“The cube root of the nth atomic weight = κ log (n q) + a small periodic correction; where κ and q are constants, the values of which are furnished by the observations.
“Either this logarithmic law, or a law that lies exceedingly close to it, must be the law of nature.”
Referring to this theory, Professor Reynolds says: “It certainly introduced points of extraordinary importance, though perhaps at present they could not all quite realise its fullest import. There were several points of some little difficulty to be grappled with, but it clearly pointed to the conclusion that we were fast approaching the time when physicists—both chemical and physicists proper—are combining to evolve out of the scientific work lying on the borderland most important and startling facts.”
The bearing which Dr. Stoney’s conclusions, like those of Mr. Crookes, have on the primitive condition of the material universe is obvious.
Dr. Stoney, like Mr. Crookes, considers that the chemical elements are subject to decay. That they are not only generated but destroyed—that they are subject not only to evolution but dissolution. He believes that the generative process probably takes place only at, or beyond, the confines of the universe, and the destructive process at the centres of overgrown stars, which is the position of lowest potential. Dr. Stoney thinks that this extinction of the chemical elements in the centre of a star is a cause which limits its size and prevents its overgrowth.
The Impact Theory in relation to the foregoing Theories of the Pre-nebular Condition of Matter.
In all these theories, as has already been observed, the primitive condition of the universe was that of matter in a state of extreme tenuity, while by aggregation the materials became successively larger and larger until they assumed the magnitude of suns and planets. For example, according to the meteoric theory, meteorites are formed out of “cosmical dust,” “fire-mist,” or condensed vapour, and then suns and planets are formed by aggregation from these meteorites. Facts seem, however, to point to the very reverse as being the true course of events.
Meteorites are undoubtedly the fragments of larger masses. It looks more likely that they are, as has already been stated, fragments of stellar masses which have been shattered to pieces by collision, and that this “cosmical dust,” from which the meteorites are alleged to have been formed, are simply the dust arising out of the destruction of the masses. After the two bodies had collided and been shattered to pieces, some of the fragments would undoubtedly be projected with a velocity that would carry them beyond the attractive power of the general mass, and thus they would escape being volatilised. These fragments would continue their wanderings through space as meteorites.
I cannot but think that the number, as well as the importance, of these wanderers has been greatly over-estimated. Mr. Lockyer states that Dr. Schmidt, of Athens, found that the mean hourly number of luminous meteors visible on a clear moonless night by one observer was fourteen. Certainly no such quantity is visible in this country. In Scotland, at least, one may often watch night after night under the most favourable conditions without having the good fortune to see a single meteor.
It is, of course, true that the immediately prior condition of a sun or a planet was that of matter in an extremely attenuated or dissociated state. This is essential to the nebular, as well as to the meteoric, hypothesis. But it is not with the immediately prior condition that we are at present concerned, but with the primitive, or pre-nebular, condition. Take, for example, the case of the solar nebula, out of which our sun and planets were formed. Was this nebulous mass formed from matter in a state of extreme tenuity, scattered through space and collected together by gravity? Or did it result from two solid globes shattered to pieces by collision, which were then converted into the nebulous condition by the heat generated from the collision? It is no doubt true that the analogies of nature would, at first sight, be apt to lead us to the conclusion that the former theory was the more likely of the two, as the larger is generally made by aggregation from the smaller. But a little consideration will show that, in the present case, the weight of this analogy is more apparent than real. The impact theory does not rest upon a purely hypothetical basis. The cause to which it appeals has a real existence. The point of uncertainty is whether the cause actually produces the effect which is attributed to it. We know from observation that there are stellar masses, some of them probably larger than our sun, moving through space with enormous velocities in all directions.[[77]] According to the ordinary laws of chance, collision at times would be an inevitable result, and when such an event did take place the destruction of the colliding bodies, and their consequent transformation into a nebulous mass, would, at least in many cases, be a necessary result. In fact, we have, in the case of these vast stellar masses, what we know occurs among the invisible molecules of a gas. So far as mere analogy is concerned, the impact theory is just about as probable as the other.