The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history.
Origins and developments Although development of the first radio wave communication system is attributed to Guglielmo Marconi, his was just the practical application of 80 years of scientific advancement in the field including the predictions of Michael Faraday, the theoretical work of James Clerk Maxwell, and the experimental demonstrations of Heinrich Rudolf Hertz.
1780–1784: George Adams notices sparks between charged and uncharged conductors when a Leyden jar was discharged nearby. 1789–1791: Luigi Galvani notices a spark generated nearby causes a convulsion in a frog's leg being touched by a scalpel. In different experiments, he notices contractions in frogs' legs caused by lightning and a luminous discharge from a charged Leyden jar that disappeared over time and was renewed whenever a spark occurred nearby. 1820: Hans Christian Ørsted discovers the relationship between electricity and magnetism in a very simple experiment. He demonstrates that a wire carrying a current was able to deflect a magnetized compass needle. 1831: Michael Faraday begins a series of experiments in which he discovers electromagnetic induction. The relation was mathematically modeled by Faraday's law, which subsequently becomes one of the four Maxwell equations. Faraday proposes that electromagnetic forces extended into the empty space around the conductor but does not complete his work involving that proposal. 1835: Peter Samuel Munk observes the permanent increase of the electrical conductivity of a mixture of loose metal filings in a glass tube with two metal plugs in it resulting from the passage of a discharge current of a Leyden jar through it. This is an early example of the coherer effect. 1842: Joseph Henry publishes his experimental results showing the oscillatory nature of the discharge in leyden jars and describes how a generated spark could magnetize a needle surrounded by a coil up to 220 feet away. He also describes how a lightning strike 8 miles away magnetized a needle surrounded by a coil, an effect that was most probably caused by radio waves. He considered both of these effects to be due to electromagnetic induction at the time. 1852: Samuel Alfred Varley notices a remarkable fall in the resistance of masses of metallic filings under the action of atmospheric electrical discharges. 1864: James Clerk Maxwell predicts the existence of electromagnetic waves in his paper 'a dynamical theory of the electromagnetic field'. 1871: Edwin Houston, while setting up a large sparking Ruhmkorff coil to be used in a demonstration, notices he can draw sparks from metal objects throughout the room. He attributes this to induction. 1875: While experimenting with an acoustic telegraph, Thomas Edison notices an electromagnet producing unusual sparks. He finds this strange sparking could be conducted 25 miles along telegraph wires and be detected a few feet from the wire. To prove it was not electromagnetic induction he set up an experiment where he shows sparks in a spark detector but no effect in a gold-leaf electroscope and a galvanometer along the same line. On 28 November 1875 he announces to the press what he terms a new "etheric force". December 1875: Edwin Houston, with the help of Elihu Thomson, conducts an improved version Edison's experiment at Central High School in Philadelphia, Pennsylvania using a Ruhmkorff coil and a spark detector. Thompson notices he can draw sparks from metal objects throughout the building and looks on the phenomenon as a possible new form of communication. Houston publishes his results, concluding that the phenomenon they and Edison produced was simply an induction phenomenon he had identified in 1871, claiming Edison was misidentifying a rapidly switching polarity. 1878: David E. Hughes notices that sparks generated by an induction balance cause noise in an improved telephone microphone he was developing. He rigs up a portable version of his receiver and, carrying it down a street, finds the sparking can be detected at some distance. 1879: German physicist Hermann von Helmholtz proposes the "Berlin Prize" for anyone who could experimentally prove a key aspect of Maxwell's electromagnetic theory thinking his star student, Heinrich Rudolf Hertz, could win the prize. Hertz declines working on the prize, seeing no way to produce a test apparatus. 1880: David Hughes demonstrates his discovery to the Royal Society, but is told it is merely induction. 1883: Irish physicist George Francis FitzGerald publishes a formula for the power radiated by a small loop antenna, showing it as proportional to the fourth power of the frequency. 1884: During his time as a lecturer in theoretical physics at the University of Kiel Heinrich Hertz produces an analysis of Maxwell's equations showing they did have more validity than the then prevalent "action at a distance" theories. 1884: Temistocle Calzecchi-Onesti at Fermo in Italy discovers that metal filings between two brass plates clump together in reaction to electric sparks occurring at a distance. He thinks it could be used for detecting lightning. His little noticed paper is published in an Italian journal and he does not pursue the phenomenon further. (Considered an early type of "coherer"). 1885: Edison takes out a patent on a system of wireless communication between ships via electrostatic induction through sea water. The system proves to be too short range to be practical.
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