Gravitational perturbation

“ Suppose all the stars were to be annihilated at a given instant of our earth frame. The gravitational disturbance produced by this annihilation would require a number of years to reach us, since gravitational disturbances travel with the speed of light. Hence, the metrical field, or space-time structure, round the earth would persist for a considerable time. For a number of years, therefore, centrifugal force would still continue to manifest itself. ”

“ Among small bodies gravitational forces are slight, and are altogether exceeded by magnetic and electric or chemical forces. Indeed gravitational attraction between bodies of a certain smallness can be more than counterbalanced even by the pressure which their mutual radiation exerts—almost infinitesimal though that is;—so that as a matter of fact, small enough bodies of any warmth will repel each other unless they are in an enclosure of constant temperature, i.e. unless the radiation pressure upon them is uniform all round. ”

“ If so, the maintenance of the field of strain about an atom as it moves presents no greater difficulty than the maintenance of the field of light about a moving candle, or of the field of sound about a moving bell. The propagation of such ether strains as occur in light, electricity and magnetism is very greatly influenced by the material substances present in the strained medium. It is not probable that the gravitational strain differs from others in this respect, and we may reasonably hope to find some inductive phenomena in connection with gravitation. ”

“ The actual strain is in space. It is space that takes the strain, but in normal cases, unless the masses are very large, no considerable acceleration is produced over any great distance. That law operates in the case of the pulled body; it pulls the gravitational field as a normal field, the inverse-square law applying.
"But on the other hand, the gravity-beam pulls with a constant force.
"It might be likened to the light-pressure effects of a spotlight and a star. The spotlight would push the sun with a force that was constant ”

“ In contrast to electric and magnetic fields, the gravitational field exhibits a most remarkable property, which is of fundamental importance for what follows. Bodies which are moving under the sole influence of a gravitational field receive an acceleration, which does not in the least depend either on the material or on the physical state of the body. For instance, a piece of lead and a piece of wood fall in exactly the same manner in a gravitational field (in vacuo) , when they start off from rest or with the same initial velocity. ”

“ So long as forces are confined to the thrusts and tensions of elementary mechanics, where there is supposed to be direct contact of material, there is good ground for this distinction; we can visualise the active hammering of the molecules on the body, causing it to change its motion. But when force is extended to include the gravitational field the distinction is not so clear.
For our part we deny the distinction in this last case. Gravitational force is not an active agent working against the passive tendency of inertia. Gravitation and inertia are one. ”

“ If now, as we find from experience, the acceleration is to be independent of the nature and the condition of the body and always the same for a given gravitational field, then the ratio of the gravitational to the inertial mass must likewise be the same for all bodies. ”

“ The same considerations that apply to rotation apply to acceleration, although the difficulty is less striking. We can if we like attribute to the sun some arbitrary acceleration, balancing it by introducing a uniform gravitational field. Owing to this field the rest of the stars will move with the same acceleration and no phenomena will be altered. But then it seems necessary to find a cause for this field. It is not produced by the gravitation of the stars. Our only course is to pursue the cause further and further towards infinity ”

“ Every particle of matter in the universe is found in fact to attract every other particle. The moon, for instance, attracts the earth also, but the controlling force is on the side of the much greater mass of the earth. This force of gravity or attraction of gravitation, as it is also called, is perfectly regular in its action. Its power depends first of all exactly upon the mass of the body which exerts it. The gravitational pull of the sun, for instance, reaches out to an enormous distance, controlling perhaps, in their courses, unseen planets circling far beyond the orbit of Neptune. ”

“ For smaller or hotter bodies, radiation repulsion overpowers mutual gravitation; and it increases with the fourth power of their absolute temperature. The gravitational attractive force between particles is exceedingly small; and that between two atoms or two electrons is negligibly small, even though they be within molecular distance of each other. ”

“ 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. ”

“ Its own gravitational power is trying to draw all of its materials to the center. Until there is a loss of heat no contraction can occur; but just as soon as there is such a loss gravity proceeds to diminish the stellar volume. Contraction will proceed more slowly than we should at first thought expect, because in the process of contraction additional heat is generated and this becomes a factor in resisting further compression. ”

“ The sun is giving off energy. It is giving off mass, then, in the form of light photons. The field of the sun's gravity must be constantly decreasing as its mass decreases. It is a collapsing field. It is true, the sun's gravitational field does decrease, by a minute amount, despite the fact that our sun loses a thousand million tons of matter every four minutes. The percentage change is minute, but the energy released is—immeasurable. ”

“ You know that it is gravitational force alone which keeps the suns and planets to their courses, and you know that the gravitational force of any body, sun or planet, is radiated out from it in all directions, tending to pull all things toward that body. In the same way there is radiated outward perpetually from the Galaxy the combined attractive gravitational force of all its swarming suns, and a tiny fraction of this outward-radiating force, of course, struck the dark star, pulling it weakly toward the Galaxy. ”

“ In that case there is no gravitational or centrifugal force at infinity; but there is still inertia, which is of the same nature. The distinction between force as requiring a cause and inertia as requiring no cause cannot be sustained. We shall not become any more solvent by commuting our debt into pure inertia. The debt is inevitable whatever mesh-system is used; we are only allowed to choose the form it shall take.
The debt after all is a very harmless one. At infinity we have the absolute geodesics in space-time, and we have our own arbitrarily drawn mesh-system. ”

“ Classical science had always assumed that a gravitational field, such as that of the sun, would attract material bodies, but that it would be without effect on light rays, which were considered to be immune from gravitational attractions. Had classical science been thoroughly convinced of the identity of the two types of mass, it would have realised that light waves must be possessed of gravitational mass, since they were known to manifest the characteristics of inertial mass. ”

“ Zero gravity or decreased gravity occurs during freefall, in parabolic trajectory, or during orbit around the Earth. Gravitational force decreases by the square of the distance away from the Earth's center. It is reduced about 5 percent at about 200 nautical miles' altitude. Gravitational force greater than 1 g can be obtained by acceleration, deceleration, or impact. It also can be increased by using a centrifuge which adds a radial acceleration vector to the 1 g of Earth. ”

“ Hence it appears that mass (inertia) and energy are essentially the same thing, or, at the most, two aspects of the same thing. It must be remembered that on this view the greater part of the mass of matter is due to concealed energy, which is not as yet releasable.
The question whether electrical energy not bound to electric charges has mass, is answered in the affirmative in the case of light. Light has mass. Presumably also gravitational energy has mass; or, if not, mass will be created when, as often happens, gravitational energy is converted into kinetic energy. ”

“ Calculation shows that for very great masses the gravitational pressure is almost entirely balanced by radiational pressure. This implies that any additional force such as that due to a centrifugal field of rotation would lead to an unstable condition. ”

“ Probably the mass necessary to demonstrate any action of the gravitational kind would be impractically large, unless the earth itself could be used. Now, by staking out mirrors at the corners of a field, it is arithmetically quite possible to arrange for a perceptible shift of the bands due to the rotation of the earth, if it carries ether round with it; but it does not seem possible to experimentally observe that shift, unless some method could be devised of making the observer and his apparatus independent of the rotation. ”

“ From the present state of theory it looks as if the electromagnetic field, as opposed to the gravitational field, rests upon an entirely new formal motif, as though nature might just as well have endowed the gravitational ether with fields of quite another type, for example, with fields of a scalar potential, instead of fields of the electromagnetic type.
Since according to our present conceptions the elementary particles of matter are also, in their essence, nothing else than condensations of the electromagnetic field, our present view of the universe presents two realities which are completely separated from each other conceptually, although connected causally, namely, gravitational ether and electromagnetic field, or — as they might also be called — space and matter. ”

“ When mass becomes overaggregated and threatens to unbalance energy, to deplete the physical power circuits, the physical controllers intervene unless gravity's own further tendency to overmaterialize energy is defeated by the occurrence of a collision among the dead giants of space, thus in an instant completely dissipating the cumulative collections of gravity. ”

“ One of these forces is the bond of gravitative attraction between planet and primary which is never severed, and when complete separation of the two masses finally occurs, the incessant combination of this force with the tangential force of disruption acting on the planet will compel it into a fixed orbit, which it will pursue around the central axis. When all material links have thus been severed, the two bodies will then be absolutely separate masses in space. ”

“ All this risk, in so far as gravitation is concerned, would have been completely averted if an original projected velocity of some thirty or forty miles per second had been conferred on the dark mass; for, in this case, the attractive force of the sun would fail to arrest its motion, and the mass would pass onward through space, never to return. ”

“ Innumerable other laws of force, beside that of the inversed square, might be conceived but this is only one consistent with stability in a system subject to perturbations. If the law of gravitation varied according to the inverse cube, instead of square, the slightest disturbance would precipitate the planet on the sun, or cause it to fly off from its control. With the existing law of gravity, though a planet were pushed out of its course by an impulse from a comet, it would pursue its new orbit with undeviating regularity; the primitive disturbance would not have a progressive tendency. ”

“ The effect of the gravitation of the sun on a light-wave, or very fast particle, proceeding radially is actually a repulsion!
The track of a transverse light-wave, coming out from the plane of the paper, will be affected like that of a particle of zero velocity in distorting from Fig. 14 to Fig. 15. Hence the sun's influence on a transverse light-wave is always an attraction. The acceleration is simply as for a particle at rest. ”