Arnold Sommerfeld, a renowned German physicist, made significant contributions to the field of quantum physics. His work on the X-ray wave theory and the introduction of quantum numbers revolutionized atomic physics. Despite initially being interested in literature and history, Sommerfeld found his true calling after interacting with mathematical geniuses such as David Hilbert and Adolf Hurwitz. He also served in the military voluntarily for eight years, unlike his contemporaries. Sommerfeld’s collaboration with mathematician Felix Klein greatly influenced his career. Throughout his teaching career, spanning over three decades, Sommerfeld served as the doctoral advisor for numerous Nobel laureates. Discover more about Sommerfeld’s remarkable contributions to the world of quantum physics.

## Quick Facts

- German Celebrities Born In December
- Died At Age: 82
- Physicists
- German Men
- Died on: April 26, 1951
- Place of death: Munich
- Cause of Death: Accident
- City: Königsberg, Germany
- Education: University of Königsberg
- Awards: 1931 – Max Planck Medal, 1939 – Lorentz Medal

## Childhood & Early Life

Arnold Sommerfeld was born on 5 December 1868 in the East Prussian city of Königsberg. His parents were Cäcile Matthias and Franz Sommerfeld, who was a medical practitioner. Sommerfeld attended High School at the ‘Altstädtisches Gymnasium’ where he was classmates with German physicist Wilhelm Wien and German mathematician Hermann Minkowski. After completing his matriculation in 1886, he pursued higher education at the ‘University of Königsberg’. Though his primary interest was in studying mathematics, he also engaged in courses such as natural sciences, philosophy, and political economy at the University. It was under the tutelage of expert mathematicians like Hilbert, Hurwitz, and Lindemann that Sommerfeld finally decided to conduct research on pure mathematics for his dissertation. His thesis catered to Eigen functions and partial differential equations and was titled ‘Die willkürlichen Functionen in der mathematischen Physik’ (The arbitrary functions in mathematical physics). In 1891, he received a doctorate from the ‘University of Königsberg’. Soon after, he joined the military in 1892 and was posted at Königsberg with the ‘reserve regiment’.

## Career

Sommerfeld moved to Gottingen in 1893, where he took up the job of an assistant at the ‘Mineralogical Institute’ to earn a living. In Gottingen, he made an acquaintance with the renowned German mathematician Felix Klein, who eventually accepted Sommerfeld as his apprentice. Under Klein’s guidance, Sommerfeld produced his second work on the ‘mathematical theory of diffraction’. In 1895, his research work qualified for achieving the highest academic qualification in the country and he was designated as a ‘Privatdozent’, allowing him to teach at the university level. Sommerfeld and Klein began a 13-year-long mathematical alliance, resulting in a four-volume text ‘Die Theorie des Kreisels’ which dealt with the theory of rotating bodies and its application to geophysics, astronomy, and technology. Due to financial difficulties, Sommerfeld took up a less lucrative assignment as a mathematics professor at the ‘Mining Academy’ in Clausthal. He then taught mechanics at ‘RWTH Aachen University’ and in 1901, he undertook the task of editing the fifth volume of ‘Mathematical Encyclopaedia’ at the insistence of Felix Klein. In 1906, he moved to Munich and was appointed as ordinarius professor of physics at the ‘University of Munich’. He also became the director of the new ‘Theoretical Physics Institute’ affiliated with the university.

## Contributions to Science

Sommerfeld made significant contributions to the field of science throughout his career. He worked on proving the X-ray wave theory, derived the mathematical proof of Albert Einstein’s theory of relativity, and made modifications to Bohr’s atomic model. He helped establish the ‘Sommerfeld–Wilson quantization rules’ and developed the ‘Sommerfeld Fine-structure constant’. He also propounded the concept of ‘Magnetic Quantum Number’ and discovered the ‘Inner Quantum Number’. Sommerfeld collaborated with Walther Kossel and came up with the Sommerfeld–Kossel displacement law. In 1918, he established the journal ‘Zeitschrift für Physik’ for publishing research work by upcoming scientists. He applied statistical mechanics to refine the ‘Paul Drude model’ of electrons in metals, resulting in the ‘Drude-Sommerfeld model’. Sommerfeld was honored with numerous awards and honors throughout his life, including membership in prestigious scientific societies and honorary degrees from various universities. He passed away in a road accident on 26 April 1951.

## Personal Life & Legacy

During his time in Gottingen, Sommerfeld fell in love with Johanna Höpfner. However, due to his financial condition, he took up a high-paying job in Clausthal before marrying Johanna. They had four children together. Sommerfeld’s legacy includes the ‘Center of Theoretical Physics’ at the University of Munich, which is named after him. Despite being nominated for the Nobel Prize multiple times, he never received the award.