Carl Anderson American physicist who discovered the positron in 1932, for which he received the Nobel Prize in Physics in 1936. Date of Birth: 03.09.1905 Country: USA

1. Early Life and Education
2. PhD and Doctoral Work
3. Discovery of the Positron
4. Nobel Prize and Further Discoveries
5. Later Career and Achievements
6. Personal Life and Legacy

Early Life and Education

Carl David Anderson, an American physicist, was born in New York City to Emma Adolphine (née Ajaxson) and Carl David Anderson. He was the only son in the family. After moving to California, Anderson attended Los Angeles High School, graduating in 1924. He then pursued higher education at the California Institute of Technology (Caltech) in Pasadena.

PhD and Doctoral Work

In 1927, Anderson earned a bachelor's degree in physics and engineering from Caltech. He continued his studies as a graduate student in physics under the supervision of Robert A. Millikan. In 1930, he received his PhD for a dissertation on the spatial distribution of electrons ejected from gases by X-rays.

Discovery of the Positron

After graduating, Anderson remained at Caltech as a research fellow under Millikan. Millikan advised him to study cosmic rays, primarily consisting of electromagnetic radiation and atomic particles from extraterrestrial sources. In 1931, Anderson observed several tracks in a cloud chamber, a device used to detect charged particles. These tracks differed from electron tracks only in that they deflected in the opposite direction.

Anderson's initial observations were controversial. Other researchers had also noticed similar tracks but attributed them to experimental errors. However, in 1928, P.A.M. Dirac predicted the existence of antiparticles, particles corresponding to known particles but with opposite charge and magnetic moment. Anderson's observation aligned with Dirac's prediction. After eliminating other possible explanations, Anderson concluded that the tracks were the result of a positively charged particle with a mass similar to an electron. In September 1932, he announced the discovery of the particle, which he named the positron.

Nobel Prize and Further Discoveries

The discovery of the positron confirmed the existence of antimatter and led to extensive research on the interactions between matter and antimatter. Anderson and others demonstrated that when an electron meets a positron, both particles annihilate, releasing a burst of gamma rays. Conversely, high-energy gamma rays can be extinguished, giving rise to a newly created electron-positron pair.

Two years after discovering the positron, Anderson, along with S. Neddermeyer, identified another previously unobserved particle in cosmic rays. They named it the muon, a particle with a mass approximately 200 times greater than an electron.

Later Career and Achievements

During World War II, Anderson worked on military projects including rocket development for the National Defense Research Committee and Office of Scientific Research and Development. He returned to Caltech after the war and continued his teaching and research in cosmic rays and elementary particles until his retirement in 1976.

Anderson received the Nobel Prize in Physics in 1936 for his discovery of the positron, sharing it with Victor F. Hess, who had first discovered cosmic rays in 1912. Throughout his career, he was awarded numerous awards and honorary degrees, including the Franklin Institute's Elliott Cresson Medal (1937) and the American Society of Swedish Engineers' John Ericsson Medal (1960). He was a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the American Physical Society, and the American Philosophical Society.

Personal Life and Legacy

Anderson married Lore Ray Elwira Bergman in 1946, and they had two sons. In his leisure time, he enjoyed playing tennis. Anderson's groundbreaking discoveries continue to contribute to our understanding of subatomic particles and the fundamental nature of the universe.