“As the pattern of events is unaltered by motion, the mechanism must be the same when the electron is in motion as when it is at rest. But experiment shows that an electron in motion exerts additional forces which are not the same for all directions in space; if we picture this electron as moving head-foremost through space, these forces surround it like a belt around its waist.”

— James Jeans

Physics and Philosophy (1942)

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James Jeans 54

British mathematician and astronomer 1877–1946

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“Actually the situation is even more complicated, since a separate tentacle picture is needed for each speed of motion of the electron, the speed being measured relative to the suspended magnet or other object on which the moving electron is to act. …When the electron is at rest, the tentacles stick out equally in all directions. But an electron which is at rest relative to one magnet may be in motion relative to another, and to discuss the action of the electron on this second magnet we must picture it as having a belt of tentacles round its waist. This shows that we must have a different picture for every speed of relative motion, so that the total number of pictures is infinite, and we cannot form the picture we need unless we know the speed of the electron relative to the object it is about to meet.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“if a shower of electrons is shot on to a zinc sulfide screen, a number of flashes are produced - one for each electron - and we may picture the electrons as bullet-like projectiles hitting a target. But if the same shower is made to pass near a suspended magnet, this is found to be deflected as the electrons go by. The electrons may now be pictured as octopus-like structures with tentacles or 'tubes of force' sticking out from it in every direction.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“One has been led to the conception of electrons, i. e. of extremely small particles, charged with electricity, which are present in immense numbers in all ponderable bodies, and by whose distribution and motions we endeavor to explain all electric and optical phenomena that are not confined to the free ether…. according to our modern views, the electrons in a conducting body, or at least a certain part of them, are supposed to be in a free state, so that they can obey an electric force by which the positive particles are driven in one, and the negative electrons in the opposite direction. In the case of a non-conducting substance, on the contrary, we shall assume that the electrons are bound to certain positions of equilibrium. If, in a metallic wire, the electrons of one kind, say the negative ones, are travelling in one direction, and perhaps those of the opposite kind in the opposite direction, we have to do with a current of conduction, such as may lead to a state in which a body connected to one end of the wire has an excess of either positive or negative electrons. This excess, the charge of the body as a whole, will, in the state of equilibrium and if the body consists of a conducting substance, be found in a very thin layer at its surface.
In a ponderable dielectric there can likewise be a motion of the electrons. Indeed, though we shall think of each of them as haying a definite position of equilibrium, we shall not suppose them to be wholly immovable. They can be displaced by an electric force exerted by the ether, which we conceive to penetrate all ponderable matter… the displacement will immediately give rise to a new force by which the particle is pulled back towards its original position, and which we may therefore appropriately distinguish by the name of elastic force. The motion of the electrons in non-conducting bodies, such as glass and sulphur, kept by the elastic force within certain bounds, together with the change of the dielectric displacement in the ether itself, now constitutes what Maxwell called the displacement current. A substance in which the electrons are shifted to new positions is said to be electrically polarized.
Again, under the influence of the elastic forces, the electrons can vibrate about their positions of equilibrium. In doing so, and perhaps also on account of other more irregular motions, they become the centres of waves that travel outwards in the surrounding ether and can be observed as light if the frequency is high enough. In this manner we can account for the emission of light and heat. As to the opposite phenomenon, that of absorption, this is explained by considering the vibrations that are communicated to the electrons by the periodic forces existing in an incident beam of light. If the motion of the electrons thus set vibrating does not go on undisturbed, but is converted in one way or another into the irregular agitation which we call heat, it is clear that part of the incident energy will be stored up in the body, in other terms [words] that there is a certain absorption. Nor is it the absorption alone that can be accounted for by a communication of motion to the electrons. This optical resonance, as it may in many cases be termed, can likewise make itself felt even if there is no resistance at all, so that the body is perfectly transparent. In this case also, the electrons contained within the molecules will be set in motion, and though no vibratory energy is lost, the oscillating particles will exert an influence on the velocity with which the vibrations are propagated through the body. By taking account of this reaction of the electrons we are enabled to establish an electromagnetic theory of the refrangibility of light, in its relation to the wave-length and the state of the matter, and to form a mental picture of the beautiful and varied phenomena of double refraction and circular polarization.
On the other hand, the theory of the motion of electrons in metallic bodies has been developed to a considerable extent…. important results that have been reached by Riecke, Drude and J. J. Thomson… the free electrons in these bodies partake of the heat-motion of the molecules of ordinary matter, travelling in all directions with such velocities that the mean kinetic energy of each of them is equal to that of a gaseous molecule at the same temperature. If we further suppose the electrons to strike over and over again against metallic atoms, so that they describe irregular zigzag-lines, we can make clear to ourselves the reason that metals are at the same time good conductors of heat and of electricity, and that, as a general rule, in the series of the metals, the two conductivities change in nearly the same ratio. The larger the number of free electrons, and the longer the time that elapses between two successive encounters, the greater will be the conductivity for heat as well as that for electricity.”

Hendrik Lorentz (1853–1928) Dutch physicist

Source: The Theory of Electrons and Its Applications to the Phenomena of Light and Radiant Heat (1916), Ch. I General principles. Theory of free electrons, pp. 8-10

“We saw that radiation cannot suitably be pictured as particles when it is traveling through space. There is a corresponding property for electrons; these should not be pictured as waves so long as they are traveling through empty space.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“Gravitational force is simple, and a thing by itself, as also are electric and magnetic forces as long as the electric and magnetic poles stand at rest. But as soon as motion comes into the picture, the whole situation is changed. Forces of new kinds come into play, for moving electric charges exert magnetic forces in addition to the electric forces they exert when at rest, while moving magnets exert electric forces in addition to the magnetic forces they exert while at rest. When the exact laws governing these intricate laws had been discovered by a great number of experimenters, Clerk Maxwell succeeded in expressing them in a mathematical form which was both simple and elegant.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“It would, however, be wrong to think of an electron as a bullet-like structure with tentacles sticking out from its surface. We can calculate the mass of the bullet, and also the mass of the tentacles. The two masses are found to be identical, each agreeing with the known mass of the electron. Thus we cannot take the electron to be bullet plus tentacles… The two pictures do not depict two different parts of the electron, but two different aspects of the electron. They are not additive but alternative; as one comes into play, the other must disappear.”

James Jeans (1877–1946) British mathematician and astronomer

Physics and Philosophy (1942)

“When we say force is the cause of motion, we talk metaphysics”

Henri Poincaré book Science and Hypothesis

Source: Science and Hypothesis (1901), Ch. VI: The Classical Mechanics (1905) Tr. https://books.google.com/books?id=5nQSAAAAYAAJ George Bruce Halstead
Context: What is mass? According to Newton, it is the product of the volume by the density. According to Thomson and Tait, it would be better to say that density is the quotient of the mass by the volume. What is force? It, is replies Lagrange, that which moves or tends to move a body. It is, Kirchhoff will say, the product of the mass by the acceleration. But then, why not say the mass is the quotient of the force by the acceleration?
These difficulties are inextricable.
When we say force is the cause of motion, we talk metaphysics, and this definition, if one were content with it, would be absolutely sterile. For a definition to be of any use, it must teach us to measure force; moreover that suffices; it is not at all necessary that it teach us what force is in itself, nor whether it is the cause or the effect of motion.
We must therefore first define the equality of two forces. When shall we say two forces are equal? It is, we are told, when, applied to the same mass, they impress upon it the same acceleration, or when, opposed directly one to the other, they produce equilibrium. This definition is only a sham. A force applied to a body can not be uncoupled to hook it up to another body, as one uncouples a locomotive to attach it to another train. It is therefore impossible to know what acceleration such a force, applied to such a body, would impress upon such an other body, if it were applied to it. It is impossible to know how two forces which are not directly opposed would act, if they were directly opposed.
We are... obliged in the definition of the equality of the two forces to bring in the principle of the equality of action and reaction; on this account, this principle must no longer be regarded as an experimental law, but as a definition.<!--pp.73-74

“When a photon comes down, it interacts with electrons throughout the glass, not just on the surface. The photon and electrons do some kind of dance, the net result of which is the same as if the photon hit only on the surface.”

Richard Feynman book QED: The Strange Theory of Light and Matter

Source: QED: The Strange Theory of Light and Matter (1985), p. 17

“One possibility in this direction is to regard, classically, an electron as the end of a single Faraday line of force. The electric field in this picture from discrete Faraday lines of force, which are to be treated as physical things, like strings. One has then to develop a dynamics for such a string like structure, and quantize it…. In such a theory a bare electron would be inconceivable, since one cannot imagine the end of a piece of string without having the string.”

Paul Dirac (1902–1984) theoretical physicist

Bombay Lectures (1955)

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