Roentgen
NAME: Roentgen, Wilhelm Conrad
ACHIEVEMENT(S): X-rays
NICKNAME/ALIAS: also spelled Rontgen
DATE/PLACE OF BIRTH: 27 March 1845, at Lennep, Prussia [now Remscheid,
Germany]
DATE/PLACE/AGE AT DEATH: 10 February 1923, in Munich, Germany. Aged 77
DISCIPLINE: Physicist
FIELD: Physics
LANGUAGE: German
PARENTS: Friedrich Conrad Rontgen and Charlotte Constanze Frowein
SIBLINGS: None
SPOUSE: Anna Bertha Ludwig (d. 1919), married 1872
CHILDREN: One adopted child, Josephine Bertha (b. 1881)
EDUCATION: Institute of Martinus Herman van Doorn; Utrecht Technical School,
1862-64; Swiss Federal Institute of Technology, 1865-68; University of
Zurich, 1868-69
MAJOR WORK: 'Uber eine neue Art von Strahlen', 1898
LIFE AND TIMES:
At Zurich, Roentgen's genius was recognized by August Kundt, a German professor of physics, who encouraged him to follow graduate studies in physics rather than engineering.
Roentgen took Kundt's advice, and in 1869 he was awarded his doctoral degree for a thesis entitled "Studies on Gases" from the University of Zurich. Kundt then immediately hired Roentgen as his laboratory assistant. When in 1871 Kundt was offered the chair of physics at the University of Wurzburg, Roentgen accompanied him.
In 1879 Roentgen was appointed professor of physics at the University of Giessen, where he remained until 1888, turning down offers of the chair of physics at the universities of both Jena and Utrecht. At Giessen he published papers on his investigations into the nature of the relation between light and electricity, but also pyroelectricity, piezoelectricity, and the compressibility of liquids and solids.
His most significant contribution to physics during this period was, however, a continuation of research originally suggested by <continued work of> Maxwell's* theory of electromagnetism, which had predicted that the motion of a dielectric material (like a glass plate) within an electrostatic field (e.g. between two electrically charged condenser plates) would induce a magnetic current within the dielectric material.
During his last year at Giessen, Roentgen confirmed this effect, a phenomenon for which <theory confirmed by> Lorentz* suggested the name "Roentgen Current". Roentgen himself considered this a discovery of equal importance to that of X-rays, because it led to the theories of Lorentz, and Einstein and was the basis for modern theories of electricity.
In 1888, Roentgen returned to the University of Wurzburg as professor of physics and director of the university's Physical Institute, where he remained for the next 12 years. In 1894 he began research on cathode rays, which were then the subject of experimental research by many physicists.
Fundamental work had already been done in this field by others, beginning in 1853 when the French physicist Antoine-Philibert Masson had noticed that a high-voltage discharge between electrodes in a glass tube containing a gas at low pressure produced a purplish glow. In the 1870s, the English physicist <work related to> Crookes*, using an improved vacuum pump, achieved much lower pressures and found that, while the purple glow vanished, the glass walls of the tube fluoresced with greenish light.
Crookes demonstrated that rays were apparently coming from the negative electrode
(because a cross-shaped object placed in the tube cast a shadow on the opposite wall), and that the rays had substance and carried a negative electric charge. In 1878, Crookes proposed that the rays caused the fluorescence when they struck the glass walls and, since the negative electrode was called a cathode, the rays were named (by <work related to> Goldstein*) “cathode rays.”
Then, in the 1890s, the German physicist <work related to> Lenard* showed that cathode rays could penetrate a thin aluminium window in the tube and electrify the air immediately outside the window - a mystery that was clarified later when the English physicist <work related to> J.J. Thomson* demonstrated the nature of the particles in 1897, which became known as electrons.
Roentgen’s research took an unexpected turn on 8 November 1895 when, in order to observe the luminescence caused by cathode rays more clearly, Roentgen darkened his laboratory and enclosed his Crookes tube (without a Lenard window) within opaque black cardboard.
When he turned on the apparatus, he noticed that a screen covered with barium platinocyanide crystals, about a metre from the tube, began to glow. This was a great surprise, as Roentgen knew that cathode rays could travel no more than a few centimetres in air. What was causing the glow?
Roentgen spent the next seven weeks investigating this phenomenon, which he called “X (for unknown) -rays.” He found that its effect could be detected at great distances from the vacuum tube, suggesting that the radiation was very strong, and found that the radiation passed easily through some materials - like glass and wood - but was obstructed by other materials, like metals.
While holding a small lead disc between the tube and the screen, he noted that the lead seemed impenetrable but made the dramatic discovery that the bones in his hand produced a dark shadow surrounded by a lighter shadow of the soft tissues of his hand. He also discovered that the radiation was capable of exposing a photographic plate, which darkened after development where it had been struck by the rays.
On 22 December he brought his wife into the laboratory and made the famous X-ray photograph of her hand.
Within weeks, news of Roentgen's discovery had reached the popular press, and both scientists and the general public were immediately fascinated by the idea of seeing living skeletons.
Roentgen accepted the first Nobel Prize in physics, awarded to him in 1901, and gave the prize money to the University of Wurzburg for scientific research. Having determined the uses of the new rays for medicine and metallurgy, and having founded radiology, he left
further investigation of X-rays to others.
Between 1896 and 1911, <influenced> Cannon* invented the fluoroscope and barium meal, both soon used in every hospital in the world to diagnose gastric and duodenal ulcers and tumours of the digestive tract.
Meanwhile, in physics, Roentgen's discovery inspired the investigations of <influenced> Becquerel* which led (with the work of Pierre and <influenced> Marie Curie*) to the discovery of radiation and a revolution in atomic theory, while in 1912 <influenced> Laue* demonstrated X-ray diffraction using a crystal as a diffraction grating.
In 1899, shortly after declining the chair of physics at the University of Leipzig, Roentgen left Wurzburg and accepted the post of professor physics and director of the Physical Institute at the University of Munich. In 1920 he retired and moved to his country home in Weilheim, near Munich, where he died of cancer of the intestine.
ASSESSMENT: Roentgen’s research also included work on elasticity, capillary action of fluids, specific heats of gases, conduction of heat in crystals, absorption of heat by gases, and piezoelectricity.
EXTRA CONNECTIONS: He influenced the work of <influenced> Swinton*, <influenced> CTR Wilson*, and <influenced> Rutherford*
ONELINER: Wilhelm Roentgen, discoverer of X-rays
BIBLIOGRAPHY:
DSB, EB
Nitzke, W. Robert, The Life of Wilhelm Conrad Rontgen, Discoverer of the X Ray, Tucson: University of Arizona Press, 1971