On the evening of Friday 8 November 1895, a fifty-year-old physics professor was working alone in his darkened laboratory at the University of Würzburg. Wilhelm Conrad Röntgen had wrapped his cathode-ray tube in black cardboard so that no light could leak out, and when he switched on the high-voltage current he expected to see nothing at all. Instead, on a bench a metre or so away, a paper screen coated with barium platinocyanide began to glow with a faint green shimmer. That should have been impossible. Cathode rays could travel only a few centimetres through open air, and the tube was sealed in card anyway. Something invisible was streaming across the room, sailing through the cardboard as if it were not there, and lighting up the screen.
Röntgen barely left the laboratory for the next seven weeks, taking meals there and telling almost no one what he was doing; by his own account he could scarcely believe the observations himself. He put whatever came to hand in the path of the rays: a thousand-page book, blocks of wood, sheets of rubber and aluminium, all of which the rays penetrated with ease. Lead stopped them — and so, he noticed with a jolt, did the bones of his own hand, which cast a shadow on the screen while the flesh around them barely registered. Not knowing what the rays were, he borrowed the mathematician's symbol for an unknown quantity and called them X-rays. The placeholder name stuck for good.
On 22 December 1895 he brought his wife, Anna Bertha, into the laboratory and asked her to hold her hand still on a photographic plate for around fifteen minutes. The developed image showed the bones of her fingers, dark and skeletal, with her wedding ring hanging loosely around one of them — the first X-ray photograph of the human body. The much-repeated story has Bertha recoiling from her own skeleton with the words "I have seen my death!" The quote reaches us secondhand and may well have been polished in the retelling, but it captures the shudder the pictures genuinely produced: for the first time in history, the living could inspect their own bones.
Röntgen delivered his paper, On a New Kind of Rays, to the Würzburg Physical-Medical Society on 28 December 1895, and the news travelled at a speed any modern press office would envy. Within weeks the image of Bertha's hand was appearing in newspapers around the world; within months doctors were using the rays to locate broken bones and lodged bullets. The craze had its absurd side — London firms advertised supposedly X-ray-proof underwear to the anxious — and its tragic one, because nobody yet understood the danger. Thomas Edison's assistant Clarence Dally, who for years tested tubes on his own hands, died of radiation-induced cancer in 1904, after which a shaken Edison abandoned X-ray work altogether.
The prize he would not cash in
What Röntgen did next is a large part of why he is remembered so warmly. He refused on principle to patent the discovery, insisting that his findings belonged to humanity and that no single firm should control them — a decision that let X-ray apparatus spread through the world's hospitals within a few years. When the first Nobel Prize in Physics ever awarded came to him in 1901, he donated the entire prize money to the University of Würzburg, skipped the customary Nobel lecture, and asked that the rays not be named after him. German usage ignored his modesty: to this day an X-ray image in German is a Röntgenbild, and röntgen is simply the verb for taking one.
His unworldliness came at a price. The hyperinflation that followed the First World War devoured his savings, and Röntgen died in Munich in 1923, close to poverty, while the industries his rays had spawned flourished around him. The honours have kept coming since: the old unit of radiation exposure is the roentgen, element 111 — first synthesised in 1994 — is officially roentgenium, and 8 November, the night of the glowing screen, is now marked each year as the International Day of Radiology.
Physics later revealed what he had stumbled on: X-rays are simply light of extremely short wavelength, energetic enough to slip through flesh and card alike. Whole sciences grew from them, from crystallography to radiotherapy, and the double-helix structure of DNA itself was teased out of an X-ray photograph. But the founding image of the field remains a domestic one — a woman's hand, a wedding ring, and the bones no one was ever meant to see.
Quiz nuggets
- Wilhelm Röntgen discovered X-rays on 8 November 1895 at the University of Würzburg, naming them after the mathematical symbol for an unknown.
- The first X-ray photograph of the human body, taken on 22 December 1895, showed the hand and wedding ring of his wife, Anna Bertha.
- Röntgen received the first ever Nobel Prize in Physics in 1901 and donated the entire prize money to the University of Würzburg.
- He refused to patent X-rays, and after Germany's post-war hyperinflation he died close to poverty in Munich in 1923.
- Element 111, roentgenium, and the roentgen unit of radiation exposure are both named in his honour.