1925

Nobel Prize in Physics

An Accident That Proved the Quantum

James Franck · Gustav Hertz

In 1914, James Franck and Gustav Hertz were doing something rather unglamorous: firing electrons at mercury vapour and measuring how much energy came back. When the electrons' speed fell below a certain threshold, they bounced off the atoms perfectly, losing nothing; above it, they lost energy in precise, fixed lumps and the mercury emitted ultraviolet light of a very particular wavelength. The two men published their results and didn't initially appreciate — to be fair, almost nobody did — that they had just handed Niels Bohr his most direct experimental confirmation. Bohr's model required atoms to absorb and emit energy in exact discrete quantities, and Franck and Hertz had measured exactly that, albeit without meaning to. It took the rest of the physics community several years to catch up with what the experiment actually implied, and the Nobel committee another eleven. A world without their accident is one where the quantisation of energy remains a theoretical convenience rather than something you can measure with a tube and a voltmeter.

Nobel Prize in Chemistry

Dust in a Sideways Beam of Light

Richard Zsigmondy

The trouble with very small things is that the wavelength of visible light is bigger than they are, which means an ordinary microscope simply cannot see them — the optics refuse. Richard Zsigmondy, working with the optical instrument-maker Henry Siedentopf at the Zeiss company in Jena, got around this in 1902 with characteristic ingenuity: he illuminated the sample from the side rather than from beneath, so that particles far below the resolution limit could still be detected as scattering points of light, like dust in a sunbeam. The instrument, called the ultramicroscope, let him peer into colloidal solutions — fluids like gold-tinted glass or opalescent rubber — and watch particles jittering in Brownian motion that was otherwise invisible. What he found settled, or rather sharpened, a debate that had been running for decades: atoms and molecules were real, and these particles were being jostled by them. Zsigmondy's device and the quantitative work that followed it gave physical chemistry its modern footing on the nanoscale — every technique for characterising particles you cannot directly see descends from the logic he established in that darkened beam of sideways light.

Nobel Prize in Literature

A Lifebuoy Thrown to a Swimmer Ashore

George Bernard Shaw

George Bernard Shaw had spent five decades making the British theatregoing public simultaneously uncomfortable and delighted, which is a harder trick than it looks. His plays — Major Barbara, Saint Joan, Heartbreak House, and above all Pygmalion — were engines for examining the way class, gender, money, and received ideas arrange themselves into something society calls civilisation and Shaw called a confidence trick. When the Nobel committee came for him in 1925, he accepted the medal with the remark that the prize was a lifebuoy thrown to a swimmer who had already reached shore; the money he declined, suggesting it be used to fund translations of Swedish literature into English, a gesture somewhere between generosity and a light rebuke. The committee described his work as marked by idealism and humanity with satirical fire — a description Shaw would have found flattering only in parts, since he considered idealism a variety of wilful blindness. The plays have outlasted the controversies they ignited, which is what plays are supposed to do.

Wolfgang Pauli announces the exclusion principle

Why the Chair Beneath You Holds

Wolfgang Pauli was twenty-four years old and already famous for being difficult when he published, in January 1925, the rule that bears his name: no two electrons in an atom can occupy the same quantum state simultaneously — the same energy level, angular momentum, spin, and every other quantum number must differ. He arrived at this not from a derivation but from the flat empirical fact that it was true; there was no more fundamental principle to appeal to, just the observation that nature behaved as if the rule existed. The consequences were staggering. The entire architecture of the periodic table — why lithium behaves nothing like helium, why the noble gases are inert, why elements organise into periods and shells — follows directly from this single prohibition. More fundamentally, Pauli's exclusion principle is why matter is solid: electrons in atoms cannot all collapse into the lowest energy state, and so atoms themselves resist compression. A world without the principle is one where the chair beneath you would not exist, or you would fall through it, which amounts to the same problem.

Werner Heisenberg develops matrix mechanics

A Theory Rebuilt on a Windswept Island

In June 1925, Werner Heisenberg's hay fever had become bad enough that his supervisor sent him to Heligoland — a small, flat, windswept island in the North Sea — to recover. He had been brooding for months on a problem: the existing quantum mechanics, patched together from classical ideas and Bohr's planetary orbits, kept producing infinities and wrong answers, largely because it was built on quantities no one could actually observe. On the island, working through the night and making arithmetic errors that he caught at three in the morning, Heisenberg reconstructed the theory using only measurable things: transition frequencies, intensities of spectral lines. The mathematics he needed turned out to be matrix algebra, which he had reinvented for himself without recognising it. Back in Göttingen, Max Born and Pascual Jordan supplied the formal scaffolding, and by autumn the three had the complete framework of matrix mechanics — the first fully consistent mathematical theory of the quantum world. It was opaque, algebraically demanding, and correct, which put it slightly ahead of its time.

Discovery of rhenium

The Last Stable Element, Named for a River

By 1925 the periodic table was nearly complete — nearly, but not quite. Two elements remained stubbornly missing from the predicted slots: numbers 43 and 75. Walter Noddack and Ida Tacke, working in Berlin with the physicist Otto Berg, processed enormous quantities of molybdenite and columbite ore and identified, by X-ray spectroscopy, faint but unmistakable signatures of element 75 in May of that year. They named it rhenium after the Rhine — the Rhein — with the quiet Rhineland patriotism of the era. It was the last naturally occurring stable element on the periodic table to be discovered, arriving decades after most of the others; it is also one of the rarest metals in the Earth's crust, with a higher melting point than almost anything else solid. Rhenium now lives primarily in the turbine blades of jet engines, where its ability to withstand extraordinary temperatures without creeping or deforming keeps the whole enterprise of commercial aviation from becoming considerably more exciting than it already is.

Cecilia Payne proves stars consist of hydrogen and helium

The Sun Is Mostly the Lightest Thing

Cecilia Payne arrived at Harvard's observatory from Cambridge in 1923, bringing with her a thorough knowledge of the new atomic physics that most of the astronomers already there did not possess. In her doctoral thesis, completed at Radcliffe in January 1925, she applied the Saha ionisation equations to the absorption lines in stellar spectra and arrived at a conclusion that the consensus regarded as essentially impossible: the sun and other stars are made overwhelmingly of hydrogen and helium, not of iron, silicon, and rock as geologists' instincts about heavenly bodies had suggested. Henry Norris Russell, then the most eminent American astronomer, reviewed her thesis and persuaded her to walk back the finding in print, calling it "almost certainly not real." He confirmed it himself in 1929, with considerably less compulsion to soften the language. Payne received no credit for the priority at the time, a situation Russell later acknowledged; the history has since been corrected, though slowly and with some reluctance. Her thesis is now recognised as among the most significant doctoral works in twentieth-century astrophysics, and everything we understand about stellar evolution — the hydrogen burning, the sequences, the deaths of stars — starts from what she established that January.

Charles Francis Jenkins demonstrates synchronized television and sound

Silhouettes with Sound, Five Miles Out

Charles Francis Jenkins had been inventing things since the 1890s — he had a credible claim on the first practical film projector, which he called the Phantoscope — and by 1925 he had turned his considerable ingenuity toward the problem of transmitting moving pictures through the air. On 13 June, he demonstrated a system he called radiovision, transmitting a synchronised moving image and sound signal over roughly five miles near Washington, DC, to a small audience that included members of the Department of the Navy. The picture was not good: Jenkins was using a rotating disk system that produced silhouettes more than images, and the resolution was decidedly coarse. The sound was present, which was the notable part. The demonstration was real enough that it attracted press coverage and prompted a broadcast licence, though the word "radiovision" did not survive its inventor. Jenkins was pipped to the lasting credit for television by better-funded and more photogenic rivals, which is the particular fate of the person who arrives at an idea first but lacks the time to make it work beautifully.

John Logie Baird transmits greyscale television images

A Dummy's Face, in Shades of Grey

John Logie Baird had been working in a rented attic room in Soho since 1923, building his television apparatus from salvaged lenses, a hatbox, darning needles, bicycle lamp, sealing wax, and enough string to suggest a man operating at the very edge of his financial resources. On 2 October 1925, he managed to transmit the first recognisably greyscale television image — not a mere silhouette, but an actual face in shades of grey — through his apparatus, the subject being a ventriloquist's dummy named Stooky Bill, whose waxy complexion proved to be fortuitously well-suited to the lighting requirements. The resolution was thirty lines and the frame rate was around five frames per second, which placed it somewhere between a flickering shadow and something a generous person might call a picture. Baird was delighted, rushed downstairs to the offices below to fetch a human subject, and transmitted the face of a twenty-year-old office boy named William Taynton — who thus became the first person to appear live on television, for which he was reportedly paid half a crown. It was not good television. It was, however, television, and everything else followed.