James Croll

“ Eternal motion is just as warrantable an assumption as eternal matter. When we reflect that space is infinite—at least in thought—and that, for aught we know to the contrary, bodies may be found moving throughout its every region, we see that the amount of energy may be perfectly illimitable.
But, illimitable as the amount of the energy may be, it could be of no direct service while it existed simply as the motion of stellar masses. The motion, to be available, must be transformed into heat: the motion of translation into molecular, or some other form of motion. ”

“ There are no ‘missing links’ such as the zoologist longs to discover when he tries to explain the origin of species. First, we have a nebula containing little more than hydrogen, then a very hot star with calcium, magnesium, and one or two other metals added; next comes a cooler sun in which free hydrogen is missing, but whose chemical complexity is much increased; at last we reach the true planets with their multitudes of material forms. Could there well be a more straightforward story? Could the unity of creation receive a much more ringing emphasis? ”

“ 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. ”

“ 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. ”

“ A comet, for example, having an orbit extending to the path of the planet Neptune, approaching so near the sun as to almost graze his surface in passing, would have a velocity within 86 miles of what we have assumed. Twice this assumed velocity would give 200,000,000 years’ heat; four times the velocity would give 800,000,000 years’ heat; and so on.
We are at perfect liberty to begin by assuming the existence of stellar masses in motion; for we are not called upon to explain how the masses obtained their motion, any more than we have to explain how they came to have their existence. ”

“ The same gravitating force which makes the dark bodies liable to come into collision with each other must, of course, make them equally liable to come into collision with the luminous bodies, and with our sun amongst the rest. Our sun would, accordingly, be at the mercy of any of those masses which might happen to come within the reach of its attractive influence. It would pull the mass towards it, and a collision would be inevitable, unless it so happened that a transverse motion of the sun itself might enable it to escape destruction. ”

“ That all the purely physical sciences will one day be brought under a few general laws and principles, and the whole of the recognised chemical elements will be resolved into one or two material elements, is a conclusion towards which physical science seems at present slowly tending. There is certainly something fascinating in this view of the unity of nature. There is in this idea more than a purely physical interest attached to it. It has, as I hope to show in a future work, an important bearing on questions relating to the foundations of the true theory of evolution. ”

“ In the case of a fault, for example, with a displacement of, say, one mile, where no indication of it is seen at the surface of the ground, we know that on one side of the fault a thickness of rock equal to one mile must have been denuded, but we do not know how much more than that may have been removed. For anything which we know to the contrary, hundreds of feet of rock may have been removed before the dislocation took place, and as many more hundreds after all indications of dislocation had been effaced at the surface. ”

“ With such a motion, not only would the risk to our solar system be removed, but the collisions between the dark bodies themselves would be a matter of rare occurrence; and hence the energy of the universe would be conserved. And when a collision did happen it would be on a grand scale, and the result would be not an imperfect sun without planets, but an incandescent nebula, out of which, by condensation, a complete solar system would be evolved. ”

“ Everybody knows that the nebular hypothesis, as it is to-day, draws its strongest support from spectroscopic facts. There shine the nebulæ in the heavens, and the spectroscope tells us what they really are, namely, vast clouds of incandescent gas, mainly, if not entirely, hydrogen and nitrogen. If we attempt to trace the chain of evolution through which our planet is supposed to have grown, we shall find the sky is full of intermediate forms. The nebulæ themselves appear to be in various stages of development; the fixed stars or suns differ widely in chemical constitution and in temperature ”

“ For if it can be proved from the admitted facts of geology, biology, and other sciences, that the amount of energy in the form of heat which has been radiated into space by the sun during geological time is far greater than the amount which could possibly have been derived from gravitation, this will undoubtedly show that gravitation cannot account for the energy originally possessed by our system. ”

“ 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. ”

“ The material particles, either as atoms or less probably as molecules, are drawn by mutual attraction into groups and swarms. Any central attractive force, as of a sun or planet, by causing the particles to move in converging lines, would cause them to become approximated and ultimately aggregated. Thus both mutual attractions and centric movements would tend to produce aggregations dispersed through space. But in the presence of two or more attractive centres, as in the present constitution of the Cosmos, it is impossible that any mass shall fall directly upon its centre of attraction. ”

“ When we come to the question of the age of the sun’s heat, and the length of time during which that orb has illuminated our globe, it becomes a matter of the utmost importance which of the two theories is to be adopted. ”

“ This can be done in no other way than by arresting the motion of the masses. But how is such motion to be arrested? How are bodies as large as our earth, moving at the rate of hundreds of miles per second, to have their motion stopped? According to the theory this is effected by collision: by employing the motion of the one body to arrest that of the other.
Take the case of the formation of our sun according to the theory. Suppose two bodies, each one-half of the mass of the sun, moving directly towards each other with a velocity of 476 miles per second. ”

“ Gravitation cannot, therefore, be the cause of the motion of translation of the mass. The stars are not supposed to be gravitating towards, or around, a great centre of attraction, for they are found moving in straight lines in all directions, which could not be the case if gravity were the cause of their motion. To what cause is their motion, therefore, to be attributed? A meteorite or other small body might be ejected from any system, by the explosive force of heat or some other cause, with a velocity which might carry it into boundless space ”

“ If the heat momentum of the particles be insufficient to constitute a centrifugal energy equal to the centripetal energy of gravitation, then the material contents of space will be drawn into the attracting spheres as atmospheric substance, and outer space, in this case, will be left destitute of matter. If, on the contrary, the centrifugal energy of the particles be sufficient to resist gravitation, then the particles will remain free, and space will continue to be occupied with matter. ”

“ It has been thought that at some remote epoch of the earth’s history, when the moon was much nearer and the day much shorter than now, the rate of denudation would, owing to the erosive power of the enormous tides which would then prevail, be much greater than at the present day. This, however, is very doubtful. There is nothing in the stratified rocks which affords any support to the idea of great tidal waves having swept over the land, at least since the time when life began on our globe. Such a state of things would have destroyed all animal life. ”

“ Evolution could look for no grander triumph.” In fact, it is difficult to understand how our sun and the stars could have been evolved from nebulæ without assuming an evolution of the chemical elements. The true nebulæ show the presence of only two elements, nitrogen and hydrogen, but our sun contains more than a dozen of distinct elements, and the planets more than three times that number. How, then, could all these have arisen out of nebulæ composed simply of nitrogen and hydrogen? The matter is plain if we assume an evolution of the elements. ”

“ In fact, we have here one hypothesis built upon another.
The vortex theory appears to me to be beset by a difficulty of another kind, viz. that of reconciling it with the First Law of Motion. According to that law no body possessing inertia can deviate from the straight line unless forced to do so. A planet will not move round the sun unless it be constantly acted upon by a force deflecting it from the straight path. A grindstone will not rotate on its axis unless its particles are held together by a force preventing them from flying off at a tangent to the curve in which they are moving. ”

“ In so far as protyle is capable of radiating or reflecting light, this vast sea of incandescent mist, to an astronomer in a distant star, might have appeared as a nebula, showing in the spectroscope a few isolated lines, forecasts of hydrogen, carbon, and nitrogen spectra.
“But in course of time some process akin to cooling, probably internal, reduces the temperature of the cosmic protyle to a point at which the first step in granulation takes place; matter as we know it comes into existence, and atoms are formed. ”

“ It will not do to state in a loose and general way, as has been frequently done, that the sun may have been supplying our globe with heat at its present rate for 20,000,000 or 100,000,000 years, for gravitation could have done no such thing; a period of 20,000,000, not 100,000,000, years is the lowest which is admissible on that theory. Not even that length of time would be actually available; for this period is founded on Pouillet’s estimate of the rate of solar radiation, which has been proved by Langley to be too small, the correct rate being 1·7 times greater. ”

“ There is not a single class of vertebrated animals which, when it first appears, is represented by analogues of the lowest known members of the same class. Therefore, if there is any truth in the doctrine of evolution, every class must be vastly older than the first record of its appearance upon the surface of the globe. ”

“ The theories do not account for the motion of the stars.—According to all the foregoing theories aggregation and condensation are produced by gravity. The materials dispersed throughout space are drawn together by their mutual attraction, and aggregated round a centre of gravity. Gravitation, although it imparts motion to the materials, can impart no motion of translation to the mass itself. ”

“ As soon as an atom is formed out of protyle it is a store of energy, potential (from its tendency to coalesce with other atoms by gravitation or chemically) and kinetic (from its internal motions) . To obtain this energy, the neighbouring protyle must be refrigerated by it, and thereby the subsequent formation of other atoms will be accelerated. But with atomic matter the various forms of energy which require matter to render them evident begin to act; and, amongst others, that form of energy which has for one of its factors what we now call atomic weight. ”

“ 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. ”

“ Suppose, now, that 29,000,000 cold, solid globes, each of about the same mass as the moon, and amounting in all to a total mass equal to the sun’s, are scattered as uniformly as possible on a spherical surface of radius equal to one hundred times the radius of the earth’s orbit, and that they are left absolutely at rest in that position. ”

“ We can be far more certain of the time which must have been required to remove by denudation, say, a thousand feet of rock than we can possibly be of the time required to have deposited a thousand feet of sediment. The thousand feet of sediment may, under certain conditions, have been deposited in a hundred years, while under other conditions they may have required a million of years. In fact, nothing can be more uncertain than the rate of deposition: it depends upon such a multitude of circumstances. ”

“ If the nebular theory be a true theory of the origin of the solar system, then this nebulous mass must have had an antecedent history, and we cannot help feeling the instinctive desire of tracing the chain of causation farther back. The mind presses towards an absolute beginning. ”

“ Such occasional imperfections give variety and add perfection to the whole. How dreary and monotonous would nature be, were every blade of grass, every plant, every animal, and every face we met formed after the most perfect model! ”

“ This motor energy yet exists in space as a motion of the particles of matter, which, therefore, press upon each other, or seek to extend their limits, with increasing vigour, so that the elasticity of interspheral matter is constantly increasing. ”