Radio waves are produced by electrons when they are agitated. The radio band of the electromagnetic spectrum is from 100 kilometers down to 0.1 centimeter.
All objects in the universe give off radio waves, as all objects are above absolute zero (-459ºF). Radio telescopes are one of the main tools used by astronomers today. They have given us a great deal of the information we now have about the universe. By analyzing the radio waves given off by celestial objects, scientists have been able to determine features, such as the surface temperature, of many planets.
In addition to naturally occurring radio waves, there are many forms of manmade radio waves.
In 1886, an American dentist, Mahlon Loomis, sent the first wireless telegraphy between two kites.
In 1893, Nikola Tesla, in St Louis, Missouri, demonstrated wireless radio signals and filled a number of patents.
Guiglielmo Marconi used Tesla’s patents and began to develop a radio system in 1895. He was the first to send a telegraph signal (a form of radio wave) in 1896. In December 1901, Marconi successfully conducted an experiment in which the first transatlantic radio signals were sent and received. The first broadcast of the human voice took place in 1906 in Massachusetts.