Werner Karl Heisenberg

German physicist Werner Karl Heisenberg (1901-1976) was a pioneer in the formalization of atomic theory. He won the 1932 Nobel Prize in physics for his discovery of the uncertainty principle, which states that it is impossible to specify the precise position and momentum of a particle at the same time. Heisenberg also developed the theory of matrix mechanics. During World War II he was director of the German atomic bomb project, which led to his brief imprisonment following the war and some controversy during the remainder of his career.

Werner Karl Heisenberg was born on December 5, 1901, in Würzburg, Germany, the son of August and Annie Wecklein Heisenberg. He received his education at the Maximilian Gymnasium in Munich and at the University of Munich, where his father was professor of Greek language and literature. Shortly before he began his university studies, he worked on a farm for several months and took active part in youth movements, searching for a way out of the social collapse that hit Germany at the end of World War I.

Heisenberg was also a talented pianist, an avid hiker, and an eager student of classical literature and philosophy. At the university, where he enrolled in 1920, Heisenberg soon established close contact with Arthur Sommerfeld, a chief figure in early modern physics, and with Sommerfeld's most outstanding student, Wolfgang Pauli, later a Nobel laureate. Heisenberg spent the winter of 1922-1923 at the University of Goettingen, where the physics department was rapidly establishing itself, with the help of Max Born, James Franck, and David Hilbert, as a center of theoretical physics. After taking his doctorate in Munich in 1923, Heisenberg went on a Rockefeller grant to Niels Bohr's institute in Copenhagen, where he eagerly studied the most creative and up-to-date speculations on atomic theory.

His Landmark Papers

The fusion of the influence of these mentors with the receptiveness of a most talented mind worked unusually well. No sooner had Heisenberg completed his stay in Copenhagen than he worked out, while recuperating on the shores of Helgoland from a heavy attack of hay fever, a comprehensive method of calculating the energy levels of "atomic oscillators." The method yielded very good results but appeared so strange that Heisenberg was undecided whether to submit his report for publication or "to throw it into the flames." Happily for science, he sent a copy of it to Pauli and, after receiving a favorable reply, he showed it to Born on his return to Goettingen in June 1925. Born realized its importance and had it sent to the Physikalische Zeitschrift, where it was immediately printed under the title, "On Quantum Mechanical Interpretation of Kinematic and Mechanical Relations." The person most preoccupied with the "strange" mathematical formalism in Heisenberg's paper was Born himself, who after eight days of constant reflection discovered that it corresponded to the rules of matrix calculus.

Heisenberg's paper earned its author immediate fame and recognition. At Bohr's recommendation, in 1926 he was appointed lecturer in theoretical physics at the University of Copenhagen. It was there that Heisenberg gave much thought to the apparent discrepancy between two formulations of quantum theory, one based on matrix calculus, the other on wave equations elaborated by Erwin Schroedinger. In the course of his work on this question, Heisenberg realized that only those physical situations are "meaningful" in quantum mechanics in which the differences of the noncommutative products of conjugate variables occur. He immediately saw that, because of these differences, one cannot determine simultaneously the position and velocity of an atomic particle or the energy level and its timing of an atomic oscillator.

The recognition of this fact led Heisenberg to the formulation of the famous uncertainty principle, which appeared in 1927 on the pages of the Physikalische Zeitschrift in an article entitled, "On the Visualizable Content of Quantum Theoretical Kinematics and Mechanics." Heisenberg's The Physical Principles of the Quantum Theory (1930) also is considered a classic in this field. Heisenberg's rise was now as rapid in the academic as in the scientific world. In 1927, at the age of 26, he became professor of theoretical physics at the University of Leipzig. He was the recipient, along with Schroedinger and Paul Dirac, of the Nobel Prize for physics for 1932. In 1941 he took the chair of theoretical physics at the University of Berlin and the directorship of the Kaiser Wilhelm Institute for Physics. During this flurry of academic activity, in 1937 he married Elisabeth Schumacher, and they had seven children.

Questionable Role in War

As a theoretical scientist, Heisenberg was initially held in low regard and even considered suspect by the Nazi government. However, when World War II began, the government appointed him as director of the German uranium project, and he worked on developing an atomic bomb for Germany throughout the war. Heisenberg was arrested and placed in Allied captivity in England from April 1945 until the summer of 1946. His role during the war continues to be a source of controversy.

Later Career

After World War II Heisenberg did much to reorganize scientific research as head of the Max Planck Institute of Physics and of the Alexander von Humboldt Foundation. In the early 1950s Heisenberg turned with great vigor toward the formulation of a "unified theory of fundamental particles," stressing the role of symmetry principles. This theory was intensively discussed at an international conference in 1958, the year he moved to the University of Munich as professor of physics. He presented his thought on this subject in Introduction to the Unified Field Theory of Elementary Particles (1966).

In 1955-1956 Heisenberg gave the Gifford Lectures at the University of St. Andrews, Scotland, which were printed under the title Physics and Philosophy: The Revolution in Modern Science. He also published the autobiographical Physics and Beyond (1971) and several books dealing with the philosophical and cultural implications of atomic and nuclear physics, all of which are available in English translation.

Heisenberg retired in 1970, although he continued to write on a variety of topics. His health began to fail in 1973, and shortly thereafter he became seriously ill. He died on February 1, 1976 in Munich.

Further Reading

• The best treatment of the conceptual foundations of Heisenberg's achievements in physics is the study by Patrick A. Heelan, Quantum Mechanics and Objectivity: A Study of the Physical Philosophy of Werner Heisenberg (1965); The place of Heisenberg's discoveries in the development of modern physics is given with all the technical details in the work by Max Jammer, The Conceptual Development of Quantum Mechanics (1966); For a popular but still informative presentation of the origins and techniques of quantum mechanics see Banesh Hoffmann, The Strange Story of the Quantum (1959); For an account sprinkled with anecdotal details see the works of George Gamow, Biography of Physics (1961) and Thirty Years That Shook Physics: The Story of Quantum Theory (1966).
• Finkelstein, David, Quantum Relativity: A Synthesis of the Ideas of Einstein and Heisenberg, Springer-Verlag, 1996.
• Peierls, Rudolf Ernst, Atomic Histories, American Institute of Physics, 1996.
• See Walker, Mark, Nazi Science: Myth, Truth, and the German Atomic Bomb, Plenum Press, 1995, for a critical examination of Heisenberg's role in developing an atomic bomb for Germany during World War II.