Planetary evolution

“ These planetary globes themselves, as they coalesced and contracted, left behind or threw off rings of their outer matter, which, in turn, became moons, and finally our solar system with its central sun was evolved as we now see it; development continued, the planets cooled and condensed, life appeared when the conditions became suitable, and the original progressive condensation of the central mass—the sun—still continuing, the evolution of light and heat continues, and will continue in a correlative degree. ”

“ We can say only that there is strong evidence of its possession of the conditions of life in some degree, and that living things, even on the earth, display a remarkable power of adaptation to widely differing conditions.
Passing over the 700 planetoids, which circulate between Mars and Jupiter, and for which we may account either by the absence of one large nucleus in that part of the nebulous stream or by the disturbing influence of Jupiter, we come to the largest planet of the system. Here we find a surprising confirmation of the theory of planetary development which we are following. ”

“ A planet runs through its grand period of life from a formless nebula to a globe, which solidifies into a planet with or without satellites. It is involution as long as the planet is in process of formation; but when matter begins to manifest, the first step in evolution is taken, which goes on from protoplasm to man. Then comes the blooming-time, when this flower of space will scatter its seeds, as did the huge planet once revolving between Jupiter and Mars. ”

“ It may therefore be expected that the small planet will proceed much more rapidly in its evolution than the large one; we might, therefore, anticipate that Mars and his satellites have attained a more advanced stage of their history than is the case with the earth and her satellite. ”

“ It was a comparatively easy task to show how the diurnal rising and setting could be accounted for by the rotation of the earth. It was a much more difficult undertaking to demonstrate that the planetary movements, which Ptolemy had represented with so much success, could be completely explained by the supposition that each of those planets revolved uniformly round the sun, and that the earth was also a planet, accomplishing a complete circuit of the sun once in the course of a year. ”

“ There are numerous other techniques for evolving suns and segregating planets, but the foregoing procedures suggest the methods whereby the vast majority of stellar systems and planetary families are brought into existence. ”

“ The interpretation of phenomena as results of Evolution, has been independently showing itself in various fields of inquiry, quite remote from one another. The supposition that the Solar System has been evolved out of diffused matter, is a supposition wholly astronomical in its origin and application. Geologists, without being led thereto by astronomical considerations, have been step by step advancing towards the conviction that the Earth has reached its present varied structure by modification upon modification. ”

“ But taken in conjunction with the geological evidence already referred to, taken in conjunction with the immense periods of time that have been required for the evolution of life on the globe by the process of natural selection, the conclusion arrived at is inevitable. It seems impossible to doubt that the sun must have been shining and that our solar system must have existed in practically the same form as it is at present for periods enormously greater than would have been possible if the heat of the sun had been sustained by the solar contraction only. ”

“ When this day opens, cosmic evolution, so far as relates to this solar system, begins and occupies between one and two billions of years in evolving the very ethereal first matter before the astral kingdoms of mineral, vegetable, animal and men are possible. This second step takes some three hundred millions of years, and then still more material processes go forward for the production of the tangible kingdoms of nature, including man. This covers over one and one-half billions of years. And the number of solar years included in the present “human” period is over eighteen millions of years. ”

“ On contemplating our Solar System the first fact which strikes us, is, that all its members are in motion; and that their motion is of a two-fold, or rather of a three-fold, kind. Each planet and satellite has a movement of rotation and a movement of translation; besides the movement through space which all have in common with their rotating primary. Whence this unceasing change of place?
The hypothesis of Evolution supplies us with an answer. Impossible as it is to assign a reason for the pre-existence of matter in the diffused form supposed ”

“ Now, the earth as a planet is in process of evolution. Not many things are more certain than this. The earth has come out of fire. It has grown to be what it is. Its mountains, valleys, plains, seas, shores, islands, lakes, rivers, and continents—these were not always here. They have been evolved. Not only the earth, but the entire family of spheres of which the earth is a member—the solar system—are all evolving. ”

“ Now, adopting this theory as the last word of science upon the subject of the origin of planets, we see that it affords immense scope for diversity in results depending on the total amount of matter available within the range of attraction of an incipient planetary mass, and the rates at which this matter becomes available. ”

“ Within the solar system there are planetary surfaces to be watched, asteroids to be scanned for variability or change of it, meteor swarms to be correlated with their sources, occultations to be minutely examined, and when one runs short of these, our nearest neighbor the Moon offers a wild and physically unknown country for exploration. It is suspected with good reason of dynamic changes, to say nothing of the possible last remnants of organic life. ”

“ Doubtless there are other bodies in our solar system whose equilibration is even more complete than that of the moon—as, perhaps, some asteroids, or the satellites cf the outer planets. They have run their long cosmical course, and have arrived at last at the final state of complete, stable equilibrium. This state is the goal of the whole process of evolution. It must, therefore, be regarded, when viewed from this standpoint, as the state of greatest perfection in the life of every aggregate. ”

“ If, therefore, stellar globes can become planetary systems in the progress of ages, it will not be at all inconsistent with what we know of the order of nature, that only a few, or even that only one, should have yet reached that condition. ”

“ Then, going away from the earth, we could interrogate the planetary atmospheres, and seek in them the vapor of water, and with it one of the first conditions of the development of terrestrial life. We could also, comparing the composition of the planetary atmospheres with the astronomical facts which permit us to judge of the geological conditions of the surfaces of the planets, follow in them the atmospheric evolutions which on the earth belong to the domain of the past or of the future. ”

“ When, however, we bring thousands of years into consideration, then the displacements of the planetary orbits attain considerable dimensions, and have, in fact, produced a profound effect on the system. ”

“ Yet, take all these planets and all their satellites, wonderful and great as they are, and consider them melted down into one great sphere, and still our sun alone, the center of this planetary system, is upwards of 750 times as large as all these planets combined would be! ”

“ Of course their relative positions to, and their distances from central Suns, occasion differences in the bodies of Planets, particularly as to their density; then, too, in accordance with conditions, atmospheres vary as to being rarefied or dense, humid or dry and so on, but life germs of fauna and flora ever are the same, and given like or similar Planetary conditions their expressions will present more or less close resemblances. Yes, environments occasion differences, but environments are the results of Planetary conditions. ”

“ But no matter what technique of world building obtains, gravity always produces the solar system type of creation; that is, a central sun or dark island with planets, satellites, subsatellites, and meteors.
The physical aspects of the individual worlds are largely determined by mode of origin, astronomical situation, and physical environment. Age, size, rate of revolution, and velocity through space are also determining factors. Both the gas-contraction and the solid-accretion worlds are characterized by mountains and, during their earlier life, when not too small, by water and air. ”

“ Admitting, however, the hypothesis that these planetary bodies, are the remains of a larger body, which circulated round the sun, nearly in the orbit of the greatest fragment, the system resumes its order, and we discover a regular procession in the distances of the planets, and a general harmony in the form and position of their orbits. But, independently of analogical reasoning, the elements of the new planets furnish several direct arguments, drawn from the eccentricity and inclination of their orbits, and from the position of their perihelia and nodes ”

“ If it were quite immaterial to the welfare of the planetary system whether all the planets moved the same way, or whether some moved one way and some another, then the nebular hypothesis would be entitled to all the support which could be derived from the circumstances of the case. Take, for instance, the eight principal planets—Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, Neptune. All these planets move in the same way around the sun. ”

“ A nucleus once formed would increase by appropriating matter from the zone which it traversed, and, though at first much retarded in its growth, it would after many thousand revolutions attain a planetary size. Being largely composed of gaseous matter and therefore very sensitive to the resistance of a space-pervading medium, the newly formed planet would contract its large orbit ”

“ Although the uniformity in the direction of their rotation is a circumstance hitherto unaccounted for in the economy of Nature, yet from the design and adaptation of every other part to the perfection of the whole, a coincidence so remarkable cannot be accidental; and as the revolutions of the planets and satellites are also from west to east, it is evident that both must have arisen from the primitive causes which have determined the planetary motions. ”

“ The complete analogy of physical conditions which has been proved to exist in some other planets of our solar system, and which without doubt must also occur in innumerable planets of other solar systems, allowed the very probable deduction that not only on our own earth a higher organic process of evolution has taken place. ”

“ Here again it is well to remember the small size of the planet, from which we may infer that it has progressed through its physical evolution at a rate more rapid than would be possible with a larger globe like the earth. The sea is constantly wearing down the land, but by upheavals arising from the intensely heated condition of the interior of our globe the land is still able to maintain itself above water. ”

“ The result would be that the earth would be carried around the sun in a circular or an elliptical orbit. Every other planet in the solar system would be under the operation of the same compound forces governed by the same laws ”

“ The satellites of the larger planets revolve with short periodic times; for the smallness of their masses would have prevented tidal friction from being a very efficient cause of change in the dimensions of their orbits, and the largeness of the planet's masses would have caused them to proceed slowly in their evolution. ”

“ In regard to our own solar system much speculation is rife as to the existence of human creatures on the several larger planets. Theories of all kinds have been advanced; some speculative or absurd, others so plausible as to give rise to interesting questions, such as communicating with Mars, and perhaps of taking a journey to the Moon. These suggestions, while fanciful, awaken our interest and excite our curiosity. Can any one predict the excitement that would prevail in our world if a human creature from some other planet were suddenly to set foot upon our soil? ”

“ I've always believed that life would evolve along parallel lines throughout the entire solar system, assuming that it could exist at all on Venus, Mars, or on one of the outer planets. I've always believed that any life sustaining environment would produce forms familiar to us. On Earth you have the same adaptations occurring again and again in widely divergent species. ”

“ But, whatever may be the end towards which these changes are tending, we see processes of evolution taking place which may be regarded as typifying the more extensive and probably more energetic processes whereby the solar system itself reached its present condition. ”

“ And now, in the unwearied march of science, often baffled but never cast down, it has been announced as the probable solution of all the changes of the past, the progression of the whole solar system, whereby the earth, and all the sister planets, are dragged through infinite space, and brought successively within the sphere of new constellations—now in a hotter and now in a milder efflux of ether—combining its own with a more general movement in a universal whirl—and thus constantly subjected, in all its parts, to ever-varying external influences! ”