Erwin Schrödinger

A Viennese only child with a head for languages

Erwin Rudolf Josef Alexander Schrödinger was born in Vienna on the 12th of August, 1887, the only child of a botanist father and a chemistry professor’s daughter. His mother was half-English, and his maternal grandmother taught him English at home alongside the German of the streets. He spent his childhood reading widely (poetry, philosophy, Schopenhauer, the Vedanta) and the habit never left him. Even in his densest physics papers a literary cadence keeps breaking through.

He entered the University of Vienna in 1906 and worked under Franz Exner and Friedrich Hasenöhrl, finishing his doctorate in 1910 with a thesis on electrical conduction across damp insulator surfaces. He was twenty-three, and the questions that would consume him later (light, atoms, the strange new spectra of hydrogen) were not yet his. He worked on Brownian motion, dielectrics, atmospheric radioactivity. He was a careful experimentalist before he became a theorist.

Lieutenant Schrödinger, Austrian fortress artillery

From 1914 to 1918 he wore a uniform. Commissioned as a fortress artillery officer, he was posted to the Italian front (Gorizia, Duino, Sistiana, Prosecco) before returning to Vienna. He kept reading physics in the gun emplacements. The war was a four-year interruption, not a break: he came out of it still hungry for the problem of how atoms emit light, and he came out of it knowing exactly how slow theoretical progress feels when the world is on fire.

Erwin Rudolf Josef Alexander Schrödinger (12 August 1887 – 4 January 1961) was an Austrian–Irish theoretical physicist who developed fundamental results in quantum theory. In particular, he is recognized for devising the Schrödinger equation, an equation that provides a way to calculate the wave function of a system and how it changes dynamically in time. He coined the term "quantum entanglement" in 1935. Schrödinger shared the 1933 Nobel Prize in Physics with Paul Dirac "for the discovery of…

The wave equation, in a hut in the Alps

For most of the 1920s Schrödinger worked in Zurich. He had read Louis de Broglie’s 1924 thesis (the one proposing that matter, like light, had a wave nature) and the idea would not leave him alone. If electrons were waves, what equation did they obey? In late 1925 and through the first months of 1926, while recovering from a flare of tuberculosis at a sanatorium in the Swiss resort of Arosa, he wrote it down. Then he wrote it down again, in a relativistic form, threw that version away because it gave the wrong fine structure, and went back to the nonrelativistic case.

The result was four papers, all in 1926, all in Annalen der Physik, all under the same title Quantisierung als Eigenwertproblem (“Quantisation as an Eigenvalue Problem”). In them he set out iℏ∂ψ/∂t = Ĥψ, derived the hydrogen spectrum from it, proved his formulation was mathematically equivalent to Heisenberg’s matrix mechanics, and showed how the equation handled time-dependent perturbations. Four papers, one year, one equation. Quantum mechanics had its first usable differential equation, and undergraduates have been solving it ever since.

A famously vicious piece of physics gossip attributes the bursts of inspiration to a “late and passionate love affair” he was conducting at Arosa. He never named the woman. His wife Anny, who knew about the affair (she knew about all of them), is reported to have said only that one could hardly argue with the results.

A Nobel Prize and a country lost

In 1927 he succeeded Max Planck at the University of Berlin, the most prestigious chair of theoretical physics in the German-speaking world. Six years later, in 1933, two things happened. Hitler became Chancellor, and the Nobel Committee gave Schrödinger the Physics prize, shared with Paul Dirac, “for the discovery of new productive forms of atomic theory.”

He did not wait to see which way the new German state would push him. He resigned the Berlin chair the same year and took up a fellowship at Magdalen College, Oxford. Oxford did not quite suit him (his unconventional household, which involved his wife and a long-standing mistress and a child by the mistress, was not the kind of arrangement Magdalen had a precedent for), and after stints in Princeton and Graz he was once again caught by the Anschluss in 1938. He recanted his opposition to the Nazis in a published statement to keep his Graz job, was sacked anyway for “political unreliability,” and fled to Italy. He spent the rest of his life apologising to Einstein for the recantation. “I wanted to remain free,” he wrote, “and could not do so without great duplicity.”

Dublin, and a book that changed biology

Éamon de Valera, the Irish Taoiseach and a former mathematician, personally invited Schrödinger to Dublin. In 1940 Schrödinger became the founding Director of the School of Theoretical Physics at the new Dublin Institute for Advanced Studies, a post he held until 1955. He lived modestly on Kincora Road in Clontarf, biked to work, and published roughly fifty more papers. He became an Irish citizen in 1948 (while keeping his Austrian one) and spoke earnestly, if fancifully, of a Celtic kinship with the Austrians.

In 1943 he gave three public lectures at Trinity College Dublin under the title What Is Life? and turned them into a slim book the next year. It is the most consequential side-project a physicist has ever written. Schrödinger argued that the gene must be a complex aperiodic crystal carrying coded instructions, and that life maintains its order by feeding on what he called “negative entropy.” James Watson read it as an undergraduate. Francis Crick read it. Both have said, in print, that What Is Life? sent them looking for the molecule. Ten years later they found DNA.

In 1939, Schrödinger received a personal invitation from Éamon de Valera, Ireland's Taoiseach, to reside in Dublin. The following year, he joined the newly-established Dublin Institute for Advanced Studies as Director of the School of Theoretical Physics, a position he held until his retirement in 1955. He lived modestly on Kincora Road, Clontarf; a plaque has been erected at his Clontarf residence and at the address of his workplace in Merrion…

The cat that was a joke

Schrödinger’s cat (the most famous animal in twentieth-century science, alive and dead in a sealed box until you open it) was never meant to be taken seriously. He proposed it in a 1935 paper, written after long correspondence with Einstein, to mock what he called the “absurd consequences” of the Copenhagen interpretation. The cat was a reductio ad absurdum. If you really believe a wavefunction can sit in a superposition of two macroscopically distinct states until observation, fine, here is a cat that is supposedly both alive and dead. You see the problem.

The joke survived; the irony did not. Today the cat is a poster, a T-shirt, a screensaver, a name for half a dozen physics podcasts. The man who drew it on a chalkboard would have found this both funny and slightly horrifying.

Vienna again, and a quiet end

In 1956, after Austrian neutrality was re-established by treaty, Schrödinger went home. He took an emeritus chair at the University of Vienna and lectured intermittently. He had been fighting tuberculosis on and off since the 1920s; he died of it in Vienna on the 4th of January, 1961, aged seventy-three. He was buried in the small Tyrolean village of Alpbach, where he had spent summers, after the local priest discovered (to his apparent satisfaction) that the famously non-Catholic Schrödinger had been elected to the Pontifical Academy of Sciences.

What he means to the quantum story

Schrödinger gave physics the equation. Everything that flows in this book (orbitals, tunnelling, bonds, the periodic table, every exam-answer in undergraduate chemistry) is, in the end, a solution to something he wrote down in a sanatorium in 1926. He spent the rest of his life uncomfortable with what others did with it. That, too, is part of the story.