Technology Milestones
1805 Theory of induced current: Michael Faraday (England) and Joseph Henry (US) each individually developed the theory that a current flowing in one wire could induce a current flow in another wire not physically connected to the first wire.
1820 Hans Christian Oersted (Denmark) showed that a current flowing in a wire sets up a magnetic field around that wire. A changing current causes a changing magnetic field which in turn can cause a changing current to flow in an adjacent wire. This principle, electromagnetic induction, explained the observations of Faraday and Henry.
1864 James Clerk Maxwell (Scotland) publishes a set of equations describing the propagation of electromagnetic waves through space at the speed of light.
1883 Edison (US), seeking the cause of blackening of incandescent lamps, discovers current flow inside an evacuated bulb. The "Edison effect", current flow in a vacuum between a heated wire and a positively charged electrode, demonstrates electron flow through a vacuum.
1887 Heinrich Hertz (Germany) builds a spark gap transmitter and a tuned pickup loop receiver to transmit and receive electromagnetic waves. He was also able to verify Maxwell's prediction that radio waves travel at the speed of light.


Start
Previous
Next