Werner Heisenberg
Werner Karl Heisenberg 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.
Heisenberg published his Umdeutung paper in 1925, a major reinterpretation of old quantum theory. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, his matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. He received the Nobel Prize in Physics in 1932 "for the creation of quantum mechanics".
Heisenberg also made contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles. He introduced the concept of a wave function collapse. He was also instrumental in planning the first West German nuclear reactor in Karlsruhe, together with a research reactor in Munich, in 1957.
Following World War II, Heisenberg was appointed Director of the Kaiser Wilhelm Institute for Physics, which soon thereafter was renamed the Max Planck Institute for Physics. He was director until it was moved to Munich in 1958. He was Director of the Max Planck Institute for Physics and Astrophysics from 1960 to 1970.
Heisenberg was also President of the German Research Council, Chairman of the Commission for Atomic Physics, Chairman of the Nuclear Physics Working Group, and President of the Alexander von Humboldt Foundation.
Early life and education
Early years
Werner Karl Heisenberg was born in Würzburg, Germany, to Kaspar Ernst August Heisenberg, and his wife, Annie Wecklein. His father was a secondary school teacher of classical languages who became Germany's only ordentlicher Professor of medieval and modern Greek studies in the university system.Heisenberg was raised and lived as a Lutheran Christian. In his late teenage years, Heisenberg read Plato's Timaeus while hiking in the Bavarian Alps. He recounted philosophical conversations with his fellow students and teachers about understanding the atom while receiving his scientific training in Munich, Göttingen and Copenhagen. Heisenberg later stated that "My mind was formed by studying philosophy, Plato and that sort of thing" and that "Modern physics has definitely decided in favor of Plato. In fact the smallest units of matter are not physical objects in the ordinary sense; they are forms, ideas which can be expressed unambiguously only in mathematical language".
In 1919 Heisenberg arrived in Munich as a member of the Freikorps to fight the Bavarian Soviet Republic established a year earlier. Five decades later he recalled those days as youthful fun, like "playing cops and robbers and so on; it was nothing serious at all"; his duties were restricted to "seizing bicycles or typewriters from 'red' administrative buildings", and guarding suspected "red" prisoners.
University studies
From 1920 to 1923, he studied physics and mathematics at the Ludwig Maximilian University of Munich under Arnold Sommerfeld and Wilhelm Wien and at the Georg-August University of Göttingen with Max Born and James Franck and mathematics with David Hilbert. He received his doctorate in 1923 at Munich under Sommerfeld.In June 1922, Sommerfeld took Heisenberg to Göttingen to attend the Bohr Festival, because Sommerfeld had a sincere interest in his students and knew of Heisenberg's interest in Niels Bohr's theories on atomic physics. At the event, Bohr was a guest lecturer and gave a series of comprehensive lectures on quantum atomic physics and Heisenberg met Bohr for the first time, which had a lasting effect on him.
Heisenberg's doctoral thesis, the topic of which was suggested by Sommerfeld, was on turbulence; the thesis discussed both the stability of laminar flow and the nature of turbulent flow. The problem of stability was investigated by the use of the Orr–Sommerfeld equation, a fourth-order linear differential equation for small disturbances from laminar flow. He briefly returned to this topic after World War II.
At Göttingen, under Born, he completed his habilitation in 1924 with a Habilitationsschrift on the anomalous Zeeman effect.
In his youth he was a member and Scoutleader of the Neupfadfinder, a German Scout association and part of the German Youth Movement. In August 1923 Robert Honsell and Heisenberg organized a trip to Finland with a Scout group of this association from Munich.
Personal life
Heisenberg enjoyed classical music and was an accomplished pianist; playing for others was a prominent part of his social life. During the late 1920s and early 1930s he would often play music and dance at the Berlin home of his aristocratic student Carl Friedrich von Weizsäcker, during which time he carried on a courtship with Carl's high-school-age sister Adelheid, which led to him being unwelcome at their home for a time.Years later, his interest in music also led to meeting his future wife. In January 1937, Heisenberg met Elisabeth Schumacher at a private music recital. Schumacher was the daughter of a well-known Berlin economics professor, and her brother was the economist E. F. Schumacher, author of Small Is Beautiful. Heisenberg and Schumacher were married on 29 April. Fraternal twins Maria and Wolfgang were born in January 1938, whereupon Wolfgang Pauli congratulated Heisenberg on his "pair creation"a wordplay on a process from elementary particle physics, pair production. They had five more children over the next 12 years: Barbara, Christine, Jochen, Martin and Verena. In 1939 he bought a summer home for his family in Urfeld am Walchensee, in southern Germany.
One of Heisenberg's sons, Martin Heisenberg, became a neurobiologist at the University of Würzburg, while another son, Jochen Heisenberg, became a physics professor at the University of New Hampshire.
Academic career
Göttingen, Copenhagen and Leipzig
From 1924 to 1927, Heisenberg was a Privatdozent at Göttingen, meaning he was qualified to teach and examine independently, without having a chair. From 17 September 1924 to 1 May 1925, under an International Education Board Rockefeller Foundation fellowship, Heisenberg went to do research with Niels Bohr, director of the Institute of Theoretical Physics at the University of Copenhagen. On 7 June, after weeks of failing to alleviate a severe bout of hay fever with aspirin and cocaine, Heisenberg retreated to the pollen-free North Sea island of Helgoland to focus on quantum mechanics. His seminal paper, "Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen" also called the Umdeutung paper, was published in September 1925. He returned to Göttingen and, with Max Born and Pascual Jordan over a period of about six months, developed the matrix mechanics formulation of quantum mechanics. On 1 May 1926, Heisenberg began his appointment as a university lecturer and assistant to Bohr in Copenhagen. It was in Copenhagen, in 1927, that Heisenberg developed his uncertainty principle, while working on the mathematical foundations of quantum mechanics. On 23 February, Heisenberg wrote a letter to fellow physicist Wolfgang Pauli, in which he first described his new principle. In his paper on the principle, Heisenberg used the word "Ungenauigkeit", not uncertainty, to describe it.In 1927, Heisenberg was appointed ordentlicher Professor of theoretical physics and head of the department of physics at the University of Leipzig; he gave his inaugural lecture there on 1 February 1928. In his first paper published from Leipzig, Heisenberg used the Pauli exclusion principle to solve the mystery of ferromagnetism.
At 25 years old, Heisenberg gained the title of the youngest full-time professor in Germany and professorial chair of the Institute for Theoretical Physics at the University of Leipzig. He gave lectures that were attended by physicists like Edward Teller and Robert Oppenheimer, who would later work on the Manhattan Project for the United States.
During Heisenberg's tenure at Leipzig, the high quality of the doctoral students and post-graduate and research associates who studied and worked with him is clear from the acclaim that many later earned. They included Erich Bagge, Felix Bloch, Ugo Fano, Siegfried Flügge, William Vermillion Houston, Friedrich Hund, Robert S. Mulliken, Rudolf Peierls, George Placzek, Isidor Isaac Rabi, Fritz Sauter, John C. Slater, Edward Teller, John Hasbrouck van Vleck, Victor Frederick Weisskopf, Carl Friedrich von Weizsäcker, Gregor Wentzel, and Clarence Zener.
In early 1929, Heisenberg and Pauli submitted the first of two papers laying the foundation for relativistic quantum field theory. Also in 1929, Heisenberg went on a lecture tour of China, Japan, India, and the United States. In the spring of 1929, he was a visiting lecturer at the University of Chicago, where he lectured on quantum mechanics.
In 1928, the British mathematical physicist Paul Dirac had derived his relativistic wave equation of quantum mechanics, which implied the existence of positive electrons, later to be named positrons. In 1932, from a cloud chamber photograph of cosmic rays, the American physicist Carl David Anderson identified a track as having been made by a positron. In mid-1933, Heisenberg presented his theory of the positron. His thinking on Dirac's theory and further development of the theory were set forth in two papers. The first, "Bemerkungen zur Diracschen Theorie des Positrons" was published in 1934, and the second, "Folgerungen aus der Diracschen Theorie des Positrons", was published in 1936. In these papers Heisenberg was the first to reinterpret the Dirac equation as a "classical" field equation for any point particle of spin ħ/2, itself subject to quantization conditions involving anti-commutators. Thus reinterpreting it as a field equation accurately describing electrons, Heisenberg put matter on the same footing as electromagnetism: as being described by relativistic quantum field equations which allowed the possibility of particle creation and destruction.