Edison's second great contribution was the Edison Effect. The Edison Effect actually was an accidental byproduct of Edison's invention of the incandescent light bulb in 1879. In 1883, while tinkering with ways to make his bulb last longer, he discovered that the flow of electrons inside a vacuum could be controlled by electronic and magnetic fields.

Since Edison was essentially a highly imaginative mechanic, not a university-educated physicist, he didn't quite understand the consequences of the effect nor could he envision the practical application of his discovery. He simply patented what later scientists would call thermionic emission and forgot about it.

In fact, what Edison had discovered was a precursor to the vacuum tube, the basis of every piece of electronics invented, manufactured and sold during the next 65 years, and still the basis of the cathode ray tube used in TVs and computer monitors.

The reason Edison's electron tube was useless at the time was that no one knew that radio waves existed. In 1872, Scottish physicist John Clerk Maxwell theorized that electromagnetic waves existed. But it wasn't until 1888 that German physicist Heinrich Hertz detected and produced electromagnetic waves. The peripatetic Tesla described the basics of radio as a potential carrier of electrical signals and even power in a scientific journal article, a series of lectures before several scientific organizations and the first demonstration of radio in St. Louis, all in 1893.

Once the existence of radio waves was proven and demonstrated, Italian physicist Guglielmo Marconi also realized that they could transmit signals the way a wire carried electricity. In 1896, Marconi went to England and set up the Wireless Telegraph and Signal Co. In St. John's, Newfoundland, Canada, on December 12, 1901, he received the Morse letter "S" transmitted from Poldhu, Cornwall, England, the first wireless signal to cross the Atlantic Ocean.

Transmitting dots and dashes was, however, quite a long way from transmitting voice. Twenty years after Edison discovered his effect, English scientist John Ambrose Fleming, working for Marconi, put the effect to practical use, inventing the diode vacuum tube, used in Marconi's first transatlantic transmission.

In 1912, American inventor Lee deForest took the vacuum tube concept a step further. He created an amplifying vacuum tube that he called the audion tube, the essential component in what would become known as radio.

While the development of transmitting technology progressed, Canadian engineer and inventor Dr. Reginald Fessenden was figuring out ways to transmit something more useful than telegraph code. In December 1900, he succeeded in transmitting his voice a mile; by 1904 he had discovered amplitude modulation (AM).

In 1906, Fessenden convinced several ships off the coast of Massachusetts to install AM receivers. On Christmas Eve, Fessenden played the violin, read from the Bible and played Gramophone records to become the first "DJ." His transmissions, received by operators as far away as Virginia, became the first true radio broadcast. Wireless operators became folk heroes. They included a 21-year-old Marconi telegraph operator named David Sarnoff, who made himself famous as the man who first broadcast news of the Titanic disaster in April 1912 (although his heroic claims were disputed later).

A year later, 24-year-old Edwin Howard Armstrong patented an improved receiver that he had tinkered with while attending Columbia University. In 1918, he invented the super heterodyne radio receiver, the principle that is still used in every radio device made today.