Bruno Pontecorvo facts for kids
Quick facts for kids
Bruno Pontecorvo
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Pontecorvo in 1955
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| Born | 22 August 1913 Marina di Pisa, Italy
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| Died | 24 September 1993 (aged 80) Dubna, Moscow Oblast, Russia
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| Citizenship | Italy, Britain, Soviet Union, Russia |
| Alma mater | University of Rome La Sapienza |
| Known for |
Neutrino oscillation
Pontecorvo–Maki–Nagakawa–Sakata matrix |
| Relatives | Gillo Pontecorvo (brother) Guido Pontecorvo (brother) Marco Pontecorvo (nephew) |
| Scientific career | |
| Fields | Nuclear physics |
| Institutions | Collège de France Well Surveys Montreal Laboratory Chalk River Laboratories Atomic Energy Research Establishment Joint Institute for Nuclear Research |
| Academic advisors | Enrico Fermi |
Bruno Pontecorvo (Italian: [ponteˈkɔrvo]; Russian: Бру́но Макси́мович Понтеко́рво, Bruno Maksimovich Pontecorvo; 22 August 1913 – 24 September 1993) was an Italian and Soviet scientist who studied atoms. He was an early helper of Enrico Fermi and wrote many important studies about how tiny particles behave, especially about neutrinos. Neutrinos are very tiny particles with almost no mass and no electric charge.
Pontecorvo was a strong believer in communism. In 1950, he moved to the Soviet Union. There, he continued his research on how muons decay and on neutrinos. The special Pontecorvo Prize was created in his honor in 1995.
Bruno was the fourth of eight children in a wealthy Jewish-Italian family. He studied physics at the Sapienza University of Rome with Enrico Fermi. He was the youngest of Fermi's famous group of scientists, known as the Via Panisperna boys. In 1934, he helped with Fermi's important experiment. This experiment showed how slow neutrons work, which later helped lead to the discovery of nuclear fission (splitting atoms).
In 1936, he moved to Paris to do research with Irène and Frédéric Joliot-Curie. He joined the Italian Communist Party because of his cousin, Emilio Sereni. In 1938, Italy passed laws against Jewish people. This caused his family to leave Italy and move to Britain, France, and the United States.
During World War II, when the German Army got close to Paris, Pontecorvo and his family had to leave. He eventually went to Tulsa, Oklahoma. There, he used his knowledge of physics to help find oil and minerals. In 1943, he joined the British Tube Alloys team in Canada. This team was part of the Manhattan Project, which worked to develop the first atomic bombs.
At Chalk River Laboratories, he helped design the nuclear reactor ZEEP. This was the first reactor outside the United States, and it started working in 1945. Later, the NRX reactor started in 1947. He also studied cosmic rays, the decay of muons, and his main interest, neutrinos. In 1949, he moved to Britain and worked for the Atomic Energy Research Establishment at Harwell.
After he moved to the Soviet Union in 1950, he worked at the Joint Institute for Nuclear Research (JINR) in Dubna. He had suggested using chlorine to find neutrinos. In 1959, he wrote a paper saying that the electron neutrino (Error no symbol defined) and the muon neutrino (Error no symbol defined) were different particles.
Scientists later detected solar neutrinos with the Homestake experiment. But they found only about one-third to one-half of the number they expected. This was called the solar neutrino problem. To solve this, Pontecorvo suggested that neutrinos might change from one type to another. This idea is called neutrino oscillation. The existence of these changes was finally proven by the Super-Kamiokande experiment in 1998. He also predicted in 1958 that supernovae (exploding stars) would release many neutrinos. This was confirmed in 1987 when Supernova SN1987A was detected by special neutrino detectors.
Contents
Biography
Early Life and Education
Bruno Pontecorvo was born on 22 August 1913 in Marina di Pisa, Italy. He was the fourth of eight children. His older brother Guido became a geneticist (a scientist who studies genes). His younger brother Gillo became a famous film director. His family was wealthy, and his father owned textile factories. The family was Jewish but did not strictly follow religious traditions.
Bruno first started studying engineering at the University of Pisa. But after two years, in 1931, he decided to switch to physics. His brother Guido suggested he study at the University of Rome La Sapienza. There, Enrico Fermi had gathered a group of bright young scientists. They were known as the Via Panisperna boys, named after the street where their physics institute was located. Bruno was admitted to the third year of physics at age 18. Fermi described Pontecorvo as "one of the brightest men" he had met. Since he was the youngest, the group nicknamed him Cucciolo, which means "puppy".
In 1934, Pontecorvo helped with Fermi's famous experiment. This experiment showed how slow neutrons behave. This discovery was very important and led to the understanding of nuclear fission. Pontecorvo's name was on the patent for "To increase the production of artificial radioactivity with neutron bombardment." He also helped write an important paper about slow neutrons. This paper showed that hydrogen slowed neutrons more than heavy elements. It also showed that slow neutrons were absorbed more easily.
Early Career and World War II
In February 1936, Pontecorvo left Italy and moved to Paris. He worked in the laboratory of Irène and Frédéric Joliot-Curie at the Collège de France. He studied how neutrons collide with protons and how atoms change their energy levels. During this time, he became interested in communism, a political idea. He met Helene Marianne Nordblom, a Swedish woman, and they later married.
In 1938, Italy passed new laws against Jewish people. Because of these laws, Pontecorvo could not return to Italy. Many of his family members also had to leave Italy. Fermi, his mentor, moved to the United States.
Working with French physicist André Lazard, Pontecorvo discovered "nuclear phosphorescence." This is when X-rays are released when neutrons and protons are excited and then return to their normal state. He also found that some types of atoms do not change into other elements when they decay. This discovery was important for using these atoms in medicine.
Escape from France
In June 1939, Pontecorvo tried to get a visa to visit Sweden, but it was not approved. On 23 August, he heard about the Molotov–Ribbentrop Pact, a non-aggression agreement between Germany and the Soviet Union. The next day, he joined the French Communist Party. Marianne joined him in Paris in September 1939, just after Britain and France declared war on Germany. They married in January 1940.
In May 1940, as German forces approached Paris, Bruno and Marianne decided to leave. On 13 June, just before the Germans entered Paris, Pontecorvo, his brother Gillo, cousin Emilio Sereni, and Salvador Luria left the city on bicycles. They traveled for ten days to reach Toulouse. Eventually, Pontecorvo, Marianne, and their son Gil, along with other family members, traveled to Lisbon. From there, they took a ship to New York City in August 1940. In New York, he visited Fermi.
Working in Oklahoma
In Tulsa, Oklahoma, Pontecorvo started working for a company called Well Surveys. This company wanted to use physics to find minerals. Pontecorvo used his knowledge of neutrons to create a device. This device could find different elements underground by making the rocks slightly radioactive. By June 1941, his device could tell the difference between different types of rock, like shale, limestone, and sandstone. This technique was one of the first practical uses of slow neutrons and is still used today for finding oil and gas. He filed four patents for his inventions.
The Tube Alloys Project
In 1942, Pontecorvo was offered a job with the Tube Alloys team in Canada. This was a British project to develop nuclear energy. He moved to Montreal with his family in February 1943. The Montreal team designed a nuclear reactor that used heavy water. In August 1943, the Tube Alloys project joined the American Manhattan Project.
John Cockcroft became the director of the Montreal Laboratory in 1944. He decided to build the reactor at the Chalk River Laboratories for safety. Pontecorvo worked on the design of the ZEEP reactor, which started working on 5 September 1945. This was the first nuclear reactor outside the United States. His second son was born in 1944, and his third son in 1945. Pontecorvo also studied cosmic rays, the decay of muons, and neutrinos. He wrote many papers about reactor design. He also helped search for uranium deposits in Canada.
After the war, Pontecorvo received many job offers from universities in the United States. But he chose to join the British Atomic Energy Research Establishment (AERE) in February 1946. He stayed at Chalk River to help start the new NRX reactor in 1947. The NRX reactor was very powerful, five times stronger than any other reactor at the time. In 1948, he became a British citizen. He finally moved to the United Kingdom in January 1949.
Move to the Soviet Union
At Harwell, Pontecorvo continued to work on reactor design. He was part of a committee that discussed how to produce and use materials for reactors. In 1950, another scientist at Harwell, Klaus Fuchs, was arrested for being a spy. This made security at AERE much stricter. Pontecorvo was interviewed, and it was suggested he move to a job where he would not have access to top-secret information. He was offered a professorship at the University of Liverpool.
On 1 September 1950, while on holiday in Italy, Pontecorvo suddenly flew from Rome to Stockholm with his wife and three sons. He did not tell his friends or family. On 2 September, he was helped by Soviet agents to enter the Soviet Union from Finland. His sudden disappearance caused concern among Western intelligence agencies. They worried about atomic secrets being passed to the Soviet Union.
In the Soviet Union, Pontecorvo was welcomed with honors and special privileges. He worked at the Joint Institute for Nuclear Research (JINR) in Dubna until his death. He focused entirely on studying tiny particles and continued his research on neutrinos and muon decay. He received many awards for his research, including the Stalin Prize in 1953 and the Lenin Prize in 1964. In 1955, he gave a public press conference. He explained why he chose to leave the West and work in the Soviet Union. The United Kingdom took away his British citizenship in 1955. For many years, Pontecorvo was not allowed to leave the Soviet Union. His first trip abroad was in 1978, when he visited Italy. After that, he often visited Italy and sometimes other countries.
Later Life and Discoveries
Bruno Pontecorvo's scientific work was full of brilliant ideas. Many of these ideas were about the neutrino. The neutrino is a subatomic particle that was first suggested by Wolfgang Pauli in 1930. Pauli thought neutrinos existed to explain why some energy seemed to disappear during a process called beta decay. Fermi later named it the "neutrino," which means "little neutral one" in Italian.
In 1945, Pontecorvo suggested that a neutrino hitting a chlorine atom could turn it into a different, unstable atom called argon-37. This argon-37 would then release a tiny electron, which could be detected. This idea was later used in experiments to find neutrinos.
Scientists later used this idea to search for solar neutrinos. These are neutrinos produced by the Sun during nuclear fusion reactions. In the late 1960s, Ray Davis and John N. Bahcall detected solar neutrinos in the Homestake Experiment. This was the first time solar neutrinos were successfully found. However, they found only about one-third to one-half of the number they expected. This became known as the solar neutrino problem. For a while, scientists even wondered if the Sun might be burning out!
Pontecorvo had already found a solution to this problem in 1968. In 1959, he was thinking about experiments that could be done with a powerful accelerator. He considered a project to study muons. In a 1959 paper, Pontecorvo listed many possible reactions involving neutrinos. He noted that some reactions could not happen unless the electron neutrino (Error no symbol defined) and the muon neutrino (Error no symbol defined) were the same particle. This paper introduced the way we write about neutrinos today. It also explained why he thought there were two types of neutrinos. The prediction that electron neutrinos are different from muon neutrinos was confirmed in 1962.
Pontecorvo's solution to the solar neutrino problem involved an idea he had first thought about in 1957. This was the idea that neutrinos might change into other types of neutrinos. This is called neutrino oscillation. It meant that somewhere between the Sun and Earth, electron neutrinos could transform into muon neutrinos. For this to happen, neutrinos could not have zero mass. The existence of these oscillations was finally proven by the Super-Kamiokande experiment in 1998 and later by other experiments.
This important prediction was recognized by the 2015 Nobel Prize in physics. It was awarded to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass." Pontecorvo also predicted in 1958 that supernovae (exploding stars) would produce strong bursts of neutrinos. This was confirmed in 1987 when Supernova SN1987A was detected by neutrino detectors.
Pontecorvo died in Dubna, Russia, on 24 September 1993. He had Parkinson's disease. As he wished, half of his ashes were buried in the Protestant Cemetery in Rome, Italy. The other half were buried in Dubna, Russia. In 1995, the special Pontecorvo Prize was created in his honor by the Joint Institute for Nuclear Research. This prize is given every year to a scientist for important discoveries in particle physics. In 2006, a special plaque was placed on Pontecorvo's house in Moscow to celebrate him.
See also
In Spanish: Bruno Pontecorvo para niños
