Perhaps the greatest theoretical achievement of
physics in the 19th century was the discovery of
electromagnetic waves. The first hint was an
unexpected connection between electric phenomena
and the velocity of light.
About 150 years ago, James Clerk Maxwell, an English
scientist, developed a scientific theory to explain
electromagnetic waves. He noticed that electrical fields
and magnetic fields can couple together to form
electromagnetic waves. Neither an electrical field (like
the static which forms when you rub your feet on a
carpet), nor a magnetic field (like the one that holds a
magnet onto your refrigerator) will go anywhere by
themselves. But, Maxwell discovered that a
CHANGING magnetic field will induce a CHANGING
electric field and vice-versa.
An electromagnetic wave exists when the changing magnetic field causes a
changing electric field, which then causes another changing magnetic field,
and so on forever. Unlike a STATIC field, a wave cannot exist unless it is
moving. Once created, an electromagnetic wave will continue on forever
unless it is absorbed by matter.
After Maxwell and Hertz, the next physicist who
continued with the discovery of more developed
magnetic waves, was Guglielmo Marconi.
The Italian physicist began his experiments when he was
barely 20, building on Heinrich Hertz's discovery of radio
waves in 1888. In 1895 Marconi transmitted
recognizable electronic signals from his family home in
Pontecchio to a vertical raised antenna more than a mile
away. As radio transmission of telegraph messages and,
later, spoken words became more common and popular.
Marconi also had the first transatlantic Morse code
transmission from England to Newfoundland through
Fessenden's most notable
achievements include the first audio
radio transmission in 1900, the first
two way transatlantic transmission in
1906 and the first broadcast of
entertainment, also in 1906. Many of
these were well ahead of their time,
and showed his insight, not only into
the technical aspects of radio, but also
the commercial elements as well.