Wilhelm Röntgen

The discovery of the Röntgen rays and the events connected to it are extraordinary in many respects. Röntgen never disclosed the full details of the experiment which led to the discovery on November 8, 1895. He observed the x-rays by chance. Neither he nor any other scientist had an idea that such radiation might exist. It needed a Röntgen to make the discovery, an experimenter of his superior capabilities.                                                  

Wilhelm Conrad Röntgen was a German mechanical engineer and physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range known as X-rays or Röntgen rays, an achievement that earned him the inaugural Nobel Prize in Physics in 1901. His achievement was the culmination point of the development of physics as an experimental science in the 19th Century. The impact of his discovery was enormous. In physics it gave impulses to the discovery of radioactivity, of the identification of the electron, and the development of the model of the atom; and in medicine in its immediate applications in diagnosis and therapy.

Early Life & Career

Wilhelm Conrad Röntgen was born on March 27, 1845, at Lennep in the Lower Rhine Province of Germany, as the only child of a merchant in, and manufacturer of, cloth. In 1862, he was expelled from a technical school in Utrecht, albeit unfairly, for a caricature of a teacher that was made by another pupil. Without that diploma, Wilhelm was not qualified to matriculate at German universities, but after hearing that he could enter the new Federal Polytechnic Institute in Zurich by passing one exam, he moved there and began studying mechanical engineering. From that point, Wilhelm’s career took off, landing him a Ph.D. in experimental physics in 1869 and a lecturing position at the University of Strasbourg in 1874. Röntgen’s first work was published in 1870, dealing with the specific heats of gases, followed a few years later by a paper on the thermal conductivity of crystals. Among other problems he studied were the electrical and other characteristics of quartz; the influence of pressure on the refractive indices of various fluids; the modification of the planes of polarised light by electromagnetic influences; the variations in the functions of the temperature and the compressibility of water and other fluids; the phenomena accompanying the spreading of oil drops on water.

Over the next several years, he moved all over the region, moving to Württemburg in 1875, back to Strasbourg in 1876, to Giessen in 1879, and to Würzburg in 1888. It was in Munich that he finally settled down, after the Bavarian government asked him to chair the University of Munich’s physics department in 1900.

Discovery of x-rays

On the evening of 8 November 1895, Röntgen was in his laboratory studying how cathode-ray tubes emit light. His attention was distracted by a glowing fluorescent screen that was too far from the tube to be affected by the cathode rays. Röntgen didn’t leave his lab for weeks as he tried to investigate the source of the glow. He found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, and if he worked in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent even when it was as far as two metres from the discharge tube. During subsequent experiments he found that objects of different thicknesses interposed in the path of the rays showed variable transparency to them when recorded on a photographic plate. When he immobilised his wife's hand for some moments in the path of the rays over a photographic plate, he observed after development of the plate an image of her hand which showed the shadows thrown by the bones of her hand and that of a ring she was wearing, surrounded by the penumbra of the flesh, which was more permeable to the rays and therefore threw a fainter shadow. In further experiments, Röntgen showed that the new rays are produced by the impact of cathode rays on a material object. The rays had extraordinary penetrative power – they could travel long distances and make the screen glow, even when wood, copper and aluminium were placed in the way – and could be recorded on photographic plates.

 Over Christmas, he wrote a 10-page article entitled “On a new kind of rays”, which was accepted by the Proceedings of the Würzburg Physical-Medical Society on 28 December. Röntgen named the discovery X-radiation, or X-rays, to underline the fact that their nature was unknown. The reaction to Röntgen’s X-rays made him an instant celebrity. Many honours were bestowed upon him, streets were named after him, and Röntgen received countless honorary doctorates and Prizes, including the first Nobel Prize for Physics in 1901. The new 'wonder rays' appeared in rapid succession in the press around the world. Physicians and physicists began as early as January 1896 to use X-rays on patients to investigate the skeleton and subsequently other organs. This was the birth or radiology. By the end of 1896, more than 1,000 books and papers had been published on X-rays and its applications.

Legacy

It is difficult to appreciate fully the genius of the man who made this remarkable discovery and beneficently gave it to the world. Remarkably, Röntgen was not only intellectual but also a very inspirational personality. In spite of his splendid contribution to the mankind, he remained a courteous, dignified, and modest man. Röntgen is credited with three standard components of X-ray investigation that are in current use. In the 100 years since the discovery of X-rays, several museums have been erected to collect and preserve the X-ray record and the heritage of Röntgen. Several books and review articles have been published that overviewed the developments within the various fields of technical and life sciences based on his discovery of X-rays. Röntgen's discovery had an enormous impact on the world, both at that time and today.