WHAT THE WORLDS ARE MADE OF.
The present century was already well advanced before there was any solid ground for the belief that the worlds of space are made of analogous or identical materials. It was only with the invention of the spectroscope and the analysis of light that the material identity of universal nature was proved by methods which could not be doubted. The proof came by the spectroscope.
This little instrument, though not famed as is its lordly kinsman the telescope, or even regarded with the popular favor of the microscope, has nevertheless carried us as far, and, we were about to say, taught us as much, as either of the others. It is one thing to see the worlds afar, to note them visibly, to describe their outlines, to measure their mass and determine their motions. It is another thing to know their constitution, the substances of which they are composed, the material condition in which they exist and the state of their progress in worldhood. The latter work is the task of the spectroscope; and right well has it accomplished its mission.
The solar spectrum has been known from the earliest ages. When the sun-bow was set on the background of cloud over the diluvial floods, the living beings of that age saw a spectrum—the glorious spectrum of rain and shine. Wherever the rays of light have been diffracted under given conditions by the agency of water drops, prism of glass or other such transparent medium, and the ray has fallen on a suitable screen, lo! there has been the beautiful spectrum of light.
The artificial, intentional production of this phenomenon of light has long been known, and both novice and scientist have tested and improved the methods of getting given results. The child's soap-bubble shows it in miniature splendor. The pressure of one wet pane of glass against another reveals it. The breakage of nearly all crystalline substances brings something of the colored effects of light; but the triangular prism of glass, suitably prepared, best of all displays the analysis of the sun-beam into the colors of which it is composed.
The spectroscope is the improved instrument by which the diffracting prism is best employed in producing the spectrum. The reader no doubt has seen a spectroscope, and has observed its beautiful work. In this place we pass, however, from the instrument of production to the spectrum, or analyzed result, as the same is shown on a screen. There the pencil of white light falling from the sun is spread out in the manner of a fan, presenting on the screen the following arrangement of colors: red, orange, yellow, green, blue, indigo and violet.
This order of colors, beginning with red, starts from that side of the spectrum which is least bent from the right line in which the white ray was traveling. The violet rays are most bent. The red rays are thus said to be at the lower edge of the prism, and the violet rays at the upper edge. Below the red rays there are now known to be certain invisible rays, as of heat and electricity. Above the violet rays are other invisible rays, such as the actinic influence. In fact, the spectrum, beginning invisibly, passes by way of the visible rays to the invisible again. Nor can any scientist in the world say at the present time how much is really included in the spread-out fan of analyzed sunlight.
Thus much scientists have known for some time. Certain other facts, however, in connection with the solar spectrum are of greater importance than are its more sensible phenomena. It was in the year 1802 that the English physicist, William Hyde Wollaston, discovered that the solar spectrum is crossed with a large number of dark lines. He it was who first mapped these lines and showed their relative position. He it was also who discovered the existence of invisible rays above the violet. Twelve years afterward Joseph von Fraunhofer, of Munich, a German optician of remarkable talents, took up the examination of the Wollaston lines, and by his success in the investigation succeeded in attracting the attention of the world.
This second stage in scientific discovery is generally that which receives the plaudits of mankind. It was so in the case of Fraunhofer. His name was given to the dark lines in the solar spectrum, and the nomenclature is retained to the present time. They are called the "Fraunhofer lines." It was soon discovered that the lines in question as produced in the spectrum are due to the presence of gases in the producing flame or source of light. It was also discovered that each substance in, the process of combustion yields its own line or set of lines. These appear at regular intervals in the spectrum. When several substances are consumed at the same time; the lines of each appear in the spectrum. The result is a system of lines, becoming more and more complex as the number of elements in the consuming materials is increased.
The lines in a narrow spectrum fall so closely together that they cannot be critically examined; but when more than one prism is used and the spectrum by this means spread out widely, the dark lines are made to stand apart. They are then found to number many thousands. We speak now of the analysis of sunlight. Experimentation was naturally turned, however, to terrestrial gases and solids on fire, and it was found that these also produce like series of dark lines in the spectrum. Or when the substances are consumed as solids, then the spectral effects are reversed, and the lines that would be dark lines in the luminous colored spectrum become themselves luminous lines on the screen; but these lines hold the same relation in mathematical measurement, etc., as do the dark lines in the colored spectrum.
Skillful spectroscopists succeeded in detecting and delineating the lines that were peculiar to each substance. By burning such substances in flame, they were able to produce the lines, and thus verify results. By such experimentation the various lines present in the solar spectrum were separated from the complex result, and the conclusion was reached that in the burning surface of the sun certain substances well known on earth are present; for the lines of those substances are shown in the spectrum.
No other known substances would produce the given lines. The conclusion is overwhelming that the substances in question are present in a gaseous condition in the burning flames of the sun. Down to the present time the examination of the sun's atmosphere has shown the existence therein of thirty-six known elements. These include sodium, potassium, calcium, magnesium, iron, copper, cobalt, silver, lead, tin, zinc, titanium, aluminium, chromium, silicon, carbon, hydrogen and several others.
It was thus established that in the constitution of the sun many of the well-known elements of the earth are present. There could be no mistake about it. An identity of lines in such a case proved beyond dispute the identity of the substance from which such lines are derived. The existence of common materials in the central sphere of our system and in one of his attendant orbs—our own—could not be doubted. The discovery of such a fact led by immediate inference to the expectation and belief that the other planets were of like constitution, or in a word, that the whole solar system was essentially composed of identical materials.
As the inquiry proceeded, it was found, however, that the agreement in the lines of different spectra was not perfect. Lines would be found in the spectrum derived from one source that were not present in a spectrum derived from another source. Materials were therefore suggested as present in one body that were not present in another. Still further inquiry confirmed the belief that while there is a general uniformity in the materials of our solar system, the identity is not complete in all. An element is found in one part that may not be found in another. Hydrogen shows its line in the spectrum derived from every heavenly body that has been investigated; but not so aluminium or cobalt. Sodium, that is, the salt-producing base, is discovered everywhere, but not nickel or arsenium. The result, in a word, shows a certain variability in the distribution of solar and planetary matter, but a general identity of most.
The question next presented itself as to the character of the luminous bodies beyond the solar system. Of what kind of matter are the comets? Of what kind are the fixed stars? Of what kind are the nebulæ? Could the spectroscope be used in determining also the character of the materials in those orbs that we see shining in the depths of space? The instrument was turned in answer to these questions to the sidereal heavens. No other branch of science has been prosecuted in the after half of this century with more zeal and success than has the spectroscopic analysis of the fixed stars. These are known by the telescope to have the character of suns. The most general fact of the visible heavens is the plentiful distribution of suns. They sparkle everywhere as the so-called fixed stars. To them the telescope has been virtually turned in vain. We say in vain because no single fixed star has, we believe, ever been made by aid of the telescope to show a disc.
On turning the telescope to a fixed star, its brightness, its brilliancy, increases according to the power of the instrument. Coming into the field of one of these great suns of space, the telescope shows a miraculous dawn spreading and blazing into a glorious sunrise, and a sun itself flaming like infinite majesty on the sight; but there is no disc—nothing but a blaze of glory. Thus in a sense the telescope has worked in vain on the visible heavens. But not so the spectroscope. The latter has done its glorious work. Turning to a given fixed star, it shows that the tremendous combustion going on therein is virtually the same as that in our own sun. There, too, is flaming hydrogen, and there is carbon and oxygen and iron and sodium and potassium and many other of the leading elements of what we thus know to be universal nature. The suns are all akin; they are cousins-german. They are of the same family—they and their progeny. They were born of the same universal fact. They are of the same Father! They are builded on the same plan, and they have a common destiny. Aye, more, the nebulæ that float far off, swanlike, in the infinitudes, are of the same family. The nebulæ may be regarded as the mothers of universes. It is out of their bosoms that the life and substance of all suns and worlds are drawn! And these, too, are composed of the common matter of universal nature. It is the same matter that we eat and drink. It is the same that we breathe. It is the same that we see aflame in our lamps and grates. It is the same that is borne to us in the fragrance of flowers planted on the graves of our dead. It is the common hydrogen and carbon and oxygen and nitrogen of our earth and its envelope. It is the soda of our bread; the potassa of our ashes; the phosphorus of our bones and brain! Indeed, the universe throughout is of one form and one substance, and there is one Father over all. Sooner or later the concepts of science and of religion will come together; and the small agitations and conflicts of human thought and hope will pass away in a sublime unity of human faith.