: Wilhelm Roentgen

Professor Wilhelm Roentgen was fascinated by the mysterious illumination produced by an electric discharge in a tube without any air. The illumination seemed to start at the negative electrode, or "cathode". Accordingly, the phenomenon was referred to as "cathode rays". When the rays hit the glass of the tube, it glowed with a greenish light.
On November 5, 1895, Roentgen enclosed his cathode ray tube in a box of black cardboard and darkened the room. He wanted to observe the luminescence without the interference of outside light.
He turned on the electricity. Almost at once a flash of light that did not come from the tube caught his eye. He looked up. Quite a distance from the tube, he happened to have a sheet of paper coated with a chemical, barium platinocyanide. He had been using the paper in experiments because this was one of the chemicals that glowed when placed near the cathode ray tube.
But wny should it be glowing now? After all, the tube was in a cardboard box!
Roentgen walked into the next room with the coated paper, closed the door, and pulled down the blinds. Still the paper continued the glow so long as the tube was in operation.
He had discovered something invisible that acted through cardboard and walls!
Wilhelm Roentgen was born on March 27, 1845, in Lennep, a small town in Germany. For most of his early life, however, he lived outside Germany. He received his primary education in Holland and went to college in Switzerland.
After completing his college course, Roentgen continued his studies in Switzerland, concentrating on research in physics. In 1888 a new institute of physics was opened at the University of Wurzburg in Bavaria, and Roentgen was invited there. It was there that he discovered his penetrating rays and won world fame.
His mysterious rays, which penetrated cardboard and doors, causing chemicals to luminesce, were called "Roentgen rays" in honour of their discoverer.
Roentgen himself, in view of their mysterious origin, . gave his rays the mathematical symbol for the unknown. He called them "X-rays", the name by which they are commonly referred to in English.
As we have seen in previous chapters of this book, careful investigations of some phenomenon often result in unexpected discoveries of related, but previously unknown phenomena. To an outsider such discoveries often seem accidents or luck. But, as Pasteur once remarked, in science chance favours the prepared mind. The mind must be prepared in two ways. It must know the subject very well, well enough to recognize something new when it turns up. But it must also be receptive to something new or strange. There is only a narrow line between the understandable refusal of a scientist to be distracted by side effects and a willingness to notice and to investigate a strange or annoying effect in an experiment. In the last decades of the nineteenth century there were many scientists with more or less "prepared minds" working with cathode rays. But the astonishing discovery of X-rays was made by a man both lucky and wise -lucky enough to observe something peculiar (although oihers had already observed it) and wise enough to investigate it.
When Roentgen announced his discovery, the scientific world was amazed. A number of scientists found that they had encountered these mysterious rays earlier. William Crookes, a British scientist who had worked with cathode rays, had noticed several times that photographic film nearby had become fogged." He had thought it accidental and paid no attention. In 1890 A. Goodspeed, an American physicist, had actually produced what we now call an X-ray photograph, but he was not sufficiently interested to follow it up and establish the nature of the phenomenon.
Within a few weeks of his discovery, Roentgen was -able to establish many important characteristics of X-rays. He demonstrated that X-rays have a much greater penetrating power than cathode rays and that they are not bent by magnetic or electric fields.
Usually years or even decades pass between a new scientific discovery and its practical application. But with X-rays the applications came quickly. Roentgen's discovery was made in November, 1895. His first publication on the subject appeared in December. And already in January, 1896, the broken arm of an American, Edward McCarthy, was set with the help of X-rays. Soon X-rays were in common use in medical practice. Doctors now had a way of looking into the human body quickly, easily, and — above all — without cutting. Small breaks in bones could be discovered, the beginnings of tuberculosis in the lungs, foreign objects in the stomach — in short, the doctor had a magic eye at his disposal.
In industry, too, X-rays have applications. They can detect internal flaws in the structure of metals, flaws that would be invisible otherwise. In chemical research they are used to probe the structure of crystals and of complex molecules, for example, of proteins. In short, Roentgen's discovery provided a new means of making the invisible visible.