Werner Heisenberg

German physicist

• Born: December 5, 1901; Würzburg, Germany
• Died: February 1, 1976; Munich, Germany

Twentieth-century German theoretical physicist Werner Heisenberg won the Nobel Prize in Physics in 1932 and is best remembered as one of the founders of quantum mechanics. His most important contribution to quantum mechanical ideas is the Heisenberg uncertainty principle, which has become a cornerstone of modern physics.

Primary field: Physics

Specialties: Theoretical physics; quantum mechanics; nuclear physics

Early Life

Werner Karl Heisenberg was born on December 5, 1901, in Würzburg, Germany, to August Heisenberg and Anna Wecklein Heisenberg. August was a scholar of ancient Greek language and literature and was a stern and demanding teacher. He encouraged his children to take academics seriously, and Werner excelled in his studies, particularly in science and math.

When his father received a teaching appointment at the University of Munich in 1910, Heisenberg entered the Maximilians Gymnasium (an academically rigorous secondary school) in the fall of 1911. He impressed his teachers with his intelligence and ambition, and he also developed interests in music and languages. Heisenberg graduated in 1920 and had already begun to focus on physics and mathematics, teaching himself calculus and the principles of Einstein’s theory of relativity while in high school.

Following the end of World War I in 1918, Heisenberg became part of a nationalistic youth movement and accepted a leadership position of a group of young male activists who spent time discussing politics, philosophy, and science.

Heisenberg entered the University of Munich in 1920 and began to focus primarily on theoretical physics. Professor Arnold Sommerfeld was Heisenberg’s mentor and encouraged his interest in atomic theory (the study of the parts and structure of the atom) and introduced him to two luminaries in the field, Max Born and Niels Bohr, both of whom would later mentor Heisenberg and collaborate on the formation of the theory of quantum mechanics and the uncertainty principle.

Heisenberg received his doctoral degree in 1923 and enrolled at the University of Göttingen to study physics under Max Born. In the fall of 1924, he travelled to the University Institute for Theoretical Physics in Copenhagen to study under Niels Bohr. In 1927, at the age of twenty-five, Heisenberg was appointed professor of theoretical physics and head of the physics department at the University of Leipzig.

Heisenberg met his future wife, Elisabeth Schumacher, at a private music recital in 1937. They were married four months later and had seven children, one of whom became a physics professor at the University of New Hampshire.

Life’s Work

When Heisenberg became a theoretical physicist, the current hypothesis surrounding atomic structure was known as quantum theory, which was pioneered by Bohr and Sommerfeld. They held that atoms were composed of a positively charged center called a nucleus. The nucleus, containing most of the physical substance of the atom, was continuously being circled by negatively-charged particles called electrons. Quantum theory came from the idea that the amount of electrical energy an electron could possess was limited to a number of specific quantities, called quanta.

Although quantum theory was an important breakthrough, experimental results showed that it was flawed. Heisenberg set out to devise a new quantum theory that was based solely on observable information. He was unhappy with the imagined picture of electrons orbiting an atomic nucleus, since this behavior could not be seen or proven with existing technology. Instead, Heisenberg concentrated on what could be seen: the light reflecting off and being absorbed by atoms.

By 1925, Heisenberg published a paper that would help to win him the Nobel Prize in Physics seven years later. The paper described a new set of equations for calculating the position and momentum of subatomic particles (particles, like electrons, that are smaller than the atom). However, it was difficult for many scientists to give up the image of electrons moving in orbits around the nucleus.

At the same time, physicist Erwin Schrödinger came up with a competing theory of wave mechanics. This theory gave the same mathematical results as Heisenberg’s theory and was also consistent with the electrons-in-orbit idea. The scientific community fell into an argument over the theories.

Since both sets of equations gave the same results, Heisenberg set out to determine what the particles were doing in reality, not just in numbers; in other words, he wanted to explain the physical basis for the mathematics, which would lead him toward what would be called the Heisenberg uncertainty principle. The uncertainty principle states that it is impossible to know with great precision both a particle’s position (where it is in space) and its velocity (how fast it is moving). Before the uncertainty principle, physics had been a deterministic science: Physicists believed that if enough information was known about a particle, its past behavior and future actions could be determined. Heisenberg’s principle showed this to be impossible and concluded that only an estimate of the probability of past or future particle behavior could be determined.

When World War II began in 1939, Heisenberg belonged to a German military reserve unit, but rather than being sent to the front lines to fight, he and other scientists were ordered instead to conduct research on the recently advanced field of nuclear fission. Nuclear fission involved the splitting of nuclei, which in turn released enormous amounts of energy.

Heisenberg and his colleagues were asked to investigate nuclear fission as a means to create an atomic bomb for the Nazis. Such a device would be capable of causing more destruction than any weapon previously built, and the German government felt the cause was urgent since they were not the only country working on the problem. The United States, which would join the Allies in the battle to defeat Germany, created its own nuclear research facility during the war, and eventually succeeded in developing the atomic bomb.

Heisenberg’s scientific expertise was important to the Nazis, who moved him from his small lab in Leipzig to their main research center in Berlin halfway through the war. He was heavily involved in the German nuclear effort, but Germany never managed to develop a bomb. Many were fascinated by a private conversation Heisenberg had with his old mentor Bohr in 1941, in which it was known that the atomic bomb was discussed. Some thought that Heisenberg had identified a method for building the bomb, but hid it because he did not want to help the Nazis. Most historians now believe that Heisenberg did his best to solve the problem of how to build an atomic bomb, but as a theoretical physicist, he did not have much experience with experimental work, and he simply failed to make the necessary discoveries.

Heisenberg and the other scientists were taken prisoner at the end of the war and held in Cambridge, England, for six months. After their release, Heisenberg returned to Germany, where he continued research on high-energy particle physics and joined various scientific foundations and committees. He headed the Institute for Physics at Göttingen, which was moved to Munich and renamed the Max Planck Institute for Physics and Astrophysics in 1958. He also taught at the University of Munich.

Heisenberg retired from active research in 1970 and died of cancer on February 1, 1976.

Impact

Heisenberg helped to establish the modern science of quantum mechanics and contributed significant refinements to a conceptual understanding of the atomic nucleus, ferromagnetism, cosmic rays, and elementary particles. Heisenberg’s work continues to stimulate questions in the philosophy of science involving the certainty and probability of scientific knowledge. In addition to receiving the Nobel Prize in Physics in 1932, Heisenberg earned such honors as the Max Planck Medal, the Matteucci Medal, and the Barnard College Medal of Columbia University.

Bibliography

Dardo, Mauro. Nobel Laureates and Twentieth-Century Physics. Cambridge: Cambridge UP, 2004. Print. Provides a history of physics and the physicists who were instrumental in advancing the field.

Heisenberg, Elisabeth. Inner Exile: Recollections of a Life with Werner Heisenberg. Trans. S. Cappelari and C. Morris. Boston: Birkhäuser, 1984. Print. Heisenberg’s wife provides insight into her husband’s personal and professional life.

Heisenberg, Werner. Physics and Philosophy: The Revolution in Modern Science. New York: HarperCollins, 2007. Print. Heisenberg examines the effect of scientific advances on society and explains that science allows for cultural change only when society accepts the philosophical assumptions underlying the science.