Carl David Anderson

Carl David Anderson (September 3, 1905 – January 11, 1991) was an American physicist. He is best known for his discovery of the positron in 1932, an achievement for which he received the 1936 Nobel Prize in Physics, and of the muon in 1936.

Carl David Anderson
Carl David Anderson
Anderson in 1936
BornSeptember 3, 1905
DiedJanuary 11, 1991 (aged 85)
Alma materCalifornia Institute of Technology (B.S. and Ph.D)
Known forDiscovery of the positron
Discovery of the muon
AwardsNobel Prize in Physics (1936)
Elliott Cresson Medal (1937)
Scientific career
InstitutionsCalifornia Institute of Technology
ThesisSpace-distribution of x-ray photoelectrons ejected from the K and L atomic energy-levels (1930)
Doctoral advisorRobert A. Millikan
Other academic advisorsWilliam Smythe
Doctoral students
Other notable studentsCinna Lomnitz


Anderson was born in New York City, the son of Swedish immigrants. He studied physics and engineering at Caltech (B.S., 1927; Ph.D., 1930). Under the supervision of Robert A. Millikan, he began investigations into cosmic rays during the course of which he encountered unexpected particle tracks in his (modern versions now commonly referred to as an Anderson) cloud chamber photographs that he correctly interpreted as having been created by a particle with the same mass as the electron, but with opposite electrical charge. This discovery, announced in 1932 and later confirmed by others, validated Paul Dirac's theoretical prediction of the existence of the positron. Anderson first detected the particles in cosmic rays. He then produced more conclusive proof by shooting gamma rays produced by the natural radioactive nuclide ThC'' (208Tl)[1] into other materials, resulting in the creation of positron-electron pairs. For this work, Anderson shared the 1936 Nobel Prize in Physics with Victor Hess.[2] Fifty years later, Anderson acknowledged that his discovery was inspired by the work of his Caltech classmate Chung-Yao Chao, whose research formed the foundation from which much of Anderson's work developed but was not credited at the time.[3]

Also in 1936, Anderson and his first graduate student, Seth Neddermeyer, discovered the muon (or 'mu-meson', as it was known for many years), a subatomic particle 207 times more massive than the electron, but with the same negative electric charge and spin 1/2 as the electron, again in cosmic rays. Anderson and Neddermeyer at first believed that they had seen the pion, a particle which Hideki Yukawa had postulated in his theory of the strong interaction. When it became clear that what Anderson had seen was not the pion, the physicist I. I. Rabi, puzzled as to how the unexpected discovery could fit into any logical scheme of particle physics, quizzically asked "Who ordered that?" (sometimes the story goes that he was dining with colleagues at a Chinese restaurant at the time). The muon was the first of a long list of subatomic particles whose discovery initially baffled theoreticians who could not make the confusing "zoo" fit into some tidy conceptual scheme. Willis Lamb, in his 1955 Nobel Prize Lecture, joked that he had heard it said that "the finder of a new elementary particle used to be rewarded by a Nobel Prize, but such a discovery now ought to be punished by a 10,000 dollar fine."[4]

Anderson spent all of his academic and research career at Caltech. During World War II, he conducted research in rocketry there. He was elected a Fellow of the American Academy of Arts and Sciences in 1950.[5] He died on January 11, 1991, and his remains were interred in the Forest Lawn, Hollywood Hills Cemetery in Los Angeles, California. His wife Lorraine died in 1984.

Select publications

  • Anderson, C. D. (1933). "The Positive Electron". Physical Review. 43 (6): 491. Bibcode:1933PhRv...43..491A. doi:10.1103/PhysRev.43.491.
  • Anderson, C. D. (1932). "The Apparent Existence of Easily Deflectable Positives". Science. 76 (1967): 238–9. Bibcode:1932Sci....76..238A. doi:10.1126/science.76.1967.238. PMID 17731542.
  • Anderson, C. D. (technical advisor) (1957). The Strange Case of the Cosmic Rays. The Bell Laboratory Science Series.


  1. ^ ThC" is a historical designation of 208Tl, see Decay chains
  2. ^ The Nobel Prize in Physics 1936.
  3. ^ Cao, Cong (2004). "Chinese Science and the 'Nobel Prize Complex'" (PDF). Minerva. 42 (2): 154. doi:10.1023/b:mine.0000030020.28625.7e. ISSN 0026-4695.
  4. ^ Willis E. Lamb, Jr. (December 12, 1955) Fine structure of the hydrogen atom. Nobel Lecture
  5. ^ "Book of Members, 1780–2010: Chapter A" (PDF). American Academy of Arts and Sciences. Retrieved April 17, 2011.

External links


1905 (MCMV)

was a common year starting on Sunday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1905th year of the Common Era (CE) and Anno Domini (AD) designations, the 905th year of the 2nd millennium, the 5th year of the 20th century, and the 6th year of the 1900s decade. As of the start of 1905, the Gregorian calendar was

13 days ahead of the Julian calendar, which remained in localized use until 1923.

As the second year of the massive Russo-Japanese War begins, more than 100,000 die in the largest world battles of that era, and the war chaos leads to the 1905 Russian Revolution against the Tsar (Shostakovich's 11th Symphony is subtitled The Year 1905 to commemorate this) and the start of Revolution in the Kingdom of Poland. Canada and the U.S. expand west, with the Alberta and Saskatchewan provinces and the founding of Las Vegas. 1905 is also the annus mirabilis of Albert Einstein, who publishes papers which lay the foundations for quantum physics, introduces the special theory of relativity, explains Brownian motion and establishes mass–energy equivalence.

1905 in science

The year 1905 in science and technology involved some significant events, particularly in physics, listed below.

1936 in science

The year 1936 in science and technology involved some significant events, listed below.

Antimatter weapon

An antimatter weapon is a theoretically possible device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons cannot yet be produced due to the current cost of production of antimatter (estimated at 63 trillion dollars per gram) given the extremely limited technology available to create it in sufficient masses to be viable in a weapon, and the fact that it annihilates upon touching ordinary matter, making containment very difficult.

The paramount advantage of such a theoretical weapon is that antimatter and matter collisions result in the entire sum of their mass energy equivalent being released as energy, which is at least an order of magnitude greater than the energy release of the most efficient fusion weapons (100% vs 7-10%). Annihilation requires and converts exactly equal masses of antimatter and matter by the collision which releases the entire mass-energy of both, which for 1 gram is ~1.8×1014 joules. Using the convention that 1 kiloton TNT equivalent = 4.184×1012 joules (or one trillion calories of energy), one gram of antimatter reacting with one gram of ordinary matter results in 42.96 kilotons-equivalent of energy (though there is considerable "loss" by production of neutrinos).


The antineutron is the antiparticle of the neutron with symbol n. It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number (+1 for neutron, −1 for the antineutron). This is because the antineutron is composed of antiquarks, while neutrons are composed of quarks. The antineutron consists of one up antiquark and two down antiquarks.

Since the antineutron is electrically neutral, it cannot easily be observed directly. Instead, the products of its annihilation with ordinary matter are observed. In theory, a free antineutron should decay into an antiproton, a positron and a neutrino in a process analogous to the beta decay of free neutrons. There are theoretical proposals of neutron–antineutron oscillations, a process that implies the violation of the baryon number conservation.The antineutron was discovered in proton–antiproton collisions at the Bevatron (Lawrence Berkeley National Laboratory) by Bruce Cork in 1956, one year after the antiproton was discovered.


The antiproton,
, (pronounced p-bar) is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.

The existence of the antiproton with −1 electric charge, opposite to the +1 electric charge of the proton, was predicted by Paul Dirac in his 1933 Nobel Prize lecture. Dirac received the Nobel Prize for his previous 1928 publication of his Dirac equation that predicted the existence of positive and negative solutions to the Energy Equation () of Einstein and the existence of the positron, the antimatter analog to the electron, with positive charge and opposite spin.

The antiproton was first experimentally confirmed in 1955 at the Bevatron particle accelerator by University of California, Berkeley physicists Emilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics. In terms of valence quarks, an antiproton consists of two up antiquarks and one down antiquark (uud). The properties of the antiproton that have been measured all match the corresponding properties of the proton, with the exception that the antiproton has electric charge and magnetic moment that are the opposites of those in the proton. The questions of how matter is different from antimatter, and the relevance of antimatter in explaining how our universe survived the Big Bang, remain open problems—open, in part, due to the relative scarcity of antimatter in today's universe.

Carl Anderson

Carl Anderson may refer to:

Carl Anderson (American football) (1898–1978), American college football coach

Carl Anderson (art director) (1903–1989), American art director

Carl Anderson (basketball) (1913–2001), American professional basketball player

Carl Anderson (North Dakota politician) (1897–1945), North Dakota State Treasurer

Carl Anderson (South Carolina politician) (born 1961), member of the South Carolina House of Representatives

Carl Anderson (singer) (1945–2004), American singer, film and theatre actor

Carl A. Anderson (born 1951), Supreme Knight of the Knights of Columbus

Carl C. Anderson (1877–1912), U.S. Representative from Ohio

Carl David Anderson (1905–1991), physicist

Carl Thomas Anderson (1865–1948), cartoonist

Carl Anderson (Toronto official)

Chung-Yao Chao

Chung-Yao Chao (simplified Chinese: 赵忠尧; traditional Chinese: 趙忠堯; pinyin: Zhào Zhōngyáo; Wade–Giles: Chao Chung-yao; 27 June 1902 – 28 May 1998) was a Chinese physicist. He studied the scattering of gamma rays in lead by pair production in 1930, without knowing that positrons were involved in the anomalously high scattering cross-section. When the positron was discovered by Carl David Anderson in 1932, confirming the existence of Paul Dirac's "antimatter", it became clear that positrons could explain Chung-Yao Chao's earlier experiments, with the gamma rays being emitted from electron-positron annihilation.

He entered Nanjing Higher Normal School (later renamed National Southeastern University, National Central University and Nanjing University), in 1920 and earned a B.S. in physics in 1925. Then he earned a Ph.D. degree in physics under supervision of Nobel Prize laureate Robert Andrews Millikan at California Institute of Technology in 1930. Later he went back to China and joined the physics faculty of Tsinghua University in Beijing.

Donald A. Glaser

Donald Arthur Glaser (September 21, 1926 – February 28, 2013) was an American physicist, neurobiologist, and the winner of the 1960 Nobel Prize in Physics for his invention of the bubble chamber used in subatomic particle physics.

Experimental physics

Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments. Methods vary from discipline to discipline, from simple experiments and observations, such as the Cavendish experiment, to more complicated ones, such as the Large Hadron Collider.

John H. Francis Polytechnic High School

John H. Francis Polytechnic High School is a secondary school located in the Sun Valley neighborhood of Los Angeles, California, United States. It serves grades 9 through 12 and is a part of the Los Angeles Unified School District. Despite its name, Polytechnic is a comprehensive high school.

List of Nobel laureates

The Nobel Prizes (Swedish: Nobelpriset, Norwegian: Nobelprisen) are prizes awarded annually by the Royal Swedish Academy of Sciences, the Swedish Academy, the Karolinska Institutet, and the Norwegian Nobel Committee to individuals and organizations who make outstanding contributions in the fields of chemistry, physics, literature, peace, and physiology or medicine. They were established by the 1895 will of Alfred Nobel, which dictates that the awards should be administered by the Nobel Foundation. The Nobel Memorial Prize in Economic Sciences was established in 1968 by the Sveriges Riksbank, the central bank of Sweden, for contributions to the field of economics. Each recipient, or "laureate", receives a gold medal, a diploma, and a sum of money, which is decided annually by the Nobel Foundation.

List of Swedish Americans

The following is a list of notable Swedish Americans. Including both original immigrants who obtained American citizenship and their American descendants.

To be included in this list, the person must have a Wikipedia article showing they are Swedish American or must have references showing they are Swedish American and are notable.

Marcello Conversi

Marcello Conversi (August 25, 1917 – September 22, 1988) was an Italian particle physicist. He is best known for his 1946 cosmic ray experiment where he showed that the "mesotron", now known as the muon, was not a strongly interacting particle.Conversi studied under Enrico Fermi at the University of Rome, and received his doctorate in 1940, doing his thesis under Bruno Ferretti. During World War II, Conversi remained in Italy, doing research and teaching at the University of Rome. Together with Oreste Piccioni and Ettore Pancini he conducted the experiment that Luis Walter Alvarez, Nobel Prize laureate of 1968, called the "start of modern particle physics" in his Nobel lecture. In 1946, they showed that the "mesotron", now known as the muon, which had been discovered in 1937 by Seth Neddermeyer and Carl David Anderson, was not the particle predicted by Hideki Yukawa as mediator of the strong force. If the "mesotron", a cosmic ray particle of negative charge, was indeed the meson postulated by Yukawa, it should be captured without decaying.

Conversi, Piccioni and Pancini moved their experiment to a high school to avoid air raids. In their experimental setup negative and positive particles were separated by large pieces of iron on the roof of the high school. The negative particles were absorbed in matter. After switching from iron to graphene absorbers, the 1946 experiment dramatically showed that the negatively charged component of cosmic rays decayed radioactive rather than being captured by the graphite.From 1947 to 1946 Conversi held a position as a post-doctoral fellow at the University of Chicago, before he returned to Italy as a Professor of Experimental Physics and Director of the Physics Institute at the University of Pisa. During his time in Pisa, he founded the Centro Studi Calcolatrici Elettroniche (CSCE), where the first Italian computer was built. For this work he received the gold medal of the President of Italy in 1961. He also developed a new track detector, known as the flash chamber — a precursor to the spark chamber — which went on to become the standard tool in particle and cosmic ray physics.

In 1958 he returned to the University of Rome, as a Professor of Advanced Physics. He had two appointments as director of the institute, one from 1960 to 1962 and the second from 1964 to 1966. His influential school, from 1950 at Pisa and from 1958 at Rome, produced many famous Italian particle physicists, such as Marcello Creti, Carlo Rubbia and Luigi Di Lella.From 1962 to 1964, and again from 1975 to 1977, Conversi was affiliated CERN. At CERN, Conversi was a member of the Scientific Committee from 1969 to 1975, becoming its Vice-President. From 1959, he participated in a series of quests at the Synchro-Cyclotron (CERN) for “forbidden” processes in weak interaction. When the new Super Proton Synchrotron began its operation in 1976 he played a prominent role in searches for short-lived particles using a stack of nuclear emulsion coupled to the BEBC bubble chamber.Conversi was vice president of Italian National Institute of Nuclear Physics from 1967 to 1970.He was a fellow of the American Physical Society since 1950 and a member of the Italian science academy.


The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1 e, a spin of 1/2 (same as electron), and has the same mass as an electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more gamma ray photons.

Positrons can be created by positron emission radioactive decay (through weak interactions), or by pair production from a sufficiently energetic photon which is interacting with an atom in a material.

Positron emission

Positron emission or beta plus decay (β+ decay) is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (νe). Positron emission is mediated by the weak force. The positron is a type of beta particle (β+), the other beta particle being the electron (β−) emitted from the β− decay of a nucleus.

An example of positron emission (β+ decay) is shown with magnesium-23 decaying into sodium-23:

2312Mg → 2311Na + e+ + νeBecause positron emission decreases proton number relative to neutron number, positron decay happens typically in large "proton-rich" radionuclides. Positron decay results in nuclear transmutation, changing an atom of one chemical element into an atom of an element with an atomic number that is less by one unit.

Positron emission should not be confused with electron emission or beta minus decay (β− decay), which occurs when a neutron turns into a proton and the nucleus emits an electron and an antineutrino.

Positron emission is different from proton decay, the hypothetical decay of protons, not necessarily those bound with neutrons, not necessarily through the emission of a positron and not as part of nuclear physics, but rather of particle physics.

September 3

September 3 is the 246th day of the year (247th in leap years) in the Gregorian calendar. 119 days remain until the end of the year.

Victor Francis Hess

Victor Franz Hess (24 June 1883 – 17 December 1964) was an Austrian-American physicist, and Nobel laureate in physics, who discovered cosmic rays.


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