Edward Victor Appleton
After returning from active service in World War I, Appleton became assistant demonstrator in experimental physics at the Cavendish Laboratory in 1920. He was professor of physics at the University of London (1924–36) and professor of natural philosophy at Cambridge University (1936–39). From 1939 to 1949 he was secretary of the Department of Scientific and Industrial Research. Knighted in 1941, he received the 1947 Nobel Prize in Physics for his contributions to the knowledge of the ionosphere, which led to the development of radar.
For many years it had been postulated that there was a conducting layer in the upper reaches of the atmosphere. Marconi had been able to make his historic transatlantic transmissions; to achieve this the signals had to be "bent" (refracted) if they were to reach their destination. In 1902 Oliver Heaviside and A E Kennelly independently proposed the idea of their being a conducting layer that reflected radio signals.
In his work, Appleton had observed that the strength of the radio signal from a transmitter a on a frequency such as the medium wave band and over a path of a hundred miles or so was constant during the day but that it varied during the night. This led to him to believe that it was possible that two radio signals were being received. One was traveling along the ground, and another was reflected by a layer in the upper atmosphere. The fading or variation in strength of the overall radio signal received resulted from the interference pattern of the two signals.
To prove his theory, Appleton used the British Broadcasting Corporation (BBC) radio broadcast transmitter at Bournemouth, England. This transmitted a signal towards the upper reaches of the atmosphere. He received the radio signals near Cambridge, proving they were being reflected. By making a periodic change to the frequency of the broadcast radio signal he was able to measure the time taken for the signals to travel to the layers in the upper atmosphere and back. In this way he was able to calculate that the height of the reflecting layer was 60 miles above the ground.
In 1974 the Radio and Space Research Station was renamed the Appleton Laboratory in honour of the man who had done so much to establish the UK as a leading force in ionospheric research, and had been involved with the station first as a researcher and then as secretary of its parent body, the Department of Scientific and Industrial Research. His name is perpetuated today in the Rutherford Appleton Laboratory and Appleton Tower in Edinburgh.
- Sir Edward Victor Appleton
- Sir Edward Appleton A summary of the life and work of Sir Edward Appleton and his contribution to radio science.