Existence of a reflective layer was predicted in 1902 independently and almost simultaneously by the American electrical engineer
Arthur Edwin Kennelly (1861–1939) for which he received the 1947
Nobel Prize in Physics. Physicists resisted the idea of the reflecting layer for one very good reason; it would require
total internal reflection, which in turn would require that the speed of light in the ionosphere would be greater than in the atmosphere below it. Since the latter speed is essentially the same as the speed of light in vacuum (
c), scientists were unwilling to believe the speed in the ionosphere could be higher. Nevertheless, Marconi had received signals in Newfoundland that were broadcast in England, so clearly there must be some mechanism allowing the transmission to reach that far. The paradox was resolved by the discovery that there were two velocities of light, the
phase velocity and the
group velocity. The phase velocity can in fact be greater than
c, but the group velocity, being capable of transmitting information, cannot, by
special relativity, be greater than
c. The phase velocity for radio waves in the ionosphere is indeed greater than
c, and that makes total internal reflection possible, and so the ionosphere can reflect radio waves. The geometric mean of the phase velocity and the group velocity cannot exceed
c, so when the phase velocity goes above
c, the group velocity must go below it. In 1925, Americans
Gregory Breit and
Merle A. Tuve first mapped the Heaviside layer's variations in altitude. The
ITU standard model of absorption and reflection of radio waves by the Heaviside Layer was developed by the British Ionospheric physicist
Louis Muggleton in the 1970s. ==Etymology==