The taxonomy of the cosmos: Why our categories blur between nebulae, galaxies, and star clusters

“ CLASSIFICATION OF FISHES
Taxonomy.—Classification, as Dr. Elliott Coues has well said, [147] is a natural function of "the mind which always strives to make orderly disposition of its knowledge and so to discover the reciprocal relations and interdependencies of the things it knows. Classification presupposes that there do exist such relations, according to which we may arrange objects in the manner which facilitates their comprehension, by bringing together what is like and separating what is unlike, and that such relations are the result of fixed inevitable law. ”

“ In order to qualify ourselves to judge of the degree of affinity in physical organisation between Man and the lower animals, we cannot do better than study those systems of classification which have been proposed by the most eminent teachers of natural history. ”

“ If a great, nay, far the greatest part of the several ranks of bodies in the universe escape our notice by their remoteness, there are others that are no less concealed from us by their minuteness. These insensible corpuscles, being the active parts of matter, and the great instruments of nature, on which depend not only all their secondary qualities, but also most of their natural operations, our want of precise distinct ideas of their primary qualities keeps us in an incurable ignorance of what we desire to know about them. ”

“ The “clusters” of which this Universal “cluster of clusters” consists, are merely what we have been in the practice of designating “nebulæ”—and, of these “nebulæ,” one is of paramount interest to mankind. I allude to the Galaxy, or Milky Way. This interests us, first and most obviously, on account of its great superiority in apparent size, not only to any one other cluster in the firmament, but to all the other clusters taken together. The largest of these latter occupies a mere point, comparatively, and is distinctly seen only with the aid of a telescope. ”

“ After a few years, however, when powerful telescopes showed that many of the nebulæ were only clusters of very minute stars, astronomers thought that Laplace's teaching had been wrong. But now the spectroscope has revealed to us glowing [Pg 153] gas actually filling large spaces in the sky, and every year accurate observations and experiments tell us more and more about these marvellous distant mists. Some day, though perhaps not while you or I are here to know it, Orion's nebula, with its glowing gas and minute star-dust, may give some clue to the early history of the heavenly bodies ”

“ When the accumulating clouds of dust become so heavy that gravitation begins to draw their particles together, heat is generated and the mass begins to glow, although sometimes dark masses, if they are close to stars, will glow with reflected starlight. The gaseous clouds are devoid of solid or liquid matter, and consist, the spectroscope shows, of glowing gases, apparently nebulium and hydrogen. Thus the Nebula of Orion, which is a gaseous nebula, is never spoken of as a "universe," like the Nebula of Andromeda, which may be resolved into stars. ”

“ But the sorting of things by us, or the making of determinate species, being in order to naming and comprehending them under general terms, I cannot see how it can be properly said, that Nature sets the boundaries of the species of things: or, if it be so, our boundaries of species are not exactly conformable to those in nature. ”

“ I have chosen to explain this uncertainty of propositions in this scholastic way, and have made use of the terms of essences, and species, on purpose to show the absurdity and inconvenience there is to think of them as of any other sort of realities, than barely abstract ideas with names to them. To suppose that the species of things are anything but the sorting of them under general names, according as they agree to several abstract ideas of which we make those names the signs, is to confound truth, and introduce uncertainty into all general propositions that can be made about them. ”

“ In the imaginary systems of celestial architecture which Aristotle and Ptolemy gave to mankind, there was a very narrow limit assigned to the extent of the heavens; the entire stellar host was supposed to be confined to a very scanty domain, and the human mind was prevented by these erroneous dogmas from rising to a knowledge of the magnitude or the riches of the universe. ”

“ Nor shou’d we despair of attaining this end, because of the many chimerical systems, which have successively arisen and decay’d away among men, wou’d we consider the shortness of that period, wherein these questions have been the subjects of enquiry and reasoning. Two thousand years with such long interruptions, and under such mighty discouragements are a small space of time to give any tolerable perfection to the sciences; and perhaps we are still in too early an age of the world to discover any principles, which will bear the examination of the latest posterity. ”

“ A gigantic mass of glowing gas that stretches across countless billions of miles of space, its mighty bulk flames in the heavens like a universe of fire. Beside its vast dimensions all the suns of the Galaxy are but as sparks beside a great, consuming blaze. Here and there in our Galaxy lie these mighty mysteries, these flaming nebulæ, and mightiest of all is that one which we call the Orion Nebula, that gigantic globe of flaming gas which measures light-years in diameter, burning in giant splendor at the Galaxy's heart. ”

“ Night is unknown in the regions illumined by their brilliant radiance. This stupendous aggregation of suns testifies to the magnificence of the starry heavens, and to the omnipotence of the Creator.
Galaxies.—These consist of vast aggregations of stars which form separate ‘island universes’ floating in the depths of space; they are believed to equal in magnitude and magnificence the Milky Way—the galaxy to which our system belongs. ”

“ Secondly, granting the universe to be finite, what is the arrangement of the stars in space? Especially, what is the relation of the galaxy to the other stars? In what sense, if any, can the stars be said to form a permanent system? Do the stars which form the Milky Way belong to a different system from the other stars, or are the latter a part of one universal system? ”

“ What it is, only God knows. In terms of matter I suppose the thing Ammi described would be called a gas, but this gas obeyed laws that are not of our cosmos. This was no fruit of such worlds and suns as shine on the telescopes and photographic plates of our observatories. This was no breath from the skies whose motions and dimensions our astronomers measure or deem too vast to measure. It was just a colour out of space—a frightful messenger from unformed realms of infinity beyond all Nature as we know it; ”

“ To base a classification of the human race on the character of the hair only, as Haeckel has done, was a hazardous venture, and could but end as all other artificial systems have ended."
If all artificial systems of classifying human races have ended in failure, shall we renounce all attempts at such classification, and affirm that there is no such science as ethnology? Or shall we endeavor to discover some natural method by which the numerous varieties that we all recognize in the populations of the globe can be clearly and positively distinguished and classified? ”

“ We need not wonder that gradations between species and varieties should occur, or that genera and other groups should not be absolutely limited, though they are represented to be so in our systems. The classifications of the naturalist define abruptly where nature more or less blends. Our systems are nothing if not definite. ”

“ The living sun is shut out finally. A false sun, like a lamp, shines.
All absolutes are prison-walls. These “laws” which science has invented, like conservation of{65} energy, indestructibility of matter, gravitation, the will-to-live, survival of the fittest: and even these absolute facts, like—the earth goes round the sun, or the doubtful atoms, electrons, or ether—they are all prison-walls, unless we realise that we don’t know what they mean. We don’t know what we mean, ultimately, by conservation, or indestructibility. Our atoms, electrons, ether, are caps that fit exceeding badly. ”

“ So, proceeding from the facts of experience and ideas of modern science, we inevitably come to the only integral, the only monistic understanding of the universe. It appears before us as an infinitely evolving fabric of forms of various types and levels of organisation, from elements of the ether unknown to us to human collectives and stellar systems. ”

“ One great idea pervades all the theories of the evolution of worlds, and that idea is firmly established. The stars and their planets are enormous aggregations of cosmic dust, swept together and compressed by the action of gravitation. The precise nature of this cosmic dust—whether it was gas, meteorites and gas, or other particles—is open to question.
As we saw in the first chapter, the universe has the word evolution written, literally, in letters of fire across it. The stars are of all ages, from sturdy youth to decrepit age, and even to the darkness of death. ”

“ Again, it has been said, that the discussions which are always arising between naturalists as to whether a species should be preserved or regarded as a race, as to the genus, family, order, and sometimes the class in which it should be placed, betray a want of precision in general ideas.—Those who talk in this manner forget the immense number of species and races accepted and classified without discussion. ”

“ We are also made aware of the difficulty of arriving at a true classification, even in a small and perfect group;—in the actual state of nature it is almost impossible, the species being so numerous and the modifications of form and structure so varied, arising probably from the immense number of species which have served as antitypes for the existing species, and thus produced a complicated branching of [8] the lines of affinity, as intricate as the twigs of a gnarled oak or the vascular system of the human body. ”

“ The difficulty is very strongly felt in the study of living human races; it is still greater in dealing with fossil races. Even if the materials were as [300] abundant as they are rare, we no longer have the perfect individual, and cannot attempt to apply the natural method; we are forced to be content with a systematic classification. This is what M. Hamy and I have been obliged to do; and without sharing the absolute opinions which were once advanced by Retzius, we took the general form of the skull as the starting point for our classification. ”

“ I shall, moreover, refuse to dispute with those who, rejecting on their own authority a whole century of work accomplished by the greatest naturalists, and by a number of men distinguished in botany and zoology, declare that it [82] is useless to try and discover what species and race are, and laugh at those who take the trouble to do so. I say the same to those who regard species and race as more or less arbitrary groups which may be compared to the genus, family and order. ”

“ Nevertheless, science may even now approach the general aspects of the problem. We are well acquainted with the circumstances under which varieties originate and races are formed among plants and animals: we have established in man the occurrence of a number of phenomena, which are in this respect identical, or very similar to those exhibited by the two inferior kingdoms. ”