born May 18, 1850, London, Eng.
died Feb. 3, 1925, Torquay, Devon
English physicist.
In 1902 he predicted the presence of the ionosphere . Since Arthur Kennelly (1861–1939) had made a similar prediction, the ionosphere was long known as the Kennelly-Heaviside layer. Heaviside's work on telephone theory made long-distance service practical. In his Electromagnetic Theory (1893–1912) he postulated that an electric charge would increase in mass as its velocity increased, anticipating one aspect of Albert Einstein 's special theory of relativity. He also developed the system of mathematical transforms known as Heaviside calculus.