An unfortunate experiment, Hertz and the nature of cathode rays

In making sense of a complicated set of scientific facts, or claimed facts, it often happens that one turns out to be wrong, but it is rare for the villain to be an experiment by as great a physicist as H. Hertz, the first man to prove experimentally that electromagnetic waves exist and can be propagated in free space. The experiment in question had nothing to do with these waves, it concerned the nature of cathode rays. These are one of the many strange phenomena which occur when electricity is made to pass through highly rarificd gases. When for example the air in a glass tube is reduced to a density about 1/ 3000 of the normal an electric current can be passed through it with far less than the voltage which would be needed if most of the air had not been pumped out, though if the density is reduced by still another factor of io or so it again becomes harder to pass a current. Some gas is needed, in fact, but not too much. Soon after the stage when the density allows the discharge to pass most easily the brilliantly coloured display of lights in the tube begins to show a new feature, called the cathode rays. These get their name because they come from the (conventionally) negative of the two terminals which lead the current in and out, which Whewell, then Master of Trinity College, Cambridge, called ‘cathode’ after Faraday had asked him for suggestions.* They appear as straight lines diverging from points on the cathode and show up as phosphorescence when they reach the glass walls. This phosphorescence gets stronger as more gas is pumped out but the lines in the gas get fainter

Cathode · Current (fluid) · Electrical engineering · Electricity · Engineering physics · Epistemology · Faraday cage · Hertz · Magnetic field · Nothing · Optics · Physics · Quantum mechanics · Engineering · Experimental and Theoretical Physics Studies · Philosophy

• Heinrich Hertz — A Bibliography

  Alfred Nordmann•Heinrich Hertz: Classical…•1998

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• H. Hertz

  Open Access•Giora Hon•Studies in History and Philosophy…•1987

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