Wilhelm Röntgen

Wilhelm Röntgen: The Glow That Should Not Have Been There

On 8 November 1895, in a darkened room at the University of Würzburg, a fifty-year-old professor of physics noticed a faint gleam on a small fluorescent screen some distance from a discharge tube he had wrapped completely in light-proof cardboard. Nothing was supposed to be reaching it. Seven weeks later he had photographed the bones inside his wife's living hand, and within months doctors on four continents were looking inside their patients. It is arguably the fastest journey from laboratory curiosity to clinical practice in the history of science.

An Only Child Between Two Countries

Wilhelm Conrad Röntgen was born on 27 March 1845 at Lennep, in the Lower Rhine Province of Germany, the only child of a cloth merchant. When he was three the family moved to Apeldoorn in the Netherlands, and he was sent to boarding school there. He showed an early mechanical aptitude and a lifelong love of the outdoors, neither of which ever left him.

Expelled for Someone Else's Drawing

In 1862 he was thrown out of the technical school at Utrecht, wrongly accused of producing a caricature of one of the masters. It was an injustice with real consequences: without the certificate, the ordinary route into a German university was closed to him.

He worked around it. He entered the University of Utrecht in 1865, then passed the entrance examinations for the Polytechnic at Zürich, where he read mechanical engineering and was taught by Rudolf Clausius and August Kundt. He took his doctorate at Zürich in 1869 and became Kundt's assistant, following him to Würzburg and then Strasbourg — the classic apprenticeship of nineteenth-century German physics, and the making of him as an experimentalist.

The Long Apprenticeship

What followed was a career of steady, unglamorous competence. He lectured at Strasbourg from 1874, took a professorship at the agricultural academy at Hohenheim in 1875, returned to Strasbourg as professor of physics in 1876, moved to Giessen in 1879, and in 1888 obtained the chair at Würzburg, where he was elected rector in 1893. He lived with his family in a seven-room apartment at Röntgenring 8 and taught the whole of experimental physics, five hours a week, to a class that grew from about a hundred students to a hundred and eighty-five.

His published work over these decades ranged widely and modestly: the specific heats of gases, thermal conduction in crystals, the electrical properties of quartz, the influence of pressure on the refractive indices of fluids, electromagnetic effects in polarised light, the spreading of oil films on water. Nothing in it announced what was coming.

8 November 1895

He was studying cathode rays — the streams produced when high voltage is discharged through a nearly evacuated tube — a subject then being worked on in laboratories all over Europe. Röntgen enclosed the tube so that no visible light could escape, darkened the laboratory, and observed a screen coated with barium platinocyanide fluorescing anyway.

Some invisible radiation was passing through cardboard. He did not know what it was, and he said so in the name: X-Strahlen, X-rays, the algebraic symbol for an unknown. Then, rather than rushing into print, he shut himself in for seven weeks and characterised the new rays methodically — what they passed through, what stopped them, what they did to a photographic plate.

The Hand

On 22 December 1895 he made the image that changed everything: a radiograph of the hand of his wife, Anna Bertha Ludwig, showing the bones within and the ring on her finger. It was the first röntgenogram, and it was instantly and universally legible in a way no scientific result had ever been.

His preliminary paper, *Ueber eine neue Art von Strahlen* — "On a New Kind of Rays" — was read to the Physical-Medical Society of Würzburg on 28 December 1895 and published almost at once in the society's proceedings, in the final issue of the year. At a demonstration on 23 January 1896 the anatomist Albert von Kölliker proposed from the chair that the rays be named after their discoverer; the room erupted in what one account records as *allgemeinen Jubelruf* — general cheering.

The First of the Nobels

In 1901 Röntgen was awarded the very first Nobel Prize in Physics, "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him." Shy by nature, he declined to deliver a Nobel address.

He had married Anna Bertha Ludwig of Zürich in 1872; in 1887 the couple adopted her niece Josephine. Contemporaries described him as strikingly modest and reticent, happiest mountaineering. In 1900 he took the chair of physics at Munich, where he remained for the rest of his life. He died there on 10 February 1923 of intestinal carcinoma.

Why Wilhelm Is Called a Genius

The case does not rest on theoretical power, and it is more interesting for that. Cathode-ray tubes were running in dozens of European laboratories in the 1890s, and several physicists had almost certainly generated X-rays already without registering that anything unusual had occurred. Röntgen's gift was the harder one to name: an attention so disciplined that a faint glow in the wrong part of a dark room registered as a fact demanding explanation rather than as a nuisance to be ignored.

What followed is the real evidence. He did not announce; he worked alone for seven weeks and produced a first paper so thoroughly grounded that it needed almost no correction. The institutional verdict came fast and was unambiguous — the first Nobel Prize in Physics ever awarded, and a room of scientists cheering the proposal to put his name on the phenomenon.

The counter-case is straightforward and he would probably have endorsed most of it. He discovered the rays; he did not explain them, and the X in the name is an admission. Establishing their nature as short-wavelength electromagnetic radiation was the work of other physicists in the following years. His thirty years of prior research — gases, crystals, quartz, oil films — was capable second-rank work that has left no mark. There is an irreducible element of luck in the story, and Röntgen never pretended otherwise. He founded no school, left no theoretical framework, and was so reticent that he would not even give a Nobel lecture. Whether that adds up to genius, or to the most consequential act of noticing in modern science, is a fair question.

Legacy

X-rays gave medicine its first sight of the living interior of the body, and gave physics the tool that would later reveal the structure of crystals and of matter itself. A discovery made in a dark room in seven weeks by one careful man is still, every day, in every hospital on earth.

Achievements

• Pour le Mérite for Sciences and Arts order
• Rumford Medal — 1896
• Nobel Prize in Physics — 1901
• Matteucci Medal — 1896
• Notable work: X-ray
• Held posts at Ludwig-Maximilians-Universität München, University of Giessen and University of Hohenheim
• Educated at ETH Zurich, Ludwig-Maximilians-Universität München and University of Strasbourg
• Fields of research: physics