An American physicist who, with Victor Francis Hess of Austria, won the Nobel Prize for Physics in 1936 for his discovery of the positron, or positive electron, the first known particle of antimatter, Carl David Anderson was born on September 3, 1905, in New York City, New York, U.S. Anderson opened up the entire field of particle physics, the study of the atom, the smallest unit of matter.
Born to Swedish immigrant parents, Anderson showed a knack for science from an early age. After completing his preliminary education, he enrolled at the California Institute of Technology for higher studies. His association with the institution remained life-long as first he earned his academic degrees from the same and later continued his research work at it. It was during his academic and research career at Caltech that he began his cosmic ray studies which eventually led to the discovery of positron. The discovery was important for the advancement of physics as positron became the first antimatter to be discovered. Later on, he carried out further research that led to the discovery of muon, a subatomic particle. For his discovery of positron, he was conferred with the Nobel Prize in Physics in 1936. Additionally, he was honored with several other scientific awards as well.
Childhood, Family and Educational Life
A renowned American physicist, Carl David Anderson was born to Swedish immigrant parents, Carl David Anderson and Emma Adolfina Ajaxson, in New York City, New York, U.S. on September 3, 1905. His father, also named Carl David Anderson, was a restaurant manager. His mother was a housewife. Carl was their only child. When he was a child Anderson wanted a career in athletics, as a high jumper. The Anderson family moved to Los Angeles, where Carl David attended Los Angeles Polytechnic High School and first became interested in science.
In 1924 Anderson entered the California Institute of Technology (Cal Tech), with which he would remain associated throughout his life. In 1927 Anderson received his bachelor’s degree. He then continued his education in graduate school on a research grant, centering his graduate work on physics and mathematics. Three years later, he was awarded a Ph.D. degree. He completed his thesis on the space distribution of photoelectrons ejected from various gases by X-rays.
In 1946, age 40, Carl David Anderson married Lorraine Bergman. She had been married previously and her son Marshall, who was three, moved into the new family home. Anderson adopted him. Marshall became a mathematician. The couple had a son of their own, David, who became a physicist. Lorraine passed away in 1984.
Career and Works
Carl David Anderson received his Ph.D. in 1930 from the California Institute of Technology, Pasadena, where he worked with physicist Robert Andrews Millikan. Having studied X-ray photoelectrons (electrons ejected from atoms by interaction with high-energy photons) since 1927, he began research in 1930 on gamma rays and cosmic rays. While studying cloud-chamber photographs of cosmic rays, Anderson found a number of tracks whose orientation suggested that they were caused by positively charged particles but particles too small to be protons.
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) 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. 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.
In 1933, Anderson took up the position of Assistant Professorship in Physics, which he served for six years after which he was promoted to the position of Professor of Physics.
In 1936 Anderson made a second important experimental discovery: the existence of a charged particle in cosmic radiation (rays from the sun) with a mass (an amount of matter) of about 200 electron masses, or of about one-tenth the mass of a proton. Anderson named these particles mesotrons (later shortened to mesons). He believed them to be identical to the nuclear particle H. Yukawa (1907-1981) had theoretically predicted less than two years earlier. It was later realized, however, that Anderson’s meson is actually the mu meson (or muon), and Yukawa’s meson is actually the pi meson (or pion). After World War II (1939-45) Anderson continued to develop the field of particle physics, which his groundbreaking 1932 discovery had opened up for research.
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. 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.”
Till the end of his life, Anderson continued his research work on radiation and fundamental particles. Most of his discoveries have been published in ‘Physical Review’ and ‘Science’.
Awards and Honor
In 1936, Carl David Anderson was awarded Nobel Prize for his discovery of the positron. He shared the same with Victor Franz Hess, who too had made an important discovery in cosmic radiation.
In 1945, Anderson was conferred with the prestigious Presidential Certificate of Merit. He was elected as a Fellow of the American Academy of Arts and Sciences in 1950.
In 1976, Anderson was named Professor Emeritus at Caltech. Other highly esteemed and prolific scientific awards and honors won by him include Gold Medal of the American Institute of City of New York, Sc.D. of Colgate University, Elliott Cresson Medal of the Franklin Institute, LL.D. Temple University and John Ericsson Medal of the American Society of Swedish Engineers
Death and Legacy
Carl David Anderson died on January 11, 1991, and his remains were interred in the Forest Lawn, Hollywood Hills Cemetery in Los Angeles, California.
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. Anderson received several honorary doctoral degrees and became a member of the National Academy of Sciences.
Carl David Anderson Credit: Dibner Library of the History of Science and Technology/Smithsonian Institution Libraries
September 3 is Carl David Anderson’s birthday. Anderson was the American physicist who discovered the positron.
Anderson attended Caltech as an electrical engineering student but switched to physics after attending a lecture. He worked as a research assistant to Robert Millikan who was trying to prove a theory of his dealing with cosmic rays.
Cosmic rays were a newly discovered phenomenon in the 1920s. Henri Becquerel had discovered radioactivity in 1896 and scientists had been detecting radiation everywhere ever since. It was widely accepted radioactivity detected in the air originated from radioactive elements in the Earth’s crust. In 1909, German physicist Theodor Wulf constructed a particle detector to test this belief. He wanted to show radiation levels decreased as you got further from the Earth. He set up his experiment to measure the difference between radiation at the base and top of the tallest building in the world, the Eiffel Tower. Wulf ended up showing there was more radiation as you gained altitude. This would imply the radiation was coming from a source other than the Earth’s crust. Austrian physicist Victor Hess expanded this experiment by measuring radiation during balloon flights and during eclipses to eliminate the Sun as the source. Hess would earn half the 1936 Nobel Prize in Physics for discovering cosmic rays came from space. Millikan coined the term cosmic rays and believed cosmic rays were actually gamma rays and the charged particle radiation was a secondary radiation caused by the gamma rays being scattered by the atmosphere. Anderson was one of the students looking for these secondary reactions.
Anderson worked with a cloud chamber to detect charged particles. Cloud chambers are sealed containers of supersaturated water vapor. When a charged particle passes through the vapor, the vapor is ionized. These ions form condensation nuclei and bubbles of water are formed along the ionization path. If you place your chamber in a strong magnetic field, the path any moving charged particle will curve according to its charge and energy. The direction of the curve is determined by the particle’s charge while the radius of the curve is determined by the energy of the particle. Since these interactions are generally very fast, photographs of the chamber are taken to make measurements and analyze later. In several of Anderson’s photographs, he detected a bubble path that indicated the mass of an electron but curved in the opposite direction. Anderson had discovered the anti-electron predicted by Paul Dirac. This discovery would earn Anderson the other half of the 1936 Nobel Prize in Physics.
The year he won his Prize, he and his graduate student, Seth Neddermeyer were continuing research into cosmic rays when they detected another new particle. This particle had the same charge of the electron but was 207 times more massive. Since this particle seemed to have a mass midway between an electron and a proton, he called the particle a mesotron (meso – middle in Greek). The name was later shortened to meson. Anderson believed this discovery matched the theoretical existence of a particle predicted by Hideki Yukawa, but while it had the correct mass, it didn’t interact with the nucleus in the predicted manner. Yukawa’s particle would be discovered 10 years later and called a pi meson or pion for short. Anderson’s meson is now called a mu meson or muon. Anderson’s discoveries would be the first steps towards the Standard Model of particle physics.
Like most American physicists working with radiation, Anderson was approached during World War II to work on the Manhattan Project and the atomic bomb. He declined the offer, choosing instead to work with the US Navy and the Office of Scientific Research and Development to develop new rocket technology.
Notable Science Events for September 3
1976 – NASA’s Viking II lander lands on Mars.
NASA’s Viking II lander touched down on the surface of Mars. The Viking II was identical to the Viking I lander that landed the previous month. Viking II conducted a visual survey of the Utopia Planitia region of Mars and sampled the soil and found mostly silicon and iron with levels of magnesium, aluminum, sulfur, calcium, and titanium.
One of the first images of the surface of Mars taken by Viking 2 lander. The rounded part in the lower right corner is the Viking 2 lander. NASA
1938 – Ryoji Noyori was born.
Noyori is a Japanese chemist who shares half the 2001 Nobel Prize in Chemistry with William Knowles for their work with chirally catalyzed hydrogenations. These reactions are used to prepare many pharmaceutical compounds where one chiral molecule is desired over its mirrored twin molecule. Noyori developed catalysts that produced more of the desired molecule than the undesired molecule.
1905 – Carl David Anderson was born.
1905 – Frank Macfarlane Burnet was born.
Frank Macfarlane Burnet (1899 – 1985)
Burnet was an Australian virologist who shares the 1960 Nobel Prize in Medicine with Peter Medawar for their work in immunology and discovery of acquired immunological tolerance. This occurs when the body adapts to external antigens without causing an immune system response.
He refined and improved laboratory techniques to incubate viruses in hen eggs. He applied this method to culture and detect influenza virus. Burnet also identified the cause for ornithosis and Q fever.
1869 – Fritz Pregl was born.
Fritz Pregl (1869 – 1930). Nobel Foundation
Pregl was an Austrian physician and chemist who was awarded the 1923 Nobel Prize in Chemistry for his method of micro-analysis of organic substances. While he was researching bile acids, he had difficulty using the analytic techniques of the time to determine the elemental makeup of his samples. He improved the techniques such that there were fewer steps and less sample was needed.
He also developed a sensitive microbalance and new ways to identify chemical functional groups.