, the body would seek to remain stationary at the centre, but so strong would be the impetus that for many years it would prevent it from so doing. ”