Wilhelm Conrad R?ntgen: The modest visionary who discovered x-rays
On the evening of November 8, 1895, Wilhelm Conrad R?ntgen made a momentous discovery when working alone in his lab in Würzburg, Germany. It was a new kind of ray, invisible yet powerful, that penetrated common objects to enable the visualization of internal structures.?
Soon known as x-rays, R?ntgen’s achievement quickly led to a series of other scientific advances while paving the way for the creation of the medical discipline known today as radiology.?
The date of R?ntgen’s discovery is commemorated as the International Day of Radiology, observed every year on November 8.?
Humble beginnings
R?ntgen was born March 27, 1845, in Lennep, a town known for cloth manufacturing in what was then the Kingdom of Prussia (now western Germany). When he was just three years old, R?ntgen’s family moved to the Netherlands; his academic career took a detour when he was expelled from technical school after being accused of drawing a caricature of a teacher that was in fact the handiwork of another student.?
The home where Wilhelm Conrad R?ntgen was born. Photo by Markus Schweiss.
R?ntgen’s checkered academic history required him to take an entrance exam for the University of Utrecht, which he promptly passed and began his studies in mechanical engineering. He was heavily influenced by German physicist Rudolf Clausius, who gave lectures at the university, and he worked in the laboratory of another German physicist, August Kundt. R?ntgen went on to earn a PhD in mechanical engineering from the University of Zurich in 1869.
R?ntgen followed Kundt to the University of Würzburg, and then on to the University of Strasbourg after that. He served in positions at several universities in the Netherlands and Germany in the 1880s through the 1890s, finally in 1900 accepting an offer as chair of the department of physics at the University of Munich. He kept this position for the rest of his life.
R?ntgen’s publishing history began in 1870 with a paper on the temperatures of gasses, and he continued this work over the years with other research into topics such as the influence of pressure and temperature on water and other fluids.?
The fateful discovery
But the discovery for which R?ntgen would win everlasting renown occurred in 1895, while he was a professor at the University of Würzburg. R?ntgen was studying the passage of an electric current through a gas of very low pressure. In particular, he was investigating the passage of electrical currents through a Crookes tube, an early type of discharge tube with a cathode and anode inside a partial vacuum. By applying a high voltage of electricity, scientists could project cathode rays from the cathode.?
R?ntgen was working with the tube on the evening of November 8, 1895 when he made the fateful discovery of x-rays. He had seated the discharge tube in a black carton to block out light; he found that a paper screen coated with a film of barium platinum cyanide became fluorescent in the darkened lab if it was placed in the path of the rays – even if located several meters away.? Because there was no way for light to leave the darkened carton, R?ntgen deduced that the fluorescence was being caused by a new type of radiation.?
R?ntgen continued his experiments on this intriguing phenomenon, taking his meals in the laboratory and some nights even sleeping there. He soon found that the transparency on the fluorescent screen varied when objects were placed in the path of the rays, based on the thickness of the objects.?
The new rays had remarkable penetrating power, passing through cardboard, cloth, large books, and even a thick plank of wood – but not metal, in particular lead. The fluorescent screen was soon replaced by a photographic plate to permanently record the images. R?ntgen soon moved on to a human experiment, placing the hand of his wife Anna Bertha in the path of the rays directly in front of a photographic plate. In this first x-ray of a human, the skeletal structure of Anna Bertha’s hand is clearly visible, complete with her wedding ring, and her skin is visible as a faint shadow.?
The first x-ray of a human, of the hand of R?ntgen's wife Anna Bertha.
A new kind of rays
The rest is history. Because the exact nature of the phenomenon was unknown, R?ntgen dubbed the new rays “x-rays.” He didn’t report on the discovery until seven weeks later, in December 1895, after several more weeks of experimentation. Entitled “On a New Kind of Rays," his paper was published in the Proceedings of the Würzburg Physico-Medical Society, and immediately caused a global sensation.?
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News of the discovery spread around the world like wildfire in January 1896 – and much of the initial reaction was incredulous. But researchers and clinicians around the world immediately began replicating R?ntgen’s experiments, finding that they too were able to reproduce the phenomenon.?
The significance to medical practice of the new rays was instantly recognized: a paper published in 1899 in The Hospital noted the following:?
“Photographs of the most deeply buried bones could now be obtained without difficulty. Measurements of such structures as the pelvis could be taken without subjecting the patient to the least inconvenience, and the clinical records of the past year were full of instances showing what could be done in medical and surgical practice.”?
R?ntgen’s achievement quickly led to other follow-on scientific discoveries, such as the discovery of radioactivity by Antoine Henri Becquerel in March 1896. The realization that x-rays could cause skin erythema (redness) led to the development of radiation therapy, used on the first patient in 1896. Pierre and Marie Curie leveraged this knowledge for new discoveries of the radioactive elements polonium and radium.?
A modest man of science
A truly modest man of science, R?ntgen declined to seek profit from his momentous new discovery. He declined to patent his technique for producing x-rays, instead believing that the technology would be of greater benefit to humanity if it were allowed to disseminate freely. He even turned down some early invitations from medical scientific societies to discuss x-rays (one source claims he only spoke publicly about x-rays on one occasion, in January 1896).
But recognition was not long in coming for the German physicist. In 1901 he won the Nobel Prize in Physics – the first Nobel awarded in the discipline – and chose to donate proceeds from the award to the University of Würzburg. He was decorated by German Kaiser Wilhelm II, and the Prince Regent of Bavaria proposed giving him the honorific title “von,” a sign of nobility – a proposal that the ever-modest?R?ntgen declined.?
R?ntgen declined to profit from his discovery of x-rays.
R?ntgen lived for almost three decades after his discovery of x-rays, continuing his experiments and publishing additional papers. He was said to have been devastated by the onset of World War I and its aftermath, and his melancholy deepened when his wife Anna Bertha died in 1919. R?ntgen died of intestinal carcinoma in Munich on February 10, 1923, at the age of 77.
Today, over 125 years after?R?ntgen’s momentous discovery, x-ray remains the most widely used medical imaging technology, despite the arrival of more sophisticated modalities like CT, MRI, ultrasound, and PET. To recognize his achievements, the International Day of Radiology (IDoR) was created in 2012 by several prominent radiology organizations, including the European Society of Radiology (ESR), the Radiological Society of North America (RSNA) , and the American College of Radiology (ACR).
Wilhelm Conrad R?ntgen is recognized as one of the titans of scientific inquiry who birthed a new medical specialty, one that is indispensable for diagnosing disease and guiding treatment as healthcare moves toward precision medicine.?
Sources
“W. C.? R?ntgen and the Discovery of the? R?ntgen Rays,” American Journal of? R?ntgenology, November 1995.?