Date of Birth: 09/03/1905
Place of birth: New York
Citizenship: United States
Having at Caltech undergraduate degree in physics and engineering in 1927, Alexander began graduate work in physics under the direction of Robert E. Millikan. In 1930 he brilliantly defended his doctoral thesis on the spatial distribution of electrons ejected from gases by X-rays. Then Alexander went on to work in a research fellow Millikan, who advised him to study cosmic radiation (electromagnetic radiation and atomic particles from extraterrestrial sources). A year later, he decided to entrust A. Millikan daily implementation of the project for the identification and measurement of energy of various types of cosmic radiation, and together they have developed a more efficient version of the condensing chamber, created more CH.T.R. Wilson and designed to detect charged particles. The condensation chamber is a closed vessel filled with a gas (usually - air), which is saturated with water vapor; the vessel is placed between the poles of an electromagnet. When charged particles pass through the vessel, they ionize the gas in its path the molecule, and the last act as centers of condensation of water vapor. Each type of particle leaves a characteristic trail of condensation, which can be photographed, and the positively charged and negatively charged particles are deflected in opposite directions.
Studying thousands of photos condensing tracks left behind by high-energy particles emitted from an extraterrestrial space A. zametilneskolko tracks that differ from those of the electrons only one: they deviate in the opposite direction. Other researchers have also noticed from time to time these traces, but as a theoretical justification for the existence of a positively charged particle similar to an electron missing, they carried them through experimental error, however in 1928, PAM Dirac predicted the existence of a whole family of antiparticles - particles, corresponding to known, but with an opposite charge and magnetic moment. Initially, physicists were skeptical of this prediction, and A. was not looking for antiparticles until, until he noticed strange tracks. Discovery for which he received the Nobel Prize, he said later, it was completely random. However, rather than dismiss the detected fact, he tried to determine whether these tracks traces hypothetical "anti-electrons." Experimentally, eliminating all other possible explanations, A. came to the conclusion that his observation can be explained only by recognizing the existence of a positively charged particle with a mass approximately equal to the mass of an electron. In September 1932, he announced the discovery of the particle, which he called a positron.
A. Opening confirmed the existence of antimatter and led to intensive studies of the interaction of matter with antimatter, A. and others have found that, when an electron meets a positron, the two annihilate, producing a flash of gamma rays (high-energy electromagnetic radiation). Conversely, if the gamma-rays of sufficiently high energy to stop, then they disappear, leaving only the newly created pair of electron - positron. These transitions are expressive confirmation of the equivalence of mass and energy, expressed in the formula of Albert Einstein`s E = mc2. Other antiparticles (antiprotons and antineutrons) were not found until the 50-ies., But by the time the physicists were convinced that each particle has its own antiparticle. Antiparticles reaching the earth from the cosmic rays or by gamma rays from a lab, quickly destroyed when interacting with ordinary particles. However, physicists tend to think that somewhere in the galaxy may be composed of antimatter, in which atomic nuclei contain antiprotons and positrons are surrounded, thus providing an inverse relationship between charges compared to our "local" atoms.
, "For his discovery of the positron" A. received in 1936 the Nobel Prize in physics. He shared it with Victor F. Hess, who discovered cosmic rays in 1912, and proved their extraterrestrial origin. When presenting the winner, Hans Pleyel, a member of the Royal Swedish Academy of Sciences, said, referring to Anderson: "Using ingenious devices, you could find one of the building blocks of the universe - positive electron."
A. was appointed assistant professor of physics at Caltech in 1933, associate professor in 1937 and full professor in 1939. Two years later, after he discovered the positron, he together with S. Neddermayerom managed to find another previously colliding particles in cosmic rays, but they waited until 1937, patiently collecting additional evidence from photographs of tracks before announced the discovery of a particle, now known as the muon. The weight of this particle was about 200 times greater than that of the electron.
During World War II, A. worked on military projects, including the creation of missiles for the National Committee for the Defence Research and the Office of Research and Development, in 1944, he spent a month on the coast of Normandy, to oversee the functioning of the aircraft missiles in combat conditions. A. After the war, he returned to Caltech, where he held teaching and research work, especially in the field of cosmic rays and elementary particles, until his retirement in 1976,
A married Lorraine Elvira Bergman in 1946 .; they raised two sons. In his spare time he likes to play tennis.
In addition to the Nobel Prize, A. received numerous awards and honorary degrees. including the Elliott Cresson Medal Franklin Institute (1937) and the Medal of John Erickson of the American Society of Swedish Engineers (1960). He holds honorary degrees Colgate University and Temple. Alexander is a member of the US National Academy of Sciences, the American Academy of Arts and Sciences. The American Physical Society and the American Philosophical Society.