Discovery Of The Positron, 1932

by Science Source

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Discovery Of The Positron, 1932

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Science Source

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Photograph - Photograph

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First evidence existence of positron single track antiparticle of electron from California Institute of Technology; Cloud Chamber; adduced by C.D. Anderson's photo, 1932. Carl David Anderson (September 3, 1905 - January 11, 1991) was an American physicist. 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 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. Also in 1936, Anderson and his first graduate student, Seth Neddermeyer, discovered the muon (mu-meson), 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. The muon was the first of a long list of subatomic particles whose discovery initially baffled theoreticians. He spent all of his academic and research career at Caltech. During WWII, he conducted research in rocketry there. He was elected a Fellow of the American Academy of Arts and Sciences in 1950. He died in 1991 at the age of 85.

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August 3rd, 2015

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