[He] did not belong to the types who bubble with ideas... His strength lay in another talent...the unremitting critique of the reliability of physical observations and measurements.
William Wien on the occassion of Roentgen's death in 1923

When you saw the screen shining ,"What did you think?", asked a reporter. "I did not think, I investigated." was the reply from Roentgen. "What is it?", the reporter pressed. "I don't know," was the reply.

In a few days I was disgusted with the whole thing. I could not recognize my own work in the reports any more. For exactly four full weeks I have been unable to make a single experiment! Other people could work, but not I. You have no idea how upset things were here.
Roentgen in a letter a month after sending his report around Europe

Advertisement from the turn of the century.


ONE OF THE WELL KNOWN STORIES in physics is the tale of the discovery of X-rays. While the null search for the ether indeed ushered in the modern physics world, the connection between that phenomenon and the rapid understanding of the fundamentals of matter comes much later. The accepted birth of modern physics of matter begins in the remarkable few years between 1895 and 1898. In Germany, England, and France, laboratory surprises occurred which have promoted Michelson's ill-timed comment about the future of physics to embarrassing prominece for its wrongheadedness!
     The stage for the first surprised was set by Philipp Lenard [1862-1947], who was an assistant of Hertz's (and a later ardent Nazi and an embarrassment to his former scientific colleagues). In 1892 he managed to coat the end of a Crooke's tube with a very thin layer of aluminum...through which he was able to transmit the cathode rays into air beyond the tube. Now, this was quite spectacular: the cathode rays penetrated what was presumed to be an opaque, solid wall of metal. It was this experiment that led a careful and rather unspectacular German professor to world-wide recognition.

William Roentgen-The First Nobel

William Konrad Roentgen [1845-1923] in the 1890's was a middle aged professor of Physics at Wurzburg. He had been transfered within the German university system four different times and was not likely to go much higher. At Wurzburg, he lived upstairs from his laboratory and from there, he continued his pedantic and careful work. A competent experimenter, he made good measurements of standard quantities in electromagnetics and materials. Indeed, Lorentz dubbed a pheonomenon that Roentgen had painstakingly discovered and characterized as the "Roentgen Current" (the observation of a magnetic field generated by a moving dielectric placed in a homogeneous electric field). He was productive, an author of 48 careful, unspectacular papers at the age of 50 when lightening struck.
     The year that Babe Ruth was born was the turning point. During the evening of November 8th, 1895 Roentgen was working alone in his laboratory, studying the Lenard effect, the penetration of cathode rays through different materials. In his darkened room, he covered his Hittorf tube (a variant on the glow tube of Hertz) with black cardboard. Quite by accident, on the wall six feet from the end of his tube, was a sheet of paper which had been treated with the salt barium platinum-cyanide which he used as a screen for other experiments. Because it was dark he noticed that the paper was glowing, flourescing. Further study demonstrated that this flourescent glow originated from the tube and that it exibited amazing properties! He knew from his earlier work that source of the glow could not be the cathode rays themselves, as they seemed unable to penetrate the tube's glass wall and the cardboard. Rather, they were of unknown origin, so he called them "X-rays".
      He fussed for some time in his little lab. He moved the screen away....it continued to glow. He turned the treated side to the wall....it still glowed. He changed from a Crooke's tube to a Lenard tube. He started to put various objects between the tube and the paper and most materials appeared to actually be transparent: the screen continued to glow. The rays coming from the end of the tube were even capable of discharging electrified objects placed in their path. But, when he inserted his hand in the beam...he saw his bones! (The photograph is actually Rontgen wife's hand and her ring).

Roentgen Has Gone Crazy...

You can imagine how incredible this must have seemed. Imagine standing in the dark in your basement realizing that you knew something that nobody else had evern known...that it would likely raise a ruckus. Because of this, he was careful. For weeks afterwards, he secretly kept repeating the experiments, telling nobody but his wife. He told her that he was doing something so strange that if people learned about it they would say that "Rontgen has really gone crazy." Finally, on January 1st, 1896 he sent numerous copies of a report of his findings, with a picture of the bones of his hand, to various labs around Europe. Then he waited.
      One of those to receive his mailing was Henri Poincare [1854-1912], who hastened to transmit it the French Academie des Sciences on January 20, 1896. Roentgen's paper was quickly reprinted in Nature, Science and other journals within weeks. He received letters of congratulations from around the world. Rutherford wrote about his boss to his fiancee in late January, 1896, "The Professor [J.J. Thomson] has been very busy lately over the new method of photography discovered by Professor Roentgen...nearly every Professor in Europe is now on the warpath."
     The reaction, world-wide was proportional to the magnitude of this discovery: five more observations were reported in a week of the Paris announcement. Within three more weeks, X-rays were used to set the broken arm of a young boy in Dartmouth, New Hampshire. Within a year, a thousand papers were published on the phenomenon.
     Roentgen only gave one talk on his discovery. In late January of 1896, he addressed the Physical-Medical Society from his home institution where he was received with tumultulous applause. Inexplicably, Rontgen, himself, published only two more papers on the subject, returning instead to his previous work. In 1900 he moved to Munich where he became the director of the Institute for Experimental Physics and then received the first Nobel Prize for Physics in 1901. Shy about public speaking and the publicity that his work had generated, he literally snuck out of Sweden to avoid having to give the Nobel Lecture. While Nobel required a speech on the subject of the prize, the specific requirements did not require that speech to be given at the ceremony, as it is traditionally done now. Rather, Roentgen managed to substitute his single Physical-Medical Society talk.
      The rest of Roentgen's life was not a storybook tale. He suffered terribly during WWI, as did many in the institutes around Germany. He never allowed himself to profit financially from his discovery and died in poverty during the post-war inflation at the age of 73.

Created: 9:07 PM, 27-Nov-99
Modified: 4:20 PM, 26-Dec-99


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History of Elementary Particle Physics
Copyright © 1998-99
Raymond Brock
Department of Physics and Astronomy
Michigan State University | East Lansing, MI 48824