100 years ago today 32 year-old Edward Appleton was able to experimentally confirm the existence of the Heaviside Layer[1] and its height, with the help of the BBC Bournemouth station 6BM. This confirmation that radio waves could "bounce off" the upper atmosphere under the right circumstances opened the way for true worldwide radio communication using short waves -- previously any frequency higher than today's medium-wave band had been considered "useless".

[1] The term "ionosphere" was not coined until two years later, by Scottish physicist Robert Watson-Watt.

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