Technology & Medicine › Electric age › Electric power and the grid
X-rays (Röntgen)
November 8, 1895· Invention or discovery· Medicine & surgery
Well documentedSolid records, physical evidence or scientific consensus.
Invisible rays that pass through flesh but not bone, discovered by Wilhelm Röntgen in 1895 and used within weeks to image the body.
See it on the Technology & Medicine map →How it works
In Würzburg, Germany, Röntgen ran high voltage through a glass vacuum tube covered in black card and saw a nearby fluorescent screen glow. Unknown rays were passing through the card; he called them 'X' for unknown. On December 22 he photographed his wife Anna Bertha's hand, bones and ring showing. His paper appeared that month, and by early 1896 doctors were using X-rays to find bullets and broken bones. Early users suffered burns before the dangers were understood.
Why it mattered
For the first time doctors could see inside a living body without cutting. X-rays later revealed the structure of crystals and DNA and led to CT scanning.
How we know
Röntgen's paper 'On a New Kind of Rays' (December 1895); the famous hand radiograph; his 1901 Nobel Prize, the first ever in physics; reports of X-ray units in hospitals during 1896.
Still unknown or debated
Others, including Arthur Goodspeed in 1890, may have made X-rays without recognizing them. Röntgen asked that his papers be burned after his death, so details of his discovery are uncertain.
Inside this (1)
Connections (6)
▸Photography recorded the first images made by X-rays (Röntgen)Well documented
The connection
Röntgen first saw X-rays as a glow on a fluorescent screen, but to study and share them he used photographic plates, which X-rays darken much as light does. The plate image of his wife's hand made the discovery famous within weeks. Film stayed the main way to record X-ray images until digital detectors spread from the 1980s.
When and how
Würzburg, Germany, December 22, 1895: Röntgen photographed Anna Bertha Röntgen's hand in a 15-minute exposure; prints reached scientists in early January 1896.
How we know
The original radiograph survives, and Röntgen's paper describes the photographic plates; newspapers in Vienna and London printed the images in January 1896.
Debates and open questions
In 1890 Arthur Goodspeed in Philadelphia accidentally made an X-ray photograph without knowing it; why fogged plates went unexplained in other labs is unclear.
▸X-rays (Röntgen) led, via Becquerel, to Marie Curie and radioactivityWell documented
The connection
Röntgen's X-rays seemed to come from the glowing spot on his tube, so Henri Becquerel tested whether glowing uranium salts gave off similar rays. In 1896 he found uranium emitted rays even in the dark. Marie Curie picked these 'Becquerel rays' for her doctorate in late 1897, which led to radioactivity, polonium and radium.
When and how
Paris, 1896–98: Becquerel at the Natural History Museum in February–March 1896; Marie and Pierre Curie at the School of Industrial Physics and Chemistry.
How we know
Becquerel's 1896 reports to the French Academy of Sciences, Curie's lab notebooks and her 1903 thesis trace the sequence directly.
Debates and open questions
Becquerel's discovery was partly luck: cloudy weather made him store plates with uranium in a drawer. Whether he expected to see an image when he developed them is debated.
▸X-rays (Röntgen) were combined with computers in the CT scannerWell documented
The connection
An ordinary X-ray squashes the whole body onto one flat picture, so organs overlap. The CT scanner sends thin X-ray beams through the body from hundreds of angles and measures how much each is absorbed. A computer then works out the density of each tiny block, building a clear cross-section slice.
When and how
Röntgen in Würzburg, Germany, 1895; Hounsfield at EMI's laboratories in Hayes, near London, from 1967, with the first patient scanned in Wimbledon in October 1971.
How we know
Hounsfield's 1973 paper and 1979 Nobel lecture describe an X-ray tube and detectors rotating around the head; CT density is still measured in 'Hounsfield units.'
Debates and open questions
The underlying mathematics had been solved earlier, by Johann Radon in 1917, but Hounsfield and Cormack each worked without knowing it; this is a footnote, not a dispute.
▸X-rays (Röntgen) were used in crystallography by Rosalind Franklin and Photo 51Well documented
The connection
Röntgen's X-rays have wavelengths about as small as the spacing between atoms. In 1912–13 Max von Laue and the Braggs showed that crystals scatter X-rays into patterns revealing how their atoms are arranged. Franklin, an expert in this X-ray crystallography, applied it to DNA fibers to reveal their shape.
When and how
Würzburg, 1895 (Röntgen); Munich, Leeds and Cambridge, 1912–13 (von Laue; William and Lawrence Bragg); King's College London, 1951–53 (Franklin).
How we know
Franklin's notebooks and papers detail her X-ray methods; Lawrence Bragg, a founder of the technique, headed the Cambridge lab where Watson and Crick worked.
Debates and open questions
Did Franklin's insistence on data before models slow her, or protect her from errors like Watson and Crick's failed 1951 model? Opinions differ.
▸X-rays (Röntgen) supplied, via crystallography, the training data of AlphaFold protein structure predictionWell documented
The connection
X-ray wavelengths are about the size of atoms, so beams passing through a crystal scatter into patterns that reveal how atoms are arranged (X-ray crystallography). Over decades scientists used it to solve most of the 170,000-plus protein structures in the public Protein Data Bank. AlphaFold learned to predict shapes by studying those structures.
When and how
Max von Laue and the Braggs, 1912–13; Kendrew and Perutz's first protein structures at Cambridge, 1958–60; DeepMind trained AlphaFold in London on Protein Data Bank entries before 2020.
How we know
DeepMind's papers state AlphaFold was trained on Protein Data Bank structures, the large majority determined by X-ray crystallography.
Debates and open questions
Because AlphaFold learned largely from crystals, it may favor rigid, crystal-friendly shapes and be less reliable for flexible proteins.
▸Electric power and the grid powered the tubes that produced X-rays (Röntgen)Well documented
The connection
X-rays come from fast electrons slamming into metal, which takes very high voltage. Röntgen's tube was driven by a Ruhmkorff induction coil, which turns low-voltage current into high-voltage sparks. As grids spread, mains-powered transformers let hospitals run stronger, steadier X-ray machines, especially with William Coolidge's 1913 hot-cathode tube.
When and how
Würzburg, Germany, 1895, using an induction coil and a Hittorf–Crookes tube; Coolidge's tube at General Electric in Schenectady, New York, 1913.
How we know
Röntgen's paper describes his apparatus; GE patents and hospital equipment records document mains-powered X-ray units from the 1910s.
Debates and open questions
Little is debated about the link; how many early operators were injured by uncontrolled doses before radiation-safety standards arrived in the 1920s is unknown.