Science › Quantum world
Antimatter
1932· Discovery / experiment
ProvenTested many times; part of working physics.
Every particle has an antimatter twin with the same mass and opposite charge; when the two meet, both turn into energy.
See it on the Science map →How it works
The positron is the electron's twin, the antiproton the proton's. Antimatter is made routinely in particle accelerators, in cosmic rays, and even in bananas through rare potassium decays. When matter and antimatter touch, their entire mass converts to energy, following E = mc². CERN makes and traps antihydrogen atoms for study. Producing it is extremely expensive and slow.
Why it matters
It showed theory could predict new kinds of matter. Hospital PET scans use positrons. It also raises the puzzle of why the universe is made of matter at all.
How we know
Anderson's 1932 positron discovery; antiprotons at Berkeley in 1955; antihydrogen at CERN in 1995, trapped from 2010. In 2023 CERN showed antimatter falls downward under gravity, like ordinary matter.
Still a mystery
The Big Bang should have made equal matter and antimatter, which would have annihilated. Why a small excess of matter survived, leaving us, is unexplained.
Connections (3)
▸E = mc² lets energy become matter and AntimatterProven
The relationship
Because mass and energy are interchangeable, enough concentrated energy can become new particles. Electric charge must still balance, so energy produces matter paired with antimatter, such as an electron plus a positron. In reverse, when a particle meets its antiparticle, their whole mass converts back into energy, usually gamma rays.
How the link was found
Einstein's 1905 formula set the exchange rate. Dirac predicted antimatter in 1931; Anderson found the positron in 1932, and Blackett and Occhialini saw electron–positron pairs created from cosmic-ray energy in 1933.
Why it's proven
Pair creation and annihilation are seen daily in accelerators and hospitals. PET scanners detect the two 511 keV gamma rays from each annihilation, exactly the electron's mass times c².
Open questions and mysteries
If energy always makes matter and antimatter in equal amounts, why does our universe contain almost only matter?
▸Paul Dirac predicted AntimatterProven
The relationship
Dirac's 1928 relativistic electron equation had unavoidable negative-energy solutions. He first suggested they were protons, which failed because the masses differ. In 1931 he proposed they meant a new particle: the anti-electron, with the electron's mass and positive charge. The mathematics demanded antimatter before anyone had seen it.
How the link was found
Paul Dirac: equation 1928, prediction 1931. Carl Anderson at Caltech found the positron in cloud-chamber photos of cosmic rays in 1932, apparently unaware of Dirac's prediction.
Why it's proven
Positrons, antiprotons (1955) and antineutrons (1956) were all found, as Dirac's framework implies every particle has an antiparticle.
Open questions and mysteries
Why the universe kept matter but almost no antimatter is unresolved; known physics explains only a tiny fraction of the imbalance.
▸Antimatter almost all vanished in Matter beats antimatter (baryogenesis)Open question
The relationship
Antimatter all but vanished because, as the universe cooled, every antiparticle met a particle and both turned to light; only matter's surplus was left. For that surplus to arise, antimatter must behave slightly differently from matter. Experiments find it does: some particles decay at different rates than their antiparticles. Such a difference, acting early, could tilt the balance.
How the link was found
James Cronin and Val Fitch found the first matter–antimatter difference in kaon decays in 1964 (Nobel 1980). The BaBar and Belle experiments saw it in B mesons in 2001; LHCb saw it in baryons in 2025.
Is it proven?
The differences are precisely measured. But the Standard Model's known differences are billions of times too weak to explain the surplus, so the link is real but incomplete.
Open questions and mysteries
Do neutrinos and antineutrinos differ more? Japan's T2K experiment hinted so in 2020; DUNE and Hyper-Kamiokande will test it from the late 2020s.