High-pressure mercury lamps are invented, but do not become commercially available until more than 20 years later.
While still a student at Columbia University, Edwin Armstrong invents the regenerative circuit, which enables amplification of a signal many times by the same vacuum tube.
German physicist Max von Laue proves that x-rays are electromagnetic in nature.
German physicist Heinrich Barkhausen discovers that a ferromagnetic material to which an increasing magnetic field is gradually applied is magnetized in small steps rather than on a continuous basis. Known as the Barkhausen effect, this phenomenon provided clear support for the theory of ferromagnetic domains.
American inventor Edwin Armstrong invents the superheterodyne circuit, providing the broadcasting industry a greatly improved way to receive, convert and amplify weak, high-frequency electromagnetic waves.
Quench-hardened steel magnets are introduced commercially.
English electrophysiologist Edgar Adrian demonstrates that nerve cells generate voltages that trigger muscle contractions.
The first radio broadcasting station in the world, station KDKA in Pittsburgh, Pennsylvania, is launched by the Westinghouse Electric and Manufacturing Company.
Neon tube lighting becomes available commercially and is especially popular for advertising purposes.
German physicists Otto Stern and Walther Gerlach demonstrate through the use of a molecular beam that the spatial orientation of atomic particles in a magnetic field is restricted (a concept termed space quantization).
As part of his doctoral dissertation, German physicist Ernst Ising introduces a model, now known as the Ising model, to explain the behavior of ferromagnetic materials.
While graduate students in the Netherlands, George Uhlenbeck and Samuel Goudsmit postulate that in addition to their orbital motions, electrons spin about their axes.
Japanese geophysicist Motonori Matuyama studies the reversal of magnetic fields in rock strata and reasons that the Earth must occasionally undergo reversals of its polarity.