When Guglielmo Marconi (1874-1937) made his remarkable transatlantic Morse code transmission on December 11, 1901, the world was stunned. Several experts had said such a thing was impossible.

Radio waves, like light waves, are a part of the electromagnetic spectrum. Like light waves, they should travel in a straight line, making their transmission beyond the curvature of the earth impossible. At the time it was believed that transmission as far as 180 miles (300 km) was the absolute limit. Yet Marconi had been successful; the question now was why. Arthur Kennelly (1861-1939) and Oliver Heaviside (1850-1925) had theorized that the upper atmosphere, or ionosphere, might contain a layer of charged particles that could reflect radio waves. The existence of a Kennelly-Heaviside layer was ultimately proven by Edward Appleton. He was born on September 6, 1892, at Bradford, Yorkshire. After graduation from Cambridge, he served as a radio officer with the Royal Engineers in World...