# Werner Heisenberg

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## Heisenberg, Werner

(vĕr`nər hī`zənbĕrk), 1901–76, German physicist. One of the founders of the quantum theory, he is best known for his uncertainty principle**uncertainty principle,**

physical principle, enunciated by Werner Heisenberg in 1927, that places an absolute, theoretical limit on the combined accuracy of certain pairs of simultaneous, related measurements.

**.....**Click the link for more information. , or indeterminacy principle, which states that it is impossible to determine with arbitrarily high accuracy both the position and momentum (essentially velocity) of a subatomic particle like the electron. The effect of this principle is to convert the laws of physics into statements about relative probabilities instead of absolute certainties. In 1926, Heisenberg developed a form of the quantum theory

**quantum theory,**

modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.

**.....**Click the link for more information. known as matrix mechanics, which was quickly shown to be fully equivalent to Erwin Schrödinger

**Schrödinger, Erwin**

, 1887–1961, Austrian theoretical physicist. He was educated at Vienna, taught at Breslau and Zürich, and was professor at the Univ. of Berlin (1927–33), fellow of Magdalen College, Oxford (1933–36), and professor at the Univ.

**.....**Click the link for more information. 's wave mechanics. His 1932 Nobel Prize in Physics cited not only his work on quantum theory but also work in nuclear physics in which he predicted the subsequently verified existence of two allotropic forms of molecular hydrogen, differing in their values of nuclear spin.

Heisenberg was a student of Arnold Sommerfeld**Sommerfeld, Arnold Johannes Wilhelm**

, 1868–1951, German physicist and teacher. He received a Ph.D. at Königsburg Univ. in 1891 and was a professor of physics at the Univ. of Munich from 1906 to 1940.**.....** Click the link for more information. , an assistant to Max Born**Born, Max,**

1882–1970, British physicist, b. Germany, Ph.D. Univ. of Göttingen, 1907. He was head of the physics department at the Univ. of Göttingen from 1921 to 1933.**.....** Click the link for more information. , and later a close associate of Niels Bohr**Bohr, Niels Henrik David**

, 1885–1962, Danish physicist, one of the foremost scientists of modern physics. He studied at the Univ. of Copenhagen (Ph.D. 1911) and carried on research on the structure of the atom at Cambridge under Sir James J.**.....** Click the link for more information. . He taught at the universities of Leipzig (1927–41) and Berlin (1942–45). During World War II he headed German efforts in nuclear fission research, which failed to develop a nuclear reactor or atomic bomb. Although he claimed after the war to have had qualms about building nuclear weapons, it seems likely that the reasons Germany failed to do so were technical and logistical.

In 1958 he became director of the Max Planck Institute for Physics and Astrophysics, now located in Munich. His later work concerned the so-called S-matrix approach to nuclear forces and the possibility that space and time are quantized, or granular, in structure. His *Physics and Philosophy* (1962) and *Physics and Beyond* (1971) remain popular accounts of the revolutions in modern physics.

### Bibliography

See D. C. Cassidy, *Uncertainty: The Life and Science of Werner Heisenberg* (1993); R. P. Brennan, *Heisenberg Probably Slept Here: The Lives, Times and Ideas of the Great Physicists of the 20th Century* (1996).

## Heisenberg, Werner

Born Dec. 5, 1901, in Würzburg. German physicist; one of the creators of quantum mechanics.

In 1923, Heisenberg graduated from the University of Munich, where he attended the lectures of A. Sommerfeld. From 1923 to 1927 he was an assistant to M. Born, and from 1927 to 1941 he was a professor at the universities of Berlin and Leipzig. Since 1941 he has been a professor at and director of the Max Planck Institute for Physics first in Berlin, then in Göttingen, and since 1955 in Munich.

In 1925, together with M. Born, Heisenberg developed the so-called matrix mechanics, the first variant of quantum mechanics, making it possible to calculate the intensities of the spectral lines emitted by the simplest quantum system, the linear oscillator. He performed the quantum-mechanical calculation of the helium atom, showing the possibility of its existence in two different states. In 1927 he formulated the uncertainty relation, which expresses the connection between the momentum and coordinates of a microparticle caused by its corpuscular-wave nature. Heisenberg received a Nobel Prize in 1933 for his work in quantum mechanics. He worked out (independently of and simultaneously with Ia. I. Frenkel’) the theory of the spontaneous magnetization of ferromagnets and the exchange interaction that orients the elementary magnets during the magnetization of a substance. He is the author of works on the structure of the atomic nucleus, in which he revealed the exchange character of the interaction of nucleons in the nucleus as well as of works on relativistic quantum mechanics and the unified field theory, a nonlinear theory that poses the problem of creating a unified theory of all existing physical fields.

### WORKS

“Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen.”*Zeitschrift für Physik*, 1925, vol. 33, issue 12.

“Mehrkörperproblem und Resonanz in der Quantenmechanik.”

*Zeitschrift für Physik*, 1926, vol. 38, issues 6-7 and vol. 41, issues 4-5.

“Über den anschaulichen Inhalt der quantentheoritschen Kinematik und Mechanik.”

*Zeitschrift für Physik*, 1927, vol. 43, issues

*3-4*.

“Zur Theorie des Ferromagnetismus.”

*Zeitschrift für Physik*, 1927, vol. 49, issues 9-10.

*In Russian translation:*

*Fizicheskie printsipy kvantovoi teorii*. Moscow-Leningrad, 1932.

*Fizika atomnogo iadra*. Moscow-Leningrad, 1947.

*Teoriia atomnogo iadra*. Moscow, 1953.

*Filosofskie problemy sovremennoi atomnoi fiziki*. Moscow, 1953.

*Vvedenie v edinuiu polevuiu teoriiu elementarnykh chastits*. Moscow, 1968.

### REFERENCE

Hörz, H.*Werner Heisenberg und die Philosophie*. Berlin, 1966.