’Tis a short sight to limit our faith in laws to those of gravity, of chemistry, of botany, and so forth. Those laws do not stop where our eyes lose them, but push the same geometry and chemistry up into the invisible plane of social and rational life, so that, look where we will, in a boy's game, or in the strifes of races, a perfect reaction, a perpetual judgment keeps watch and ward.

[About his invention of an invisible paint, Pop Porter (Victor Moore):] You paint something with it and you can't see it. I'm worried about it though ... I painted the can with it and now I can't find it.

Mahomet’s tombe at Mecha is said strangely to hang up, attracted by some invisible Loadstone, but the Memory of this Doctor will never fall to the ground, which his incomparable Book ‘De Magnete’ will support to Eternity.

A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux ... is that the vast majority of the mass of the universe seems to be missing.
[Reporting a Nature article discrediting explanation of invisible mass being due to neutrinos]

A modern mathematical proof is not very different from a modern machine, or a modern test setup: the simple fundamental principles are hidden and almost invisible under a mass of technical details.

All cell biologists are condemned to suffer an incurable secret sorrow: the size of the objects of their passion. … But those of us enamored of the cell must resign ourselves to the perverse, lonely fascination of a human being for things invisible to the naked human eye.

All human affairs follow nature's great analogue, the growth of vegetation. There are three periods of growth in every plant. The first, and slowest, is the invisible growth by the root; the second and much accelerated is the visible growth by the stem; but when root and stem have gathered their forces, there comes the third period, in which the plant quickly flashes into blossom and rushes into fruit.
The beginnings of moral enterprises in this world are never to be measured by any apparent growth. ... At length comes the sudden ripeness and the full success, and he who is called in at the final moment deems this success his own. He is but the reaper and not the labourer. Other men sowed and tilled and he but enters into their labours.

All Nature is linked together by invisible bonds and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life.

Although I am a typical loner in daily life, my consciousness of belonging to the invisible community of those who strive for truth, beaut y, and justice has preserved me from feeling isolated.

An Englishman, unless asleep, feels an invisible compulsion to be doing something, to consider time as of some importance. With us, according to custom and tradition, the charm of life consists in ease—ease from the absence of compulsion to do anything.

Anaximenes ... said that infinite air was the principle, from which the things that are becoming, and that are, and that shall be, and gods and things divine, all come into being, and the rest from its products. The form of air is of this kind: whenever it is most equable it is invisible to sight, but is revealed by the cold and the hot and the damp and by movement. It is always in motion; for things that change do not change unless there be movement. Through becoming denser or finer it has different appearances; for when it is dissolved into what is finer it becomes fire, while winds, again, are air that is becoming condensed, and cloud is produced from air by felting. When it is condensed still more, water is produced; with a further degree of condensation earth is produced, and when condensed as far as possible, stones. The result is that the most influential components of the generation are opposites, hot and cold.

And when with excellent Microscopes I discern in otherwise invisible Objects the Inimitable Subtlety of Nature’s Curious Workmanship; And when, in a word, by the help of Anatomicall Knives, and the light of Chymicall Furnaces, I study the Book of Nature, and consult the Glosses of Aristotle, Epicurus, Paracelsus, Harvey, Helmont, and other learn'd Expositors of that instructive Volumne; I find my self oftentimes reduc’d to exclaim with the Psalmist, How manifold are thy works, O Lord? In wisdom hast thou made them all.

As to the position of the earth, then, this is the view which some advance, and the views advanced concerning its rest or motion are similar. For here too there is no general agreement. All who deny that the earth lies at the centre think that it revolves about the centre, and not the earth only but, as we said before, the counter-earth as well. Some of them even consider it possible that there are several bodies so moving, which are invisible to us owing to the interposition of the earth. This, they say, accounts for the fact that eclipses of the moon are more frequent than eclipses of the sun; for in addition to the earth each of these moving bodies can obstruct it.

Ask a follower of Bacon what [science] the new philosophy, as it was called in the time of Charles the Second, has effected for mankind, and his answer is ready; “It has lengthened life; it has mitigated pain; it has extinguished diseases; it has increased the fertility of the soil; it has given new securities to the mariner; it has furnished new arms to the warrior; it has spanned great rivers and estuaries with bridges of form unknown to our fathers; it has guided the thunderbolt innocuously from heaven to earth; it has lighted up the night with the splendour of the day; it has extended the range of the human vision; it has multiplied the power of the human muscles; it has accelerated motion; it has annihilated distance; it has facilitated intercourse, correspondence, all friendly offices, all dispatch of business; it has enabled man to descend to the depths of the sea, to soar into the air, to penetrate securely into the noxious recesses of the earth, to traverse the land in cars which whirl along without horses, to cross the ocean in ships which run ten knots an hour against the wind. These are but a part of its fruits, and of its first-fruits; for it is a philosophy which never rests, which has never attained, which is never perfect. Its law is progress. A point which yesterday was invisible is its goal to-day, and will be its starting-point to-morrow.”

But by far the greatest hindrance and aberration of the human understanding proceeds from the dullness, incompetency, and deceptions of the senses; in that things which strike the sense outweigh things which do not immediately strike it, though they be more important. Hence it is that speculation commonly ceases where sight ceases; insomuch that of things invisible there is little or no observation.

Deep beneath the surface of the Sun, enormous forces were gathering. At any moment, the energies of a million hydrogen bombs might burst forth in the awesome explosion…. Climbing at millions of miles per hour, an invisible fireball many times the size of Earth would leap from the Sun and head out across space.

Everything is becoming science fiction; From the margins of an almost invisible literature has sprung the intact reality of the 20th century

Everything is determined … by forces over which we have no control. It is determined for the insect as well as the star. Human beings, vegetables, or cosmic dust—we all dance to a mysterious tune, intoned in the distance by an invisible piper.

Fear of things invisible is the natural seed of that which every one in himself calleth religion.

I was working with a Crookes tube covered by a shield of black cardboard. A piece of barium platino-cyanide paper lay on the bench there. I had been passing a current through the tube, and I noticed a peculiar black line across the paper. …
The effect was one which could only be produced in ordinary parlance by the passage of light. No light could come from the tube because the shield which covered it was impervious to any light known even that of the electric arc. …
I did not think; I investigated. …
I assumed that the effect must have come from the tube since its character indicated that it could come from nowhere else. … It seemed at first a new kind of invisible light. It was clearly something new something unrecorded. …
There is much to do, and I am busy, very busy. [Describing to a journalist the discovery of X-rays that he had made on 8 Nov 1895.]

I will insist particularly upon the following fact, which seems to me quite important and beyond the phenomena which one could expect to observe: The same [double sulfate of uranium and potassium] crystalline crusts, arranged the same way [as reported to the French academy on 24 Feb 1896] with respect to the photographic plates, in the same conditions and through the same screens, but sheltered from the excitation of incident rays and kept in darkness, still produce the same photographic images … [when kept from 26 Feb 1896] in the darkness of a bureau drawer. … I developed the photographic plates on the 1st of March, expecting to find the images very weak. Instead the silhouettes appeared with great intensity.
It is important to observe that it appears this phenomenon must not be attributed to the luminous radiation emitted by phosphorescence … One hypothesis which presents itself to the mind naturally enough would be to suppose that these rays, whose effects have a great similarity to the effects produced by the rays studied by M. Lenard and M. Röntgen, are invisible rays …
[Having eliminated phosphorescence as a cause, he has further revealed the effect of the as yet unknown radioactivity.]

If we take a survey of our own world … our portion in the immense system of creation, we find every part of it, the earth, the waters, and the air that surround it, filled, and as it were crouded with life, down from the largest animals that we know of to the smallest insects the naked eye can behold, and from thence to others still smaller, and totally invisible without the assistance of the microscope. Every tree, every plant, every leaf, serves not only as an habitation, but as a world to some numerous race, till animal existence becomes so exceedingly refined, that the effluvia of a blade of grass would be food for thousands.

In Cairo, I secured a few grains of wheat that had slumbered for more than thirty centuries in an Egyptian tomb. As I looked at them this thought came into my mind: If one of those grains had been planted on the banks of the Nile the year after it grew, and all its lineal descendants had been planted and replanted from that time until now, its progeny would to-day be sufficiently numerous to feed the teeming millions of the world. An unbroken chain of life connects the earliest grains of wheat with the grains that we sow and reap. There is in the grain of wheat an invisible something which has power to discard the body that we see, and from earth and air fashion a new body so much like the old one that we cannot tell the one from the other.…This invisible germ of life can thus pass through three thousand resurrections.

In matters eternal it is Belief that makes all works visible, in matters corporeal it is the light of Nature that reveals things invisible.

In my youth I regarded the universe as an open book, printed in the language of physical equations, whereas now it appears to me as a text written in invisible ink, of which in our rare moments of grace we are able to decipher a small fragment.

In space there are countless constellations, suns and planets; we see only the suns because they give light; the planets remain invisible, for they are small and dark. There are also numberless earths circling around their suns, no worse and no less than this globe of ours. For no reasonable mind can assume that heavenly bodies that may be far more magnificent than ours would not bear upon them creatures similar or even superior to those upon our human earth.

In the streets of a modern city the night sky is invisible; in rural districts, we move in cars with bright headlights. We have blotted out the heavens, and only a few scientists remain aware of stars and planets, meteorites and comets.

Intelligence, in diapers, is invisible. And when it matures, out the window it flies. We have to pounce on it earlier.

It is only with the heart that one can see rightly—what is essential is invisible to the eye.

It is the destiny of the sciences, which must necessarily be in the hands of a few, that the utility of their progress should be invisible to the greater part of mankind, especially if those sciences are associated with unobtrusive pursuits. Let a greater facility in using our navigable waters and opening new lines of communication but once exist, simply because at present we know vastly better how to level the ground and construct locks and flood-gates—what does it amount to? The workmen have had their labors lightened, but they themselves have not the least idea of the skill of the geometer who directed them; they have been put in motion nearly as the body is by a soul of which it knows nothing; the rest of the world has even less perception of the genius which presided over the enterprise, and enjoys the success it has attained only with a species of ingratitude.

Jupiter is the largest of all the solar system’s planets, more than ten times bigger and three hundred times as massive as Earth. Jupiter is so immense it could swallow all the other planets easily. Its Great Red Spot, a storm that has raged for centuries, is itself wider than Earth. And the Spot is merely one feature visible among the innumerable vortexes and streams of Jupiter’s frenetically racing cloud tops. Yet Jupiter is composed mainly of the lightest elements, hydrogen and helium, more like a star than a planet. All that size and mass, yet Jupiter spins on its axis in less than ten hours, so fast that the planet is clearly not spherical: Its poles are noticeably flattened. Jupiter looks like a big, colorfully striped beach ball that’s squashed down as if some invisible child were sitting on it. Spinning that fast, Jupiter’s deep, deep atmosphere is swirled into bands and ribbons of multihued clouds: pale yellow, saffron orange, white, tawny yellow-brown, dark brown, bluish, pink and red. Titanic winds push the clouds across the face of Jupiter at hundreds of kilometers per hour.

M. Waldman … concluded with a panegyric upon modern chemistry…:— “The ancient teachers of this science” said he, “Promised impossibilities and performed nothing. The modern masters promise very little; they know that metals cannot be transmuted and that the elixir of life is a chimera. But these philosophers seem only made to dabble in dirt, and their eyes to pore over the microscope or crucible, have indeed performed miracles. They penetrate into the recesses of nature and show how she works in her hiding-places. They ascend into the heavens; they have discovered how the blood circulates, and the nature of the air we breathe. They can command the thunders of heaven, mimic the earthquake, and even mock the invisible world with its own shadows.”

Nature, … in order to carry out the marvelous operations [that occur] in animals and plants has been pleased to construct their organized bodies with a very large number of machines, which are of necessity made up of extremely minute parts so shaped and situated as to form a marvelous organ, the structure and composition of which are usually invisible to the naked eye without the aid of a microscope. … Just as Nature deserves praise and admiration for making machines so small, so too the physician who observes them to the best of his ability is worthy of praise, not blame, for he must also correct and repair these machines as well as he can every time they get out of order.

Ninety-nine and nine-tenths of the earth’s volume must forever remain invisible and untouchable. Because more than 97 per cent of it is too hot to crystallize, its body is extremely weak. The crust, being so thin, must bend, if, over wide areas, it becomes loaded with glacial ice, ocean water or deposits of sand and mud. It must bend in the opposite sense if widely extended loads of such material be removed. This accounts for … the origin of chains of high mountains … and the rise of lava to the earth’s surface.

On opening the incubator I experienced one of those rare moments of intense emotion which reward the research worker for all his pains: at first glance I saw that the broth culture, which the night before had been very turbid was perfectly clear: all the bacteria had vanished…as for my agar spread it was devoid of all growth and what caused my emotion was that in a flash I understood: what causes my spots was in fact an invisible microbe, a filterable virus, but a virus parasitic on bacteria. Another thought came to me also, If this is true, the same thing will have probably occurred in the sick man. In his intestine, as in my test-tube, the dysentery bacilli will have dissolved away under the action of their parasite. He should now be cured.

Our earth is very old, an old warrior that has lived through many battles. Nevertheless, the face of it is still changing, and science sees no certain limit of time for its stately evolution. Our solid earth, apparently so stable, inert, and finished, is changing, mobile, and still evolving. Its major quakings are largely the echoes of that divine far-off event, the building of our noble mountains. The lava floods and intriguing volcanoes tell us of the plasticity, mobility, of the deep interior of the globe. The slow coming and going of ancient shallow seas on the continental plateaus tell us of the rhythmic distortion of the deep interior-deep-seated flow and changes of volume. Mountain chains prove the earth’s solid crust itself to be mobile in high degree. And the secret of it all—the secret of the earthquake, the secret of the “temple of fire,” the secret of the ocean basin, the secret of the highland—is in the heart of the earth, forever invisible to human eyes.

Phenomena unfold on their own appropriate scales of space and time and may be invisible in our myopic world of dimensions assessed by comparison with human height and times metered by human lifespans. So much of accumulating importance at earthly scales ... is invisible by the measuring rod of a human life. So much that matters to particles in the microscopic world of molecules ... either averages out to stability at our scale or simply stands below our limits of perception.

Placed in a universe of constant change, on an isolated globe surrounded by distant celestial objects on all sides, subjected to influences of various kinds, it is a sublime occupation to measure the earth and weigh the planets, to predict their changes, and even to discover the materials of which they are composed; to investigate the causes of the tempest and volcano; to bring the lightning from the clouds; to submit it to experiment by which it shall reveal its character; and to estimate the size and weight of those invisible atoms which constitute the universe of things.

Science is not the enemy of humanity but one of the deepest expressions of the human desire to realize that vision of infinite knowledge. Science shows us that the visible world is neither matter nor spirit; the visible world is the invisible organization of energy.

So, then, the Tincture of the Philosophers is a universal medicine, and consumes all diseases, by whatsoever name they are called, just like an invisible fire. The dose is very small, but its effect is most powerful. By means thereof I have cured the leprosy, venereal disease, dropsy, the falling sickness, colic, scab, and similar afflictions; also lupus, cancer, noli-metangere, fistulas, and the whole race of internal diseases, more surely than one could believe.

Some people believe in fate, others don’t. I do, and I don't. It may seem at times as if invisible fingers move us about like puppets on strings. But for sure, we are not born to be dragged along. We can grab the strings ourselves and adjust our course at every crossroad, or take off at any little trail into the unknown.

The fertilized germ of one of the higher animals … is perhaps the most wonderful object in nature… . On the doctrine of reversion [atavism] … the germ becomes a far more marvelous object, for, besides the visible changes which it undergoes, we must believe that it is crowded with invisible characters … separated by hundreds or even thousands of generations from the present time: and these characters, like those written on paper with invisible ink, lie ready to be evolved whenever the organization is disturbed by certain known or unknown conditions.

The great upheavals which precede changes of civilisation, such as the fall of the Roman Empire and the founding of the Arabian Empire, for example, seem to have been determined mainly by considerable political transformations, invasions, or the overthrow of dynasties. But … most often, the real cause is … a profound modification in the ideas of the peoples. … The memorable events of history are the visible effects of the invisible changes of human thought. … The present epoch is one of these critical moments in which the thought of mankind is undergoing a process of transformation.

The growing complexity of civilized life demands with each age broader and more exact knowledge as to the material surroundings and greater precision in our recognition of the invisible forces or tendencies about us.

The man who proportions the several parts of a mill, uses the same scientific principles [mechanics], as if he had the power of constructing an universe; but as he cannot give to matter that invisible agency, by which all the component parts of the immense machine of the universe have influence upon each other, and set in motional unison together without any apparent contact, and to which man has given the name of attraction, gravitation, and repulsion, he supplies the place of that agency by the humble imitation of teeth and cogs. All the parts of man’s microcosm must visibly touch.

The moment of truth, the sudden emergence of new insight, is an act of intuition. Such intuitions give the appearance of miraculous flashes, or short circuits of reasoning. In fact they may be likened to an immersed chain, of which only the beginning and the end are visible above the surface of consciousness. The diver vanishes at one end of the chain and comes up at the other end, guided by invisible links.

The rigid career path of a professor at a modern university is that One Must Build the Big Research Group, recruit doctoral students more vigorously than the head football coach, bombard the federal agencies with grant applications more numerous than the pollen falling from the heavens in spring, and leave the paper writing and the research to the postdocs, research associates, and students who do all the bench work and all the computer programming. A professor is chained to his previous topics by his Big Group, his network of contacts built up laboriously over decades, and the impossibility of large funding except in areas where the grantee has grown the group from a corner of the building to an entire floor. The senior tenure-track faculty at a research university–the “silverbacks” in anthropological jargon–are bound by invisible chains stronger than the strongest steel to a narrow range of what the Prevailing Consensus agrees are Very Important Problems. The aspiring scientist is confronted with the reality that his mentors are all business managers.

The thinker makes a great mistake when he asks after cause and effect. They both together make up the invisible phenomenon.

The traditional boundaries between various fields of science are rapidly disappearing and what is more important science does not know any national borders. The scientists of the world are forming an invisible network with a very free flow of scientific information - a freedom accepted by the countries of the world irrespective of political systems or religions. ... Great care must be taken that the scientific network is utilized only for scientific purposes - if it gets involved in political questions it loses its special status and utility as a nonpolitical force for development.

These neutrino observations are so exciting and significant that I think we're about to see the birth of an entirely new branch of astronomy: neutrino astronomy. Supernova explosions that are invisible to us because of dust clouds may occur in our galaxy as often as once every 10 years, and neutrino bursts could give us a way to study them.

They had neither compass, nor astronomical instruments, nor any of the appliances of our time for finding their position at sea; they could only sail by the sun, moon, and stars, and it seems incomprehensible how for days and weeks, when these were invisible, they were able to find their course through fog and bad weather; but they found it, and in the open craft of the Norwegian Vikings, with their square sails, fared north and west over the whole ocean, from Novaya Zemlya and Spitsbergen to Greenland, Baffin Bay, Newfoundland, and North America.

This is the right cavity of the two cavities of the heart. When the blood in this cavity has become thin, it must be transferred into the left cavity, where the pneuma is generated. But there is no passage between these two cavities, the substance of the heart there being impermeable. It neither contains a visible passage, as some people have thought, nor does it contain an invisible passage which would permit the passage of blood, as Galen thought. The pores of the heart there are compact and the substance of the heart is thick. It must, therefore, be that when the blood has become thin, it is passed into the arterial vein [pulmonary artery] to the lung, in order to be dispersed inside the substance of the lung, and to mix with the air. The finest parts of the blood are then strained, passing into the venous artery [pulmonary vein] reaching the left of the two cavities of the heart, after mixing with the air and becoming fit for the generation of pneuma.

This success permits us to hope that after thirty or forty years of observation on the new Planet [Neptune], we may employ it, in its turn, for the discovery of the one following it in its order of distances from the Sun. Thus, at least, we should unhappily soon fall among bodies invisible by reason of their immense distance, but whose orbits might yet be traced in a succession of ages, with the greatest exactness, by the theory of Secular Inequalities.
[Following the success of the confirmation of the existence of the planet Neptune, he considered the possibility of the discovery of a yet further planet.]

This theme of mutually invisible life at widely differing scales bears an important implication for the ‘culture wars’ that supposedly now envelop our universities and our intellectual discourse in general ... One side of this false dichotomy features the postmodern relativists who argue that all culturally bound modes of perception must be equally valid, and that no factual truth therefore exists. The other side includes the benighted, old-fashioned realists who insist that flies truly have two wings, and that Shakespeare really did mean what he thought he was saying. The principle of scaling provides a resolution for the false parts of this silly dichotomy. Facts are facts and cannot be denied by any rational being. (Often, facts are also not at all easy to determine or specify–but this question raises different issues for another time.) Facts, however, may also be highly scale dependent–and the perceptions of one world may have no validity or expression in the domain of another. The one-page map of Maine cannot recognize the separate boulders of Acadia, but both provide equally valid representations of a factual coastline.

This therefore is Mathematics:
She reminds you of the invisible forms of the soul;
She gives life to her own discoveries;
She awakens the mind and purifies the intellect;
She brings light to our intrinsic ideas;
She abolishes oblivion and ignorance which are ours by birth...

To every Form of being is assigned’
Thus calmly spoke the venerable Sage,
An active Principle:—howe’er remove!
From sense and observation, it subsists.
In all things, in all natures; in the stars
Of azure heaven, the unenduring clouds,
In flower and tree, in every pebbly stone
That paves the brooks, the stationary rocks,
The moving waters, and the invisible air.’

To most of us nothing is so invisible as an unpleasant truth. Though it is held before our eyes, pushed under our noses, rammed down our throats- we know it not.

To trace in Nature's most minute design
The signature and stamp of power divine.
...
The Invisible in things scarce seen revealed,
To whom an atom is an ample field.

We do whatever we can to deny intuition of the invisible realms. We clog up our senses with smog, jam our minds with media overload. We drown ourselves in alcohol or medicate ourselves into rigidly artificial states... we take pride in our cynicism and detachment. Perhaps we are terrified to discover that our “rationality” is itself a kind of faith, an artifice, that beneath it lies the vast territory of the unknown.

We have been scourged by invisible thongs, attacked from impenetrable ambuscades, and it is only to-day that the light of science is being let in upon the murderous dominion of our foes.

We live in a glass-soaked civilization, but as for the bird in the Chinese proverb who finds it so difficult to discover air, the substance is almost invisible to us. To use a metaphor drawn from glass, it may be revealing for us to re-focus, to stop looking through glass, and let our eyes dwell on it for a moment to contemplate its wonder. [Co-author with Gerry Martin.]

Were the succession of stars endless, then the background of the sky would present us an uniform luminosity, like that displayed by the Galaxy—since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all.

What we see in history is not a transformation, a passing of one race into another, but entirely new and perfect creations, which the ever-youthful productivity of nature sends forth from the invisible realm of Hades.

When the boy begins to understand that the visible point is preceded by an invisible point, that the shortest distance between two points is conceived as a straight line before it is ever drawn with the pencil on paper, he experiences a feeling of pride, of satisfaction. And justly so, for the fountain of all thought has been opened to him, the difference between the ideal and the real, potentia et actu, has become clear to him; henceforth the philosopher can reveal him nothing new, as a geometrician he has discovered the basis of all thought.

When the child outgrows the narrow circle of family life … then comes the period of the school, whose object is to initiate him into the technicalities of intercommunication with his fellow-men, and to familiarize him with the ideas that underlie his civilization, and which he must use as tools of thought if he would observe and understand the phases of human life around him; for these … are invisible to the human being who has not the aid of elementary ideas with which to see them.

You tell me of an invisible planetary system in which electrons gravitate around a nucleus. You explain this world to me with an image. I realize that you have been reduced to poetry. … So that science that was to teach me everything ends up in a hypothesis, that lucidity founders in metaphor, that uncertainty is resolved in a work of art.