1920

Nobel Prize in Physics

An Alloy That Refuses to Grow

Charles Edouard Guillaume

Charles Edouard Guillaume spent the better part of the 1890s at the International Bureau of Weights and Measures in Sèvres, where his professional obsession was precision — the sort that can be ruined by a thermometer reading off by a fraction of a degree on a warm afternoon. While searching for a material stable enough to serve as a metrological standard, he discovered that certain nickel-steel alloys, containing roughly 36 percent nickel, have a thermal expansion coefficient so close to zero as to be almost philosophically negliging: they barely change size as temperature varies, and he named the most useful one Invar, for invariable. The alloy was not glamorous physics — no new forces were unmasked, no constants were measured — but it gave makers of pendulum clocks, surveying instruments, and measuring standards something more valuable than a theory: a dependable substance. The Nobel committee, awarding a prize to a man whose life's work was stopping things from moving when they shouldn't, showed an admirable respect for engineering virtue. Without Invar, the precision infrastructure that underpins all experimental physics would have been considerably less precise.

Nobel Prize in Chemistry

Absolute Zero Keeps Receding

Walther Nernst

Walther Nernst, already celebrated for his work on electrochemistry and solution theory, formulated his heat theorem around 1906 after noticing that entropy changes in chemical reactions seemed to vanish as temperatures approached absolute zero — a regularity so fundamental it would eventually be codified as the third law of thermodynamics. What the law says, in spare terms, is that no system can be cooled to absolute zero in a finite number of steps: the last fraction of a kelvin recedes before you like a horizon. That a working chemist in Berlin derived a cosmic limit by careful measurement of heat capacities is a reminder that thermodynamics has always been the most philosophical of the physical sciences. The prize reached Nernst in 1920, a full fourteen years after the work, which suggests the committee also moved slowly toward their conclusions. Today the third law underpins cryogenics, quantum computing, and our understanding of what perfect order would cost — namely, infinite effort.

Nobel Prize in Physiology or Medicine

The Capillaries Decide for Themselves

August Krogh

August Krogh, a Danish physiologist with a gift for elegant apparatus, found himself wondering why a resting frog's capillaries looked so different from those of a working one under the microscope: most were simply shut, collapsed and empty, while vigorous muscle threw them all open. He went on to demonstrate that capillaries are not passive conduits but actively regulated structures, opening and closing in response to the metabolic demands of surrounding tissue — so that oxygen delivery scales, with surprising precision, to oxygen need. The mechanism was so well matched to purpose that it had struck earlier investigators as implausibly convenient, which is what physiological reality occasionally is. Krogh's finding explained how a body can support the full exertion of a sprint and the full idleness of a library afternoon with the same cardiovascular system, simply by calibrating which vessels bother to open. We think of the heart as the engine, but Krogh showed the capillaries are the governors.

Nobel Prize in Literature

A Farmer's Patience, A Poet's Ruin

Knut Hamsun

Knut Hamsun had shocked Norwegian letters in 1890 with Hunger, a claustrophobic portrait of starvation and degradation in Christiania that dispensed with the social realism then fashionable and went straight for the nervous system. By the time the Swedish Academy gave him the prize in 1920, he had settled into a different register: Growth of the Soil, published in 1917, is the story of Isak, a man who walks into the wilderness with a pack and begins to farm, patiently and without fuss, building something that lasts. It is a novel of almost geological slowness, and it won the prize for a body of work the Academy found incomparable in its sweep and vitality. The biography, however, does not end cleanly. Hamsun's veneration of peasant rootedness curdled, over decades, into sympathy for National Socialism; he met Hitler, wrote newspaper eulogies for him, and was tried for collaboration after the war. The work endures, and so does that knowledge of it, and readers continue to carry both at once — which is, it turns out, one of the things literature demands.

Nobel Peace Prize

Thirty Years Early, Then Right on Time

Léon Bourgeois

Léon Bourgeois had been making the case for international arbitration and collective security since at least the Hague Peace Conferences of 1899 and 1907, well before the world had been given sufficient reason to listen seriously. He served as French prime minister, as a senator, as a tireless delegate to international bodies, arguing with the particular tenacity of a man who believes ideas have futures even when their moment has not yet come. By 1920 the League of Nations had shuffled into existence — imperfect, under-armed, and already without the United States, which the Senate had declined to join — and it bore a strong resemblance to what Bourgeois had spent thirty years proposing. He accepted the prize as an old man, in the knowledge that the institution he helped conjure had arrived too late, too compromised, and would last twenty-six years before disbanding. The arc is not triumphant, but it is not nothing: the League established habits of multilateral deliberation that its successor organisation, built on its ruins, would inherit.

Rutherford predicts the neutron

A Particle Invisible to Charge

Ernest Rutherford had spent the previous decade dismantling the atom: first the plum-pudding model fell, then the nuclear picture emerged from Geiger and Marsden's gold-foil scattering, and by 1920 he had a new puzzle on his hands. Atomic masses refused to equal atomic numbers — helium weighed four but had a charge of two, and heavier elements were worse — and no arrangement of protons and electrons quite resolved the arithmetic. In his Bakerian Lecture to the Royal Society that year, Rutherford proposed a solution: inside the nucleus there must be a neutral particle of roughly proton-like mass, electrically invisible and therefore immune to the Coulomb repulsion that made packing protons together so problematic. He called it the neutron. The suggestion was elegant and, as it turned out, correct; but it sat patiently in the literature for twelve years until James Chadwick, Rutherford's own student, found it experimentally in 1932. The neutron would go on to make fission possible, which is both the most consequential and the most morally complicated footnote in the history of nuclear physics.

Aston demonstrates chlorine's isotopic composition

Two Weights Hiding in One Element

For decades, chlorine had embarrassed atomic theory with its molar mass of 35.45 — conspicuously and stubbornly non-integer in a system that was supposed to be built from whole-number units. Various explanations were proposed and found wanting. In 1920 Frederick Aston brought his freshly built mass spectrograph to bear on the problem, separating ionised chlorine atoms by the ratio of their mass to their charge and finding not one peak but two: one at mass 35, one at mass 37, mixed in a ratio that averages neatly to 35.45. Chlorine, in other words, was not a single substance but a standing mixture of two isotopes — atoms with the same chemistry and different weights, the same number of protons and different numbers of neutrons. The non-integer molar mass was not an impurity or a measurement error; it was arithmetic. Aston's demonstration of isotopic composition for a common element was among the first clear evidence that the atomic weights enshrined in chemistry textbooks were, in effect, population averages masquerading as individual portraits.

Betelgeuse's diameter measured by interferometry

A Star Big Enough to Eat Mars

On 13 December 1920, Albert Michelson and Francis Pease bolted a 20-foot steel beam across the aperture of the Mount Wilson 100-inch telescope — the largest in the world — and trained it on Betelgeuse, the red supergiant marking Orion's right shoulder. By measuring the interference fringes produced by light arriving at two separated mirrors, they could extract the star's angular diameter: 0.047 arcseconds, a quantity so small it has no useful analogy at human scale. Combined with estimates of the star's distance, the figure implied a physical diameter of roughly 300 million miles, large enough that a star placed at the Sun's position would engulf Mercury, Venus, Earth, and Mars and make a reasonable start on the asteroid belt. It was the first direct measurement of a stellar diameter other than the Sun's — the first time anyone had treated a star not as a point of light but as a sphere with dimensions. The universe, it turned out, contained objects in front of which the solar system looked like a courtyard.

First transatlantic two-way radio broadcast

A Conversation Crosses the Ocean

Radio waves had crossed the Atlantic one-way since Marconi's famous 1901 demonstration, but maintaining a coherent conversation — not a signal sent, but voices exchanged — required solving a pile of compounding engineering problems: antenna design, vacuum tube amplification, frequency selection, interference suppression, and the question of what the ionosphere does to a signal at night that it declines to do by day. On 25 July 1920, engineers achieved the first confirmed two-way voice communication across the Atlantic, between stations in the United States and England. The achievement was simultaneously a practical milestone and a proof of concept for everything that would follow: the same transmitter and receiver designs, the same amplification chains, the same attention to propagation physics were being adapted at that very moment for commercial broadcasting. Two-way transatlantic radio was the infrastructure test; the entertainment industry was the product.

Commercial radio receivers go on sale in the United States

The Living Room Gets a Wireless Voice

For the first two decades of radio's existence, it was a medium for trained operators: Morse code, naval stations, ship-to-shore distress signals, the occasional amateur enthusiast in a cluttered shed. In November 1920, KDKA in Pittsburgh began broadcasting scheduled programming — election returns first, then news, then music — and American shops simultaneously began selling domestic receivers that required no licence, no training, and no ability to read Morse. The alignment was not accidental; broadcaster and receiver manufacturer needed each other. Within a few years the living-room wireless set became as unremarkable as the kitchen stove, its dial the nightly destination for millions of households that had never owned a telegraph, never operated a transmitter, and had no particular interest in the technology — only in the voices coming through it. The transformation of radio from specialist tool to ambient domestic presence happened in roughly the time it takes a child to start school and learn to read, which is fast, historically speaking.