Wilhelm Röntgen
Wilhelm Röntgen observes the unknown radiation he called X-rays
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Original prompt & settings (JSON) ↗A screen glowed even though Röntgen had wrapped the discharge tube so that visible light could not escape — reportedly nine feet away.
8 November 1895: a glow at nine feet
On 8 November 1895, while experimenting in his Würzburg laboratory with electrical discharges in an evacuated tube, Wilhelm Conrad Röntgen observed a fluorescent screen glowing at a distance from the apparatus — reportedly nine feet, far beyond the known range of cathode rays in air.
The glow persisted even though the tube was screened from visible light, leading Röntgen to infer that an unknown, invisible radiation was leaving the tube and passing through the covering. He labelled it with the algebraic symbol for an unknown: X.
Weeks alone with the rays
Röntgen began systematic experiments on the penetrating rays, isolating himself for weeks of follow-up work testing how they passed through materials and affected fluorescent screens and photographic plates.
The initial evidence was fluorescence on a coated screen; he did not immediately understand X-rays as electromagnetic radiation. On 28 December he submitted “On a New Kind of Rays” to the Würzburg Physical-Medical Society.
What the traditional date can carry
8 November is the conventionally commemorated discovery date and is supported by major scientific institutions, but the detailed chronology was reconstructed later: Röntgen reportedly described finding something new after working for several days near the end of October, and his laboratory notes were not preserved.
The celebrated radiograph of his wife Anna Bertha's hand belongs to 22 December, roughly six weeks after the first glow. Researchers before him may unknowingly have produced similar effects; what he did was recognize that the glow revealed a new radiation and investigate it systematically.
Sources
Researched 23 Aug 2026 5 sources 3 audit passes Traditional date
How this was checked
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Traditional date. This date is the conventional one, not one fixed by a contemporary record.
What the sources leave uncertain
- 8 November is the conventionally commemorated discovery date and is supported by major scientific institutions, but the detailed chronology was reconstructed later. Röntgen reportedly described finding something new after working for several days near the end of October, and his laboratory notes were not preserved.
- Institutional sources conflict over whether the famous hand radiograph was made on 8 November. The Science Museum Group and specialist historical accounts date Anna Bertha’s hand image to 22 December; that better-supported date is used here.
- The exact tube is variously described as a Crookes, Hittorf, or Lenard-type tube in secondary accounts.