Feature

He Named Them X Because He Did Not Know What They Were

By , Tech Cheat Codes Team

Published 6 min read

Photo: German physicist Wilhelm Conrad Röntgen in a dark suit, photographed by Nicola Perscheid in 1915.
Image: Nicola Perscheid, 1915 (public domain), via Wikimedia Commons; resized and placed on a blurred background
On this page · 2 sections
  1. Weeks of nights, then a plate
  2. References

One hundred thirty-one years ago today, on the evening of Nov 8, 1895, Wilhelm Conrad Röntgen stood in a darkened physics lab in Würzburg with a cathode tube wrapped so tight in thick black carton that no visible light could leak. He switched on the discharge. Across the room — as far as two meters in later checks — a paper screen coated with barium platinocyanide lit up apple-green anyway.

That should not have happened. Cathode rays, as everyone understood them, did not travel that far through air. Something else was coming out of the tube. Röntgen moved books, wood, and lead between the carton and the screen. Soft things barely dimmed the glow. A thin lead sheet stopped it cold. He did not know what the rays were, so he named them the way an algebraist names a blank: X-rays.

Weeks of nights, then a plate

He barely left the institute for the next six weeks, working almost alone and telling almost no one what he had found. He tested photographic plates through their paper wrappers. He watched shadows of metal weights and of his own hand on the fluorescent board. Bones showed up as darker strokes than flesh.

The famous radiograph was not that November night. On Dec 22, 1895 — six weeks after the glowing screen — he asked Bertha to hold her left hand still over a photographic plate while the tube ran. When the plate developed, her finger bones stood out as dark shadows inside the fainter flesh, and on one finger sat the black oval of her wedding ring.

Photo: 1895 radiograph of Anna Bertha Röntgen's left hand, showing finger bones and a wedding ring. Hand mit Ringen — Anna Bertha Röntgen's left hand, Dec 22, 1895. Wilhelm Röntgen (public domain), via Wikimedia Commons.

Six days later he handed the Würzburg Physical-Medical Society a short paper titled Über eine neue Art von Strahlen — On a New Kind of Rays. By early 1896 clinics were already making bone portraits.

The line that has come down with the image is Bertha's — she had seen her own death. He took no patent on the rays. In 1901 he collected the first Nobel Prize in Physics.

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References