The impact theory seems to remove all these difficulties. It is just as likely à priori, if not more so, that the primitive form of the protyle should have been that of large cold masses moving through space in all directions, with excessive velocities, as that it should have been that of a gaseous mass in a state of unstable equilibrium. If we assume the former condition, then the colliding of these masses would account not only for the ultra-gaseous state, but also for its inconceivably high temperature. Besides, in this case we are not called upon to account for any other antecedent state of the masses before collision, for they may have existed from the beginning of creation in the form of masses in motion through space.
Had space and time permitted, it might have been shown that there are other obscure points on which the theory seems to shed additional light. I shall now, in conclusion, refer to a point wherein the theory differs radically from that of all other theories of stellar evolution. But before doing so I may briefly refer to an objection which has been frequently urged against the theory.
Objection considered.—The objection to which I refer is this, that, had the nebulæ been produced by impact in the way implied in the theory, then we ought to have had some historical record of such an event. I can perceive no force in such an objection. Our historical records, I presume, do not extend much farther back than about 3,000 years, and we have no evidence to conclude that a new nebula makes its appearance in the visible firmament with such frequency; and supposing it did, we have no grounds for assuming that its production by impact in the way supposed by the theory would attract general notice. It is doubtful if the nebula produced would, in the first instance, be actually visible. I have shown that the temperature of the nebula could not have been less than about 300,000,000° C., and it is very doubtful if the gaseous mass enveloping all that was solid in the nebula would, at such a temperature, be self-luminous. The probability is that all the chemical elements composing it would be in a state of utter dissociation, and converted back into the original protyle from which they were derived, again to be slowly reconverted into their former atomic condition as the temperature fell.
Can we on scientific grounds trace back the evolution of the universe to an absolute first condition?—As has been repeatedly stated, all inquiries into the evolutionary history of the stellar universe begin in the middle of a process. Evolution is a process. The changes that now occur arose out of preceding changes, and these, preceding changes out of changes still prior, and so on indefinitely back into the unknown past. This chain of causation—this succession of change—of consequent and antecedent—could not in this manner have extended back to infinity, or else the present stage of the universe’s evolution ought to have been reached infinite ages ago. The evolution of things must therefore have had a beginning in time. Professor Winchell, in his final generalisation to his work, “World Life,” has stated this matter so clearly and forcibly that I cannot do better than here quote his words on the subject.
“We have not,” says Professor Winchell, “the slightest scientific grounds for assuming that matter existed in a certain condition from all eternity, and only began undergoing its changes a few millions or billions of years ago. The essential activity of the powers ascribed to it forbids the thought. For all that we know—and, indeed, as the conclusion from all that we know—primal matter began its progressive changes on the morning of its existence. As, therefore, the series of changes is demonstrably finite, the lifetime of matter itself is necessarily finite. There is no real refuge from this conclusion; for, if we suppose the beginning of the present cycle to have been only a restitution of an older order effected by the operations of natural causes, and suppose—what science is unable to comprehend—that older order to be a similar re-inauguration, and so on indefinitely through the past, we only postpone the predication of an absolute beginning, since, by all the admissions of modern scientific philosophy, it is a necessity of nature to run down.”
These are consequences which necessarily follow from every theory of stellar evolution which has hitherto been advanced. The impact theory, however, completely removes the difficulty, for according to it the evolutionary process can, on purely scientific grounds, be traced back to an absolute beginning in time. If huge solid masses moving through space were the original condition of the universe, then, in so far as either philosophy or science can demonstrate to the contrary, it might have been in this condition from all eternity. We are therefore not called upon to account for this primitive condition of things. Now it is evident, unless a collision should take place, the universe would remain in this condition for ever: without a collision there could be no change, no work performed, and absolutely no loss or gain of energy, and therefore no process of evolution. The first collision would be the absolute commencement of evolution—the beginning of the process of the development of the universe. Evolution would, in this case, have its absolute beginning in time, and consequently was not eternal. If, on the other hand, we assume, what is far more in harmony with physics, metaphysics, and common sense, that the universe was created in time, we are still led to the same result as to an absolute commencement of evolution. In both cases we reach a point beyond which there can be no legitimate inquiry; no further question which the scientists can reasonably ask.
We have no grounds to conclude that there is anything eternal, except God, Time, and Space. But if time and space be subjective, as Kant supposes, and not modes pertaining to the existence of things in themselves, then God alone was uncreated, and of Him and to Him are all things.