November 2, 1920: KDKA, the first commercial radio station in the United States, goes on the air in Pittsburgh. July 1, 1941: WBNT, the first commercial TV station, starts broadcasting. April 3, 1973: Martin Cooper of Motorola makes the world’s first cell phone call.
Radio has transformed society three times, not to mention giving birth to the entire field of electronics. Perhaps no invention of modern times has delivered so much while initially promising so little. When radio arrived at the end of the 19th century, few thought that “wireless” communications, in which intangible signals could be sent through the air over long distances, would be competitive in a world dominated by the telegraph and telephone. The early inventors studied the work of Scottish physicist James Clerk Maxwell, who had formulated a set of equations — “Maxwell’s equations” — that expressed the basic laws of electricity and magnetism, but as a purely theoretical exercise in understanding how nature works. His equations explained light as one form of electromagnetic radiation and predicted that there should be many other forms, invisible to the human eye. In the 1880s the German physicist Heinrich Rudolf Hertz validated Maxwell’s laws by detecting radio waves — fundamentally similar to light but with wavelengths a million times longer. “Maestro Maxwell was right,” Hertz said, but he concluded that the existence of these other waves was “of no use whatsoever.”
