Thomson on "ether"

William Thomson (later Lord Kelvin) wrote the following note in 1887. At this time, of course, the ether was a firmly established concept. However Michelson had carried out an experiment in 1881 which he claimed showed the ether did not exist:

The result of the hypothesis of a stationary ether is shown to be incorrect, and the necessary conclusion follows that the hypothesis is erroneous.

Thomson asked Michelson to repeat the experiment and, quite coincidently, 1887 was the year when he reported that he had again failed to detect an ether. The note by Thomson justifies his use of 'ether' in place of 'luminiferous ether'.

The sun warms and lights the earth by wave motion, excited in virtue of his white-hot temperature, and transmitted through a material commonly called the luminiferous ether, which fills all space as far as the remotest star, and has the property of transmitting radiant heat (or light) without itself becoming heated. I feel that I have a right to drop the adjective luminiferous, because the medium, far above the earth's surface, through which we receive sun-heat (or light), and through which the planets move, was called ether 2000 years before chemists usurped the name for "sulphuric ether," "muriatic ether," and other compounds, fancifully supposed to be peculiarly ethereal; and I trust that chemists of the present day will not be angry with me if I use the word ether, pure and simple, to denote the medium whose undulatory motions constitute radiant heat (or light).


JOC/EFR April 2007

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