Several scientists made X-rays by accident before Röntgen noticed what they were
In 1890 two Pennsylvania experimenters developed photographic plates and found mysterious disks on them, shrugged, and moved on. Six years later they realised they had taken an X-ray picture. They were not alone: glowing tubes had been leaking the invisible radiation for decades before anyone stopped to ask why.
X-rays sit between ultraviolet light and gamma rays on the electromagnetic spectrum, with wavelengths from about 10 nanometres down to 10 picometres. They pass through wood, brick and flesh, which is why they reveal broken bones, but they also ionise atoms, so exposure can damage DNA and cause cancer.
The trail of near misses is long. William Morgan described a glow from an electrified, partly emptied glass tube to the Royal Society in 1785, almost certainly X-rays. Philipp Lenard, from 1888, fired cathode rays through a thin aluminium window and found something that fogged photographic plates. The Stanford physicist Fernando Sanford may have caught X-rays while photographing coins by spark light, and Nikola Tesla puzzled over damaged film in his lab in 1894.
Wilhelm Röntgen was the one who pursued it. On 8 November 1895, working with a tube wrapped in black cardboard, he saw a screen coated with barium platinocyanide glowing faintly green about a metre away. The rays passed through cardboard, then through books on his desk. He called them X, for unknown, and submitted his first paper on 28 December. A picture of his wife Anna Bertha's hand became the first X-ray image of a human body part; seeing it, she reportedly said she had seen her death. Colleagues wanted to name the rays after him, over his strong objections, and many languages, German among them, still do. He won the first Nobel Prize in Physics.
The news travelled astonishingly fast. His biographer Otto Glasser counted 1044 articles about the rays in 1896 alone. By 11 January that year John Hall-Edwards in Birmingham had imaged a needle lodged in a colleague's hand, and in May Thomas Edison produced the first mass-produced live viewer, later called the fluoroscope. Early carelessness had a cost: one of Edison's glassblowers, Clarence Dally, became in 1904 the first known death attributed to X-ray exposure.
Source: X-ray
