WARNING: The article is not historically or scientifically correct in many places - for example, the notion of Röntgen stumbling across x-rays by "one of the happiest chances that ever happened in the world" is fiction, along with many details of the story of the discovery. In actual fact Röntgen was experimenting with a paper-covered Crookes' tube, which caused a paper screen covered in fluorescent barium platinocyanide to glow. And Röntgen published his findings seven weeks later, not two years later as the following article says!
For accurate information on Röntgen, I suggest checking web sites like Rontgen And The Discovery Of X Rays and a reprint of Röntgen's December 1895 paper On a New Kind of Ray. Or try the library for fascinating books like A History of X-rays and Radium by R. F. Mould, IPC Business Press Ltd., 1980.
But, regardless of its lack of accuracy, I hope you enjoy "This World of Shadows" with its flowery prose, run-on sentences and unbridled enthusiasm. Remember, it was written for children of Britain - children of the Empire upon which the sun still had not set.
A THING is happening in the world which is almost beyond men's dreams. Slowly but surely the veil is lifting from the invisible foundations upon which this world rests, and the invisible world, with all its powers and hopes for the future of mankind, is revealing itself to the human mind.
For centuries wise men have been building up the great book of buman knowledge, and a wonderful book it is. But most of its pages deal with the things we see, the things that our hands can touch. Now there is being written a second volume of the story of our world, and its pages deal with the things our eyes have never seen, the things our hands have never touched. The visible Earth is nearly all explored. Men are exploring now the invisible world that lies about us on every hand.
The proess of their knowledge of electricity, and magnetisin (the two great invisible forces that influence our lives in a thousand ways) is the most striking piece of exploration of this unseen world. Its value is plain. An invisible force, which our five senses cannot detect, carries a cry for help for hundreds of miles over lonely, stormy seas, and hundreds of passengers on some sinking ship are rescued.
The same invisible force is now used in another form for saving life in our hospitals. It is turned into an unseen ray which strikes through the flesh of our bodies and leaves photographs which enable doctors and surgeons to see what is going on inside us and discern what can be done to cure us if we are ill. The X-ray and the wireless telegraph are both forms of the same unseen energy, which science calls electro-magnetism. And this force is employed in other ways to help us and work for us. It runs our trams and many of our trains, it drives our machines, it makes chemicals for us, it helps to send our motor-cars along, it helps to propel our aeroplanes faster than the fastest bird can fly.
We are, in fact, living in the age of electricity - the most wonderful of the new forces of the invisible world. But modern men of science know other new things besides this unseen form of energy. They have found out that man is in some ways blind, and that he cannot even see many objects in the broad sunlight. For they have taken the sunlight and broken it up by passing it through a prism of glass, which spreads it out into a rainbow band of colour.
Our eyes can see only a little ribbon of colours with long bands of darkness stretching away at either end. Both these long, dark parts of the band are composed of real sunlight; one is a part that acts on a photographic plate, the other is the part that acts on an instrument for measuring heat. But our eves can see neither of these parts of ordinary sunshine, because our optic nerve works in a very limited way and does not use this part of light. We are surrounded by invisible forces - strange, glorious colours that we cannot see, delicate perfumes that we cannot smell, sounds that we cannot hear, and powerful things that our sense of touch cannot feel. Yet the things in this invisible world are of more practical importance, than the things we see.
The visible world is a land of myths and legends and phantoms. If it were the whole reality we could not live in it. The Earth would be a desert, emptied of all forms of life, or, rather, the Earth would not exist, it would be blown into bits of rock whirling in wild and scattered ruin around the Sun. Unseen forms of life work in the soil beneath our feet and make it fertile. If these invisible things did not exist, not a tree or a blade of grass would grow; there would be no food for animals or men.
The real world of power and infinite life around us is an invisible world. Before we become the lords of the Earth we must be awake and alive to the miracles that our eyes cannot perceive.
To see a World in a grain of sand,was the dream of an English poet a hundred years ago - a poet who was looked upon as a madman. But the dreams of William Blake have now become the realities of the man of science. He does not want a grain of sand in which to see the world. He can divide that grain into more than a million parts, and in one of these parts he finds a universe as complicated as our solar system.
And a Heaven in a wild flower;
Hold Infinity'in the palm of your hand,
And Eternity in an hour,
The Men Who Stand on the Edge of a New World of Invisible Forces
At present our wisest men are only standing on the edge, as it were, of the new world of invisible forces. They grope, they guess they fumble, but they cannot tell us much about it. Some of the greatest discoveries are happy accidents - things men hit upon by mistake when seeking something else. A scientist in these days feels somewhat like a child in a fairy tale wandering through an enchanted forest. Somewhere in the depths of the forest is the great treasure of invisible power. If it is found it will abolish poverty from the world. But the seekers after this wonderful treasure never boast even to themselves that they will find it. They do not even go so far as to proclaim that some man, some day, before life perishes from our planet, will find the great secret power. All they do is to work on in hope, amazed at their own ignorance of invisible things, yet joyful at the unknown fields of adventure that stretch before them awaiting discovery.
There are two kinds of ignorance. There is the unconscious ignorance of those who do not know they are ignorant, and there is the conscious ignorance of those who know that their knowledge is scanty. A hundred years ago mankind did not know that it did not know; but now the wisest men are humbled in mind and aware of our lack of knowledge of everything around us.
How Mankind is Recovering Its Sense of Wonder and Awe
We are recovering our sense of wonder, awe, and mystery. Conscious ignorance of this kind is in itself a stimulus to discovery. It was only when mankind became aware that it knew nothing about the North Pole or the South Pole that daring adventurers began to explore the unknown regions of the Earth. So it is with the exploration of the invisible worlds of power and life in which we live and move. They were so, near us, and yet so intangible, that we never thought they existed.
Had it not been for some of the famous scientists of those days, including Professor Huxley and Sir Gabriel Stokes, the invisible force behind the wireless telegraph might have been discovered and put to use, in 1879. In that year David Edward Hughes was making experiments with a telephone instrument. He put up a machine that produced electric sparks, and as he listened, hundreds of yards away, it seemed as if something happened every time the machine gave out a spark.
He made other experiments, and came to the conclusion that he had found a new way of sending electric impulses like waves through the air. It was already known that light consisted of ripples of electro-magnetic energy which spread from a flaming substance in the same way that ripples spread from a stone thrown into a still pond.
The Wonderful Waves Which No Human Eye Can See
But nobody would believe there were such things as electromagnetic waves which rippled along like rays of light but remained invisible, because they were too long or too short to affect the nerves of our eyes.
David Hughes found that his telephone microphone was a new kind of eye. It responded to the waves set up by the electric spark hundreds of yards away. By varying his spark the professor obtained different kinds of waves, and all that remained for him to do was to continue his experiments until he had measured the waves and found whether they could be reflected from one point to another in the waylight is reflected.
This was a long and difficult piece of work, and before entering upon it Professor Hughes submitted his discoveries to Sir Gabriel Stokes, Huxley, and the President of the Royal Society. They told him he was mistaken about the nature of his discoveries, and he was so discouraged that he did not publish any account of his work on the great problem. The other men only believed in visible things, and formed a theory about ordinary electric currents by means of which they explained away the strange things that had happened in Professor Hughes' telephone. So wireless telegraphy was held back.
Nine years afterwards, however, a brilliant young German, Heinrich Hertz, came to the conclusion that electro-magnetic waves other than light, such as had been predicted by the mathematician Clerk Maxwell, could be found and detected. He told nobody but a friend what he was doing, and asked for nobody's advice or assistance. He set up a sparking electric machine in his room and then walked slowly about, holding in his hand a bent piece of brass with two bright knobs. The brass was bent until the two knobs almost touched, and Hertz found that he could pick up little electric sparks between the knobs, even when he was far away from the machine.
The Electric Waves Which Can Be Reflected Like Waves of Light
What happened was this. The big spark set up invisible electric waves, which rippled on until they touched the end of the brass rod, and there they, in turn, produced a tiny spark of electric energy. Hertz measured the waves, and discovered how they could be reflected like waves of light; and when he had worked out the details, so that there could be no doubt about the existence of these strange waves, he published his discoveries. Some years afterwards a Frenchman, Edouard Branly, rediscovered the principle of Professor Hughes' more ingenious detector of the unseen electric waves, and this, in turn, was improved by Sir Oliver Lodge and others, especially by a brilliant boy in Italy, who grew up to be Senatore Marconi.
Since then thousands of lives have been saved by the invisible electric waves, and much of the business messages and news reports of the world is flashed for thousands of miles over lands and seas and deserts by means of this unseen force. Men can even speak to each other by means of the waves which Sir Gabriel Stokes would not believe in. A man may sit in his office in London and ask the telephone operator to put him through to a friend in New York or some other American city. His voice is carried over land lines as far as Rugby, where electric waves are made to carry the voice, with no visible means of communication, to a wireless station near New York. There the wireless waves carrying the voice are again transferred to a land line, and the man in New York hears quite clearly in his telephone his friend speaking in far-off London.
A Great Discovery That Was Made by Accident
Such is the story of the first striking discovery of some of the forces of the invisible world. In 1895 the X-ray was discovered by accident. At that time many men of science were interested in certain experiments with a glass tube. The glass tube was emptied of air and connected with the wires of an electric battery. By this means a discharge of electricity could be sent through the glass tube. The result mainly depended on getting the air out of the tube by means of air pumps and charcoal, and Sir William Crookes was the first man to produce a really high vacuum.
Just a little air remained in the glass, and when the electric current jumped from one side of the tube to the other it created a ray out of the rarefied particles of the air. It was a visible ray, and Crookes maintained it consisted, not of light, nor of electric waves, but of matter in a radiant state. Many German men of science then took up the problem with the intention of proving that Crookes was wrong, and that the ray was merely a ray of light.
Professor Röntgen, of Würzburg, was among these men. He was studying other matters at the time, and one day his table was in great disorder. There was a vacuum tube placed on a stand and connected by wires to a battery; close beside it was a book the professor was reading, and in its pages was a metal key used as a bookmark. The professor was, among other things, an enthusiastic amateur photographer, and some of his photographic plates were scattered about the table. By one of the happiest chances that ever happened in the world, the book with the key in it was placed on the top of one of these plates.
The professor spent some time in sending currents through the glass tube and studying the results, but he could get no new idea from his experiments, and he thought he would clear his mind by going for a walk and taking photographs. He picked up all the plates he could find on his table, including the one that lay beneath the book. Then, seeing his camera, he went out to take photographs. When he developed and fixed his plates, however, he found that one of them was quite spoiled by the shadow of a big key. He recognised the key - it was the one he had put in the book.
PROFESSOR RÖNTGEN DISCOVERING THE MYSTERIOUS PHOTOGRAPH OF A KEY - THE FIRST KNOWN WORK OF THE X-RAYS.
So far all was accident, but the professor felt that he was on the edge of a new world of mystery. He began by putting everything back on the table as he had found it before he went out for his walk. He put the key back in his book, and placed the book on another photographic plate near the vacuum tube, and then sent an electrical discharge through the tube as he had done before. Then he developed the plate and fixed it, and found the photograph of the key again revealed. It was now clear to him that he had hit upon an unknown ray which had the power of penetrating a book and affecting a photographic plate.
In his great excitement the professor called a few of his best students into the laboratory, told them of his strange discovery, and planned a series of researches.
Happily, the professor had a curious screen which had been devised for studying various forms of light. It was coated with certain chemicals which made invisible rays of light (what are called ultra-violet rays) into visible rays of light. When his screen was placed near the vacuum tube it glowed at each electrical discharge. A student placed his hand between the screen and the tube, and the bones of his hand at once became visible through the flesh! The X-ray was discovered!
Professor Röntgen spent two years in attempting to develop his discovery, and to ascertain the nature of the new force, and at last published all his researches, giving the strange, unknown ray the name of X-ray, in remembrance of his algebra lessons at school, where X always stood for something unknown. It was a good many years before the X-ray was found to be a form of electro-magnetic energy which traveled in waves so much shorter than those of light that it could be hardly regarded as light at all. But one thing discovered was that the ray was a power for evil as well as good. It has greatly relieved various kinds of sufferers, and taken away many of the difficulties of surgeons and physicians, and it has produced good results in the cure of certain maladies. But many of the men who first used it for medical purposes have been attacked by a strange, new disease - the X-ray disease. The operators of X-rays in our hospitals have now to be protected with leaden shields and rubber gloves from this powerful ray, which injures those who work with it regularly, but benefits those who are exposed to it only for a few times in their lives. The man who works all day by an X-ray tube is in extreme danger, and if he continually exposes his hands to the rays he suffers terribly. The new way is to build in a hospital a small room of lead, which the patient enters, while the operator stands outside and works the X-rays by means of a mirror. So the patient benefits and the operator does not suffer.
In spite of all the work done on the new rays it was long before men discovered what they were made of. Some thought that they were tiny particles of matter in a radiant state; others thought they were spurts of electric energy. The trouble was that no experimenter could find a way of turning them from their path and make them shoot in another direction.
We can do this with a beam of visible light by means of a mirror, and men of science can just as easily deflect the invisible trains of electric waves used in wireless telegraphy. But for seventeen years nobody could turn an X-ray from the path it took when it shot from the vacuum tube. It has been discovered, however, that if a crystal is placed in the path of an X-ray, and a photographic plate is placed behind the crystal, the photograph will show that the ray has been turned from its course. By using various kinds of crystals it has been found that the X-ray is of the same nature as visible light and invisible wireless rays. The only difference is that the electric waves in an X-ray are extremely small - smaller than an atom.
The Lantern of the World of Unseen Forces
The X-ray, with its dark, invisible light, has become the lantern of the newly discovered world of unseen forces. In some cases it has led men astray, but their wanderings have brought them to still stranger and more unexpected sources of power. For instance, a French man of science, M. Becquerel, thought the X-ray was probably a form of radiant matter, and began to search for other things that shone with an invisible light. He started by using an ordinary photographic plate. Each plate was placed in a box with some metal or other substance; the box was sealed and set in a dark cupboard. It was soon found that certain forms of matter emitted an unseen radiance - something that could not be seen with human eyes but that affected the chemicals on a photographic plate, even though a sheet of metal or wood covered the plate.
THE WONDERFUL WAY IN WHICH LIGHT IS MADE TO SEE THROUGH DARKNESS AND PHOTOGRAPH THE INSIDE OF THINGS. By the invisible Röntgen rays a hand can be photographed in this way on a plate in a dark box.
The Key to the Secret of the Invisible Universe
It was also discovered that this dark light was connected with an emission of electrical energy. So an instrument for measuring electricity was used instead of a photographic plate, and a Frenchman and his wife, Professor and Madame Curie, offered to undertake the laborious task of tracing the principal source of the strange light that xame from a mineral substance called pitchblende.
This is a dark, metallic substance found in various mines, and usually regarded as a nuisance. The Curies broke it up into its elements, using all sorts of devices to get rid of the stuff that did not make their electrical instrument work. Gradually they obtained a tiny amount of a new substance which showed great electrical power, and at last they were able to announce to the astonished world the discovery of the new and mysterious element of radium.
HOW RADIUM WRITES ITS AUTOGRAPH.
The dark patches of pitchblende on the left, placed over a photographic plate in darkness, were photographed as patches of light, showing that the radium rays are emanating from them.
Radium is the key to the great secret of the invisible universe. It contains many sorts of power, each manifested by a different kind of ray. There are X-rays in it twice as strong as the ordinary X-ray; there is another ray which can be collected in a leaden vessel and shown to be, not a form of light, but a form of matter; and there are other rays in radium which are called after various letters of the alphabet. Some of them can be split from the others and turned out of their path by bringing a strong magnet to play upon them. Others rush through the strongest kind of magnetism that man can make, and show not the least swerve as they do so.
The X-ray was a mystery of man's unfolding, and man is slowly mastering this strange new power that he has found. Radium is a mystery of Nature's making, and it may be hundreds or thousands of years before man is able to master it. Perhaps he will never master it. But he lives in hope, and it is the hope of discovering the great secret of the invisible world that now inspires our men of science.
The Cave of Illusion in Which Plato Declared Mankind to be Living
Plato declared that mankind was living in a dark, narrow, underground cave, into which entered only a feeble glimmer of light from the real world, so that the things in the real world were known to men only by dim shadows cast on the walls and floor of the cave. If some of the prisoners were to escape to the upper world of light, said Plato, their eyes would be so dazzled that they would not at first be able to see anything real. They would still mistake the shadow cast by a tree for the tree itself. It would take them a long time to see real things as they really are.
One of the first men to escape from the cave of illusion, and so get a glimpse of the realities of the invisible world, was Sir. J. J. Thomson, the famous scientist of Cambridge University. He was experimenting in 1897 with a vacuum tube such as that with which Professor Röntgen had found the X-ray. It was not the new invisible ray that Professor Thomson was studying, but the ordinary visible ray that shines feebly through the glass tube during an electrical discharge. He had been studying it for fourteen years without obtaining any result, and when he at last obtained a result he could not believe it. He thought he had made a mistake.
He was trying to measure the particles of electrified air that formed the visible ray, and he hoped that they would prove to be atoms, but when he discovered a way of measuring them he found he had got hold of the matter out of which the material Universe is built. He had broken the thin air in the tube intoatoms by his electrical discharges, and had then broken these atoms into something smaller still.
The Intellectual Power of the Human Spirit Which Discerns Nature's Mysteries
It is extraordinarily difficult, it is almost impossible, to give an idea of the extreme smallness of the things that Sir J. J. Thomson discovered, but the attempt is worth making.
Let us suppose that a drop of water was magnified to the size of the Earth. It would then be possible to distinguish the molecules of which it was composed. The molecule is made up of atoms. Now, suppose, again, that we could magnify the atom to the size of a large room, then the particles which Sir J. J. Thomson discovered would look like specks of dust spinning about inside the room.
It is surely wonderful to think that man, with his five dim senses, is able to penetrate to this extraordinary limit of the invisible world. Our real eye is invisible; it is the intellectual power of the human spirit that discerns these mysteries of the material Universe. Our intellect constructs instruments which see and feel and weigh better than we can, and with these new mechanical senses we are beginning to explore the unseen worlds about us.
THE REMARKABLE INSTRUMENT AT CAMBRIDGE UNIVERSITY WITH WHICH SIR &J. J. THOMSON STUDIED THE ATOM AND ITS INVISIBLE PARTS
Power Enough in a Pebble to Supply London With Electricity
Sir Joseph Thomson's discovery of the electron, as the infinitesimal part of an atom is called, has enabled other men to understand a little about radium. It appears that an electron is not an ordinary form of matter, it is merely a centre of electrical force. The material atom is only formed when certain electrons attract each other, as a magnet attracts little bits of iron, and so forms a system of forces.
In every atom is a centre of electric force, perhaps a spinning electron, which attracts some small electrons, just as the Sun attracts the planets and keeps them whirling around in perfect order.
Matter, indeed, is built up of electromagnetic energy. In an ordinary pebble by the seashore, or a broken flint on a road, there is enough electrical energy to supply London for some hours with electric light and run all the trains in the tubes. But this wonderful store of electrical power contained in everything material around us is locked up beyond our reach.
We cannot break the bonds that hold together the electrons in a pebble and make the energy stream out for our use in the same way as energy streams out of burning coal. Even in burning coal we do not touch the ultimate supplier power. The heat we set up in a furnace only makes the electrons vibrate, and their vibrations produce electric waves, which we use in the form of light and heat. We never break up the atom of carbon in coal in the same way as Sir Joseph Thomson broke up the atoms of air in a vacuum tube. At present it costs more to break up the atom and liberate some of the electrons than it does to get electricity from burning coal, but our men of science hope they may one day be able to discover the key to the great treasure chamber of power that surrounds us on every side. It is only right to say that Sir Ernest Rutherford, who has carried on Sir J. J. Thomson's work, declares that science has made very little progress to this goal.
Radium and Its Amazing Possibilitiesfor Mankind
It is radium that is pointing the way to the solution of this great problem. Radium is matter in a radiant state. It burns with terrific force, yet it never goes out. All the radium now used in our hospitals will continue to give out energy for more than a thousand years. If radium were so cheap and plentiful that we could use it instead of coal our fires would never go out. Our electric generating stations, if kept in repair, would produce electricity for twenty centuries out of a single piece of radium. Our steamships could sail round and round the world without needing fresh fuel. We should need no coaling stations for our battleships. When ships were quite worn out their store of radium would be carried to a new vessel, and used again and again.
We could make most of our machinery automatic by inserting a piece of radium as driving power, and the machines would go on working day and night. The Earth would be a playground, for none of us would have to work more than an hour a day. We should grow our crops with electricity, and so increase the supply of food that twice the number of people could live comfortably on our planet.
The trouble is that radium at present is the rarest and dearest of elements. It exists in invisible quantities, and costs about £500,000 an ounce to collect it. Our only course is to discover the source of its wonderful energies and imitate the mechanism if we can. Radium is composed, of course, of atoms, and these atoms are composed of the electrons Sir Joseph Thomson discovered. But the electrons of radium atoms are not stable. Some fly about and produce wild disorder, and then the atoms break down, and bits of them stream out and produce the wonderful radium rays. We could change any bit of matter (a stone, a brick, a piece of wood) into something that would burn with great energy for a thousand years if only we could set free some of its electrons in the way the electrons of radium set themselves free.
Before we can do this, however, we have to solve the great radium mystery. We have to discover the cause of its radiancy - the thing that loosens some of its electrons and sends them in a fierce bombardment against the other atoms, and that unlocks some of the vast store of electrical energy hidden within it. When this has been found out mankind may be able to set free the electrons in some common form of matter, and thus make it a radiant source of practically everlasting energy. The secret of perpetual motion might then seem a less absurd quest than in the past.
If ever this should happen coal-mines and oil-wells and wood fires would be unnecessary. We should have more power than we knew what to do with. Working energy for light, heat, chemical operations, and power machinery would be almost as cheap and plentiful as the air we breathe. A quick and easy way of breaking up an atom into the electrical energy of which it is composed would entirely change the fortunes of the human race. Man would then be, indeed, lord of the Earth.
And that day will come. Slowly but surely the truth is dawning upon mankind that the invisible forces of the world are the great reality, and that the things our eyes can see are but the dim shadows of the wonderful unseen Universe.