On Action at a Distance (Preston)
IN the last Number of the Philosophical Magazine is a paper by Mr. Walter R. Browne, " On Action at a Distance ", in which some conclusions of mine relating to the explanation of gravitation, or the general phenomena of approach, under the kinetic theory of the aether, are noticed. Although some of the objections cited by Mr. Browne do not appear to me to be of much weight, and some will, I think, be found to be answered in my previous papers, I will nevertheless comment upon a few points here.
First, on page 440, a difficulty originally brought forward by Dr. Croll, in a notice of my papers, is alluded to, relating to the porosity of matter required by the kinetic theory of gravity. It should be observed, however, that this difficulty was considered by me (Philosophical Magazine, Feb. 1878), and a means suggested for surmounting it.
Secondly, Mr. Browne concludes, apparently rather gratuitously, on page 441 as follows, viz.: — " Hence our conception of the gravity-gas must practically be that of an indefinite number of indefinitely small particles moving in all directions with indefinitely high velocities — a conception from which it hardly seems safe to draw any definite conclusion whatever." It is scarcely necessary to add that the number of particles in unit of volume, their dimensions, and mean velocity, are not actually assumed by me to be indefinite (but strictly finite). Any finite values, however great, are still an unlimited distance from indefinite values. .
Thirdly, on page 442, the fact is seemingly overlooked that, according to the vortex-atom theory (alluded to in the context), it appears that molecules would be elastic; so that it would not seem necessary to assume that the molecules of a solid bar are normally at a distance from each other in order to explain  the contraction of the bar (within certain limits) under an applied pressure — the bar being elastic partly through the elasticity of the open structure of its molecules.
Fourthly, it appears to be assumed by Mr. Browne that the postulate of "action at a distance "affords an alternative explanation of facts, as on page 444 it is remarked as follows, viz.:— .... "it must be held to be demonstrated that the phenomena of cohesion cannot be explained except on the hypothesis of action at a distance."
It may, surely, well be asked here how that which is in itself inexplicable can explain any thing, or how the assumption of an occult quality can throw light upon any problem whatever.
In conclusion, it cannot fail, I think, to be apparent (as an important fact) to an impartial observer, that a movement in accordance with the kinetic theory is the only possible (or conceivable) motion that can naturally maintain itself among particles of matter left to themselves in free space (if we refrain from attributing to matter occult and mystical qualities, which only involve every thing in obscurity).
The application of the kinetic theory to the phenomena of sound, light, gravity, and (possibly) to the motions of the larger-scale stellar masses of the universe immersed in the kinetic aether (as developed by me in former essays in this Journal and elsewhere) would seem to afford some hope of ultimately correlating a wide range of phenomena under one fundamental cause of extreme simplicity.
- Read before the Physical Society, November 13, 1880.
- Philosophical Magazine, Sept. and Nov. 1877, Feb. 1878.
- Ibid. Jan. 1878.
- It is obvious that if the molecules of matter themselves have an open structure, then matter may possess any degree of porosity (or permeability to the particles of the gravific aether) that observed facts may require. The open structure of molecules is only & priori natural, since a solid ( block) structure of molecules would involve useless waste of material.
- The high velocity of the particles is the perfectly natural consequence of their minute mass.
- It is sufficiently clear that if " elasticity " were not yet explained, the first step towards this end would have to be the rejection of " action at a distance," since the retention of an occult quality would render any explanation hopeless.
- To afford some rough idea of the mode in which molecules of open structure may be conceived to be held together (in cohesion ) by the pressure of streams of particles, I would refer to my paper entitled "A Suggestion in regard to Crystallization," Phil. Mag. April 1880.
- The italics are mine.
- 'Nature,' Jan. 15, 1880, "On a Mode of Explaining the Transverse Vibrations of Light."
- Philosophical Magazine, August 1879 and November 1880.
The difficulty of the explanation of magnetism (alluded to by Mr. Browne on page 444) may be freely admitted. But magnetism is a somewhat special phenomenon, dependent possibly on special (or secondary) conditions. It would surely be scarcely reasonable to expect that the theory should be capable of giving full satisfaction in all cases. It would be even strange if some difficulties did not present themselves at the outset. We can only say that by explaining some important or fundamental facts (such as gravitation, some effects of cohesion, &c.), the hope may be reasonably entertained that an addition to knowledge will throw light upon others — so long as we hold to strict mechanical conceptions, and do not close the door to discovery by postulating the mystery of " action at a distance." ( See also paper "On Method in Causal Research," Phil. Mag. May 1880, in connexion with this.)
Among all the arguments expended on " action at a distance," it certainly appears strange that the one firm and indisputable fact is not more clearly kept in view, viz. that this assumption or theory, opening out an absolutely limitless field of speculative hypothesis, completely annihilates all method or rational system in physical inquiry, and therefore that all progress or insight into the physical processes underlying phenomena is absolutely brought to a standstill so long aa this theory is adhered to.