Hans A. Bethe
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Hans Albrecht Bethe (; July 2, 1906 – March 6, 2005) was a
German-American German Americans (german: Deutschamerikaner, ) are Americans who have full or partial German ancestry. With an estimated size of approximately 43 million in 2019, German Americans are the largest of the self-reported ancestry groups by the Unite ...
theoretical A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be ...
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...
who made major contributions to
nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...
, astrophysics,
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and spec ...
, and solid-state physics, and who won the 1967
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
for his work on the theory of stellar nucleosynthesis. For most of his career, Bethe was a professor at
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...
.Available at www.JamesKeckCollectedWorks.or

are the class notes taken by one of his students at Cornell from the graduate courses on Nuclear Physics and on Applications of Quantum Mechanics he taught in the spring of 1947.
During World War II, he was head of the Theoretical Division at the secret Los Alamos National Laboratory, Los Alamos laboratory that developed the first atomic bombs. There he played a key role in calculating the
critical mass In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fi ...
of the weapons and developing the theory behind the implosion method used in both the
Trinity test Trinity was the code name of the first detonation of a nuclear weapon. It was conducted by the United States Army at 5:29 a.m. on July 16, 1945, as part of the Manhattan Project. The test was conducted in the Jornada del Muerto desert abo ...
and the "
Fat Man "Fat Man" (also known as Mark III) is the codename for the type of nuclear bomb the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the fir ...
" weapon dropped on Nagasaki in August 1945. After the war, Bethe also played an important role in the development of the hydrogen bomb, although he had originally joined the project with the hope of proving it could not be made. Bethe later campaigned with
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...
and the Emergency Committee of Atomic Scientists against nuclear testing and the
nuclear arms race The nuclear arms race was an arms race competition for supremacy in nuclear warfare between the United States, the Soviet Union, and their respective allies during the Cold War. During this same period, in addition to the American and Soviet nuc ...
. He helped persuade the Kennedy and
Nixon administration Richard Nixon's tenure as the 37th president of the United States began with his first inauguration on January 20, 1969, and ended when he resigned on August 9, 1974, in the face of almost certain impeachment because of the Watergate Scanda ...
s to sign, respectively, the 1963
Partial Nuclear Test Ban Treaty The Partial Test Ban Treaty (PTBT) is the abbreviated name of the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, which prohibited all test detonations of nuclear weapons except for those conducted ...
and 1972
Anti-Ballistic Missile Treaty The Anti-Ballistic Missile Treaty (ABM Treaty or ABMT) (1972–2002) was an arms control treaty between the United States and the Soviet Union on the limitation of the anti-ballistic missile (ABM) systems used in defending areas against ballisti ...
(
SALT I The Strategic Arms Limitation Talks (SALT) were two rounds of bilateral conferences and corresponding international treaties involving the United States and the Soviet Union. The Cold War superpowers dealt with arms control in two rounds o ...
). His scientific research never ceased and he was publishing papers well into his nineties, making him one of the few scientists to have published at least one major paper in his field during every decade of his career, which in Bethe's case spanned nearly seventy years.
Freeman Dyson Freeman John Dyson (15 December 1923 – 28 February 2020) was an English-American theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrices, mathematical formulation of quantum m ...
, once his doctoral student, called him the "supreme problem-solver of the 20th century".


Early years

Bethe was born in Strasbourg, which was then part of the Reichsland Elsaß-Lothringen,
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
, on July 2, 1906, the only child of Anna (née Kuhn) and Albrecht Bethe, a '' privatdozent'' of physiology at the
University of Strasbourg The University of Strasbourg (french: Université de Strasbourg, Unistra) is a public research university located in Strasbourg, Alsace, France, with over 52,000 students and 3,300 researchers. The French university traces its history to the ea ...
. Although his mother, the daughter of a professor at the University of Strasbourg, had a
Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
background, Bethe was raised
Protestant Protestantism is a branch of Christianity that follows the theological tenets of the Protestant Reformation, a movement that began seeking to reform the Catholic Church from within in the 16th century against what its followers perceived to b ...
, like his father; and he became an atheist later in life. His father accepted a position as professor and director of the Institute of Physiology at the
University of Kiel Kiel University, officially the Christian-Albrecht University of Kiel, (german: Christian-Albrechts-Universität zu Kiel, abbreviated CAU, known informally as Christiana Albertina) is a university in the city of Kiel, Germany. It was founded in ...
in 1912, and the family moved into the director's apartment at the Institute. Initially, he was schooled privately by a professional teacher as part of a group of eight girls and boys. The family moved again in 1915 when his father became the head of the new Institute of Physiology at the
University of Frankfurt am Main Goethe University (german: link=no, Johann Wolfgang Goethe-Universität Frankfurt am Main) is a university located in Frankfurt am Main, Germany. It was founded in 1914 as a citizens' university, which means it was founded and funded by the wealt ...
. Bethe attended the Goethe-Gymnasium in
Frankfurt Frankfurt, officially Frankfurt am Main (; Hessian: , " Frank ford on the Main"), is the most populous city in the German state of Hesse. Its 791,000 inhabitants as of 2022 make it the fifth-most populous city in Germany. Located on it ...
, Germany. His education was interrupted in 1916, when he contracted
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, i ...
, and he was sent to Bad Kreuznach to recuperate. By 1917, he had recovered sufficiently to attend the local ''
realschule ''Realschule'' () is a type of secondary school in Germany, Switzerland and Liechtenstein. It has also existed in Croatia (''realna gimnazija''), the Austrian Empire, the German Empire, Denmark and Norway (''realskole''), Sweden (''realskola''), ...
'' and the following year, he was sent to the '' Odenwaldschule'', a private, coeducational boarding school. He attended the ''Goethe-Gymnasium'' again for his final three years of secondary schooling, from 1922 to 1924. Having passed his '' abitur'', Bethe entered the University of Frankfurt in 1924. He decided to major in chemistry. The instruction in physics was poor, and while there were distinguished mathematicians in Frankfurt such as
Carl Ludwig Siegel Carl Ludwig Siegel (31 December 1896 – 4 April 1981) was a German mathematician specialising in analytic number theory. He is known for, amongst other things, his contributions to the Thue–Siegel–Roth theorem in Diophantine approximation, ...
and Otto Szász, Bethe disliked their approaches, which presented mathematics without reference to the other sciences. Bethe found that he was a poor experimentalist who destroyed his lab coat by spilling sulfuric acid on it, but he found the advanced physics taught by the associate professor,
Walter Gerlach Walther Gerlach (1 August 1889 – 10 August 1979) was a German physicist who co-discovered, through laboratory experiment, spin quantization in a magnetic field, the Stern–Gerlach effect. The experiment was conceived by Otto Stern in 1921 an ...
, more interesting. Gerlach left in 1925 and was replaced by
Karl Meissner Karl Wilhelm Meissner (December 15, 1891 in Reutlingen, Württemberg – April 13, 1959 on a cruise ship sailing to Europe) was a German-American physicist specializing in hyperfine spectroscopy. He spent the greater part of his career in t ...
, who advised Bethe that he should go to a university with a better school of theoretical physics, specifically the
University of Munich The Ludwig Maximilian University of Munich (simply University of Munich or LMU; german: Ludwig-Maximilians-Universität München) is a public research university in Munich, Germany. It is Germany's sixth-oldest university in continuous operatio ...
, where he could study under Arnold Sommerfeld. Bethe entered the University of Munich in April 1926, where Sommerfeld took him on as a student on Meissner's recommendation. Sommerfeld taught an advanced course on differential equations in physics, which Bethe enjoyed. Because he was such a renowned scholar, Sommerfeld frequently received advance copies of scientific papers, which he put up for discussion at weekly evening seminars. When Bethe arrived, Sommerfeld had just received
Erwin Schrödinger Erwin Rudolf Josef Alexander Schrödinger (, ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was a Nobel Prize-winning Austrian physicist with Irish citizenship who developed a number of fundamental results in quantum theo ...
's papers on
wave mechanics Wave mechanics may refer to: * the mechanics of waves * the ''wave equation'' in quantum physics, see Schrödinger equation See also * Quantum mechanics * Wave equation The (two-way) wave equation is a second-order linear partial different ...
. For his PhD thesis, Sommerfeld suggested that Bethe examine electron diffraction in
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s. As a starting point, Sommerfeld suggested Paul Ewald's 1914 paper on X-ray diffraction in crystals. Bethe later recalled that he became too ambitious, and, in pursuit of greater accuracy, his calculations became unnecessarily complicated. When he met
Wolfgang Pauli Wolfgang Ernst Pauli (; ; 25 April 1900 – 15 December 1958) was an Austrian theoretical physicist and one of the pioneers of quantum physics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics ...
for the first time, Pauli told him: "After Sommerfeld's tales about you, I had expected much better from you than your thesis." "I guess from Pauli," Bethe later recalled, "that was a compliment."


Early work

After Bethe received his doctorate,
Erwin Madelung Erwin Madelung (18 May 1881 – 1 August 1972) was a German physicist. He was born in 1881 in Bonn. His father was the surgeon Otto Wilhelm Madelung. He earned a doctorate in 1905 from the University of Göttingen, specializing in crystal structu ...
offered him an assistantship in Frankfurt, and in September 1928 Bethe moved in with his father, who had recently divorced his mother. His father had met Vera Congehl earlier that year and married her in 1929. They had two children, Doris, born in 1933, and Klaus, born in 1934. Bethe did not find the work in Frankfurt very stimulating, and in 1929 he accepted an offer from Ewald at the ''
Technische Hochschule A ''Technische Hochschule'' (, plural: ''Technische Hochschulen'', abbreviated ''TH'') is a type of university focusing on engineering sciences in Germany. Previously, it also existed in Austria, Switzerland, the Netherlands (), and Finland (, ). ...
'' in Stuttgart. While there, he wrote what he considered to be his greatest paper, ''Zur Theorie des Durchgangs schneller Korpuskularstrahlen durch Materie'' ("The Theory of the Passage of Fast Corpuscular Rays Through Matter"). Starting from Max Born's interpretation of the
Schrödinger equation The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of th ...
, Bethe produced a simplified formula for collision problems using a Fourier transform, which is known today as the
Bethe formula The Bethe formula or Bethe-Bloch formula describes the mean energy loss per distance travelled of swift charged particles (protons, alpha particles, atomic ions) traversing matter (or alternatively the stopping power of the material). For electron ...
. He submitted this paper for his '' habilitation'' in 1930. Sommerfeld recommended Bethe for a Rockefeller Foundation Travelling Scholarship in 1929. This provided $150 a month (about $,000 in dollars) to study abroad. In 1930, Bethe chose to do postdoctoral work at the Cavendish Laboratory at the
University of Cambridge The University of Cambridge is a public collegiate research university in Cambridge, England. Founded in 1209 and granted a royal charter by Henry III in 1231, Cambridge is the world's third oldest surviving university and one of its most pr ...
in England, where he worked under the supervision of Ralph Fowler. At the request of Patrick Blackett, who was working with
cloud chamber A cloud chamber, also known as a Wilson cloud chamber, is a particle detector used for visualizing the passage of ionizing radiation. A cloud chamber consists of a sealed environment containing a supersaturated vapour of water or alcohol. An ...
s, Bethe created a relativistic version of the Bethe formula. Bethe was known for his sense of humor, and with Guido Beck and , two other postdoctoral
research fellow A research fellow is an academic research position at a university or a similar research institution, usually for academic staff or faculty members. A research fellow may act either as an independent investigator or under the supervision of a pr ...
s, created a hoax paper ''On the Quantum Theory of the Temperature of Absolute Zero'' where he calculated the fine structure constant from the absolute zero temperature in Celsius units. The paper poked fun at a certain class of papers in theoretical physics of the day, which were purely speculative and based on spurious numerical arguments, such as Arthur Eddington's attempts to explain the value of the fine structure constant from fundamental quantities in an earlier paper. They were forced to issue an apology. For the second half of his scholarship, Bethe chose to go to Enrico Fermi's laboratory in Rome in February 1931. He was greatly impressed by Fermi and regretted that he had not gone to Rome first. Bethe developed the Bethe ansatz, a method for finding the exact solutions for the
eigenvalue In linear algebra, an eigenvector () or characteristic vector of a linear transformation is a nonzero vector that changes at most by a scalar factor when that linear transformation is applied to it. The corresponding eigenvalue, often denoted ...
s and
eigenvector In linear algebra, an eigenvector () or characteristic vector of a linear transformation is a nonzero vector that changes at most by a scalar factor when that linear transformation is applied to it. The corresponding eigenvalue, often denoted ...
s of certain one-dimensional quantum many-body models. He was influenced by Fermi's simplicity and Sommerfeld's rigor in approaching problems and these qualities influenced his own later research. The Rockefeller Foundation offered an extension of Bethe's fellowship, allowing him to return to Italy in 1932. In the meantime, Bethe worked for Sommerfeld in Munich as a ''privatdozent''. Since Bethe was fluent in English, Sommerfeld had Bethe supervise all his English-speaking postdoctoral fellows, including Lloyd P. Smith from
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...
. Bethe accepted a request from Karl Scheel to write an article for the ''Handbuch der Physik'' on the
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistr ...
of hydrogen and helium. Reviewing the article decades later, Robert Bacher and
Victor Weisskopf Victor Frederick "Viki" Weisskopf (also spelled Viktor; September 19, 1908 – April 22, 2002) was an Austrian-born American theoretical physicist. He did postdoctoral work with Werner Heisenberg, Erwin Schrödinger, Wolfgang Pauli, and Niels Boh ...
noted that it was unusual in the depth and breadth of its treatment of the subject that required very little updating for the 1959 edition. Bethe was then asked by Sommerfeld to help him with the ''handbuch'' article on electrons in metals. The article covered the basis of what is now called solid state physics. Bethe took a very new field and provided a clear, coherent, and complete coverage of it. His work on the ''handbuch'' articles occupied most of his time in Rome, but he also co-wrote a paper with Fermi on another new field,
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and spec ...
, describing the relativistic interactions of charged particles. In 1932, Bethe accepted an appointment as an assistant professor at the
University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public research university located in the city of Tübingen, Baden-W ...
, where
Hans Geiger Johannes Wilhelm "Hans" Geiger (; ; 30 September 1882 – 24 September 1945) was a German physicist. He is best known as the co-inventor of the detector component of the Geiger counter and for the Geiger–Marsden experiment which discover ...
was the professor of experimental physics. One of the first laws passed by the new
Nazi Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in ...
government was the Law for the Restoration of the Professional Civil Service. Due to his Jewish background, Bethe was dismissed from his job at the University, which was a government post. Geiger refused to help, but Sommerfeld immediately gave Bethe back his fellowship at Munich. Sommerfeld spent much of the summer term of 1933 finding places for Jewish students and colleagues. Bethe left Germany in 1933, moving to England after receiving an offer for a position as lecturer at the
University of Manchester , mottoeng = Knowledge, Wisdom, Humanity , established = 2004 – University of Manchester Predecessor institutions: 1956 – UMIST (as university college; university 1994) 1904 – Victoria University of Manchester 1880 – Victoria Univ ...
for a year through Sommerfeld's connection to
William Lawrence Bragg Sir William Lawrence Bragg, (31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structu ...
. He moved in with his friend
Rudolf Peierls Sir Rudolf Ernst Peierls, (; ; 5 June 1907 – 19 September 1995) was a German-born British physicist who played a major role in Tube Alloys, Britain's nuclear weapon programme, as well as the subsequent Manhattan Project, the combined Allie ...
and Peierls' wife Genia. Peierls was a fellow German physicist who had also been barred from academic positions in Germany because he was Jewish. This meant that Bethe had someone to speak to in German and he did not have to eat English food. Their relationship was professional as well as personal. Peierls aroused Bethe's interest in
nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...
. After
James Chadwick Sir James Chadwick, (20 October 1891 – 24 July 1974) was an English physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932. In 1941, he wrote the final draft of the MAUD Report, which inspi ...
and
Maurice Goldhaber Maurice Goldhaber (April 18, 1911 – May 11, 2011) was an American physicist, who in 1957 (with Lee Grodzins and Andrew Sunyar) established that neutrinos have negative helicity. Early life and childhood He was born on April 18, 1911, in ...
discovered the
photodisintegration Photodisintegration (also called phototransmutation, or a photonuclear reaction) is a nuclear process in which an atomic nucleus absorbs a high-energy gamma ray, enters an excited state, and immediately decays by emitting a subatomic particle. The ...
of
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one ...
, Chadwick challenged Bethe and Peierls to come up with a theoretical explanation of this phenomenon. This they did on the four-hour train ride from Cambridge back to Manchester. Bethe would investigate further in the years ahead. In 1933, the physics department at Cornell was looking for a new theoretical physicist, and Lloyd Smith strongly recommended Bethe. This was supported by Bragg, who was visiting Cornell at the time. In August 1934, Cornell offered Bethe a position as an acting assistant professor. Bethe had already accepted a fellowship for a year to work with Nevill Mott at the
University of Bristol , mottoeng = earningpromotes one's innate power (from Horace, ''Ode 4.4'') , established = 1595 – Merchant Venturers School1876 – University College, Bristol1909 – received royal charter , type ...
for a semester, but Cornell agreed to let him start in the spring of 1935. Before leaving for the United States, he visited the Niels Bohr Institute in
Copenhagen Copenhagen ( or .; da, København ) is the capital and most populous city of Denmark, with a proper population of around 815.000 in the last quarter of 2022; and some 1.370,000 in the urban area; and the wider Copenhagen metropolitan ar ...
in September 1934, where he proposed to Hilde Levi, who accepted. The match was opposed by Bethe's mother, who despite having a Jewish background, did not want him to marry a Jewish woman. A few days before their wedding date in December, Bethe broke off their engagement.
Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 ...
and
James Franck James Franck (; 26 August 1882 – 21 May 1964) was a German physicist who won the 1925 Nobel Prize for Physics with Gustav Hertz "for their discovery of the laws governing the impact of an electron upon an atom". He completed his doctorate i ...
were so shocked by this action by Bethe that he was not invited to the Institute again until after
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
.


United States

Bethe arrived in the United States in February 1935, and joined the faculty at Cornell University on a salary of $3,000. Bethe's appointment was part of a deliberate effort on the part of the new head of its physics department, Roswell Clifton Gibbs, to move into nuclear physics. Gibbs had hired
Stanley Livingston Stanley Bernard Livingston (born November 24, 1950) is an American actor, director, producer, editor and writer. Biography He is best known for playing Richard "Chip" Douglas, the third son of Steve Douglas (Fred MacMurray) on the television ...
, who had worked with
Ernest Lawrence Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American nuclear physicist and winner of the Nobel Prize in Physics in 1939 for his invention of the cyclotron. He is known for his work on uranium-isotope separation fo ...
, to build a
cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Jan ...
at Cornell. To complete the team, Cornell needed an experimentalist, and, on the advice of Bethe and Livingston, recruited Robert Bacher. Bethe received requests to visit
Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...
from
Isidor Isaac Rabi Isidor Isaac Rabi (; born Israel Isaac Rabi, July 29, 1898 – January 11, 1988) was an American physicist who won the Nobel Prize in Physics in 1944 for his discovery of nuclear magnetic resonance, which is used in magnetic resonance ima ...
,
Princeton University Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the ...
from
Edward Condon Edward Uhler Condon (March 2, 1902 – March 26, 1974) was an American nuclear physicist, a pioneer in quantum mechanics, and a participant during World War II in the development of radar and, very briefly, of nuclear weapons as part of the ...
,
University of Rochester The University of Rochester (U of R, UR, or U of Rochester) is a private university, private research university in Rochester, New York. The university grants Undergraduate education, undergraduate and graduate degrees, including Doctorate, do ...
from Lee DuBridge,
Purdue University Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and mone ...
from Karl Lark-Horovitz, the
University of Illinois at Urbana–Champaign The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Univer ...
from
Francis Wheeler Loomis Francis Wheeler Loomis (August 4, 1889 – February 9, 1976), born in Parkersburg, West Virginia, was an American scientist most widely known for his contributions in the field of physics. Loomis received his undergraduate degree and, in 1917, hi ...
, and
Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...
from
John Hasbrouck Van Vleck John Hasbrouck Van Vleck (March 13, 1899 – October 27, 1980) was an American physicist and mathematician. He was co-awarded the Nobel Prize in Physics in 1977, for his contributions to the understanding of the behavior of electronic magnetism ...
. Gibbs moved to prevent Bethe from being poached by having him appointed as a regular assistant professor in 1936, with an assurance that promotion to professor would soon follow. Together with Bacher and Livingston, Bethe published a series of three articles, which summarized most of what was known on the subject of nuclear physics until that time, an account that became known informally as "Bethe's Bible". It remained the standard work on the subject for many years. In this account, he also continued where others left off, filling in gaps in the older literature. Loomis offered Bethe a full professorship at the University of Illinois at Urbana–Champaign, but Cornell matched the position offered, and the salary of $6,000. He wrote to his mother: On March 17, 1938, Bethe attended the Carnegie Institute and
George Washington University The George Washington University (GW or GWU) is a Private university, private University charter#Federal, federally chartered research university in Washington, D.C. Chartered in 1821 by the United States Congress, GWU is the largest Higher educat ...
's fourth annual Washington Conference of Theoretical Physics. There were only 34 invited attendees, but they included Gregory Breit, Subrahmanyan Chandrasekhar,
George Gamow George Gamow (March 4, 1904 – August 19, 1968), born Georgiy Antonovich Gamov ( uk, Георгій Антонович Гамов, russian: Георгий Антонович Гамов), was a Russian-born Soviet and American polymath, theoret ...
,
Donald Menzel Donald Howard Menzel (April 11, 1901 – December 14, 1976) was one of the first theoretical astronomers and astrophysicists in the United States. He discovered the physical properties of the solar chromosphere, the chemistry of stars, the atmos ...
,
John von Neumann John von Neumann (; hu, Neumann János Lajos, ; December 28, 1903 – February 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. He was regarded as having perhaps the widest cove ...
, Bengt Strömgren,
Edward Teller Edward Teller ( hu, Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb" (see the Teller–Ulam design), although he did not care for ...
, and Merle Tuve. Bethe initially declined the invitation to attend, because the conference's topic, stellar energy generation, did not interest him, but Teller persuaded him to go. At the conference, Strömgren detailed what was known about the temperature, density, and chemical composition of the Sun, and challenged the physicists to come up with an explanation. Gamow and
Carl Friedrich von Weizsäcker Carl Friedrich Freiherr von Weizsäcker (; 28 June 1912 – 28 April 2007) was a German physicist and philosopher. He was the longest-living member of the team which performed nuclear research in Germany during the Second World War, under ...
had proposed in a 1937 paper that the Sun's energy was the result of a proton–proton chain reaction: But this did not account for the observation of elements heavier than helium. By the end of the conference, Bethe, working in collaboration with
Charles Critchfield Charles Louis Critchfield (June 7, 1910 – February 12, 1994) was an Americans, American mathematical physicist. A graduate of George Washington University, where he earned his Doctor of Philosophy, PhD in Physics under the direction of Edward T ...
, had come up with a series of subsequent nuclear reactions that explained how the Sun shines: That this did not explain the processes in heavier stars was not overlooked. At the time there were doubts about whether the proton–proton cycle described the processes in the Sun, but more recent measurements of the Sun's core temperature and luminosity show that it does. When he returned to Cornell, Bethe studied the relevant
nuclear reaction In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformatio ...
s and reaction cross sections, leading to his discovery of the carbon-nitrogen-oxygen cycle (CNO cycle): The two papers, one on the proton–proton cycle, co-authored with Critchfield, and the other on the carbon-oxygen-nitrogen (CNO) cycle, were sent to the '' Physical Review'' for publication. After ''
Kristallnacht () or the Night of Broken Glass, also called the November pogrom(s) (german: Novemberpogrome, ), was a pogrom against Jews carried out by the Nazi Party's (SA) paramilitary and (SS) paramilitary forces along with some participation fro ...
'', Bethe's mother had become afraid to remain in Germany. Taking advantage of her Strasbourg origin, she was able to emigrate to the United States in June 1939 on the French quota, rather than the German one, which was full. Bethe's graduate student
Robert Marshak Robert Eugene Marshak (October 11, 1916 – December 23, 1992) was an American physicist, educator, and eighth president of the City College of New York. Biography Marshak was born in the Bronx, New York City. His parents, Harry and Rose Marshak ...
noted that the
New York Academy of Sciences The New York Academy of Sciences (originally the Lyceum of Natural History) was founded in January 1817 as the Lyceum of Natural History. It is the fourth oldest scientific society in the United States. An independent, nonprofit organization wi ...
was offering a $500 prize for the best unpublished paper on the topic of solar and stellar energy. So Bethe, in need of $250 to release his mother's furniture, withdrew the CNO cycle paper and sent it in to the New York Academy of Sciences. It won the prize, and Bethe gave Marshak $50 finder's fee and used $250 to release his mother's furniture. The paper was subsequently published in the ''Physical Review'' in March. It was a breakthrough in the understanding of the stars, and would win Bethe the
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
in 1967. In 2002, at age 96, Bethe sent a handwritten note to John N. Bahcall congratulating him on the use of solar neutrino observations to show that the CNO cycle accounts for approximately 7% of the Sun's energy; the neutrino observations had started with
Raymond Davis Jr. Raymond Davis Jr. (October 14, 1914 – May 31, 2006) was an American chemist and physicist. He is best known as the leader of the Homestake experiment in the 1960s-1980s, which was the first experiment to detect neutrinos emitted from the Sun; ...
, whose experiment was based on Bahcall's calculations and encouragement, and the note led to Davis's receiving a share of the 2002 Nobel Prize. Bethe married Rose Ewald, the daughter of Paul Ewald, on September 13, 1939, in a simple civil ceremony. She had emigrated to the United States and was a student at Duke University and they met while Bethe was lecturing there in 1937. They had two children, Henry and Monica. (Henry was a
contract bridge Contract bridge, or simply bridge, is a trick-taking card game using a standard 52-card deck. In its basic format, it is played by four players in two competing partnerships, with partners sitting opposite each other around a table. Millions ...
expert and former husband of Kitty Munson Cooper.) Bethe became a
naturalized citizen Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the in ...
of the United States in March 1941. Writing to Sommerfeld in 1947, Bethe confided that "I am much more at home in America than I ever was in Germany. As if I was born in Germany only by mistake, and only came to my true homeland at 28."


Manhattan Project

When the Second World War began, Bethe wanted to contribute to the war effort, but was unable to work on classified projects until he became a citizen. Following the advice of the
Caltech The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
aerodynamicist Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
Theodore von Kármán Theodore von Kármán ( hu, ( szőllőskislaki) Kármán Tódor ; born Tivadar Mihály Kármán; 11 May 18816 May 1963) was a Hungarian-American mathematician, aerospace engineer, and physicist who was active primarily in the fields of aeronaut ...
, Bethe collaborated with his friend Edward Teller on a theory of shock waves that are generated by the passage of a projectile through a gas. Bethe considered it one of their most influential papers. He also worked on a theory of armor penetration, which was immediately classified by the army, thus making it impossible for Bethe (who was not an American citizen at the time) to access further research on the theory. After receiving security clearance in December 1941, Bethe joined the
MIT Radiation Laboratory The Radiation Laboratory, commonly called the Rad Lab, was a microwave and radar research laboratory located at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. It was first created in October 1940 and operated until 31 ...
, where he invented the Bethe-hole directional coupler, which is used in
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
waveguide A waveguide is a structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction. Without the physical constraint of a waveguide, wave intensities de ...
s such as those used in
radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...
sets. In Chicago in June 1942, and then in July at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
, he participated in a series of meetings at the invitation of Robert Oppenheimer, which discussed the first designs for the atomic bomb. They went over the preliminary calculations by
Robert Serber Robert Serber (March 14, 1909 – June 1, 1997) was an American physicist who participated in the Manhattan Project. Serber's lectures explaining the basic principles and goals of the project were printed and supplied to all incoming scientific st ...
,
Stan Frankel Stanley Phillips Frankel (1919 – May, 1978) was an American computer scientist. He worked in the Manhattan Project and developed various computers as a consultant. Early life He was born in Los Angeles, attended graduate school at the Univers ...
, and others, and discussed the possibilities of using
uranium-235 Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exi ...
and
plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
. (Teller then raised the prospect of a thermonuclear device, Teller's "Super" bomb. At one point Teller asked if the nitrogen in the atmosphere could be set alight. It fell to Bethe and Emil Konopinski to perform the calculations demonstrating the virtual impossibility of such an occurrence.) "The fission bomb had to be done," he later recalled, "because the Germans were presumably doing it." When Oppenheimer was put in charge of forming a secret weapons design laboratory, Los Alamos, he appointed Bethe director of the T (Theoretical) Division, the laboratory's smallest, but most prestigious division. This move irked the equally qualified, but more difficult to manage Teller and
Felix Bloch Felix Bloch (23 October 1905 – 10 September 1983) was a Swiss-American physicist and Nobel physics laureate who worked mainly in the U.S. He and Edward Mills Purcell were awarded the 1952 Nobel Prize for Physics for "their development of new ...
, who had coveted the job. A series of disagreements between Bethe and Teller between February and June 1944 over the relative priority of Super research led to Teller's group being removed from T Division and placed directly under Oppenheimer. In September it became part of Fermi's new F Division. Bethe's work at Los Alamos included calculating the
critical mass In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fi ...
and efficiency of
uranium-235 Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exi ...
and the multiplication of nuclear fission in an exploding atomic bomb. Along with
Richard Feynman Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfl ...
, he developed a formula for calculating the bomb's explosive yield. After August 1944, when the laboratory was reorganized and reoriented to solve the problem of the implosion of the
plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
bomb, Bethe spent much of his time studying the hydrodynamic aspects of implosion, a job that he continued into 1944. In 1945, he worked on the
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
initiator, and later, on radiation propagation from an exploding atomic bomb. The
Trinity nuclear test Trinity was the code name of the first detonation of a nuclear weapon. It was conducted by the United States Army at 5:29 a.m. on July 16, 1945, as part of the Manhattan Project. The test was conducted in the Jornada del Muerto desert abo ...
validated the accuracy of T Division's results. When it was detonated in the New Mexico desert on July 16, 1945, Bethe's immediate concern was for its efficient operation, and not its moral implications. He is reported to have commented: "I am not a philosopher."


Hydrogen bomb

After the war, Bethe argued that a crash project for the hydrogen bomb should not be attempted, although after President
Harry Truman Harry S. Truman (May 8, 1884December 26, 1972) was the 33rd president of the United States, serving from 1945 to 1953. A leader of the Democratic Party, he previously served as the 34th vice president from January to April 1945 under Franklin ...
announced the beginning of such a project and the outbreak of the
Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...
, Bethe signed up and played a key role in the weapon's development. Although he saw the project through to its end, Bethe had hoped that it would be impossible to create the hydrogen bomb. He later remarked in 1968 on the apparent contradiction in his stance, having first opposed the development of the weapon and later helping to create it: As for his own role in the project and its relation to the dispute over who was responsible for the design, Bethe later said that: In 1954, Bethe testified on behalf of
J. Robert Oppenheimer J. Robert Oppenheimer (; April 22, 1904 – February 18, 1967) was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is oft ...
during the
Oppenheimer security hearing The Oppenheimer security hearing was a 1954 proceeding by the United States Atomic Energy Commission (AEC) that explored the background, actions, and associations of J. Robert Oppenheimer, the American scientist who had headed the Los Alamos Lab ...
. Specifically, Bethe argued that Oppenheimer's stances against developing the hydrogen bomb in the late 1940s had not hindered its development, a topic which was seen as a key motivating factor behind the hearing. Bethe contended that the developments that led to the successful
Teller–Ulam design A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a low ...
were a matter of serendipity and not a question of manpower or logical development of previously existing ideas. During the hearing, Bethe and his wife also tried hard to persuade
Edward Teller Edward Teller ( hu, Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb" (see the Teller–Ulam design), although he did not care for ...
against testifying. However, Teller did not agree, and his testimony played a major role in the revocation of Oppenheimer's
security clearance A security clearance is a status granted to individuals allowing them access to classified information (state or organizational secrets) or to restricted areas, after completion of a thorough background check. The term "security clearance" is ...
. While Bethe and Teller had been on very good terms during the prewar years, the conflict between them during the
Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
, and especially during the Oppenheimer episode, permanently marred their relationship.


Later work


Lamb shift

After the war ended, Bethe returned to Cornell. In June 1947, he participated in the Shelter Island Conference. Sponsored by the National Academy of Sciences and held at the Ram's Head Inn on
Shelter Island, New York Shelter Island is an island town in Suffolk County, New York, United States, near the eastern end of Long Island. The population was 3,253 at the 2020 census. Geography Shelter Island is nestled between the North and South Forks of Long Isla ...
, the conference on the "Foundations of Quantum Mechanics" was the first major physics conference held after the war. It was a chance for American physicists to come together, pick up where they had left off before the war, and establish the direction of post-war research. A major talking point at the conference was the discovery by
Willis Lamb Willis Eugene Lamb Jr. (; July 12, 1913 – May 15, 2008) was an American physicist who won the Nobel Prize in Physics in 1955 "for his discoveries concerning the fine structure of the hydrogen spectrum." The Nobel Committee that year awarded hal ...
and his graduate student, Robert Retherford, shortly before the conference began that one of the two possible quantum states of hydrogen atoms had slightly more energy than that predicted by the theory of
Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...
; this became known as the
Lamb shift In physics, the Lamb shift, named after Willis Lamb, is a difference in energy between two energy levels 2''S''1/2 and 2''P''1/2 (in term symbol notation) of the hydrogen atom which was not predicted by the Dirac equation, according to which th ...
. Oppenheimer and Weisskopf suggested that this was a result of
quantum fluctuation In quantum physics, a quantum fluctuation (also known as a vacuum state fluctuation or vacuum fluctuation) is the temporary random change in the amount of energy in a point in space, as prescribed by Werner Heisenberg's uncertainty principle. ...
s of the electromagnetic field, which gave the electron more energy. According to pre-war
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and spec ...
(QED), the energy of the electron consisted of the bare energy it had when uncoupled from an electromagnetic field, and the self-energy resulting from the electromagnetic coupling, but both were unobservable, since the electromagnetic field cannot be switched off. QED gave infinite values for the self-energies; but the Lamb shift showed that they were both real and finite.
Hans Kramers Hendrik Anthony "Hans" Kramers (17 December 1894 – 24 April 1952) was a Dutch physicist who worked with Niels Bohr to understand how electromagnetic waves interact with matter and made important contributions to quantum mechanics and statistical ...
proposed
renormalization Renormalization is a collection of techniques in quantum field theory, the statistical mechanics of fields, and the theory of self-similar geometric structures, that are used to treat infinities arising in calculated quantities by altering va ...
as a solution, but no one knew how to do the calculation. Bethe managed to perform the calculation on the train from New York to
Schenectady Schenectady () is a city in Schenectady County, New York, United States, of which it is the county seat. As of the 2020 census, the city's population of 67,047 made it the state's ninth-largest city by population. The city is in eastern New Y ...
, where he was working for
General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...
. He did so by realising that it was a non-relativistic process, which greatly simplified the calculation. The bare energy was easily removed as it was already included in the observed mass of the electron. The self energy term now increased logarithmically instead of linearly, making it mathematically convergent. Bethe arrived at a value for the Lamb shift of 1040 MHz, extremely close to that obtained experimentally by Lamb and Retherford. His paper, published in the ''Physical Review'' in August 1947, was only three pages long and contained just twelve mathematical equations, but was enormously influential. It had been presumed that the infinities indicated that QED was fundamentally flawed, and that a new, radical theory was required; Bethe demonstrated that this was not necessary. One of Bethe's most famous papers is one he never wrote: the 1948
Alpher–Bethe–Gamow paper In physical cosmology, the Alpher–Bethe–Gamow paper, or αβγ paper, was created by Ralph Alpher, then a physics PhD student, his advisor George Gamow and Hans Bethe. The work, which would become the subject of Alpher's PhD dissertation, arg ...
.
George Gamow George Gamow (March 4, 1904 – August 19, 1968), born Georgiy Antonovich Gamov ( uk, Георгій Антонович Гамов, russian: Георгий Антонович Гамов), was a Russian-born Soviet and American polymath, theoret ...
added Bethe's name (in absentia) without consulting him, knowing that Bethe would not mind, and against
Ralph Alpher Ralph Asher Alpher (February 3, 1921 – August 12, 2007) was an American cosmologist, who carried out pioneering work in the early 1950s on the Big Bang model, including Big Bang nucleosynthesis and predictions of the cosmic microwave backgroun ...
's wishes. This was apparently a reflection of Gamow's sense of humor, wanting to have a paper title that would sound like the first three letters of the Greek alphabet. As one of the ''Physical Review''s reviewers, Bethe saw the manuscript and struck out the words "in absentia".


Astrophysics

Bethe believed that the
atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron ...
was like a quantum liquid drop. He investigated the nuclear matter problem by considering the work conducted by
Keith Brueckner Keith Allen Brueckner (March 19, 1924 – September 19, 2014) was an American theoretical physicist who made important contributions in several areas of physics, including many-body theory in condensed matter physics, and laser fusion. Biography ...
on
perturbation theory In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middl ...
. Working with Jeffrey Goldstone, he produced a solution for the case where there was an infinite hard-core potential. Then, working with Baird Brandow and Albert Petschek, he came up with an approximation that converted the scattering equation into an easily solved
differential equation In mathematics, a differential equation is an equation that relates one or more unknown functions and their derivatives. In applications, the functions generally represent physical quantities, the derivatives represent their rates of change, an ...
. This then led him to the Bethe-Faddeev equation, a generalisation of
Ludvig Faddeev Ludvig Dmitrievich Faddeev (also ''Ludwig Dmitriyevich''; russian: Лю́двиг Дми́триевич Фадде́ев; 23 March 1934 – 26 February 2017) was a Soviet and Russian mathematical physicist. He is known for the discovery of the ...
's approach to three-body scattering. He then used these techniques to examine the
neutron stars A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
, which have densities similar to those of nuclei. Bethe continued to do research on supernovae, neutron stars, black holes, and other problems in theoretical astrophysics into his late nineties. In doing this, he collaborated with Gerald E. Brown of Stony Brook University. In 1978, Brown proposed that they collaborate on supernovae. These were reasonably well understood by this time, but the calculations were still a problem. Using techniques honed from decades of working with nuclear physics, and some experience with calculations involving nuclear explosions, Bethe tackled the problems involved in stellar gravitational collapse, and the way in which various factors affected a supernova explosion. Once again, he was able to reduce the problem to a set of differential equations, and to solve them. At age 85, Bethe wrote an important article about the solar neutrino problem, in which he helped establish the conversion mechanism for
electron neutrino The electron neutrino () is an elementary particle which has zero electric charge and a spin of . Together with the electron, it forms the first generation of leptons, hence the name electron neutrino. It was first hypothesized by Wolfgang Pauli ...
s into
muon neutrino The muon neutrino is an elementary particle which has the symbol () and zero electric charge. Together with the muon it forms the second generation of leptons, hence the name muon neutrino. It was discovered in 1962 by Leon Lederman, Melvin Schwar ...
s proposed by Stanislav Mikheyev, Alexei Smirnov, and
Lincoln Wolfenstein Lincoln Wolfenstein (February 10, 1923, Cleveland, Ohio – March 27, 2015, Oakland, California) was an American particle physicist who studied the weak interaction. Wolfenstein was born in 1923 and obtained his PhD in 1949 from the University o ...
to explain a vexing discrepancy between theory and experiment. Bethe argued that physics beyond the Standard Model was required to understand the solar neutrino problem, because it presumed that neutrinos have no mass, and therefore, cannot metamorphosize into each other; whereas the MSW effect required this to occur. Bethe hoped that corroborating evidence would be found by the
Sudbury Neutrino Observatory The Sudbury Neutrino Observatory (SNO) was a neutrino observatory located 2100 m underground in Vale's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large ...
(SNO) in
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...
by his 90th birthday, but he did not get the call from SNO until June 2001, when he was nearly 95. In 1996,
Kip Thorne Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist known for his contributions in gravitational physics and astrophysics. A longtime friend and colleague of Stephen Hawking and Carl Sagan, he was the Richard P. F ...
approached Bethe and Brown about
LIGO The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large ...
, the Laser Interferometer Gravitational-Wave Observatory designed to detect the gravitational waves from merging neutron stars and black holes. Since Bethe and Brown were good at calculating things that could not be seen, could they look at the mergers? The 90-year-old Bethe quickly became enthused and soon began the required calculations. The result was a 1998 paper on the "Evolution of Binary Compact Objects Which Merge", which Brown regarded as the best that the two produced together.


Political stances

In 1968, Bethe, along with IBM physicist
Richard Garwin Richard Lawrence Garwin (born April 19, 1928) is an American physicist, best known as the author of the first hydrogen bomb design. In 1978, Garwin was elected a member of the National Academy of Engineering for contributing to the application ...
, published an article criticising in detail the anti- ICBM defense system proposed by the
Department of Defense Department of Defence or Department of Defense may refer to: Current departments of defence * Department of Defence (Australia) * Department of National Defence (Canada) * Department of Defence (Ireland) * Department of National Defense (Philipp ...
. The two physicists described in the article that nearly any measure taken by the USA would be easily thwarted with the deployment of relatively simple decoys. Bethe was one of the primary voices in the scientific community behind the signing of the 1963
Partial Test Ban Treaty The Partial Test Ban Treaty (PTBT) is the abbreviated name of the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, which prohibited all test detonations of nuclear weapons except for those conducted ...
prohibiting further atmospheric testing of nuclear weapons. During the 1980s and 1990s, Bethe campaigned for the peaceful use of nuclear energy. After the Chernobyl disaster, Bethe was part of a committee of experts who analysed the incident. They concluded that the reactor suffered from a fundamentally faulty design and also, that human error had contributed significantly to the accident. "My colleagues and I established," he explained "that the Chernobyl disaster tells us about the deficiencies of the Soviet political and administrative system rather than about problems with nuclear power." Throughout his life Bethe remained a strong advocate for electricity from nuclear energy, which he described in 1977 as "a necessity, not merely an option." In the 1980s he and other physicists opposed the Strategic Defense Initiative missile system conceived by the Ronald Reagan administration. In 1995, at the age of 88, Bethe wrote an open letter calling on all scientists to "cease and desist" from working on any aspect of nuclear weapons development and manufacture. In 2004, he joined 47 other Nobel laureates in signing a letter endorsing
John Kerry John Forbes Kerry (born December 11, 1943) is an American attorney, politician and diplomat who currently serves as the first United States special presidential envoy for climate. A member of the Forbes family and the Democratic Party, he ...
for President of the United States as someone who would "restore science to its appropriate place in government". Historian Gregg Herken wrote:


Personal life

Bethe's hobbies included a passion for stamp-collecting. He loved the outdoors and was an enthusiastic hiker all his life, exploring the
Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Swi ...
and the
Rockies The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
. He died in his home in
Ithaca, New York Ithaca is a city in the Finger Lakes region of New York, United States. Situated on the southern shore of Cayuga Lake, Ithaca is the seat of Tompkins County and the largest community in the Ithaca metropolitan statistical area. It is named ...
, on March 6, 2005, of congestive heart failure. He was survived by his wife, Rose Ewald Bethe, and their two children. At the time of his death, he was the John Wendell Anderson Professor of Physics, Emeritus, at
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...
.


Honors and awards

Bethe received numerous honors and awards in his lifetime and afterward. He became a
Fellow A fellow is a concept whose exact meaning depends on context. In learned or professional societies, it refers to a privileged member who is specially elected in recognition of their work and achievements. Within the context of higher education ...
of the
American Academy of Arts and Sciences The American Academy of Arts and Sciences (abbreviation: AAA&S) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, a ...
in 1947, and that year, he also received the National Academy of Sciences's
Henry Draper Medal The Henry Draper Medal is awarded every 4 years by the United States National Academy of Sciences "for investigations in astronomical physics". Named after Henry Draper, the medal is awarded with a gift of USD $15,000. The medal was established ...
. He was awarded the
Max Planck Medal The Max Planck medal is the highest award of the German Physical Society , the world's largest organization of physicists, for extraordinary achievements in theoretical physics. The prize has been awarded annually since 1929, with few exceptions, ...
in 1955, the
Franklin Medal The Franklin Medal was a science award presented from 1915 until 1997 by the Franklin Institute The Franklin Institute is a science museum and the center of science education and research in Philadelphia, Pennsylvania. It is named after the Am ...
in 1959, the
Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NG ...
Eddington Medal and the
United States Atomic Energy Commission The United States Atomic Energy Commission (AEC) was an agency of the United States government established after World War II by U.S. Congress to foster and control the peacetime development of atomic science and technology. President ...
Enrico Fermi Award The Enrico Fermi Award is a scientific award conferred by the President of the United States. It is awarded to honor scientists of international stature for their lifetime achievement in the development, use, or production of energy. It was establ ...
in 1961, the
Rumford Prize Founded in 1796, the Rumford Prize, awarded by the American Academy of Arts and Sciences, is one of the oldest scientific prizes in the United States. The prize recognizes contributions by scientists to the fields of heat and light. These terms ...
in 1963, the
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
in 1967, the
National Medal of Science The National Medal of Science is an honor bestowed by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral and social scienc ...
in 1975, the
Oersted Medal The Oersted Medal recognizes notable contributions to the teaching of physics. Established in 1936, it is awarded by the American Association of Physics Teachers. The award is named for Hans Christian Ørsted. It is the Association's most prest ...
in 1993, the
Bruce Medal The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was fi ...
in 2001, and posthumously in 2005, the Benjamin Franklin Medal for Distinguished Achievement in the Sciences by the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
. Bethe was elected Foreign Member of the Royal Society (ForMemRS) in 1957, and he gave the 1993 Bakerian Lecture at the Royal Society on the Mechanism of Supernovae. In 1978 he was elected a Member of the
German Academy of Sciences Leopoldina The German National Academy of Sciences Leopoldina (german: Deutsche Akademie der Naturforscher Leopoldina – Nationale Akademie der Wissenschaften), short Leopoldina, is the national academy of Germany, and is located in Halle (Saale). Founde ...
. Cornell named the third of five new
residential college A residential college is a division of a university that places academic activity in a community setting of students and faculty, usually at a residence and with shared meals, the college having a degree of autonomy and a federated relationship wi ...
s, each of which is named after a distinguished former member of the Cornell faculty, as the Hans Bethe House after him. Similarly named after him is the Hans Bethe Center, 322 Fourth Street NE, Washington, D.C., home to the
Council for a Livable World Council for a Livable World is a Washington, D.C.-based non-profit advocacy organization dedicated to eliminating the U.S. arsenal of nuclear weapons. Its stated aim is for "progressive national security policies and helping elect congressional c ...
, where Bethe was a longtime board member, as well as the Bethe Center for Theoretical Physics at
University of Bonn The Rhenish Friedrich Wilhelm University of Bonn (german: Rheinische Friedrich-Wilhelms-Universität Bonn) is a public research university located in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the ( en, Rhine ...
in Germany. An asteroid, 30828 Bethe, that was discovered in 1990 was named after him. The American Physical Society
Hans Bethe Prize The Hans A. Bethe Prize, is presented annually by the American Physical Society. The prize honors outstanding work in theory, experiment or observation in the areas of astrophysics, nuclear physics, nuclear astrophysics, or closely related fields ...
was named after him as well.


Selected publications

* Bethe, H. A
"Theory of High Frequency Rectification by Silicon Crystals"
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...
(MIT) Radiation Laboratory,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(through predecessor agency the Atomic Energy Commission), (October 29, 1942). * Bethe, H. A
"Theoretical Estimate of Maximum Possible Nuclear Explosion"
Knolls Atomic Power Laboratory-Schenectady, N.Y.,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(through predecessor agency the Atomic Energy Commission), (January 31, 1950). * Bethe, H. A.; Rajaraman, R
"Three-body Problem in Nuclear Matter"
University of Southern California-Los Angeles,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(through predecessor agency the Atomic Energy Commission), (1967). * Bethe, H. A
"Note on Inverse Bremsstrahlung in a Strong Electromagnetic Field"
Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
(LANL),
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(through predecessor agency the Atomic Energy Commission), (September 1972). * Bethe, H. A
"Pauli Principle and Pion Scattering"
Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
(LANL),
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(through predecessor agency the Atomic Energy Commission), (October 1972). * Bethe, H. A
"Fusion Hybrid Reactor"
Sandia National Laboratories Sandia National Laboratories (SNL), also known as Sandia, is one of three research and development laboratories of the United States Department of Energy's National Nuclear Security Administration (NNSA). Headquartered in Kirtland Air Force Bas ...
,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
, (August 1981).


See also

*
Hydrogen anion The hydrogen anion, H−, is a negative ion of hydrogen, that is, a hydrogen atom that has captured an extra electron. The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is calle ...


Notes


Citations


References

* * * * * * * * * *


External links

*
1986 Video Interview
War and Peace in the Nuclear Age
1993 Audio Interview with Hans Bethe by Richard Rhodes
Voices of the Manhattan Project
1982 Audio Interview with Hans Bethe by Martin Sherwin
Voices of the Manhattan Project
2014 Video Interview with Rose Bethe by Cynthia C. Kelly
Voices of the Manhattan Project

from the Cornell University
Text of the Eddington Medal award speech
*
Obituaries An obituary (obit for short) is an article about a recently deceased person. Newspapers often publish obituaries as news articles. Although obituaries tend to focus on positive aspects of the subject's life, this is not always the case. Acc ...
*
Hans Bethe obituary
from
The Economist ''The Economist'' is a British weekly newspaper printed in demitab format and published digitally. It focuses on current affairs, international business, politics, technology, and culture. Based in London, the newspaper is owned by The Eco ...
magazine *
Hans Bethe obituary
from
The Guardian ''The Guardian'' is a British daily newspaper. It was founded in 1821 as ''The Manchester Guardian'', and changed its name in 1959. Along with its sister papers ''The Observer'' and ''The Guardian Weekly'', ''The Guardian'' is part of the Gu ...
Newspaper
Annotated bibliography for Hans Bethe from the Alsos Digital Library for Nuclear Issues

Oral History interview transcript with Hans Bethe on 17 January 1964, American Institute of Physics, Niels Bohr Library and Archives
- interviewed by Thomas S. Kuhn in Dwinelle Hall at
UC Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant uni ...

Oral History interview transcript with Hans Bethe on 27 October 1966, American Institute of Physics, Niels Bohr Library and Archives
- Session I, interviewed by Charles Weiner and
Jagdish Mehra Jagdish Mehra (April 8, 1931 – September 14, 2008) was an Indian-American historian of science. Academic career Mehra was educated at Allahabad University, the Max Planck Institut für Physik and the University of California at Los Angeles a ...
at
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

Oral History interview transcript with Hans Bethe on 17 November 1967, American Institute of Physics, Niels Bohr Library and Archives
- Session II, interviewed by Charles Weiner at
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

Oral History interview transcript with Hans Bethe on 8 May 1972, American Institute of Physics, Niels Bohr Library and Archives
- Session III, interviewed by Charles Weiner at
Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

Oral History interview transcript with Hans Bethe on 29 April 1981, American Institute of Physics, Niels Bohr Library and Archives
- interviewed by Lillian Hoddeson in
Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

Video of a talk entitled "Writing the Biography of a Living Scientist: Hans Bethe,"
delivered by S.S. Schweber
Hans Bethe tells his life story
at
Web of Stories Web of Stories is an online collection of thousands of autobiographical video-stories. Web of Stories, originally known as Science Archive, was set up to record the life stories of scientists. When it expanded to include the lives of authors, mov ...
* * * * {{DEFAULTSORT:Bethe, Hans 1906 births 2005 deaths Nobel laureates in Physics American Nobel laureates German Nobel laureates 20th-century American physicists Academics of the Victoria University of Manchester Alsatian-German people Alsatian Jews Jewish American atheists American people of German-Jewish descent American nuclear physicists Cornell University faculty Enrico Fermi Award recipients Jewish emigrants from Nazi Germany to the United States German atheists German nuclear physicists Jewish American scientists Jewish physicists Manhattan Project people National Medal of Science laureates People from Alsace-Lorraine Recipients of the Pour le Mérite (civil class) Goethe University Frankfurt alumni Ludwig Maximilian University of Munich alumni University of Tübingen faculty Vannevar Bush Award recipients Foreign Members of the Royal Society Foreign Members of the Russian Academy of Sciences Fellows of the American Academy of Arts and Sciences Theoretical physicists Quantum physicists Winners of the Max Planck Medal Niels Bohr International Gold Medal recipients Goethe University Frankfurt faculty Scientists from Frankfurt Members of JASON (advisory group) Members of the German Academy of Sciences Leopoldina Rare earth scientists Fellows of the American Physical Society Presidents of the American Physical Society