Spectrum (science)

“ Those who are at all conversant with that wonderful branch of knowledge known as spectrum analysis are aware how these discoveries have rendered it possible for us to determine in many cases the actual material elements found in the most distant bodies. ”

“ A SCIENCE, like a child, grows quickest in the first few years of its existence; and it is therefore not astonishing that, though twenty years only have elapsed since Spectrum Analysis first entered the world, we are able to speak to-day of a modern spectroscopy, with higher and more ambitious aims, striving to obtain results which shall surpass in importance any of those achieved by the old spectroscopy, to the astonishment of the scientific world. ”

“ Indeed, had nineteenth-century science accomplished nothing else than the discovery of spectrum analysis, it would have marked the beginning of a new epoch. By this device man is put in communication with every considerable body in the universe, including even the invisible. ”

“ In the whole history of science there is nothing more wonderful than the discovery or invention (it would be difficult to say which is the more correct term) of spectrum analysis, and the sudden advance of the new method of research into a foremost position, among all the modes of scientific inquiry. ”

“ If we form a spectrum with the light emitted by an ordinary incandescent body, a gaslight for example, we shall find the series of colors to be unbroken from one end of the spectrum to the other. That is to say, there will be light in every part of the spectrum. Such a spectrum is said to be continuous. But if we form the spectrum by means of sunlight, we shall find the spectrum to be crossed by a great number of more or less dark lines. This shows that in the spectrum of the sun light of certain definite wave-lengths is wholly or partly wanting. ”

“ These observations and experiments doubled the field of investigation opened to spectrum analysis. Not only could the incandescent atmospheres of the sun and the stars now be made to reveal their nature and their composition to us, but our researches might also be extended to objects having a still greater interest for us. We could at once take our own atmosphere for an object, investigating high and inaccessible regions, and making analyses in them which could not be attempted by any other means. ”

“ A spectrum interrupted by bright lines is produced when the light emanates from flames or ignited vapors and gases. 3. A spectrum interrupted by dark lines is produced, when light emanating from a source giving a continuous spectrum, is passed through gaseous or vaporous matter giving spectra of the second order.
Now, it has been found that, when various elements are volatilized in the flame of a lamp, the light gives a spectrum interrupted by bright lines—whose character and position are different for different elements. ”

“ Have you ever reflected that we may possibly have some day an electrical spectrum—perhaps I should call it an attracting-force spectrum—in which the electro-magnetic manifestations of energy shall be spread out and differentiated, just as that part of the energy which we receive from the sun and which we call light and heat is now dispersed in the visible solar spectrum? We regard to-day the manifestations of the different colors of bodies—the tints of the objects in the room—as the visible expression of the great law of conservation of energy. ”

“ A still more wonderful result of spectrum analysis is our ability to measure the motion of a star through a slight shifting in the wave-lengths of the light which it emits. In this way we can measure, in the absence of all parallax, the direct approach or recession of a star ”

“ In the second place, one and the same element, contrary to common belief, frequently has two or three distinctly different spectra, the particular spectrum which appears depending upon the pressure and the temperature at which the element is while emitting the light. ”

“ Spectrum analysis is a rare and curious experiment, but the more familiar effects of light which we daily experience are really just as wonderful, if we will but pause to reflect upon them. Science means knowledge, and the science of optics embodies our knowledge of light ”

“ In all this work they have taken for granted that in the spectrum thus produced in their laboratories, they have been dealing with the vibration of one unique thing, call it atom, molecule, or what you will; that one unique thing has by its vibrations produced all the lines visible, which they have persistently seen and mapped in each instance. ”

“ The truth will probably be found to be, that the ordinary prismatic spectrum is a compound of two spectra:—that is, as we have the ordinary rainbow, and a supplementary bow, the colours of which are inverted, so the extraordinary may be somewhat masked by the intense light of the ordinary spectrum; and yet by overlapping produce the variations of colour in the rays. ”

“ Unfortunately, that is neither always possible nor always sufficient, and sometimes the mind must run ahead of experiment. I shall only give one example which has always struck me rather forcibly. If I decompose white light, I shall be able to isolate a portion of the spectrum, but however small it may be, it will always be a certain width. ”

“ If the stars were so physically constituted that the same chemical substances were present in both, but giving bright lines in one and dark lines in the other, the spectrum would present a series of bright lines, each accompanied by a dark one, on one side or the other, according as the body which contained dark lines in its spectrum was approaching the earth or receding from it. ”

“ The nascent science of spectrum analysis was materially promoted by Herschel. He noticed in 1819 the distinctive light-absorbing qualities of coloured media, studied the spectra of various flames, adverted to the definiteness and individuality of the bright lines composing them, and recommended their employment for purposes of chemical identification. ”

“ From another source, partly physical and partly chemical, the theory of the unity of matter has received strong support, and this statement brings us to another of the greatest discoveries made during the nineteenth century—that of the spectroscope and spectrum analysis. ”

“ This great idea of the specific character of luminous rays is due to Newton. It was introduced into science when that great genius gave his explanation of the action of the prism on white light. The foundations of spectrum analysis were laid at that time, and the study of it might have been begun then at once; but the human mind does not proceed with so penetrating and absolute a logic as that. ”

“ There was a long series of quiet preliminary inquiries that paved the way for the splendid demonstrations of spectrum analysis, but which were unappreciated and thrown into the shade after that brilliant discovery. A new epoch seemed to be suddenly created, and men cared little to know who had gone before and prepared for it. ”

“ A stellar spectrum with bright lines is always a highly interesting phenomenon for any one acquainted with stellar spectrum analysis, and well worthy of deep consideration. Although in the chromosphere (sierra) of our sun, near the limb, we see numerous bright lines, yet only dark lines appear in the spectrum whenever we produce a small star-like image of the sun, and examine it through the spectroscope. ”

“ In dwelling upon sound-phenomena, we have the advantage of dealing with phenomena about which Science says she does know something: from a consideration of these known facts we shall be able, slowly but surely, to grasp some of the much less familiar phenomena with which spectrum analysis is especially concerned. ”

“ Hence, when one of the stars, say A, is moving toward us, and the other, say D, from us, all the spectral lines will appear double, the lines made by A being displaced toward the blue end of the spectrum and those by B toward the red end. ”

“ THE SPECTRA OF THE STARS.
THE principles on which spectrum analysis rests can be stated so concisely that I shall set them forth for the special use of such readers as may not be entirely familiar with the subject. Every one knows that when the rays of the sun pass through a triangular prism of glass or other transparent substance they are unequally refracted, and thus separated into rays of different colors. ”

“ Such imaginary lines of demarcation between earth and heavens were forever swept away by Newton, and the recent work of spectrum analysis simply completes the demonstration that the remotest bodies which the photographic telescope can disclose are truly part and parcel of the dynamic world in which we live. ”

“ The great difficulty of interpreting the results of the spectroscopic analysis of the sun arises from the circumstance that we have no means of learning whence that part of the light comes which gives the continuous spectrum. When we recognize certain dark lines, we know certainly that the corresponding element exists in the gaseous form at a lower temperature than the substance which gives the continuous spectrum. ”

“ Alleged infallibility of spectrum analysis of suns and nebulæ, billions of miles distant, when, for terrestrial use, the Director of the United States Mint says, "it cannot be trusted," shows the present tendency to sacrifice logical mental conceptions to mere physical sense. ”

“ They have given a body of life to what was slumbering in posse; they have thus shown themselves worthy continuers of the work of Newton.
You know that this spectrum analysis made its appearance very suddenly in science. You may recollect the emotion that affected us all when it was announced that the solar atmosphere had been chemically analyzed, and a list of the metals it contained was published. You are, however, too well acquainted with the history of science to suppose that a method as complete as the one that was thus announced had no antecedents. ”

“ In the first place, if an object is shining by reflected light its spectrum is precisely similar to that of the object whose light illuminates it. Thus we cannot pronounce positively as to the nature of an object merely from the appearance of its spectrum, unless we are quite certain that the object is self-luminous. ”

“ Every one is acquainted with the spectrum which we see when a ray of sunlight coming through a narrow opening passes through a prism. With the aid of suitable instruments there can also be seen in this spectrum a considerable number of dark cross-lines; and science has shown that these lines are caused by the presence of certain simple bodies or elements, including iron, hydrogen, sodium, etc. When we examine the light of the stars through those instruments, we shall perceive that in their spectrums too the dark lines denoting these elements are present. ”

“ The new science also has the peculiar property that it recognizes mutual relations between objects apparently lying far from one another, connects with one another phenomena which appear to have no common measure, and draws fine lines of connection between earth and sky. One of these lines was drawn some thirty years ago in spectrum analysis; and by its aid man has risen in mind to remote worlds, and has sounded their physical and chemical constitution. ”

“ In the last ten years, by means of spectrum-analysis, science has made disclosures in the constitution of the most distant heavenly bodies, their component matter, their degree of heat, the speed and direction of their motions; it has firmly established the essential unity of all modes of force, and has made highly probable the unity of all matter; it is on the track of the formation and development of chemical elements, and it has learnt to understand the building up of extremely intricate organic combinations ”

“ A more delicate test would be to measure the intensity of different portions of the spectrum at a time when the light is changing most rapidly. The effect should be opposite according as the light is increasing or diminishing. ”

“ W the white light which is projected on the spectrum.
Taking all this into consideration, it is evident that when a particular color is presented to us we can affirm that it is perfectly pure, viz., entirely free from white light; or that it contains mingled with it a larger or smaller proportion of this foreign element. This furnishes us with our first clew toward a classification of colors: our pure standard colors are to be those found in the spectrum; the colored light coming from the surfaces of natural objects, or from painted surfaces, we must compare with the tints of the spectrum. ”

“ The spectra of this class show a singular mixture of bright lines and dark bands, as if three different spectra were combined, one continuous, one an absorption spectrum, and one an emission spectrum from glowing gas. Less than a hundred stars of this type have been discovered. ”

“ The glories of the sunrise and sunset, decking the fading stars of the morning and the waxing lights of the evening with the pure colors of the spectrum, elevate the heart of man to a loftier adoration for the marvels of nature, than any works of art prepared by his own hand. ”

“ Spectrum Analysis, name given to the method of determining the composition of a body by means of the spectrum of light which it gives forth or passes through it, founded on the principle that a substance powerfully absorbs exactly the rays it radiates, and every substance has its own absorbing powers ”

“ The spectrum was very brilliant, consisting of the three bright lines usually distinguished as Hα, Hβ, and Hγ, and a number of shaded bands and fainter lines between these, with a bright continuous spectrum as a background to the whole. ”

“ When they are in an extremely rarefied condition the spectrum of their light consists of a set of sharply-defined bright lines. As the substance approaches a denser condition the spectrum tends to become continuous, either by the lines becoming broader and less defined, or by new lines and bands appearing between them, till the spectrum at length loses all its characteristics and becomes identical with that of solid bodies when raised to the same temperature. ”