Physick

“ Some gentlemen have been disingenuous and unjust to me, by wresting and forcing my meaning in the Preface to another book, as if I condemned and exposed all learning, though they knew I declared that I greatly honoured and esteemed all men of superior literature and erudition; and that I only undervalued false or superficial learning, that signifies nothing for the service of mankind; and that as to physick, I expressly affirmed that learning must be joined with native genius to make a physician of the first rank ”

“ But feeling utterance fail his great desires
Sits down in silence, deeply he admires,
Thus weak brained I, reading thy lofty stile,
Thy profound learning, viewing other while;
Thy Art in natural Philosophy,
Thy Saint like mind in grave Divinity;
Thy piercing skill in high Astronomy,
And curious insight in anatomy;
Thy Physick, musick and state policy,
Valour in warr, in peace good husbandry,
Sure lib'ral Nature did with Art not small,
In all the arts make thee most liberal,
A thousand thousand times my senseless sences
Moveless stand charmed by thy sweet influences ”

“ But unless the body could recover its original figure by elasticity, there was no potential energy and force was annihilated. It is now believed, and to a large extent demonstrated, that the force, apparently lost, has been transformed into heat, electricity, or some other kind of molecular motion, of which the change of shape is only the outward sign. The establishment on a firm foundation of theory and experiment of the so-called conservation of energy, the child of the correlation of physical forces, is one of the first fruits of molecular mechanics. ”

“ Suppose now a second body is placed in the medium near the first as in the figure. It is evident that a shielding effect of each by the other is brought about. The complete symmetry of the system of impacts is disturbed and the equilibrium of each body is destroyed. By the unbalanced pressure on the remote side each will be urged towards the other, and we thus have the effect of gravitational attraction. To revert to our illustration from light, suppose that within the self luminous hollow sphere, two opaque bodies are situated. Each will cut off from the other a certain amount of light. ”

“ Whenever one surface of matter is moved in contact with another surface there is a resistance called friction, [Pg 40] the moving body loses its rate of motion, and will presently be brought to rest unless energy be continuously supplied. This is true for masses of matter of all sizes and with all kinds of motion. Friction is the condition for the transformation of all kinds of mechanical motions into heat. The test of the amount of friction is the rate of loss of motion. A top will spin some time in the air because its point is small. ”

“ But, these motions remaining the same, their circuits of motion are reduced, the frequency of contact is increased, and heat and light are evolved from the friction. The tendency of all matter under the law of gravitation, considered as an unexplained fact, is toward concentration. The evolution of heat is rather the check put upon this tendency, and, in so far as it exerts any influence, it exerts it in a direction the reverse of gravitation. There is a perpetual and rhythmic antagonism between the forces of integration and disintegration. ”

“ We thus see that a body, or system, in unstable equilibrium may become subject to a very considerable transmutation of energy, arising out of a very small cause, or antecedent. In the case now mentioned, the force is that of gravitation, the arrangement being one of visible mechanical instability. But we may have a substance, [Pg 157] or system, in which the force at work is not gravity, but chemical affinity, and the substance, or system, may, under certain peculiar conditions, become chemically unstable. ”

“ But in a non-resisting medium, the quantity of matter in the pendulous body is as the comparative weight and the square of the time directly, and the length of the pendulum inversely. For the comparative weight is the motive force of the body in any heavy medium, as was shewn above; and therefore does the same thing in such a non-resisting medium, as the absolute weight does in a vacuum. ”

“ Commencing with the generalization that " a mechanical force, or the cause of a mechanical motion, we know to be in general the condition of a difference of pressure," he infers, "hence it appears that if a general mechanical theory is possible, the ultimate property of matter must be conceived to be a mutual repulsion of its parts, and the indubitable Newtonian law of universal attraction be deduced herefrom, under the actual conditions of the world. ”

“ The long and constant persuasion that all the forces of nature are mutually dependent, having one common origin, or rather being different manifestations of one fundamental power, has made me often think upon the possibility of establishing by experiment, a connection between gravity and electricity, and so introducing the former into the group, the chain of which (including magnetism, chemical force, and heat,) binds so many and such varied exhibitions of force together by common relations. ”

“ How can one imagine to oneself a structure composed of perfectly hard molecules situated far apart which shall have only tolerable stiffness and stability? Such a body made up of widely separated spherical molecules, if no other forces but gravity acted, could at the most behave like a gas, but never as a solid or liquid body.
On the other hand, elastic molecules of open structure may be made to cohere at their boundaries by the pressure of the smaller atoms, which at the .same time easily fly through the open parts of the structure. ”

“ The metrical, gravitational and electromagnetic fields are all included. We build the quantities enumerated above; and they obey the great laws of field-physics in virtue of the way in which they have been built. That is the special feature; the field laws—conservation of energy, mass, momentum and of electric [Pg 237] charge, the law of gravitation, Maxwell’s equations—are not controlling laws. [38] They are truisms. Not truisms when approached in the way the mind looks out on the world, but truisms when we encounter them in a building up of the world from a basal structure. ”

“ Although the law of the persistence of energy or the correlation of forces is established, yet a few apprehend gravity to be an occult force, as attraction and repulsion involving actio in distans; yet gravity, when it is understood as a mode of motion, is so simple that all of its laws can be derived by the Euclidean process from the law of the persistence of energy. ”

“ The laws of conservation of energy and momentum in mechanics can be deduced from this law of world-curvature.
16. Certain phenomena such as the FitzGerald contraction and the variation of mass with velocity, which were formerly thought to depend on the behaviour of electrical forces concerned, are now seen to be general consequences of the relativity of knowledge. That is to say, length and mass being the relations of some absolute thing to the observer's mesh-system, we can foretell how these relations will be altered when referred to another mesh-system. ”

“ One knows how the cells of bees are formed by pressure, and how by pressure elastic spheres may be converted into angular, such as hexagonal-shaped, bodies.
As remarked, the gravitation theory (and many independent facts) demand that the molecules of bodies shall possess an open structure; which also satisfies the conditions of lightness and economy of material. As crystals exist, it is sometimes supposed that the molecules of bodies (whose open structure is often illustrated by cubes and other figures formed of wire) themselves represent the shapes of the crystals. ”

“ Herschel calculated the force which may be supposed, according to the undulatory theory of light, to be constantly exerted at each point in space, and finds it to be 1,148,000,000,000 times the elastic force of ordinary air at the earth’s surface, so that the pressure of ether per square inch must be about seventeen billions of pounds.‍424 Yet we live and move without appreciable resistance through this medium, immensely harder and more elastic than adamant. ”

“ Each of these two sets furnishes three components of motion or a total of six components; then we say that the perfectly unconstrained motion of the body has six degrees of freedom. If a body moves parallel to one of the co-ordinate planes, we say it has two degrees of freedom. When [Pg 17] we come to consider molecular motion in general and the independence which characterizes the motion of each of the many molecules we see that altogether we have here an extraordinary number of degrees of freedom, and composed of such is the realm of our "elementary chaos." ”

“ Later, this concept of the rigid body proves to be fruitful for the development of dynamics itself; because the rigid body as a continuous mass system of only six degrees of freedom, is not only kinematically of the highest simplicity, but also dynamically by allowing the composition of the forces – which are acting at its points – to "resulting" forces and moments of the same magnitude, whose knowledge is sufficient for the description of motion. ”

“ This illustrious physicist pointed out the advantage of introducing into the study of physical phenomena the considerations on symmetry familiar to crystallographers; for a phenomenon to take place, it is necessary that a certain dissymmetry should previously exist in the medium in which this phenomenon occurs. A body, for instance, may be animated with a certain linear velocity or a speed of rotation ”

“ Since the simplicity of the dynamics is therefore not inferior to the simplicity of kinematics of the new rigid body, then one will ascribe to this concept of rigidity the same fundamental importance in the system of the electromagnetic world-picture, as the ordinary rigid body in the system of the mechanical world-picture. ”

“ If a body whose state at rest is given by the variables , is adiabatically brought to velocity , then the state variables assume the value:
These equations are in agreement with the results of the paper of Planck [2] . Besides thermodynamics, Planck used the relativity principle, while stating equation (10) for momentum is essential in our work. ”

“ So if are the projections on the three axes of the vector joining the two positions, if the velocity of the attracted body is , and that of the attracting body , the three components of the attraction (which I can still call ) are functions of . I asked myself whether it was possible to determine these functions in a way that they are affected by the Lorentz transformation according to equations (4) and found the ordinary law of gravitation, whenever the velocities are small enough that one can neglect the squares in respect to the square of the speed of light. ”

“ In his Optical Queries, indeed, he shows that if the pressure of this medium is less in the neighbourhood of dense bodies than at great distances from them, dense bodies will be drawn towards each other, and that if the diminution of pressure is inversely as the distance from the dense body the law will be that of gravitation. ”

“ Similarly with electric and magnetic phenomena, it is capable of transforming the energy which may reside as stress in the ether, and other bodies moving in the space so affected meet with frictional resistance, for they become heated if the motion be maintained. On the other hand, there is no evidence that the body which produced the electric or magnetic stress suffers any degree of friction on moving in precisely the same space. ”

“ Let us consider in any given medium any electromagnetic field. For any volume element of the medium, the law holds that is invariant in the passage from the one to the other observer. It follows from this that is invariant; i. e., the kinetic potential of a unit volume or the “space density of kinetic potential” is invariant. ”

“ For, as we have seen, we require a large number of corpuscles impinging in quick succession to give the effect of continuous pressure ; we require a high speed to give absence of resistance to the motion of ordinary matter and to give static attraction, the same value as kinetic ; and we need small dimensions to give impalpability, while at the same time, in virtue of the high velocity, the momentum and energy remain normal. ”

“ Consider the electrons as material points and ask how their mass should vary as function of the velocity not to contravene the principle of relativity. Or, still better, ask what should be their acceleration under the influence of an electric or magnetic field, that this principle be not violated and that we come back to the ordinary laws when we suppose the velocity very slight. We shall find that the variations of this mass, or of these accelerations, must be as if the electron underwent the Lorentz deformation. ”

“ If the pull is exactly proportional to the mass, and the reaction to force, the motions induced by forces, changes in velocity, are inversely proportional to the mass. That means that two objects of different mass will change their velocity in the same manner in a gravitational field; or two diffeient things in a vacuum, no matter what their mass, will fall the same way to the earth. That is Galileo’s old experiment from the leaning tower of Pisa. ”

“ It, therefore, one attributes a massive structure to molecules, then, for the explanation of cohesion and chemical affinity, forces must be assumed which, by diminution of distance, increase quicker in intensity than according to the Newtonian gravitation law. On the other hand, the attraction of two cylinders of finite length and infinitely small section becomes infinitely great so soon as they touch each other. ”