Wilhelm Conrad Röntgen’s discovery of X rays had both practical and philosophical consequences. The penetrating power of this wavelength of electromagnetic radiation led to its wide use in medical and industrial applications. Meanwhile, the vision of the world revealed by X-radiography seemed to confirm the late nineteenth century worry that the world was less solid and less stable than it seemed.
X rays were discovered in 1895 by Wilhelm Conrad Röntgen, a professor of physics at the University of Würzburg. He was investigating the radiation produced in a partially evacuated glass bulb when a high voltage was applied. Sir William Crookes in 1869 had published a research report in which he described the bright glow that occurred inside such a bulb. Another physicist, Philipp Lenard
Röntgen was an experienced experimentalist with twenty-five years of laboratory research and more than forty technical publications. Using the same type of apparatus as Crookes
Wilhelm Conrad Röntgen.
Working by himself, Röntgen began a systematic investigation of the mysterious radiation. He observed fluorescence at a distance of as much as two meters from the discharge tube. Since the radiation had penetrated opaque, black paper, he decided to test various other materials for their transparency. Even behind a book of one thousand pages, he found that the fluorescent screen lit up brightly. Blocks of wood and sheets of aluminum transmitted the radiation fairly well, but two millimeters of lead was enough to block it. When holding his hand between the discharge apparatus and the fluorescent screen, Röntgen was able to see the shadow of the bones inside the faint outline of his fingers.
Further experiments showed that photographic
On December 22, 1895, Röntgen asked his wife to help him in the laboratory. He placed an X-ray tube just underneath a table, while she held her hand on the table surface with a photographic
Within a few days, newspapers all over Europe had published stories and photographs about this new scientific development. A flood of messages came to Röntgen with invitations to give lectures and demonstrations. He turned them all down, except one that he could not refuse from the emperor of Germany, William I. On January 13, Röntgen traveled to Berlin with his X-ray apparatus and showed to the assembled court how metal objects inside a closed box could be photographed
Over the next several weeks, Röntgen received letters from many scientists who were experimenting with X rays. One person sent a photograph of a fish showing its detailed bone structure. His friend Ludwig Zehnder
Röntgen felt that the benefits of X rays should be available to humankind without restrictions. He therefore did not take out a patent on his discovery, although doing so could have made him wealthy. His apparatus was not expensive or difficult to duplicate. The most difficult aspect of its construction was the need for a professional glass blower to make a specialized glass bulb with two metal electrodes inside that were connected by wires going through the glass to two terminals on the outside. Many hospitals and research laboratories were able to set up their own X-ray machines. Within one year of Röntgen’s initial publication, nearly one thousand articles on X rays had appeared in various technical journals.
The medical profession enthusiastically welcomed X rays as a new diagnostic tool. Doctors were able to determine the severity of broken bones and to locate swallowed objects or bullets embedded in the body. Annual chest X rays for school children became a routine procedure to diagnose early signs of tuberculosis
Among its industrial applications, the X-ray apparatus came into common use at airports to inspect baggage before boarding. X rays have been used to search for hidden microphones in the wall of a room before a diplomatic conference. In the pipeline industry, after individual sections of pipe had been welded together, portable X-ray machines have been used to detect possible hairline cracks at the welds that might later allow fluid to leak out. X-ray analysis has been widely used by chemists
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Farmelo, Graham. “The Discovery of X-rays.” Scientific American, November, 1995, 86-91. Describes Röntgen’s experimental setup and contains reprints of the earliest X-ray photographs, including the one of his wife’s hand. -
Hart, Michael H. The One Hundred: A Ranking of the Most Influential Persons in History. New York: Galahad Books, 1982. A fascinating collection of short biographies about the most famous artists, political leaders, theologians, and scientists, including Röntgen. -
Kevles, Bettyann. Naked to the Bones: Medical Imaging in the Twentieth Century. Reading, Mass.: Addison-Wesley, 1998. Discusses Röntgen’s discovery and its medical applications, with modern improvements in imaging technology using computers; intended for the general reader. -
Nitske, W. Robert. The Life of Wilhelm Conrad Röntgen: Discoverer of the X Ray. Tucson: University of Arizona Press, 1971. The best biography of Röntgen available in English, containing fascinating anecdotes about his personal life and scientific career. Photographs, a bibliography, and translations of his three X-ray publications. -
Turner, G. L. “Röntgen, Wilhelm Conrad.” Dictionary of Scientific Biography. Vol. 11. New York: Charles Scribner’s Sons, 1981. An authoritative, short biography of Röntgen’s life and professional career. -
Walker, James S. Physics. 2d ed. Upper Saddle River, N.J.: Pearson/Prentice Hall, 2004. College-level textbook describing the operation of an X-ray tube, including Röntgen’s contribution.
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Wilhelm Conrad Röntgen.