How it began
On the evening of November 8, 1895, Wilhelm Conrad Röntgen, professor of physics at Würzburg, was studying cathode rays in a glass vacuum tube. He noticed that a fluorescent screen glowed even though it was too far from the tube to be reached by cathode rays. He spent weeks investigating and concluded that it was a new kind of ray. On December 28, 1895, his paper "On a new kind of rays" was accepted by the Würzburg Physical-Medical Society. He named them X-rays because their nature was unknown.
Before it existed
Other researchers working with similar tubes, such as Crookes, Hertz, and Lenard, may have produced the effect before Röntgen, according to the German Patent and Trade Mark Office, but he was the one who drew the right conclusions. Before X-rays, there was no way to look at the inside of a living body without surgical intervention.
How it works
Röntgen found that the impact of cathode rays on the glass vacuum tube generated an invisible ray with strong penetrating power. The rays traveled long distances and made the screen glow even when cardboard, wood, copper, or aluminum were placed in the way, and they blackened photographic plates. A hand held before the screen showed the bones as dark shadows with only faint outlines of the surrounding tissue. He proved this with a photograph of the bones of his wife's hand.
How it spread
On New Year's Day 1896, Röntgen mailed 90 reprints of his paper to physicists across Europe, twelve of them with photographs. One recipient, Franz Exner in Vienna, showed the pictures to colleagues, and the news reached the press. The world learned of the discovery through newspapers before scientists had reviewed it. Röntgen declined to patent the generation of X-rays, wanting their use to be free for research and for humanity.
What changed first
Physicians and physicists began using X-rays on patients as early as January 1896 to examine the skeleton, and later the lungs and other organs, which was the start of radiology. Skin reddening was soon observed, which led to the idea of treating lesions with X-rays, and the first patient received radiotherapy in June 1896. Röntgen received the first Nobel Prize in Physics in 1901.
What lasted
X-rays prompted further research. J.J. Thomson showed that they ionize gas, a study that led to the discovery of the electron in 1897, and Henri Becquerel's attempt to understand their emission led to the discovery of radioactivity in 1896. X-ray diffraction became a tool for studying crystals and molecules, and in 1953 it made it possible to demonstrate the DNA double helix.
Where it stands today
X-rays remain a foundation of medical diagnostics. Röntgen's successors became aware of the side effects of radiation exposure, and practitioners have since weighed the benefits and risks of the procedure. His Würzburg laboratory is now a memorial site.
