Positron
The positron is the antiparticle of the electron, sometimes called the "anti-electron". It has the same mass as an electron, but its electric charge is positive instead of negative. According to CERN, the European particle physics laboratory, its existence was shown when the physicist Carl Anderson discovered it in 1932.[1]
Prediction
The positron was predicted before it was found. In 1928 the British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe an electron moving at very high speed.[2] While developing quantum mechanical theory, Dirac predicted that all matter has a kind of mirror image, called antimatter. A particle and its antiparticle, if they carry a charge, should have opposite charges.[3] CERN explains that Dirac's equation could have two solutions, one of them for a particle with negative energy, and that physicists interpreted this new particle as an "anti-electron".[2][1]
Discovery
The search for this particle was won by Carl D. Anderson, a postdoctoral researcher at the California Institute of Technology (Caltech).[4] Anderson studied the tracks left by cosmic ray particles in a cloud chamber. In 1932 he found a positively charged particle whose mass seemed equal to that of an electron. It was the first antiparticle to be proven by experiment, and it was named the positron.[5] Anderson shared the 1936 Nobel Prize in Physics "for his discovery of the positron".[6]
Meeting electrons
Particles and their antiparticles are always produced in pairs. When a particle and its antiparticle meet, they annihilate each other and leave only energy behind.[7] This energy is mostly in the form of photons, which are particles of light, and pions.[7]
In everyday life
Antimatter can seem very far from daily life, but the US Department of Energy notes that an ordinary banana produces antimatter: it releases about one positron every 75 minutes.[8]
References
- ↑ 1.0 1.1 "Antimatter". CERN. Retrieved 20 October 2026.
Physicists interpreted this new particle as an "anti-electron", a particle with a mass identical to the electron but with opposite electrical charge. The existence of this particle was demonstrated with Carl Anderson's discovery of the positron in 1932.
- ↑ 2.0 2.1 "Antimatter". CERN. Retrieved 20 October 2026.
In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behaviour of an electron moving at a relativistic speed. ... Dirac's equation could have two solutions, one for an electron with positive energy, and one for a particle with negative energy.
- ↑ "Carl D. Anderson – Facts". Nobel Prize Outreach. Retrieved 20 October 2026.
In developing quantum mechanical theory, Dirac predicted that all matter has a kind of mirror image—antimatter. A particle and its antiparticle, if charged, should have opposite charges.
- ↑ "August 1932: Discovery of the Positron". American Physical Society (APS News). Retrieved 20 October 2026.
The hunt was on to find experimental verification of this hypothesis; a Caltech postdoc named Carl D. Anderson would win the race.
- ↑ "Carl D. Anderson – Facts". Nobel Prize Outreach. Retrieved 20 October 2026.
By studying the tracks of cosmic ray particles in a cloud chamber, in 1932 Carl Anderson discovered a positively-charged particle with a mass seemingly equal to that of an electron. Anderson's particle was the first antiparticle proven by experiment and was named a "positron".
- ↑ "Carl D. Anderson – Facts". Nobel Prize Outreach. Retrieved 20 October 2026.
Prize motivation: "for his discovery of the positron" Prize share: 1/2
- ↑ 7.0 7.1 "Antimatter". CERN. Retrieved 20 October 2026.
particles and antiparticles are always produced in pairs, and they annihilate upon contact, leaving only energy behind, predominantly in the form of photons and pions.
- ↑ "DOE Explains...Antimatter". US Department of Energy. Retrieved 20 October 2026.
But ordinary bananas produce antimatter, releasing one positron—the antimatter equivalent of an electron—about every 75 minutes.