1925

Nobel Prize in Physics

James Franck · Gustav Hertz

Franck and Hertz had fired electrons at mercury atoms and discovered that the atoms only absorb energy in fixed amounts — exactly the discrete quantities that Bohr's model predicted. They had confirmed quantisation by accident, not realising at the time what their results meant. The 1925 prize rewarded a 1914 experiment.

Nobel Prize in Chemistry

Richard Zsigmondy

Zsigmondy invented the ultramicroscope, which let him observe particles far smaller than the wavelength of light by watching them scatter that light sideways. What he saw in colloid solutions — apparently smooth fluids, in fact crowded with particles in Brownian motion — settled old arguments about the reality of atoms and started new ones about surfaces.

Nobel Prize in Literature

George Bernard Shaw

Shaw declined the money while accepting the medal, explaining that the prize was a lifebelt thrown to a swimmer who had already reached shore. The committee described his work as marked by idealism and humanity, with satirical fire and occasional poetic beauty — a description Shaw would have found flattering only in parts.

Wolfgang Pauli announces the exclusion principle

Pauli stated in January that no two electrons in an atom can occupy the same quantum state — same energy level, same spin, same everything. This single rule, with no classical analogue and no obvious justification beyond the fact that it worked, explained the entire structure of the periodic table and why matter doesn't simply collapse into itself.

Werner Heisenberg develops matrix mechanics

Retreating to the island of Heligoland in June to escape his hay fever, Heisenberg discarded all quantities that couldn't in principle be observed and rebuilt quantum mechanics from scratch using arrays of numbers — matrices — that didn't commute. By autumn, he, Max Born, and Pascual Jordan had the complete mathematical framework, and physics had its first fully consistent quantum theory.

Discovery of rhenium

Walter Noddack and Ida Tacke found element 75 in a sample of columbite in Berlin in May — the last stable element on the periodic table to be discovered. They named it rhenium after the Rhine. It is one of the rarest metals in the Earth's crust and now lives mainly in jet engine turbine blades.

Cecilia Payne proves stars consist of hydrogen and helium

Payne's doctoral thesis at Radcliffe, completed in January, used the new atomic physics to interpret stellar spectra and arrived at a conclusion that seemed, at the time, preposterous: stars are made almost entirely of hydrogen and helium, not of iron and rock as the consensus held. Henry Norris Russell persuaded her to soften the finding as "spurious" in the published version. He confirmed it himself four years later.

Charles Francis Jenkins demonstrates synchronized television and sound

On 13 June, Jenkins transmitted a synchronised moving image and sound signal over five miles near Washington, DC — not a perfect picture, not broadcast-quality audio, but a demonstration that the two could travel together. He called his system "radiovision," which did not survive.

John Logie Baird transmits greyscale television images

On 2 October, Baird managed to transmit the first recognisable greyscale television images in London — a face, in shades of grey rather than simple silhouette. The resolution was thirty lines. It was not good television. It was, however, television.