X-ray of an Australian Sole

X-ray vision

28 July 2022

A major scientific discovery of the late 19th century allowed a new perception of invisible interiors

To celebrate National Science Week, we're travelling back in time to explore the history of X-rays. 

German physicist Wilhelm Röntgen discovered X-rays on 8 November 1895, when he was studying the discharges observed by passing an electric current through a cathode ray tube. He was surprised to observe fluorescence outside the tube on a nearby screen, caused by unknown rays, which he called ‘x’ rays: ‘x’ in mathematics denoting unknown. He was able to see the bones of his hand when it was placed between the tube and the screen.

X-rays were later understood to be a form of electromagnetic radiation, similar to light and radio waves. Röntgen’s was one of the great scientific discoveries of the mid-1890s, together with radioactivity and the electron.

The first X-ray photograph, by Röntgen, of his wife’s hand with her wedding ring, was published in a Vienna newspaper in January 1896. As X-rays could pass through soft tissue, suddenly the physical interior of the human body was revealed without dissection. Photographic images provided critical visible evidence for scientists, doctors and the public.

News of the discovery travelled quickly to scientists around the world, and captured the public’s imagination, fed by numerous newspaper articles and demonstrations. In Sydney, Richard Threlfall, Professor of Physics at the University of Sydney, was soon giving journalists and special interest groups demonstrations of the new rays.

On 19 June 1896, at a special meeting of the Medical Section of the Royal Society of New South Wales, held in the physics lecture room at the University of Sydney, Threlfall gave a lecture and demonstration on ‘The rays of Röntgen and their practical application’. One of his exhibits was of a ‘lost’ bullet in a bullet wound on an arm. Attendees were invited to X-ray their own hands. The physical dangers of high-energy radiation only gradually became understood as early experimenters suffered from exposure, some dying of X-ray burns.

Today, X-ray technology is a key analysis tool for museums in expanding their knowledge of objects. The Nicholson Collection has used X-rays to study ancient mummified remains as well as sculpture and ceramics. Taxidermied animals from the Macleay Collections have revealed their wire support frames when scanned at the University’s Veterinary Clinic.

Now the Chau Chak Wing Museum works closely with Sydney Analytical, one of the University’s core research facilities, with other analytical tools that rely on X-rays, including X-ray fluorescence (XRF) spectroscopy. XRF enables investigation of the elemental composition of objects, allowing them to be scanned and studied without leaving the building. Sophisticated 2D XRF mapping, at a micrometer spatial resolution, has been used to begin investigating the ‘lost’ image on a daguerreotype portrait by mapping the distribution of mercury to reveal the image.

Röntgen’s rays changed our perception of our body and interior structures forever.

Jan Brazier is Curator, History, Chau Chak Wing Museum

This article was first published in issue 28 of Muse Magazine, April 2022.