Werner Heisenberg

A Bavarian schoolboy with bad allergies

Werner Karl Heisenberg was born on December 5, 1901 in Würzburg, the son of a classics professor who would soon hold the only chair of Greek philology in Germany at the University of Munich. The household was a hothouse of formal learning: drill in Greek and Latin from childhood, piano lessons, mountaineering on weekends. Werner and his older brother Erwin were pushed into open intellectual competition by their father, a habit Werner carried into adulthood. He was a prodigy in mathematics by twelve and tutoring university students in calculus by sixteen while still in Gymnasium.

He arrived at the University of Munich in 1920 to read mathematics, ran into a frosty interview with Ferdinand von Lindemann, and switched on the spot to theoretical physics under Arnold Sommerfeld. The seminar was the densest concentration of young quantum talent in Europe; Wolfgang Pauli sat across the room. Heisenberg finished his doctorate in 1923 on hydrodynamic turbulence, scraped through the experimental viva by failing questions about microscope resolution (a grudge his examiner Wilhelm Wien held for years), and moved on to Göttingen as Max Born’s assistant.

Helgoland, June 1925

Hay fever almost ended his career first. In late May 1925 Heisenberg’s allergies were so violent that Born sent him to recover on Helgoland, a treeless island in the North Sea. Stripped of references and almost of company, he sat with a problem the old Bohr atom could not solve: why some spectral lines were intense and others were faint. He decided to throw out the idea of an electron’s orbit entirely and to keep only what could in principle be measured, the frequencies and intensities of light the atom emitted and absorbed.

Working through the small hours, he arranged those observable quantities into tables and discovered that they composed under a non-commuting multiplication rule. He did not yet know the rule was matrix multiplication. He told

later that he climbed a cliff at dawn and watched the sun rise over the sea, suspecting he had glimpsed the inside of the atom for the first time. He brought the calculation back to Göttingen, where Born and the young Pascual Jordan recognized the algebra at once. In a three-author paper that the students nicknamed the Dreimännerarbeit, the three of them turned the sketch into the first complete quantum mechanics: matrix mechanics. Heisenberg was twenty-three.

Werner Karl Heisenberg (; ; 5 December 1901 – 1 February 1976) was a German theoretical physicist, one of the main pioneers of the theory of quantum mechanics, and a principal scientist in the German nuclear program during World War II.

Uncertainty

He moved to Copenhagen in 1926 to work with Bohr, and there in February 1927, pacing the gravel paths behind the Institute, he produced his second hammer-blow. If position and momentum were operators that refused to commute, then no state could fix both at once. The product of their uncertainties had a floor, set by Planck’s constant: Δx · Δp ≥ ℏ/2. This was not a statement about clumsy instruments. It was a statement about what was. Bohr, jealous of the result and irritated that Heisenberg had published before discussing it with him fully, argued for weeks over the physical interpretation before grudgingly endorsing the paper. The two men’s friendship would survive the quarrel but never the same way.

In 1932, at thirty, Heisenberg received the Nobel Prize in Physics, awarded for the 1925 work, “for the creation of quantum mechanics, the application of which has, inter alia, led to the discovery of the allotropic forms of hydrogen.” The award was a single laureate, which embarrassed him: Born and Jordan had earned the prize as much as he had, and Born would not receive his own Nobel until 1954.

The Uranverein

When the Third Reich came to power Heisenberg refused to emigrate. He believed Germany would survive the regime and that a generation of physicists owed it their staying. The decision cost him: the Nazi physics faction publicly attacked him as a “white Jew” for teaching relativity, and only a personal appeal by his mother to Heinrich Himmler’s mother kept him out of the camps. During the war he served as scientific director of the Uranverein, the German nuclear weapons project. Whether he deliberately stalled the program, simply miscalculated the critical mass, or was honestly trying and failing is one of the most argued questions in twentieth-century science. His own postwar account claimed sabotage; Allied recordings from his internment at Farm Hall suggest genuine surprise at the news from Hiroshima.

The most famous unanswered event of his life is the September 1941 visit to

in occupied Copenhagen. Whatever Heisenberg said, the conversation ended the friendship for a decade. Michael Frayn’s 1998 play Copenhagen dramatizes the meeting as three contradictory reconstructions, none provable.

After the war

Interned at Farm Hall in England with nine other German nuclear scientists, Heisenberg returned to a ruined country in 1946 and rebuilt theoretical physics at Göttingen. He became director of what would later be renamed the Max Planck Institute for Physics, moved it to Munich in 1958, and spent his late career on unified field theory, an effort most colleagues thought misguided but which he pursued until his death. He died of cancer of the kidneys and gall bladder on February 1, 1976, in Munich. He is the youngest founder of quantum mechanics, the man who decided the atom should be described by what we can see of it rather than by what we wish it were, and whose inequality drew the first hard line under what physics is allowed to know.