# Heisenberg, Werner

# Werner Heisenberg

**Born: December 5, 1901Würzburg, GermanyDied: February 1, 1976Munich, Germany**

*German physicist*

German physicist Werner Heisenberg was a leader in physics, winning the 1932 Nobel Prize in Physics for his discovery of the uncertainty principle, which states that it is impossible to specify the exact position and momentum of a particle (tiny piece of matter) at the same time.

*Early life*

Werner Karl Heisenberg was born on December 5, 1901, in Würzburg, Germany, the son of August and Annie Wecklein Heisenberg. As a boy Heisenberg began playing the piano early and was playing master compositions by the age of thirteen. It was his father's commitment to academic learning, however, that led him to pursue the science he loved. He graduated from the University of Munich, where his father was professor of Greek language and literature.

Heisenberg was also a regular hiker and an eager student of classical literature and philosophy. He amazed family and friends when he taught himself calculus (a method of computing in a special notation) and tried to publish a scientific paper as a teen. Even though his strongest interest in life was science, music was a lifetime companion for him. A hard worker, Heisenberg worked on a farm for three summers in order to pay for his tuition to the University of Munich. At the university, where he enrolled in 1920, Heisenberg soon established close contact with Arthur Sommerfield, a chief figure in early modern physics. After more hard work he received his doctorate in Munich in 1923. From there Heisenberg, on a Rockefeller grant, went to the Niels Bohr Institute in Copenhagen, Denmark, where he eagerly studied the most creative and up-to-date thoughts on atomic (related to the smallest particles of mass) theory.

*His landmark papers*

The Bohr's institute was the perfect setting for young Heisenberg to have his knowledge and interests grow. No sooner had Heisenberg completed his stay in Copenhagen than he worked out a complete method of calculating the energy levels of "atomic oscillators" (devices for producing alternating [back and forth] current). The method brought about very good results. A fellow physicist had it sent to the *Physikalische Zeitschrift,* where it was immediately printed under the title, "On Quantum Mechanical Interpretation of Kinematic and Mechanical Relations." Heisenberg's paper earned him immediate fame and recognition. In 1926 he was appointed lecturer in theoretical
physics (physics that exists only in theory) at the University of Copenhagen.

It was at Copenhagen that Heisenberg formulated the famous uncertainty principle, which states that it is impossible to specify the exact position and momentum of a particle at the same time. This was published in an article entitled, "On the Visualizable Content of Quantum Theoretical Kinematics and Mechanics." Heisenberg's "The Physical Principles of the Quantum Theory" is also considered a classic in this field. In 1927, at the age of twenty-six, he became professor of theoretical physics at the University of Leipzig. He received the Nobel Prize for physics in 1932. During this outbreak of academic activity, he married Elisabeth Schumacher. They eventually had seven children.

*Questionable role in war*

As a theoretical scientist, Heisenberg was initially held in low regard and was even considered suspect by the Nazi (German party in control from 1933–45 under the leadership of Adolf Hitler [1889–1945]) government. However, when World War II (1939–45; a war that pitted Great Britain, France, the Soviet Union, and the United States against Germany, Italy, and Japan) began, the government appointed him as director of the German uranium (a dangerous element) project, and he worked on developing an atomic bomb for Germany. Heisenberg was arrested and placed in captivity in England from April 1945 until the summer of 1946. His role during the war continues to be a source of great debate.

*Later career*

After World War II Heisenberg did much to reorganize scientific research. In the early 1950s he worked toward the formulation of a "unified [all-encompassing] theory of fundamental [basic] particles," stressing the role of symmetry (having balanced size and features) principles. This theory was discussed at length at an international conference in 1958. He presented his thought on this subject in the introduction to the *Unified Field Theory of Elementary Particles* (1966).

In 1955 and 1956 Heisenberg wrote and published *Physics and Philosophy: The Revolution in Modern Science.* He also published the autobiographical (about oneself) *Physics and Beyond* (1971), as well as several books dealing with the philosophical and cultural significance of atomic and nuclear physics.

Heisenberg retired in 1970. His health began to fail in 1973, and shortly thereafter he became seriously ill, dying on February 1, 1976, in Munich, Germany.

*For More Information*

Cassidy, David C. *Uncertainty: The Life and Science of Werner Heisenberg.* New York: W. H. Freeman, 1992.

Finkelstein, David. *Quantum Relativity: A Synthesis of the Ideas of Einstein and Heisenberg.* New York: Springer-Verlag, 1996.

Heisenberg, Elisabeth. *Inner Exile: Recollections of a Life with Werner Heisenberg.* Boston: Birkhäuser, 1984.

Rose, Paul Lawrence. *Heisenberg and the Nazi Atomic Bomb Project.* Berkeley: University of California Press, 1998.

# Heisenberg, Werner

# Heisenberg, Werner

**GERMAN PHYSICIST1901–1976**

More so than any other physicist of the twentieth century, Werner Karl Heisenberg challenged our fundamental notions of the surrounding world. It could be argued that as the author of papers on quantum mechanics and the uncertainty principle, he nailed the coffin shut on the **deterministic Newtonian** version of the universe. Heisenberg replaced precision and accuracy with probabilities and uncertainties, and in so doing, he opened up the world of the subatomic to our understanding.

Born the second son of August and Anna Heisenberg, in Würzburg, Germany, Heisenberg demonstrated promise at an early age. At the age of nine, he entered the Maximilian Gymnasium in Munich where his maternal grandfather was headmaster. The curriculum emphasized classical languages and literature, but Heisenberg excelled in the minor subjects of mathematics and physics.

Heisenberg soon outgrew the limited curriculum; he studied Einstein's relativity on his own and taught himself calculus in order to tutor a college student for her final exams. For his final oral exams at the gymnasium, he solved the equations of projectile motion, taking into account air resistance.

His adolescence was set against the backdrop of World War I. Heisenberg participated in various youth movements and even joined a military training unit that helped to bring in the fall harvest before Germany surrendered. Food was scarce. The gymnasium was closed for long periods due to a shortage of coal. With most men serving in the military, Heisenberg and his fellow students were expected to continue their studies independently.

Heisenberg entered the University of Munich in the fall of 1920. His preparation at the gymnasium essentially earned him "junior year" status. The professor of physics at Munich, Arnold Sommerfeld, quickly recognized Heisenberg's potential, and it was not long before he was taking advanced classes. Indeed, he received his doctorate in 1923, at the young age of twenty-two, having studied with Max Born and listened to the Danish physicist Niels Bohr lecture at Göttingen.

A newly minted scientist, Heisenberg returned to Göttingen to serve as Born's assistant until the spring of 1926. It was in 1925 that he achieved his first breakthrough in quantum mechanics. In essence, Heisenberg realized that certain properties do not commute and the law of commutation does not always apply. In normal mathematics, the law of commutation says that 3 × 2 = 2 × 3 = 6 and the order of multiplication does not matter. However, in matrix algebra, commutation is not necessarily observed. The order of multiplication does matter and can produce quite different results. Heisenberg's solution to the problems facing Bohr's quantum model of the atom relied on matrix algebra and provided a different approach in which discontinuities could occur. At almost the same time, Erwin Schrödinger formulated an alternate version of quantum mechanics based on waves. Both competed for center stage, and this resulted in fierce academic debate because Schrödinger's quantum mechanics was more deterministic.

Heisenberg's response was his second major breakthrough: The uncertainty principle that places a limit on the accuracy with which certain properties can be simultaneously known. In particular, the simultaneous measurement of both the position and the momentum of a particle can be known only to *h* /4*π* (with *h* as Planck's constant). One can measure the position of a particle to an infinite level of precision, but then its momentum has an infinite uncertainty and vice versa. This sets an absolute limit on human knowledge of the physical world and leads to the idea of **quantum mechanical** probability.

Heisenberg went on to say: "If one wants to be clear about what is meant by the 'position of an object,' for example, of an electron…, then one has to specify definite experiments by which the 'position of an electron' can be measured; otherwise this term has no meaning at all" (Cassidy, "Werner Heisenberg [1901–1976]"). In effect, reality does not exist until measured. This concept not only reformulated physics, but also had a major impact on Western philosophy.

Heisenberg received, among many other honors, the Nobel Prize in physics in 1932 for his formulation of quantum mechanics and its prediction of observable experimental facts. His work in all aspects of **theoretical physics** kept Heisenberg at the forefront of modern physics until he died of cancer in 1976.

see also Bohr, Niels; Quantum Chemistry; SchrÖdinger, Erwin.

*Todd W. Whitcombe*

## Bibliography

Cassidy, D. C. (1992). *Uncertainty: The Life and Science of Werner Heisenberg.* New York: W. H. Freeman.

Heisenberg, W. (1974). *Across the Frontiers.* Translated from German by Peter Heath. New York: Harper & Row.

### Internet Resources

Cassidy, D. C. "Werner Heisenberg (1901–1976)." Available from <http://www.aip.org/history/Heisenberg>.

Nobel e-Museum. "Werner Heisenberg—Biography." Available from <http://www.nobel.se>.

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