[Otto Struve] made the remark once that he never looked at the spectrum of a star, any star, where he didn’t find something important to work on.

[W]e pity our fathers for dying before steam and galvanism, sulphuric ether and ocean telegraphs, photograph and spectrograph arrived, as cheated out of their human estate.

After a duration of a thousand years, the power of astrology broke down when, with Copernicus, Kepler, and Galileo, the progress of astronomy overthrew the false hypothesis upon which the entire structure rested, namely the geocentric system of the universe. The fact that the earth revolves in space intervened to upset the complicated play of planetary influences, and the silent stars, related to the unfathomable depths of the sky, no longer made their prophetic voices audible to mankind. Celestial mechanics and spectrum analysis finally robbed them of their mysterious prestige.

After the discovery of spectral analysis no one trained in physics could doubt the problem of the atom would be solved when physicists had learned to understand the language of spectra. So manifold was the enormous amount of material that has been accumulated in sixty years of spectroscopic research that it seemed at first beyond the possibility of disentanglement. An almost greater enlightenment has resulted from the seven years of Röntgen spectroscopy, inasmuch as it has attacked the problem of the atom at its very root, and illuminates the interior. What we are nowadays hearing of the language of spectra is a true 'music of the spheres' in order and harmony that becomes ever more perfect in spite of the manifold variety. The theory of spectral lines will bear the name of Bohr for all time. But yet another name will be permanently associated with it, that of Planck. All integral laws of spectral lines and of atomic theory spring originally from the quantum theory. It is the mysterious organon on which Nature plays her music of the spectra, and according to the rhythm of which she regulates the structure of the atoms and nuclei.

As I strayed into the study of an eminent physicist, I observed hanging against the wall, framed like a choice engraving, several dingy, ribbon-like strips of, I knew not what... My curiosity was at once aroused. What were they? ... They might be shreds of mummy-wraps or bits of friable bark-cloth from the Pacific, ... [or] remnants from a grandmother’s wedding dress... They were none of these... He explained that they were carefully-prepared photographs of portions of the Solar Spectrum. I stood and mused, absorbed in the varying yet significant intensities of light and shade, bordered by mystic letters and symbolic numbers. As I mused, the pale legend began to glow with life. Every line became luminous with meaning. Every shadow was suffused with light shining from behind, suggesting some mighty achievement of knowledge; of knowledge growing more daring in proportion to the remoteness of the object known; of knowledge becoming more positive in its answers, as the questions which were asked seemed unanswerable. No Runic legend, no Babylonish arrowhead, no Egyptian hieroglyph, no Moabite stone, could present a history like this, or suggest thoughts of such weighty import or so stimulate and exalt the imagination.

At the moment I am occupied by an investigation with Kirchoff which does not allow us to sleep. Kirchoff has made a totally unexpected discovery, inasmuch as he has found out the cause for the dark lines in the solar spectrum and can produce these lines artificially intensified both in the solar spectrum and in the continuous spectrum of a flame, their position being identical with that of Fraunhofer’s lines. Hence the path is opened for the determination of the chemical composition of the Sun and the fixed stars.

At the moment I am occupied by an investigation with Kirchoff which does not allow us to sleep. Kirchoff has made a totally unexpected discovery, inasmuch as he has found out the cause for the dark lines in the solar spectrum and can produce these lines artificially intensified both in the solar spectrum and in the continuous spectrum of a flame, their position being identical with that of Fraunhofer’s lines. Hence the path is opened for the determination of the chemical composition of the Sun and the fixed stars.

Before an experiment can be performed, it must be planned—the question to nature must be formulated before being posed. Before the result of a measurement can be used, it must be interpreted—nature's answer must be understood properly. These two tasks are those of the theorist, who finds himself always more and more dependent on the tools of abstract mathematics. Of course, this does not mean that the experimenter does not also engage in theoretical deliberations. The foremost classical example of a major achievement produced by such a division of labor is the creation of spectrum analysis by the joint efforts of Robert Bunsen, the experimenter, and Gustav Kirchoff, the theorist. Since then, spectrum analysis has been continually developing and bearing ever richer fruit.

Biology as a discipline would benefit enormously if we could bring together the scientists working at the opposite ends of the biological spectrum. Students of organisms who know natural history have abundant questions to offer the students of molecules and cells. And molecular and cellular biologists with their armory of techniques and special insights have much to offer students of organisms and ecology.

But here I stop–short of any deterministic speculation that attributes specific behaviors to the possession of specific altruist or opportunist genes. Our genetic makeup permits a wide range of behaviors–from Ebenezer Scrooge before to Ebenezer Scrooge after. I do not believe that the miser hoards through opportunist genes or that the philanthropist gives because nature endowed him with more than the normal complement of altruist genes. Upbringing, culture, class, status, and all the intangibles that we call ‘free will,’ determine how we restrict our behaviors from the wide spectrum–extreme altruism to extreme selfishness–that our genes permit.

Equipped with our five senses, along with telescopes and microscopes and mass spectrometers and seismographs and magnetometers and particle accelerators and detectors across the electromagnetic spectrum, we explore the universe around us and call the adventure science.

From what has been said it is also evident, that the Whiteness of the Sun's Light is compounded all the Colours wherewith the several sorts of Rays whereof that Light consists, when by their several Refrangibilities they are separated from one another, do tinge Paper or any other white Body whereon they fall. For those Colours ... are unchangeable, and whenever all those Rays with those their Colours are mix'd again, they reproduce the same white Light as before.

I had observed that there were different lines exhibited in the spectra of different metals when ignited in the voltaic arc; and if I had had any reasonable amount of wit I ought to have seen the converse, viz., that by ignition different bodies show in their spectral lines the materials of which they are formed. If that thought had occured to my mind, I should have discovered the spectroscope before Kirchoff; but it didn’t.

I want to know how God created this world. I am not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; the rest are details.

If we seek for the simplest arrangement, which would enable it [the eye] to receive and discriminate the impressions of the different parts of the spectrum, we may suppose three distinct sensations only to be excited by the rays of the three principal pure colours, falling on any given point of the retina, the red, the green, and the violet; while the rays occupying the intermediate spaces are capable of producing mixed sensations, the yellow those which belong to the red and green, and the blue those which belong to the green and violet.

Immediately after totality, two splendid protuberances appeared; one of them, of more than 3 minute height, shone of a splendor which it is difficult to imagine. The analysis of its light showed me immediately that it was formed by an immense incandescent gas column, mainly made up of hydrogen gas.

In my view, the proper attitude of a public-service broadcaster is that it should attempt to cover as broad as possible a spectrum of human interest and should measure success by the width of those views. There shouldn’t be all that large a number of gaps in the spectrum; and a major element in the spectrum is scientific understanding. The fact that it doesn’t necessarily get as big an audience as cookery is of no consequence.

In the absorption spectrum of chlorophyll the maximum absorption coincides with the maximum energy of the solar spectrum, a remarkable adaptation, however produced, of means to ends.

In the last four days I have got the spectrum given by Tantalum. Chromium. Manganese. Iron. Nickel. Cobalt. and Copper and part of the Silver spectrum. The chief result is that all the elements give the same kind of spectrum, the result for any metal being quite easy to guess from the results for the others. This shews that the insides of all the atoms are very much alike, and from these results it will be possible to find out something of what the insides are made up of.

Newton was probably responsible for the concept that there are seven primary colours in the spectrum—he had a strong interest in musical harmonies and, since there are seven distinct notes in the musical scale, he divided up the spectrum into spectral bands with widths corresponding to the ratios of the small whole numbers found in the just scale.

Science is spectral analysis. Art is light synthesis.

Science is spectrum analysis: Art is photosynthesis.

The earth’s atmosphere is an imperfect window on the universe. Electromagnetic waves in the optical part of the spectrum (that is, waves longer than X rays and shorter than radio waves) penetrate to the surface of the earth only in a few narrow spectral bands. The widest of the transmitted bands corresponds roughly to the colors of visible light; waves in the flanking ultraviolet and infrared regions of the optical spectrum are almost totally absorbed by the atmosphere. In addition, atmospheric turbulence blurs the images of celestial objects, even when they are viewed through the most powerful ground-based telescopes.
in an article promoting the construction of the Hubble Space Telescope

The greatest of all spectral classifiers, Antonia Maury had two strikes on her: the biggest one was, she was a woman. A woman had no chance at anything in astronomy except at Harvard in the 1880’s and 1890’s. And even there, things were rough. It now turns out that her director, E.C. Pickering, did not like the way she classified; she then refused to change to suit him; and after her great publication in Harvard Annals 28 (1897), she left Harvard—and in a sense, astronomy. ... I would say the most remarkable phenomenological investigation in modern astronomy is Miss Maury’s work in Harvard Annals 28. She didn’t have anything astrophysical to go on. Investigations between 1890 and 1900 were the origin of astrophysics. But these were solar, mostly. And there Miss Maury was on the periphery. I’ve seen pictures of groups, where she’d be standing away a little bit to one side of the other people, a little bit in the background. It was a very sad thing. When Hertzsprung wrote Pickering to congratulate him on Miss Maury’s work that had led to Hertzsprung’s discovery of super giants, Pickering is supposed to have replied that Miss Maury’s work was wrong — could not possibly be correct.

The interactions of man with his environment are so complex that only an ecological approach to nutrition permits an understanding of the whole spectrum of factors determining the nutritional problems that exist in human societies.

The solution, as all thoughtful people recognize, must lie in properly melding the themes of inborn predisposition and shaping through life’s experiences. This fruitful joining cannot take the false form of percentages adding to 100–as in ‘intelligence is 80 percent nature and 20 percent nurture,’ or ‘homosexuality is 50 percent inborn and 50 percent learned,’ and a hundred other harmful statements in this foolish format. When two ends of such a spectrum are commingled, the result is not a separable amalgam (like shuffling two decks of cards with different backs), but an entirely new and higher entity that cannot be decomposed (just as adults cannot be separated into maternal and paternal contributions to their totality).

The star spectra present such varieties that it is difficult to point out any mode of classification. For the present, I divide them into three groups: first, those having many lines and bands and most nearly resembling the sun viz., Capella, β Geminorum, α Orionis, Aldeberan, γ Leonis, Arcturus, and β Pegasi. These are all reddish or golden stars. The second group, of which Sirius is the type, presents spectra wholly unlike that of the sun, and are white stars. The third group, comprising α Virginis, Rigel &c., are also white stars, but show no lines; perhaps they contain no mineral substance or are incandescent without flame.

The Sun is no lonelier than its neighbors; indeed, it is a very common-place star,—dwarfish, though not minute,—like hundreds, nay thousands, of others. By accident the brighter component of Alpha Centauri (which is double) is almost the Sun's twin in brightness, mass, and size. Could this Earth be transported to its vicinity by some supernatural power, and set revolving about it, at a little less than a hundred million miles' distance, the star would heat and light the world just as the Sun does, and life and civilization might go on with no radical change. The Milky Way would girdle the heavens as before; some of our familiar constellations, such as Orion, would be little changed, though others would be greatly altered by the shifting of the nearer stars. An unfamiliar brilliant star, between Cassiopeia and Perseus would be—the Sun. Looking back at it with our telescopes, we could photograph its spectrum, observe its motion among the stars, and convince ourselves that it was the same old Sun; but what had happened to the rest of our planetary system we would not know.

The unprecedented identification of the spectrum of an apparently stellar object in terms of a large red-shift suggests either of the two following explanations.
The stellar object is a star with a large gravitational red-shift. Its radius would then be of the order of 10km. Preliminary considerations show that it would be extremely difficult, if not impossible, to account for the occurrence of permitted lines and a forbidden line with the same red-shift, and with widths of only 1 or 2 per cent of the wavelength.
The stellar object is the nuclear region of a galaxy with a cosmological red-shift of 0.158, corresponding to an apparent velocity of 47,400 km/sec. The distance would be around 500 megaparsecs, and the diameter of the nuclear region would have to be less than 1 kiloparsec. This nuclear region would be about 100 times brighter optically than the luminous galaxies which have been identified with radio sources thus far. If the optical jet and component A of the radio source are associated with the galaxy, they would be at a distance of 50 kiloparsecs implying a time-scale in excess of 105 years. The total energy radiated in the optical range at constant luminosity would be of the order of 1059 ergs.
Only the detection of irrefutable proper motion or parallax would definitively establish 3C 273 as an object within our Galaxy. At the present time, however, the explanation in terms of an extragalactic origin seems more direct and less objectionable.

The whole subject of the X rays is opening out wonderfully, Bragg has of course got in ahead of us, and so the credit all belongs to him, but that does not make it less interesting. We find that an X ray bulb with a platinum target gives out a sharp line spectrum of five wavelengths which the crystal separates out as if it were a diffraction grating. In this way one can get pure monochromatic X rays. Tomorrow we search for the spectra of other elements. There is here a whole new branch of spectroscopy, which is sure to tell one much about the nature of an atom.

To try to make a model of an atom by studying its spectrum is like trying to make a model of a grand piano by listening to the noise it makes when thrown downstairs.

We believe that each molecular vibration disturbs the ether; that spectra are thus begotten, each wavelength of light resulting from a molecular tremor of corresponding wavelength. The molecule is, in fact, the sender, the ether the wire, and the eye the receiving instrument, in this new telegraphy.

What beauty. I saw clouds and their light shadows on the distant dear earth…. The water looked like darkish, slightly gleaming spots…. When I watched the horizon, I saw the abrupt, contrasting transition from the earth’s light-colored surface to the absolutely black sky. I enjoyed the rich color spectrum of the earth. It is surrounded by a light blue aureole that gradually darkens, becomes turquoise, dark blue, violet, and finally coal black.

When it is considered that this light, when obtained with mercury gas, has an efficiency at least eight times as great as that obtained by an ordinary incandescent lamp, it will be appreciated that it has its use in places where lack of red is not important, for the economy of operation will much more than compensate for the somewhat unnatural color given to illuminated objects.

With crystals we are in a situation similar to an attempt to investigate an optical grating merely from the spectra it produces... But a knowledge of the positions and intensities of the spectra does not suffice for the determination of the structure. The phases with which the diffracted waves vibrate relative to one another enter in an essential way. To determine a crystal structure on the atomic scale, one must know the phase differences between the different interference spots on the photographic plate, and this task may certainly prove to be rather difficult.