Hans Bethe

The life and work of renowned German nuclear physicist, Hans Bethe

Compiled by Scott Millson on December 5, 2015

Personal Life

Early Life and Family

Hans Albrecht Bethe was born on July 2, 1906 in Strasbourg, Germany. He grew up with his Mother and his Father, who was a physiologist. His Father taught in academia and when Hans was still very young, his Father accepted a teaching position at the University of Kiel. During his tenure at this school, Hans was privately taught along with a handful of other children. However, in 1916, he began attending Goethe-Gymnasium in Frankfurt, Germany. Unfortunately his time here was short lived as he contracted Tuberculosis within the year. Quickly becoming very sick, he was sent to away to a nearby city until he was able to fully recover. Once healthy again, he continued his schooling at several different schools until eventually finishing out secondary school at Goethe-Gymnasium again.

Academic Life

By 1924, Bethe was ready to further his education by attending a University; the University of Frankfurt, the same school where his Father once taught. His choice in major was decided by a process of elimination based upon his own perceived poor level of instruction in the mathematics and the physics departments. So, he majored in Chemistry. He grew to become friends with a certain professor who must have seen Bethe's potential in physics as he recommended he attended a school with a better theoretical physics department. Bethe listened to this advice and accepted this professor's specific recommendation to attend the University of Munich and study under Arnold Sommerfeld.

Bethe went on to closely follow the work of Sommerfeld over the next several years as Bethe eventually received his PhD under Sommerfeld's slight assistance.

Over the next 5 years, Bethe moved from place to place while interning and working for several different companies. He worked on subjects from writing articles for Sommerfeld to researching and discovering new equations in England while researching with several renowned physicists.

Bethe's own life in academia began in 1932 when he accepted an assistant professor job at the University of Tübingen. He then moved on to work for the University of Manchester in 1933, for the University of Bristol in 1934, and finally for Cornell University in 1935. He was one of several of the most advanced physicists in the world at Cornell and together he helped research take giant leaps in nuclear physics. He worked at Cornell until 1941 when he began his work on the Manhattan Project.

Scientific Contributions

Early Work

During his time at Cornell University, Bethe was able to publish three advanced articles which summarized all that was known about nuclear physics at the time. These research papers became known as Bethe's Bible. Following this publication, Bethe's name began to carry much more general recognition as he was invited to a very exclusive physics convention put on by the Carnegie Institute and George Washington University. With the instrumental help of Bethe, by the end of the conference, these physicist were able to come up with a series of nuclear reactions to explain how the sun shines. Following the conference, Bethe felt there was still room for improvement in the knowledge of these reactions, so he continued to research them until he discovered the Carbon-Nitrogen-Oxygen (CNO) Cycle.

Manhattan Project

Bethe grew to love the United States as his home and in 1941 he finally became a citizen of the country he had now lived in for 6 years. He greatly wanted to aid in the war effort of World War II, but he was unable to until he gained citizenship and was given appropriate security clearance by the US.

In June 1942, Bethe met with a few other physicist including Robert Oppenheimer, while they began discussions for the world's first atomic bomb. They theorized several possibilities with different elements and their properties, to which Bethe would be able to perform calculations to determine if any of this talk was possible.

Eventually Oppenheimer was chosen as the lead to direct the creation of an atomic bomb. He chose Bethe to head the team's Theoretical Division (T Division). With this appointment, Bethe was very important in a number of calculations and decisions that eventually led to the final creation of the world's first atomic bomb. Specifically, he calculated the critical mass and efficiency of uranium-235 and the multiplication of nuclear fission in an exploding atomic bomb. In addition, he developed a formula to determine the bomb's explosive yield. All in all, the creation of the atomic bomb would not have been possible if not for the aid of Hans Bethe.

Hydrogen Bomb

At the start of the Korean War, Bethe was greatly against the creation of a Hydrogen Bomb and attempted to dissuade the Americans from attempting to make such a weapon. However, President Truman proceeded with the project regardless and while Bethe hoped its creation would not be possible, he understood that others would also be trying to make a hydrogen bomb, so he signed on as a leader in its development.

Bethe describes Ulam as the Father of the H-Bomb for planting the seed, Teller as its Mother for seeing it through its birth, and himself as the midwife.

Following the creation of the H-Bomb, Bethe returned to his position as a professor at Cornell University, where he remained until his death in March 2005.

Additional Work

Before ever working on nuclear physics, Bethe's work was centered around atomic physics and collision theory. In atomic physics, as he did so often, he helped to fill a few crucial gaps in the knowledge of the subject. In Collision theory, he developed his own theory regarding inelastic collisions between atoms and fast particles. This in turn provided a very useful tool for nuclear physics later on.

He also performed some significant work on Solid-State Theory discussing the splitting of atomic energy levels.

One of his most well known advances is in the field of the Lamb-shift in the Hydrogen Spectrum. This dealt with the discovery that one of the two possible quantum states of hydrogen atoms had slightly more energy than previously predicted.

Additional Information

Honors and Awards

1947 Henry Draper Medal
1957 ForMemRS
1959 Franklin Medal
1961 Eddington Medal
1961 Enrico Fermi Award
1963 Rumford Prize
1967 Nobel Prize in Physics
1975 Nat'l Medal of Science
1989 Lomonosov Gold Medal
1993 Oersted Medal
2001 Bruce Medal
2005 Benjamin Franklin Medal

Also, since 1998, there has been an award named after Bethe himself: The Hans A. Bethe Prize. This prize consist of $10,000 and a certificate citing the contributions made by the recipient. It is given to recognize outstanding work in the fields of astrophysics, nuclear physics, nuclear astrophysics, other subject matters which are closely related.