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1995 One hundred years ago ....

In 1895, exactly one hundred years, ago, a chance discovery in Würzburg, Germany, marked the dawn of a new science - subatomic physics. Other discoveries and new insights followed quickly. Apart from interruptions for two World Wars, this rapid succession of breakthroughs continued for 88 years. A new series of occasional articles in the CERN Courier will look back to what was happening one century ago.

In Würzburg on 8 November 1895, Wilhelm Conrad Röntgen became an immortal legend. Interested in the effects of ultra-violet radiation, he covered a cathode-ray discharge tube with black paper and darkened the room. With the glow from the tube hidden, Röntgen was surprised to see a fluorescent screen two metres away light up. For several weeks, Röntgen hid in his laboratory, finding out more about the mysterious penetrating 'X' rays, produced when the cathode rays hit the end of the discharge tube.

Since the time of Faraday, the glow produced in an evacuated tube when an electric current was passed through had intrigued physicists and entertained the public. Nobody understood what these cathode rays were. William Crookes in the UK, who had narrowly missed making the Röntgen discovery, surmised they were a new 'fourth state' of matter. Some scientists said the phenomena were due to radiation, others said particles.

In 1895, a young physics student named Ernest Rutherford arrived in Britain from New Zealand with a scholarship for further study. The scholarship, awarded to a New Zealand student only once every few years, had initially been given to a young chemist, but who decided at the last minute to get married and stay in New Zealand. The scholarship passed to Rutherford, who, thanks to a change in regulations, was able to use it at the Cavendish Laboratory in Cambridge, under J.J. Thomson.

In New Zealand, Rutherford had carried out experiments on radio telegraphy. He took his transmitter to Britain and at Cambridge continued his pioneer investigations. In 1895, Guglielmo Marconi was carrying out his first experiments on radio telegraphy in Bologna, but according to J.J. Thomson, it was Rutherford who held the world record for radio telegraphy transmission at that time.

On learning about the discovery of X-rays, J.J. Thomson plunged into this branch of research, using Rutherford as his assistant, who appeared to take the abrupt change in research topic in his stride. Whatever the loss for radio telegraphy, it became a gain for fundamental physics: Rutherford earned the Nobel chemistry prize in 1908 for his work on radioactivity. The following year Marconi shared the physics prize for his work on radio telegraphy.

Also at the Cavendish Laboratory in 1895, Charles T.R. Wilson began the study of cloud formation which led to his development of the cloud chamber, the pioneer detector of subnuclear physics.

Light and other electromagnetic radiation was believed to propagate through some kind of universal medium - the ether - filling all space. In 1887 the Michaelson-Morley experiment had shown that light always propagates at the same speed, irrespective of the velocity of its source. In 1895 George Fitzgerald in Dublin and Hendrik Lorentz in Leiden pointed out how this could be explained if moving bodies contracted along their direction of motion. Also concerned about these matters was the young Albert Einstein, at school in Aarau, Switzerland. In 1895 he wrote an essay 'On the examination of the state of the ether in a magnetic field', which was never published. In Berlin, Max Planck, who had succeeded Kirchoff in 1889, and in Vienna, Ludwig Boltzmann, who had succeeded Stefan in 1894, were were among those looking hard at the physics standard model of the time - thermodynamics.

In London in 1895 William Ramsey was analysing the gases emitted by minerals and detected traces of helium, an element which had been seen in solar spectroscopy some thirty years previously. In 1904, Ramsey was awarded the Nobel Chemistry Prize for his epic work on the inert gases.

Paris in 1895 was the scene of many interesting developments: Jean Perrin showed that cathode rays carried negative electric charge, settling once and for all the long-standing controversy whether cathode 'rays' were particles or radiation; a young Polish student named Maria Sklodowska married her Professor, Pierre Curie, after seeing a demonstration of Edison's massive 0.5 tonne 'kinetoscope', Auguste and Louis Lumière developed the lightweight cinématographe moving-picture projector and gave its first demonstration; and Louis Pasteur died.

Reproduced by permission from the CERN Courier (October 1995), 35, 21-22.
7th Nov. 1995 - Crystallographers Online - Copyright © International Union of Crystallography