Who invented radio? The answer lies in how you define "radio" or "wireless." It has something to do with whether you prefer an elite or populist view of historical causation. Was radio, however defined, the outcome of a few brilliant minds: of irreplaceable genius overcoming mind-boggling obstacles of physics and engineering? Or was it the result of many hands, minds, hearts, pocketbooks, and voices, all of which contributed to the invention, innovation, organization, regulation, content, sale, and reception of a technology that did not exist a little over a hundred years ago? These pages will not answer the question above, but it should provide you with some food for thought.
1862: Briton James Clerk Maxwell proposes that electrical and magnetic energy travel through space in waves at the speed—or more accurately, the velocity—of light. Maxwell’s theoretical unification of three basic forces of nature is considered the greatest accomplishment of nineteenth-century physics and the starting point for modern science and technology.
1875: Thomas Edison first observes what became known as the "Edison Effect," or thermionic transmission. In a vacuum, a current of electricity will flow through space from a negatively charged filament (the cathode) to a positively charged metal plate (the anode). When William J. Hammer, an engineer working for Edison, observes it again in 1883, Edison patents the effect in a device he calls an electrical indicator.
1887: German Heinrich Hertz confirms experimentally that electrical energy travels at the speed of light. Hertz described the imperceptible medium through which the energy travelled as the "ether."
1892: Briton Sir William Crookes writes "Some Possibilities of Electricity" in Fortnightly Review (vol. 51, pp. 174-6), suggesting that people could communicate using electric waves of specific wavelength on tuned equipment, or "telegraphy across space."
1895: In May, Russian Alexander Popov begin transmitting wireless electrical signals through the air over 500 meters; independently of Popov, Italian Guglielmo Marconi accomplishes the same feat three months later. By the end of the year Marconi can send signals over a mile (1.6 kilometers).
1896: Marconi, building on inventions and insights by Hertz, Nicola Tesla, Edouard Branly, John Stone Stone, Lodge, and others, applies for first patent specifically for wireless telegraphy technology and begins process of starting a communications company, founded in 1897 in Great Britain.
There is considerable debate about the relative pride of place of invention, with attention paid to Tesla as the inventor of radio among many other technologies. You can read the majority and minority opinions to the 1943 U. S. Supreme Court decision, 320 U.S. 1, disallowing many of Marconi’s early patent claims by looking it up at findlaw.com. Antenna, newsletter for historians of communications technology, contains a thoughtful analysis of how to read this decision. Few people, much less Supreme Court justices, can agree on what invention is "new, useful, and not obvious to one skilled in the art."
1897: Briton J. J. Thomson hypothesizes the existence of sub-atomic-sized "corpuscles," or electrons, based on studies using cathode-ray tubes.
1904: Briton John Ambrose Fleming invents a vacuum-tube diode, or thermionic valve, using a cathode and anode. The latest scholarship casts doubt on the connection to the Edison Effect or its intended use.
1906: In the same months that David Sarnoff began work at the Marconi Wireless Telegraph Company of America, Lee De Forest invents the three-element electron, or vacuum, tube in New York City. His "audion," as he called his invention, was at first little more than the cathode and anode that Fleming put in a vacuum tube to create a rectifier and small amplifier of received electrical signals. As is apparent in his paper and the audience’s responses at meetings of the the New York and Philadelphia sections of the American Institute of Electrical Engineers, no one understood how it worked. Nonetheless, in November, by adding a wire grid between the cathode and anode, De Forest enabled the amplification of an electrical signal applied to the cathode, whether it was received or transmitted through the circuit. The audion led to the creation of the electronics industry over the next fifty years.
In addition, that December 24, Canadian Reginald Fessenden broadcast the first radio program using a "continuous wave" of electromagnetic energy. He had begun demonstrating the technique in 1901, but this transmission from Brant Rock on Massachusetts’s Cape Cod used Ernst Alexanderson’s 10,000 cycle-per-second (hertz, or hz) alternator. It carried the sounds of his and his wife’s voices and music from his violin to shipboard wireless operators used to hearing the dots and dashes of telegraph codes.