His first students, Felix Bloch and Rudolf Peierls, pioneered with him the quantum mechanics of solids (ferromagnetism, metals and semiconductors). Together with Peter Debye and Friedrich Hund he established a new centre of atomic physics there. In the fall of 1927, Heisenberg became professor of theoretical physics at Leipzig. This relation had radical consequences – the classical causality law or, expressed more generally, the possibility of a strict separation of object and subject, ceased to be valid in quantum science. Heisenberg, from spring 1926 a lecturer and Bohr’s principal assistant in Copenhagen, contradicted this and in early 1927 derived the central result of the physical interpretation: simultaneous measurements of momentum and position of an atomic particle were limited by the famous uncertainty relation: Dp. Schrödinger claimed that nature exhibited no “quantum jumps” at all. It was in 1926 that Erwin Schrödinger created wave mechanics, formally equivalent to matrix mechanics, but working with differential equations and continuous wavefunctions. Jordan reformulated it as “matrix mechanics” and Paul Dirac as “q number theory”, and applied it successfully, as Heisenberg and Pauli did, to various atomic problems. His “quantum-theoretical reformulation” was the breakthrough to modern quantum mechanics. With this, the usual physical quantities, like position q and momentum p of an electron, did not commute but satisfied instead the relation pq – qp = h/2 π. In June 1925 when Heisenberg was recovering from a severe attack of hay fever on the island of Heligoland, he found that he could satisfy the necessary requirement of energy conservation in atomic processes. In May 1925, in Göttingen, Heisenberg began to describe atomic systems by observables only (“quantum-theoretical” Fourier series). Werner Heisenberg (right) at CERN in 1960 with Giuseppe Fidecaro (left) and Edoardo Amaldi. Heisenberg and Pauli claimed that fundamental concepts of the old theory, notably electron orbits, had to be abandoned completely. As a way out of the situation, Pauli, who was in Copenhagen, and Born and Heisenberg who were in Göttingen, proposed replacing the semiclassical differential expressions of Bohr and Sommerfeld by corresponding discrete difference terms to predict experimental quantum results (the 1925 Kramers Heisenberg formula, which predicted the Raman effect, for example). In 1923, contemporary atomic theory was in a deep crisis. In spite of this brilliant work, he nearly failed the experimental part of the doctoral exam with Willy Wien. On the publication of Heisenberg’s first paper in this field in 1922, Sommerfeld remarked to Heisenberg’s father: “You belong to an irreproachable family of philologists, and now you have the misfortune of seeing the sudden appearance of a mathematical-physical genius in your family.” In his PhD thesis, Heisenberg suggested the first method for deriving the critical Reynolds number, marking the transition from laminar to turbulent motion. Simultaneously he studied the classical hydrodynamical turbulence problem. The freshman found a perfect solution – exhibiting, however, unusual half-integral quantum numbers and a strangely behaving atomic core. In the very first semester Sommerfeld gave Heisenberg the difficult problem of explaining the anomalous Zeeman effect of sodium spectral lines. Thus he became a member of the great international post-First World War community of quantum and atomic theorists, including such brilliant talents as Paul Dirac, Enrico Fermi, Friedrich Hund, Pascual Jordan, Oskar Klein, Hendrik Kramers, Wolfgang Pauli and Gregor Wentzel. In 1924 Niels Bohr invited him to Copenhagen. He studied under Arnold Sommerfeld at the University of Munich, obtaining his PhD in July 1923 and then went on to work under Max Born in Göttingen. Werner Heisenberg, born in Würzburg, came from an academic family and after 1910 grew up in Munich, where he graduated with distinction from high school in 1920. He also established several fundamental quantum mechanics applications and pioneered the extension of the theory to high-energy phenomena. His famous uncertainty relations were a central part of its interpretation. It is to him that we owe the first breakthrough of modern atomic theory – the invention of quantum mechanics. This year, 5 December marks the centenary of Werner Heisenberg’s birth. Fame through uncertainty: quantum mechanics pioneer Werner Heisenberg in the 1920s. Helmut Rechenberg, Heisenberg’s last postgraduate, co-editor of his collected works and co-author of the multivolume opus The Historical Development of Quantum Theory, traces the life of a quantum figurehead. This year marks the centenary of the birth of Werner Heisenberg, pioneer of quantum mechanics and theoretical high-energy physics.
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